@article{chen_li_gigax_hunter_fensin_zikry_2024, title={How are microstructural defect interactions linked to simultaneous intergranular and transgranular fracture modes in polycrystalline systems?}, volume={188}, ISSN={["1873-4782"]}, url={https://doi.org/10.1016/j.jmps.2024.105674}, DOI={10.1016/j.jmps.2024.105674}, abstractNote={The major objective of this investigation is to fundamentally understand and predict how intergranular (IG) and transgranular (TG) fracture modes nucleate and propagate in f.c.c. polycrystalline systems due to defects, such as total and partial dislocation densities and grain boundary (GB) structures and misorientations. A dislocation density crystalline plasticity (DCP) formulation based on the evolution and interaction of total and partial dislocation densities was integrated with a recently developed fracture approach to investigate the fracture nucleation and propagation of simultaneous multiple fracture events, including both IG and TG fracture events. The aggregate grains and GB orientations and morphologies are based on EBSD measurements that are representative of polycrystalline copper aggregates with a broad range of random high angle and low angle GBs. The predictions indicate that dislocation density pileups induce IG fracture due to interrelated stress, slip, and total and partial dislocation density accumulations and interactions for both high angle GBs (HAGBs) and low angle GBs (LAGBs). TG fracture nucleation and propagation occurred due to normal stress accumulations, which exceeds the fracture stress, along cleavage planes. Furthermore, it is shown how IG cracks transition from the GB plane to the cleavage planes as cracks nucleate and propagate. Accumulated plastic zones due to different slip system activities can impede and blunt crack propagation and fronts. These plastic zones form due to high Lomer and Shockley partial dislocation densities. These predictions, which are consistent with experimental observations, provide a fundamental understanding of how simultaneous failure modes initiate and propagate for physically representative microstructures.}, journal={JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS}, author={Chen, Muh-Jang and Li, Nan and Gigax, Jonathan and Hunter, Abigail and Fensin, S. and Zikry, Mohammed A.}, year={2024}, month={Jul} }
 @article{xu_zikry_seyam_2024, title={Impact Performance of 3D Orthogonal Woven Composites: A Finite Element Study on Structural Parameters}, volume={8}, ISSN={["2504-477X"]}, url={https://doi.org/10.3390/jcs8060193}, DOI={10.3390/jcs8060193}, abstractNote={This study uses the finite element method (FEM) to investigate the effect of key structural parameters on the impact resistance of E-glass 3D orthogonal woven (3DOW) composites subjected to low-velocity impact. These structural parameters include the number of y-yarn layers, the path of the binder yarn (z-yarn), and the density of the x-yarn. Using ABAQUS, yarn-level finite element (FE) models are created based on the measured geometrical parameters and validated for energy absorption and damage behavior from experimental data gathered from the previous study. The results from finite element analysis (FEA) indicate that the x-yarn density and the binder path substantially influenced the composites’ damage behavior and impact performance. Increasing x-yarn density in 3DOW leads to a 15% increase in energy absorption compared to models with reduced x-yarn densities. Moreover, as the x-yarn density increases, crack lengths at the back face of the resin matrix decrease in the y-yarn direction but increase in the x-yarn direction. The basket weave structure absorbs less energy than plain and 2 × 1 twill structures due to the less constrained weft primary yarns. These results underscore the importance of these structural parameters in optimizing 3DOW composite for better impact performance, providing valuable insights for the design of advanced composite structures.}, number={6}, journal={JOURNAL OF COMPOSITES SCIENCE}, author={Xu, Wang and Zikry, Mohammed and Seyam, Abdel-Fattah M.}, year={2024}, month={Jun} }
 @article{arcari_zikry_callahan_horton_chen_2024, title={Modeling hydrogen diffusion in precipitation hardened nickel-based alloy 718 by microstructural modeling}, volume={6}, ISSN={["2191-0316"]}, DOI={10.1515/corrrev-2024-0013}, abstractNote={Abstract Environmentally assisted cracking can significantly affect the performance of high strength alloys and limit material selection to minimize the risk of subcritical crack growth in service. UNS N07718 is widely used in marine service applications and under a variety of conditions, such as: alternate immersion, different levels of cathodic protection, and freely corroding galvanic couples, because of its demonstrated corrosion and fracture resistance in these environments. In this work we developed a representative model of the material microstructure including the metal grains, the material texture, and the precipitates along the grain boundaries and within the grains. The microstructural model was subjected to the boundary conditions identified at the notch root of a fracture mechanics sample and the results are used as input for a simulation of hydrogen diffusion from the surface of the notch, assuming the material has been introduced to a hydrogen producing environment. The diffusion of hydrogen was modeled by Fick’s law and included both hydrostatic stress and mobile dislocation velocity as driving forces. The influence of immobile dislocations was also modeled to account for the irreversible trapping. The results show that hydrostatic stress and immobile dislocation trapping can significantly alter the highest concentration of hydrogen and its location within the microstructure towards the fracture process zone. Mobile dislocation velocity has a small influence in determining the hydrogen distribution near the fracture process zone.}, journal={CORROSION REVIEWS}, author={Arcari, Attilio and Zikry, Mohammed A. and Callahan, Patrick G. and Horton, Derek J. and Chen, Muh-Jang}, year={2024}, month={Jun} }
 @article{xu_zikry_seyam_2024, title={Numerical Study of the Influence of the Structural Parameters on the Stress Dissipation of 3D Orthogonal Woven Composites under Low-Velocity Impact}, volume={12}, ISSN={["2227-7080"]}, url={https://www.mdpi.com/2227-7080/12/4/49}, DOI={10.3390/technologies12040049}, abstractNote={This study investigates the effects of the number of layers, x-yarn (weft) density, and z-yarn (binder) path on the mechanical behavior of E-glass 3D orthogonal woven (3DOW) composites during low-velocity impacts. Meso-level finite element (FE) models were developed and validated for 3DOW composites with different yarn densities and z-yarn paths, providing analyses of stress distribution within reinforcement fibers and matrix, energy absorption, and failure time. Our findings revealed that lower x-yarn densities led to accumulations of stress concentrations. Furthermore, changing the z-yarn path, such as transitioning from plain weaves to twill or basket weaves had a noticeable impact on stress distributions. The research highlights the significance of designing more resilient 3DOW composites for impact applications by choosing appropriate parameters in weaving composite designs.}, number={4}, journal={TECHNOLOGIES}, author={Xu, Wang and Zikry, Mohammed and Seyam, Abdel-Fattah M.}, year={2024}, month={Apr} }
 @article{xie_chen_gigax_luscher_wang_hunter_fensin_zikry_li_2023, title={A fundamental understanding of how dislocation densities affect strain hardening behavior in copper single crystalline micropillars}, volume={184}, ISSN={["1872-7743"]}, DOI={10.1016/j.mechmat.2023.104731}, abstractNote={Under mechanical loading, the strain hardening behavior of crystalline face-centered cubic (FCC) metals is of critical importance in determining fracture behavior and overall mechanical performance. While strain hardening is typically accompanied by a decrease in ductility, it can also simultaneously enhance the material's resistance to plastic deformation and improve its load bearing capacity. Hence, we conducted a detailed study using copper (Cu) single-crystal micropillars as a model system to investigate and delineate the relationship between strain hardening and defect behavior. We employed in situ compression in a scanning electron microscope (SEM) and dislocation density-based crystal plasticity (DCP) modeling. The strain hardening rate varied with the compression crystallographic orientation, ranging from negligible values (of approximately 80 MPa) to relatively high hardening rates (of approximately 1150 MPa) for nominal strains of up to 15%. Various analysis methods were applied, including slip trace characterization, electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and transmission Kikuchi diffraction (TKD). These techniques allowed us to identify the distributions of active slip systems, dislocation structures after compression, and correlated internal lattice rotations. Furthermore, the DCP model was developed to specifically understand how serration events are related to dislocation-density evolution or strain bursts, and this was validated with the micropillar experiments. This integrated experimental and modeling investigation offers valuable insights and predictions regarding the evolution of both total and partial dislocations, including Hirth and Lomer junctions, as well as lattice rotations.}, journal={MECHANICS OF MATERIALS}, author={Xie, Dongyue and Chen, Muh-Jang and Gigax, Jonathan and Luscher, Darby and Wang, Jian and Hunter, Abigail and Fensin, Saryu and Zikry, Mohammed and Li, Nan}, year={2023}, month={Sep} }
 @article{hasan_capolungo_zikry_2023, title={A machine learning microstructurally predictive framework for the failure of hydrided zirconium alloys}, volume={7}, ISSN={["2397-2106"]}, url={https://doi.org/10.1038/s41529-023-00344-7}, DOI={10.1038/s41529-023-00344-7}, abstractNote={Abstract}, number={1}, journal={NPJ MATERIALS DEGRADATION}, author={Hasan, Tamir and Capolungo, Laurent and Zikry, Mohammed}, year={2023}, month={Mar} }
 @article{chen_xie_li_zikry_2023, title={Dislocation-density evolution and pileups in bicrystalline systems}, volume={870}, ISSN={["1873-4936"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85149441852&partnerID=MN8TOARS}, DOI={10.1016/j.msea.2023.144812}, abstractNote={A dislocation-density crystalline plasticity (DCP) framework based on total and partial dislocation densities interactions was used to investigate the behavior of Cu/Pb bicrystals with a focus on GB effects. The modeling predictions were validated with bicrystal compression micropillar experiments. A key new aspect of the modeling approach is to account for partial dislocation-densities. A GB formulation that is directly linked to GB energies was used to monitor GB transmission and blockages, such that pileups can be monitored and predicted at the GB interfaces for misorientations. The predictions indicate that pileups can form due to fully and partially blocked slip-rates and perfect and partial dislocation-densities. As the nominal strain increases from five to fifteen percent, dislocation-densities and pileups significantly increase by almost an order of magnitude. The proposed validated approach provides a microstructural scale predictive framework that accounts for a myriad of defects related to the interactions of partial and perfect dislocation densities that interact at highly misoriented GBs; it is these interactions that are critical to the formation and evolution of dislocation-density pileups that can lead to physically limiting stress accumulations in bicrystals.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Chen, Muh-Jang and Xie, Dongyue and Li, Nan and Zikry, Mohammed A.}, year={2023}, month={Apr} }
 @article{hasan_capolungo_zikry_2023, title={How can machine learning be used for accurate representations and predictions of fracture nucleation in zirconium alloys with hydride populations?}, volume={11}, ISSN={["2166-532X"]}, url={https://doi.org/10.1063/5.0155679}, DOI={10.1063/5.0155679}, abstractNote={Zirconium alloys are critical material components of systems subjected to harsh environments such as high temperatures, irradiation, and corrosion. When exposed to water in high temperature environments, these alloys can thermo-mechanically degrade by forming hydrides that have a crystalline structure that is different from that of zirconium. Cracks can nucleate near these hydrides; hence, these hydrides are a direct link to fracture failure and overall large inelastic strain deformation modes. To fundamentally understand and predict these microstructural failure modes, we interrogated a finite-element database that was deterministically tailored and generated for large strain-dislocation-density crystalline plasticity and fracture modes. A database of 210 simulations was created to randomly sample from a group of microstructural fingerprints that encompass hydride volume fraction, hydride orientation, grain orientation, hydride length, and hydride spacing for a hydride that is physically representative of an aggregate of a hydride population. Machine learning approaches were then used to understand, identify, and characterize the dominant microstructural mechanisms and characteristics. We first used fat-tailed Cauchy distributions to determine the extreme events. A multilayer perceptron was used to learn the mechanistic characteristics of the material response to predefined strain levels and accurately determine the critical fracture stress response and the accumulated shear slips in critical regions. The predictions indicate that hydride volume fraction, a population-level parameter, had a significant effect on localized parameters, such as fracture stress distribution regions, and on the accumulated immobile dislocation densities both within the face centered cubic hydrides and the hexagonal cubic packed h.c.p. matrix.}, number={7}, journal={APL MATERIALS}, author={Hasan, T. and Capolungo, L. and Zikry, M. A.}, year={2023}, month={Jul} }
 @article{arcari_horton_chen_zikry_2023, title={Precipitate and dislocation-density interactions affecting strength and ductility in inconel alloys}, volume={8}, ISSN={["1573-4803"]}, url={https://doi.org/10.1007/s10853-023-08822-8}, DOI={10.1007/s10853-023-08822-8}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Arcari, Attilio and Horton, Derek and Chen, Muh-Jang and Zikry, Mohammed A.}, year={2023}, month={Aug} }
 @article{phillips_chen_islam_ryu_zikry_2023, title={Predicting and Controlling Ribbing Instabilities of Carbon Nanotube-PDMS Thin-Film Systems for Multifunctional Applications}, volume={7}, ISSN={["1527-2648"]}, url={https://doi.org/10.1002/adem.202300582}, DOI={10.1002/adem.202300582}, abstractNote={The manufacturing of thin films with structured surfaces by large‐scale rolling has distinct advantages over other techniques, such as lithography, due to scalability. However, it is not well understood or quantified how processing conditions can affect the microstructure at different physical scales. Hence, the objective of this investigation is to develop a validated computational model of the symmetric forward‐roll coating process to understand, predict, and control the morphology of carbon nanotube (CNT)–polydimethylsiloxane (PDMS) pastes. The effects of the thin‐film rheological properties and the roller gap on the ribbing behavior are investigated and a ribbing instability prediction model is formulated from experimental measurements and computational predictions. The CNT–PDMS thin‐film system is modeled by a nonlinear implicit dynamic finite‐element method that accounts for ribbing instabilities, large displacements, rolling contact, and material viscoelasticity. Dynamic mechanical analysis is used to obtain the viscoelastic properties of the CNT–PDMS paste for various CNT weight distributions. Furthermore, a Morris sensitivity analysis is conducted to obtain insights on the dominant predicted characteristics pertaining to the ribbing microstructure. Based on the sensitivity analysis, a critical ribbing aspect ratio is identified for the CNT–PDMS system corresponding to a critical roller gap.}, journal={ADVANCED ENGINEERING MATERIALS}, publisher={Wiley}, author={Phillips, Matthew and Chen, Muh-Jang and Islam, Md Didarul and Ryu, Jong and Zikry, Mohammed}, year={2023}, month={Jul} }
 @article{phillips_chen_islam_ryu_zikry_2023, title={Predicting and Controlling Ribbing Instabilities of Carbon Nanotube–PDMS Thin‐Film Systems for Multifunctional Applications}, url={https://doi.org/10.1002/adem.202370077}, DOI={10.1002/adem.202370077}, abstractNote={In this cover image, Mohammed Zikry and co-workers, article number 2300582, present a manufacturing method for structured carbon nanotube (CNT)-PDMS thin-films for such multifunctional applications, such as superhydrophobicity and drag reduction. Finite-element models were used to design the periodic microstructure and understand how ribbing instabilities are generated for CNT-PDMS thin-films.}, journal={Advanced Engineering Materials}, author={Phillips, Matthew and Chen, Muh-Jang and Islam, Md Didarul and Ryu, Jong and Zikry, Mohammed}, year={2023}, month={Nov} }
 @article{hasan_capolungo_zikry_2023, title={Predictive machine learning approaches for the microstructural behavior of multiphase zirconium alloys}, volume={13}, ISSN={["2045-2322"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85151742870&partnerID=MN8TOARS}, DOI={10.1038/s41598-023-32582-9}, abstractNote={Abstract}, number={1}, journal={SCIENTIFIC REPORTS}, author={Hasan, Tamir and Capolungo, Laurent and Zikry, Mohammed A. A.}, year={2023}, month={Apr} }
 @article{zikry_2023, title={The Fiftieth Anniversary of the Founding of the ASME Journal of Engineering Materials and Technology}, volume={145}, ISSN={["1528-8889"]}, DOI={10.1115/1.4062506}, abstractNote={As the Editor-in-Chief for the ASME Journal of Engineering Materials and Technology and on behalf of the global research communities, we are honored to celebrate the 50th Anniversary of the ASME Journal of Engineering Materials and Technology. The journal has been in existence since 1973, and it is associated with the Materials Division of ASME. The founding of the Journal coincided with the transition of the Metals Division to the Materials Division. The Journal is one of the oldest scientific and engineering journals that is focused on material science and mechanics of materials. We are indebted to the selfless service of all the previous editors, associate editors, and ASME staff, and especially, to the first Editor, Professor Ian Le May of the University of Saskatchewan.The Journal has been providing ground-breaking research on engineering materials and technology, for a broad spectrum of issues pertaining to experimental, computational, and analytical investigations of the behavior of materials with a mechanics of materials focus, at physical scales ranging from the nano to the macro for materials, such as metals, alloys, polymers, ceramics, composites, biomaterials, and nanostructured materials. The unique aspect of the journal is that it bridges the materials science and mechanics of materials communities, and that is what renders it an innovative platform for research to significantly improve existing materials and design new materials and systems.The distinguished history of scientific discovery and curiosity of the Journal is reflected by the top three cited articles. These articles are by A. Gurson in 1977, Continuum theory of ductile rupture by void nucleation and growth: Part I—Yield criteria and flow rules for porous ductile media, Jean Lemaitre in 1985, A continuous damage mechanics model for ductile fracture, and U.F. Kocks in 1976, Laws for work-hardening and low-temperature creep. These papers related to ductile fracture, damage mechanics, and creep defined and blazed new approaches and understanding of material behavior.The journal’s overarching aim is to continue to publish research of lasting significance in areas related to engineering materials, mechanics of materials, and materials technology. The scope is broad since it encompasses interdisciplinary research that spans fundamental knowledge, which is related to mechanics of materials, materials science, mathematics, and applied physics, and technological applications, which are related to engineering innovations and applications.Over the last ten years, since the start of my Editorship, the Impact Factor has increased by 179%. The Journal will, therefore, continue to further emphasize the multidisciplinary efforts needed to advance the field in areas related to materials development, experimental and computational analysis, and scientific and engineering innovation. Our aim, as an editorial board, in conjunction with the ASME publishing team, is to establish the journal as the leading international forum for original scientific research with balanced contributions that combine theoretical, experimental, and computational investigations. We, as a research community, collectively look forward to that challenge.}, number={3}, journal={JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME}, author={Zikry, Mohammed A.}, year={2023}, month={Jul} }
 @article{elbadry_wetherington_zikry_2022, title={Coupled electromagnetic and mechanical modeling and detection of buried objects}, volume={10}, url={https://doi.org/10.1016/j.apples.2022.100106}, DOI={10.1016/j.apples.2022.100106}, abstractNote={A time domain finite element (FE) framework was used to investigate the coupled electromagnetic (EM) and mechanical behavior of buried target systems. The coupling of the EM and mechanical fields is through using the Lorentz Force as the body force in the mechanical Cauchy equation of motion. The coupling is sequential where the EM fields and Lorentz force are first solved for, then they are used as inputs for the Cauchy equations of motion. Predictions were obtained for different loading conditions and the Method of Morris sensitivity analysis was used to understand how different mechanical and EM variables affect the buried target system. These predictions indicate that target permeability and depth had the most significant and dominant effects on the behavior of the buried target system.}, journal={Applications in Engineering Science}, author={Elbadry, Mohamed and Wetherington, J. and Zikry, M.A.}, year={2022}, month={Jun} }
 @article{elbadry_wetherington_zikry_2022, title={Electromagnetic Finite-Element Modeling of Induction Effects for Buried Objects in Magnetic Soils}, volume={60}, ISSN={["1558-0644"]}, url={https://doi.org/10.1109/TGRS.2021.3124839}, DOI={10.1109/TGRS.2021.3124839}, abstractNote={A frequency-based finite element (FE) framework has been developed to predict and understand the response of an electromagnetic induction (EMI) sensor due to buried targets. The EMI sensor is used to detect buried targets in magnetic nonconducting soils. The framework was verified with an analytical model that utilizes dipole approximations. The framework was then used to predict the electromagnetic (EM) response due to interrelated stimuli and properties. The results indicate that the sensor was not sensitive to small variations (0–200 mm) in the standoff height and lateral positions, and only showed a significant change in the response due to stand-off variations that were greater than 200 mm. This low sensitivity to minor variations in standoff height and lateral position signify that there are critical distances related to the EM response of buried objects. The response to different target conductivities and permeabilities was also investigated for steel and aluminum targets. The lower conductivity steel targets had EM responses, where the inductive limit was reached at higher frequencies than the higher conductivity aluminum targets. Variations in target permeabilities for steel showed that as permeabilities increased, the frequencies at which the inductive limit was reached also increased. This verified predictive approach can provide a methodology to characterize the EM response of buried objects for a broad class of buried object EM properties, geometries, and input stimuli.}, journal={IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Elbadry, Mohamed H. and Wetherington, Josh and Zikry, Mohammed A.}, year={2022} }
 @article{field_garmestani_khraishi_zikry_2022, title={Journal of Engineering Materials and Technology}, volume={144}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85127599106&partnerID=MN8TOARS}, number={1}, journal={Journal of Engineering Materials and Technology, Transactions of the ASME}, author={Field, D. and Garmestani, H. and Khraishi, T. and Zikry, M.}, year={2022} }
 @article{field_garmestani_khraishi_zikry_2022, title={Special Issue: The Behavior of Crystalline Materials: In Honor of Professor Hussein Zbib}, volume={144}, ISSN={["1528-8889"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85144510088&partnerID=MN8TOARS}, DOI={10.1115/1.4052487}, abstractNote={This special issue of the ASME Journal of the Engineering Materials and Technology is dedicated to the memory of our friend and colleague, Professor Hussein Zbib, who passed away in February 2020. Hussein was a past editor of this journal and was an internationally recognized research leader and an innovator in numerous aspects of mechanics of materials, such as dislocation dynamics, plasticity, and irradiated materials. The articles in this special issue, through the different contributions of his collaborators, colleagues, students, and friends, truly reflect the different research areas he impacted. Furthermore, these contributions underscore how his research interests, collaborations, and achievements fundamentally influenced the experimental and modeling accomplishments of the contributing authors.Hussein was a Professor in the School of Mechanical and Materials Engineering at Washington State University since 1988. As a director of the Computational Mechanics and Materials Science Laboratory, he conducted research in the field of multiscale theoretical modeling and predictions of the thermo-mechanical behavior of advanced materials. He developed models and theories used by materials scientists and engineers throughout the world, and his research significantly improved and elevated the fundamental understanding of the behavior of metals, alloys, and composites at different physical scales.His research group, for instance, developed models to simulate the behavior of a wide array of materials that are exposed to high doses of radiation. It was well known that such materials can deform and fail, but the mechanics and defect behavior were not well understood until Hussein and his coworkers developed a new class of computational tools based on innovative formulations related to dislocation dynamics. This was a crucial breakthrough, since dislocation dynamics is essentially now recognized as an established link between atomistic and continuum approaches.Hussein published more than 250 technical articles in leading journals, edited 12 books, and presented hundreds of invited talks and seminars. Over his career, he supervised and mentored more than 30 masters and doctoral students, six postdoctoral fellows, 11 visiting scholars, and 15 undergraduate research assistants. Many of his students went on to become internationally recognized researchers and leaders in academia, in industry, and at national laboratories.Hussein was a fellow of the American Association for the Advancement of Science and the ASME as well as an executive member of the Lebanese Academy of Science. He was a recipient of the 2010 Khan International Award for outstanding contribution to the field of plasticity. He also received research excellence awards from the Voiland College of Engineering and Architecture in 1994 and 2015 and from the School of Mechanical and Materials Engineering in 2000 at Washington State University. He was named a Regents Professor, the university's highest faculty title, in 2018. He also served as the director of the School of MME from 2003 to 2011. During his tenure as a school director, he played a significant role in expanding the faculty size, research expenditures, and private donations, and fostering partnerships with industries and national laboratories, such that the School is now recognized as a leading national mechanical engineering and materials science department.Hussein was born in Beirut, Lebanon, to Mustapha and Sahjouna Zbib, and his parents were from South Lebanon. He completed his schooling in Beirut, graduating from Aamlye Technical College. Zbib received his bachelor, masters, and Ph.D. in Mechanical Engineering and Engineering Mechanics from Michigan Technological University. He married Marcia Ann Rowe in Hancock, MI, on July 12, 1986, and in 1988, they moved to Pullman when Zbib accepted a position at WSU.Hussein enjoyed being with family and friends. He enjoyed cooking and dancing, and he and his wife Marcia were active in both the Palouse dance club and gourmet club. Zbib also enjoyed golfing, fishing, boating, reading, cross country skiing, table tennis, tennis, going to fine dining restaurants, and spending time at the gym exercising and swimming. Together he and his wife Marcia enjoyed traveling throughout the world.Hussein is survived by his wife Marcia, mother Sahjouna Zbib, two brothers Ali and Bilal Zbib, three sisters Fadia, Hana, and Iman Zbib, and many nieces and nephews. He was preceded in death by his father Mustapha Zbib, brother Hassan Zbib; and two sisters Ferial and Sanaa Zbib.Hussein was the model for a research innovator and an academic leader. All of us are missing Hussein; we will never forget him, his wisdom, his easy smile, and the twinkle in his eye. His spirit will always be with us as a guiding light in our lives.}, number={1}, journal={JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME}, author={Field, David and Garmestani, Hamid and Khraishi, Tariq and Zikry, Mohammed}, year={2022}, month={Jan} }
 @article{didarul islam_perera_chockalingam_phillips_chen_liu_khan_zhu_zikry_eun ryu_2022, title={Template-free scalable fabrication of linearly periodic microstructures by controlling ribbing defects phenomenon during forward roll coating}, volume={33}, ISSN={2213-8463}, url={http://dx.doi.org/10.1016/j.mfglet.2022.08.001}, DOI={10.1016/j.mfglet.2022.08.001}, abstractNote={Linear periodic microstructures are of significant importance in various applications, including drag-reduction, biofouling, self-cleaning, and superhydrophobicity. However, practical applications of such surfaces require mass manufacturing techniques, which are highly limited. This study demonstrated a simple template-free scalable manufacturing technique to fabricate linearly periodic microstructure by controlling the ribbing defects in forward roll coating. A viscoelastic polymer nanocomposite with tailored properties was synthesized and utilized as the coating material. The ribbing instabilities were controlled with process parameters that resulted in variable periodicity of the linearly aligned microstructures with a spacing of 114 – 700 µm. The microstructure arrangement also had a linear to random transition as the instabilities increased. The manufactured surface has a high Wenzel roughness factor that ranges from 1.6 to 3.6, which results in water contact angles of 128o to 150o. The linear microstructure films can have critical applications in the mass manufacturing of drag reduction surfaces. The high aspect-ratio microstructure films can also have applications in superhydrophobic, self-cleaning, anti-icing, and anti-biofouling surfaces.}, journal={Manufacturing Letters}, publisher={Elsevier BV}, author={Didarul Islam, Md and Perera, Himendra and Chockalingam, Sekkappan and Phillips, Matthew and Chen, Muh-Jang and Liu, Yuxuan and Khan, Saad and Zhu, Yong and Zikry, Mohammed and Eun Ryu, Jong}, year={2022}, month={Sep}, pages={153–160} }
 @article{islam_perera_black_phillips_chen_hodges_jackman_liu_kim_zikry_et al._2022, title={Template‐Free Scalable Fabrication of Linearly Periodic Microstructures by Controlling Ribbing Defects Phenomenon in Forward Roll Coating for Multifunctional Applications}, volume={9}, ISSN={2196-7350 2196-7350}, url={http://dx.doi.org/10.1002/admi.202201237}, DOI={10.1002/admi.202201237}, abstractNote={Abstract}, number={27}, journal={Advanced Materials Interfaces}, publisher={Wiley}, author={Islam, Md Didarul and Perera, Himendra and Black, Benjamin and Phillips, Matthew and Chen, Muh‐Jang and Hodges, Greyson and Jackman, Allyce and Liu, Yuxuan and Kim, Chang‐Jin and Zikry, Mohammed and et al.}, year={2022}, month={Aug}, pages={2201237} }
 @article{granger_chen_brenner_zikry_2022, title={The Challenges of Modeling Defect Behavior and Plasticity across Spatial and Temporal Scales: A Case Study of Metal Bilayer Impact}, volume={12}, ISSN={["2075-4701"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85144831580&partnerID=MN8TOARS}, DOI={10.3390/met12122036}, abstractNote={Atomistic molecular dynamics (MD) and a microstructural dislocation density-based crystalline plasticity (DCP) framework were used together across time scales varying from picoseconds to nanoseconds and length scales spanning from angstroms to micrometers to model a buried copper–nickel interface subjected to high strain rates. The nucleation and evolution of defects, such as dislocations and stacking faults, as well as large inelastic strain accumulations and wave-induced stress reflections were physically represented in both approaches. Both methods showed similar qualitative behavior, such as defects originating along the impactor edges, a dominance of Shockley partial dislocations, and non-continuous dislocation distributions across the buried interface. The favorable comparison between methods justifies assumptions used in both, to model phenomena, such as the nucleation and interactions of single defects and partials with reflected tensile waves, based on MD predictions, which are consistent with the evolution of perfect and partial dislocation densities as predicted by DCP. This substantiates how the nanoscale as modeled by MD is representative of microstructural behavior as modeled by DCP.}, number={12}, journal={METALS}, author={Granger, Leah and Chen, Muh-Jang and Brenner, Donald and Zikry, Mohammed}, year={2022}, month={Dec} }
 @article{mohamed_hasan_zikry_2022, title={Thermomechanical Microstructural Predictions of Fracture Nucleation of Zircaloy-4 Alloys With delta and e Hydride Distributions}, volume={144}, ISSN={["1528-8889"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85127542533&partnerID=MN8TOARS}, DOI={10.1115/1.4051687}, abstractNote={Abstract}, number={1}, journal={JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME}, author={Mohamed, I. and Hasan, T. and Zikry, M. A.}, year={2022}, month={Jan} }
 @article{mohamed_zikry_2021, title={Correction to: Modeling of the microstructural behavior of hydrided zirconium alloys (Computational Mechanics, (2021), 68, 3, (567-578), 10.1007/s00466-020-01970-7)}, volume={68}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85108062245&partnerID=MN8TOARS}, DOI={10.1007/s00466-021-02043-z}, abstractNote={A correction to this paper has been published: https://doi.org10.1007/s00466-020-01970-7}, number={3}, journal={Computational Mechanics}, author={Mohamed, I. and Zikry, M.A.}, year={2021}, pages={579} }
 @article{mohamed_zikry_2021, title={Modeling of the microstructural behavior of hydrided zirconium alloys}, volume={68}, ISSN={["1432-0924"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85099274775&partnerID=MN8TOARS}, DOI={10.1007/s00466-020-01970-7}, number={3}, journal={COMPUTATIONAL MECHANICS}, author={Mohamed, I. and Zikry, M.A.}, year={2021}, month={Sep}, pages={567–578} }
 @article{bond_zikry_2020, title={Effects of electron beam manufacturing induced defects on fracture in Inconel 718}, volume={32}, ISSN={["2214-7810"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85077944337&partnerID=MN8TOARS}, DOI={10.1016/j.addma.2020.101059}, abstractNote={The effects of electron beam manufactured (EBM) process-induced defects on local microstructural failure initiation and propagation in IN 718 have been investigated. Predictions for transgranular fracture, based on local cleavage plane stresses, and for intergranular fracture, based on dislocation-grain boundary (GB) interactions and evolving dislocation pileups, were combined with a crystalline dislocation-density plasticity approach to understand the influence of AM process-induced defects, such as porosity, NbC precipitates, and regions of dry powder. High local stresses along the peripheries of pores caused crack nucleation, and mismatches in deformation behavior between NbC precipitates and the surrounding matrix led to local stress gradients that induced crack nucleation and decohesion at precipitate/matrix interfaces. Regions of unmelted powder had significant stress accumulations that initiated failure at low nominal strains. Failure due to high localized stresses near regions of unmelted powder was dominant over precipitate/matrix decohesion and crack nucleation near pore peripheries. Based on the predictions, the mechanical behavior of AM alloys is governed by local dislocation-density evolution near process-induced defects, which preferentially nucleate material failure. Furthermore, interactions between these different defect types can significantly accelerate failure initiation and propagation.}, journal={ADDITIVE MANUFACTURING}, author={Bond, D. M. and Zikry, M. A.}, year={2020}, month={Mar} }
 @article{ziaei_wu_fitch_elbadry_zikry_2019, title={Channel Cracking and Interfacial Delamination of Indium Tin Oxide (ITO) Nano-Sized Films on Polyethylene Terephthalate (PET) Substrates: Experiments and Modeling}, volume={59}, ISSN={["1741-2765"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85070228541&partnerID=MN8TOARS}, DOI={10.1007/s11340-019-00534-y}, abstractNote={Our research objective was to obtain a fundamental understanding of how ITO thin films layered on flexible polyethylene terephthalate (PET) substrates fail due to tensile, shear, and bending loading conditions. In our approach, we employed a nonlinear finite-element (FE) approach coupled with dislocation-density crystalline and hypoelastic material models and fracture approaches tailored for channel (film) cracking and interfacial delamination. These predictions were validated with mechanical experiments and characterization at different physical scales. Failure to strain and fracture predictions were used to account for interrelated mechanisms, such as channel and interfacial cracking nucleation and propagation along cleavage planes, interfaces, and within layers. Our predictions indicate that interfacial delamination occurred when channel cracks transitioned to interfacial cracks at the ITO/PET interface for tensile loading conditions. Furthermore, the thin film system, when subjected to three-point bending and shear loading conditions was more resistant to failure in comparison to systems subjected to tensile loading conditions.}, number={5}, journal={EXPERIMENTAL MECHANICS}, publisher={Springer Science and Business Media LLC}, author={Ziaei, S. and Wu, Q. and Fitch, J. and Elbadry, M. and Zikry, M. A.}, year={2019}, month={Jun}, pages={703–712} }
 @article{ziaei_zikry_2019, title={How semi-coherent b.c.c. hydride interfacial interactions affect the inelastic deformation and fracture behavior of h.c.p. zirconium alloys}, volume={130}, ISSN={["1872-7743"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85059460310&partnerID=MN8TOARS}, DOI={10.1016/j.mechmat.2018.12.015}, abstractNote={We analyzed how b.c.c. semi-coherent interfaces, within an h.c.p. matrix, have a central effect on the fracture of these multi-phase aggregates. We obtained 36 unique Orientation Relations (ORs) related to semi-coherent interfaces between the hydrides and the parent matrix, and calculated interfacial misfit strains between the matrix and hydride crystalline structures. We then coupled these microstructural interactions to a dislocation-density framework with a fracture nucleation and propagation approach to understand and predict different failure scenarios. The analysis indicates that misfit strains have a dominant mechanistic effect that is essential for an understanding of multi-phase crystalline aggregate behavior that spans different length scales.}, journal={MECHANICS OF MATERIALS}, author={Ziaei, S. and Zikry, M. A.}, year={2019}, month={Mar}, pages={1–8} }
 @misc{motta_capolungo_chen_cinbiz_daymond_koss_lacroix_pastore_simon_tonks_et al._2019, title={Hydrogen in zirconium alloys: A review}, volume={518}, ISSN={["1873-4820"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85062652956&partnerID=MN8TOARS}, DOI={10.1016/j.jnucmat.2019.02.042}, abstractNote={Hydrogen absorbed into zirconium alloy nuclear fuel cladding as a result of the waterside corrosion reaction can affect the properties of nuclear fuel, principally through the precipitation of brittle hydride particles. Multiple phenomena are involved in this overall process: after hydrogen pickup degradation of mechanical properties is controlled by hydrogen transport, hydride precipitation and dissolution kinetics and the formation of specific mesoscale hydride microstructures. The precipitation of hydrides especially affects cladding ductility and fracture toughness, but can also affect other phenomena, including via stress-induced hydride reorientation. These processes can affect cladding performance both during normal operation and during extended dry storage, as hydride morphology can be modified during the preparatory vacuum drying processes. We review the processes of hydrogen transport, hydride precipitation and dissolution and formation of mesoscale hydride microstructures, and highlight where more research is needed, both from an experimental and from a modeling point of view.}, journal={JOURNAL OF NUCLEAR MATERIALS}, author={Motta, Arthur T. and Capolungo, Laurent and Chen, Long-Qing and Cinbiz, Mahmut Nedim and Daymond, Mark R. and Koss, Donald A. and Lacroix, Evrard and Pastore, Giovanni and Simon, Pierre-Clement A. and Tonks, Michael R. and et al.}, year={2019}, month={May}, pages={440–460} }
 @article{hasan_ziaei_zikry_2019, title={Microstructural Modeling of the Mechanical Behavior of Face-Centered Cubic Nanocrystalline-Twinned Systems}, volume={50A}, ISSN={["1543-1940"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85056852998&partnerID=MN8TOARS}, DOI={10.1007/s11661-018-5008-2}, number={2}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Hasan, Tamir S. and Ziaei, S. and Zikry, M. A.}, year={2019}, month={Feb}, pages={609–615} }
 @article{mailen_wagner_bang_zikry_dickey_genzer_2019, title={Thermo-mechanical transformation of shape memory polymers from initially flat discs to bowls and saddles}, volume={28}, ISSN={["1361-665X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85065648786&partnerID=MN8TOARS}, DOI={10.1088/1361-665X/ab030a}, abstractNote={This paper describes the transformation of shape memory polymer (SMP) discs, from flat sheets to complex three-dimensional (3D) shapes, in response to heat generated by localized absorption of external infrared (IR) light. The gray-scale ink darkness printed on the surface of the SMP sheet determines the amount of absorbed light and the amount of heat generated on the surface of the sheet. Consequently, the lateral pattern of the ink governs the out-of-plane deformation of the SMP sheets due to variations in localized heating and shrinking. While recent studies have focused primarily on out-of-plane deformations of planar, rectangular substrates printed with linear patterns of ink and featuring either discrete or gradient ink variation, only limited studies have been performed on circular substrates with axisymmetric ink patterns. When heated by IR light, the axial symmetry of these ink designs produces unique out-of-plane deformations of the sheets, such as saddle shapes or bowl-like structures. We investigate these designs by utilizing a finite element analysis of material shrinkage and deformation, and we validate the model with experimental measurements and observations. This investigation provides insights into the mechanisms that cause axisymmetric geometries and ink patterns to form non-axisymmetric 3D structures, which can lead to the ability to program planar geometries that form complex 3D shapes when exposed to external stimuli.}, number={4}, journal={SMART MATERIALS AND STRUCTURES}, author={Mailen, Russell W. and Wagner, Catherine H. and Bang, Rachel S. and Zikry, Mohammed and Dickey, Michael D. and Genzer, Jan}, year={2019}, month={Apr} }
 @article{bond_zikry_2018, title={Differentiating between intergranular and transgranular fracture in polycrystalline aggregates}, volume={53}, ISSN={["1573-4803"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85035783334&partnerID=MN8TOARS}, DOI={10.1007/s10853-017-1847-2}, number={8}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Bond, D. M. and Zikry, M. A.}, year={2018}, month={Apr}, pages={5786–5798} }
 @article{chen_zirky_steer_2018, title={Microwave Excitation of Crystalline Energetic Composites}, volume={6}, ISSN={["2169-3536"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85044751997&partnerID=MN8TOARS}, DOI={10.1109/ACCESS.2018.2810265}, abstractNote={Hotspots produced by microwaves radiating into an energetic composite of RDX crystals and an estane binder are examined using transient electromagnetic (EM) and coupled EM-thermal analyses. Hotspots, localized regions where energetic activity is likely to initiate, manifest as regions of peak electric field or high temperature. Stress caused by these high fields and temperatures may result in molecular breakdown, creating a chain reaction leading to the release of chemical energy via deflagration (burning and melting) in the absence of a mechanical shock wave. High peak electric fields up to three times higher than the incident field result from subwavelength scattering and occur near crystalline surfaces while peak temperatures occur in the binder, with both generally coinciding at the binder-RDX interface. Abstractions enable materials to be modeled with crystals having an average characteristic dimension of 100  $\mu \text{m}$ . With an incident field of 1 MV/m the peak electric field in the composite was 2.9 MV/m and peak temperature increased by 75 K in the binder and 65 K in the RDX after 3.7 ms. The RDX fill factor of the composite was 37%, typical of an improvised explosive.}, journal={IEEE ACCESS}, author={Chen, Michael and Zirky, Mohammed A. and Steer, Michael B.}, year={2018} }
 @article{bond_zikry_2017, title={A Predictive Framework for Dislocation-Density Pile-Ups in Crystalline Systems With Coincident Site Lattice and Random Grain Boundaries}, volume={139}, ISSN={["1528-8889"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85012899751&partnerID=MN8TOARS}, DOI={10.1115/1.4035494}, abstractNote={Evolving dislocation-density pile-ups at grain-boundaries (GBs) spanning a wide range of coincident site lattice (CSL) and random GB misorientations in face-centered cubic (fcc) bicrystals and polycrystalline aggregates has been investigated. A dislocation-density GB interaction scheme coupled to a dislocation-density-based crystalline plasticity formulation was used in a nonlinear finite element (FE) framework to understand how different GB orientations and GB-dislocation-density interactions affect local and overall behavior. An effective Burger's vector of residual dislocations was obtained for fcc bicrystals and compared with molecular dynamics (MDs) predictions of static GB energy, as well as dislocation-density transmission at GB interfaces. Dislocation-density pile-ups and accumulations of residual dislocations at GBs and triple junctions (TJs) were analyzed for a polycrystalline copper aggregate with Σ1, Σ3, Σ7, Σ13, and Σ21 CSLs and random high-angle GBs to understand and predict the effects of GB misorientation on pile-up formation and evolution. The predictions indicate that dislocation-density pile-ups occur at GBs with significantly misoriented slip systems and large residual Burger's vectors, such as Σ7, Σ13, and Σ21 CSLs and random high-angle GBs, and this resulted in heterogeneous inelastic deformations across the GB and local stress accumulations. GBs with low misorientations of slip systems had high transmission, no dislocation-density pile-ups, and lower stresses than the high-angle GBs. This investigation provides a fundamental understanding of how different representative GB orientations affect GB behavior, slip transmission, and dislocation-density pile-ups at a relevant microstructural scale.}, number={2}, journal={JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME}, author={Bond, David M. and Zikry, Mohammed A.}, year={2017}, month={Apr} }
 @article{mailen_dickey_genzer_zikry_2017, title={A fully coupled thermo-viscoelastic finite element model for self-folding shape memory polymer sheets}, volume={55}, ISSN={["1099-0488"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85019544264&partnerID=MN8TOARS}, DOI={10.1002/polb.24372}, abstractNote={ABSTRACT}, number={16}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, publisher={Wiley}, author={Mailen, Russell W. and Dickey, Michael D. and Genzer, Jan and Zikry, Mohammed A.}, year={2017}, month={Aug}, pages={1207–1219} }
 @article{hubbard_mailen_zikry_dickey_genzer_2017, title={Controllable curvature from planar polymer sheets in response to light}, volume={13}, ISSN={1744-683X 1744-6848}, url={http://dx.doi.org/10.1039/C7SM00088J}, DOI={10.1039/C7SM00088J}, abstractNote={The ability to change shape and control curvature in 3D structures starting from planar sheets can aid in assembly and add functionality to an object. Herein, we convert planar sheets of shape memory polymers (SMPs) into 3D objects with controllable curvature by dictating where the sheets shrink. Ink patterned on the surface of the sheet absorbs infrared (IR) light, resulting in localized heating, and the material shrinks locally wherever the temperature exceeds the activation temperature, Ta. We introduce two different mechanisms for controlling curvature within SMP sheets. The 'direct' mechanism uses localized shrinkage to induce curvature only in regions patterned with ink. The 'indirect' mechanism uses localized shrinkage in regions patterned with ink to induce curvature in neighboring regions without ink through a balance of internal stresses. Finite element analysis predicts the final shape of the polymer sheets with excellent qualitative agreement with experimental studies. Results from this study show that curvature can be controlled by the distribution and darkness of the ink pattern on the polymer sheet. Additionally, we utilize the direct and indirect curvature mechanisms to demonstrate the formation and actuation of gripper devices, which represent the potential utility of this approach.}, number={12}, journal={Soft Matter}, publisher={Royal Society of Chemistry (RSC)}, author={Hubbard, Amber M. and Mailen, Russell W. and Zikry, Mohammed A. and Dickey, Michael D. and Genzer, Jan}, year={2017}, pages={2299–2308} }
 @article{mailen_dickey_genzer_zikry_2017, title={Effects of thermo-mechanical behavior and hinge geometry on folding response of shape memory polymer sheets}, volume={122}, ISSN={["1089-7550"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85034607215&partnerID=MN8TOARS}, DOI={10.1063/1.5000040}, abstractNote={Shape memory polymer (SMP) sheets patterned with black ink hinges change shape in response to external stimuli, such as absorbed thermal energy from an infrared (IR) light. The geometry of these hinges, including size, orientation, and location, and the applied thermal loads significantly influence the final folded shape of the sheet, but these variables have not been fully investigated. We perform a systematic study on SMP sheets to fundamentally understand the effects of single and double hinge geometries, hinge orientation and spacing, initial temperature, heat flux intensity, and pattern width on the folding behavior. We have developed thermo-viscoelastic finite element models to characterize and quantify the stresses, strains, and temperatures as they relate to SMP shape changes. Our predictions indicate that hinge orientation can be used to reduce the total bending angle, which is the angle traversed by the folding face of the sheet. Two parallel hinges increase the total bending angle, and heat conduction between the hinges affects the transient folding response. IR intensity and initial temperatures can also influence the transient folding behavior. These results can provide guidelines to optimize the transient folding response and the three-dimensional folded structure obtained from self-folding polymer origami sheets that can be applied for myriad applications.}, number={19}, journal={JOURNAL OF APPLIED PHYSICS}, publisher={AIP Publishing}, author={Mailen, Russell W. and Dickey, Michael D. and Genzer, Jan and Zikry, Mohammed}, year={2017}, month={Nov} }
 @article{bond_zikry_2017, title={Microstructural Modeling of Intergranular Fracture in Tricrystals With Random Low- and High-Angle Grain Boundaries}, volume={69}, ISSN={["1543-1851"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85014528940&partnerID=MN8TOARS}, DOI={10.1007/s11837-017-2291-0}, number={5}, journal={JOM}, author={Bond, David M. and Zikry, Mohammed A.}, year={2017}, month={May}, pages={856–862} }
 @article{zhao_zikry_2017, title={Oxidation-induced failure in semi-crystalline organic thin films}, volume={109}, ISSN={["1879-2146"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85009488974&partnerID=MN8TOARS}, DOI={10.1016/j.ijsolstr.2017.01.008}, abstractNote={Polymer oxidation is a major degradation mechanism in organic solar cells. However, microstructural details of diffusion-reaction processes and oxidation-induced failure in structured semi-crystalline active layers are difficult to be predicted or measured, due to material heterogeneities, such as different material phases, crystallinities, nano-film thickness. Hence, a diffusion-reaction process has been coupled to a crystalline-amorphous material model and fracture algorithm within a nonlinear microstructurally-based finite element (FEM) framework to investigate and predict heterogeneous oxidative degradation and embrittlement failure in semi-crystalline organic thin films due to the interrelated effects of diffusion, reaction, stress accumulations, and crystalline packing order. The edge-on packing oriented film was more susceptible to oxidation than the face-on oriented packing film due to higher local stresses and reaction accumulations that resulted in higher decrease of local toughness and extensive film cracking in the amorphous phase. The coupled effects of mechanical stresses and oxygen diffusion-reaction accelerated degradation mechanisms and resulted in film cracking and delamination occurring at lower nominal strains in comparison with the case without oxidation embrittlement. Degradation was dominated by the reaction process and exposure time, as opposed to the diffusion process due to the nano-sized films. This predictive framework can be used to understand fundamental local oxidative degradation mechanisms and the morphological effects on long term durability of semi-crystalline organic thin films.}, journal={INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES}, author={Zhao, Bingxiao and Zikry, M. A.}, year={2017}, month={Mar}, pages={72–83} }
 @inproceedings{chen_steer_zikry_2017, title={Significance of randomness in establishing hotspots in crystals}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85019680119&partnerID=MN8TOARS}, DOI={10.1109/secon.2017.7925394}, abstractNote={Microwave scattering in random mediums is known to result in localized energy concentrations known as hotspots. However, the mechanics behind this effect are not well understood. Abstractions are needed to manage the complexity required to develop understanding through simulation and lead to the establishment of the parameters for a microwave system to neutralize energetic materials. Here, two random contributions of rotation and translation are separately simulated. It is observed that the individual effects both contribute to localization, and the combined effect is greater than the sum of the individuals.}, booktitle={Southeastcon 2017}, author={Chen, M. and Steer, M. B. and Zikry, Mohammed}, year={2017} }
 @article{zhao_awartani_o'connor_zikry_2016, title={A direct correlation of x-ray diffraction orientation distributions to the in-plane stiffness of semi-crystalline organic semiconducting films}, volume={108}, ISSN={["1077-3118"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84968866659&partnerID=MN8TOARS}, DOI={10.1063/1.4948533}, abstractNote={Large charge mobilities of semi-crystalline organic semiconducting films could be obtained by mechanically aligning the material phases of the film with the loading axis. A key element is to utilize the inherent stiffness of the material for optimal or desired alignment. However, experimentally determining the moduli of semi-crystalline organic thin films for different loading directions is difficult, if not impossible, due to film thickness and material anisotropy. In this paper, we address these challenges by presenting an approach based on combining a composite mechanics stiffness orientation formulation with a Gaussian statistical distribution to directly estimate the in-plane stiffness (transverse isotropy) of aligned semi-crystalline polymer films based on crystalline orientation distributions obtained by X-ray diffraction experimentally at different applied strains. Our predicted results indicate that the in-plane stiffness of an annealing film was initially isotropic, and then it evolved to transverse isotropy with increasing mechanical strains. This study underscores the significance of accounting for the crystalline orientation distributions of the film to obtain an accurate understanding and prediction of the elastic anisotropy of semi-crystalline polymer films.}, number={18}, journal={APPLIED PHYSICS LETTERS}, author={Zhao, Bingxiao and Awartani, Omar and O'Connor, Brendan and Zikry, Mohammed A.}, year={2016}, month={May} }
 @article{awartani_zhao_currie_kline_zikry_brendan t. o'connor_2016, title={Anisotropic Elastic Modulus of Oriented Regioregular Poly(3-hexylthiophene) Films}, volume={49}, ISSN={["1520-5835"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84954288748&partnerID=MN8TOARS}, DOI={10.1021/acs.macromol.5b02680}, abstractNote={Specific morphological features of polymer semiconductors are often promoted in devices to optimize optoelectronic behavior. Less studied is the role of morphology on the mechanical properties of the film, such as elastic modulus, which is an important property for the development of flexible and stretchable devices. To gain insight into the morphological origin of elasticity in polymer semiconductors and its relationship to charge transport, we study the anisotropic in-plane elastic modulus of strain-aligned regioregular poly(3-hexylthiophene) (P3HT) films and compare the results to previously measured field effect charge mobility. The film morphology is varied through the amount of applied strain and post strain thermal annealing. Morphological characterization includes UV–vis optical spectroscopy and X-ray diffraction. The elastic modulus is measured using a buckling-based measurement technique. The elastic modulus of the film is found to decrease as the film is plastically strained. Thermally annealin...}, number={1}, journal={MACROMOLECULES}, author={Awartani, Omar M. and Zhao, Bingxiao and Currie, Tyler and Kline, R. Joseph and Zikry, Mohammed A. and Brendan T. O'Connor}, year={2016}, month={Jan}, pages={327–333} }
 @article{brown_zikry_2016, title={Coupled infrared laser-thermo-mechanical response of RDX-PCTFE energetic aggregates}, volume={57}, ISSN={["1432-0924"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84961114701&partnerID=MN8TOARS}, DOI={10.1007/s00466-015-1241-3}, number={4}, journal={COMPUTATIONAL MECHANICS}, author={Brown, Judith A. and Zikry, M. A.}, year={2016}, month={Apr}, pages={611–628} }
 @article{khanikar_wu_zikry_2016, title={Dynamic Fracture of Aluminum-Bonded Composites}, volume={138}, ISSN={["1528-8889"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84971467668&partnerID=MN8TOARS}, DOI={10.1115/1.4033036}, abstractNote={A dislocation density-based crystal plasticity framework, a nonlinear computational finite-element methodology adapted for nucleation of crack on cleavage planes, and rational crystallographic orientation relations were used to predict the failure modes associated with the high strain rate behavior of aluminum-bonded composites. A bonded aluminum composite, suitable for high strain-rate damage resistance application, was modeled with different microstructures representing precipitates, dispersed particles, and grain boundary (GB) distributions. The dynamic fracture approach is used to investigate crack nucleation and growth as a function of the different microstructural characteristics of each alloy in bonded composites with and without pre-existing cracks. The nonplanar and irregular nature of the crack paths were mainly due to the microstructural features, such as precipitates and dispersed particles distributions and orientations, ahead of the crack front. The evolution of dislocation density and the subsequent formation of localized plastic slip contributed to the blunting of the propagating crack(s). Extensive geometrical and thermal softening resulted in localized plastic slip and had a significant effect on crack path orientations and directions along cleavage planes.}, number={3}, journal={JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME}, author={Khanikar, Prasenjit and Wu, Qifeng and Zikry, M. A.}, year={2016}, month={Jul} }
 @article{fan_zhao_ren_zikry_2016, title={Effect of pulse current on the mechanical properties and fracture behaviors of Al-Mg alloys}, volume={46}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84982859304&partnerID=MN8TOARS}, DOI={10.1360/N092016-00098}, abstractNote={The influence of pulse electric current to aluminum’s flow stress and elongation under high electric energy density (0.150 J/mm3) and low energy density (0.105 J/mm3) are investigated. Since the temperatures generated by electric current are identical under same energy density with different electric conditions, non-Joule heating effect under electrically assisted forming can be proven. The results show that pulse current help to reduce aluminum’s flow stress and increase its elongation. Under the same energy density, as the density of pulse current increased, although the maximum flow stress remains unchanged, the instant stress drop due to pulse current increases as well as its elongation. Stress recovery model is proposed to estimate the stress drop under tension. The number of fracture dimple continues to decrease until completely disappearance as the density of pulse current increases; the increase of elongation results from the suppression of the nucleation and growth of voids by pulse current.}, number={7}, journal={Zhongguo Kexue Jishu Kexue/Scientia Sinica Technologica}, author={Fan, R. and Zhao, K. and Ren, D. and Zikry, M.A.}, year={2016}, pages={717–721} }
 @article{zhao_awartani_o'connor_zikry_2016, title={Microstructural Behavior and Failure Mechanisms of Organic Semicrystalline Thin Film Blends}, volume={54}, ISSN={["1099-0488"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84954289843&partnerID=MN8TOARS}, DOI={10.1002/polb.23991}, abstractNote={Organic thin film blends of P3HT semiconducting polymers and PCBM fullerenes have enabled large-scale semiconductor fabrication pertaining to flexible and stretchable electronics. However, molecular packing and film morphologies can significantly alter mechanical stability and failure behavior. To further understand and identify the fundamental mechanisms affecting failure, a multiphase microstructurally based formulation and nonlinear finite-element fracture methodology were used to investigate the heterogeneous deformation and failure modes of organic semicrystalline thin film blends. The multiphase formulation accounts for the crystalline and amorphous behavior, polymer tie-chains, and the PCBM aggregates. Face-on packing orientations resulted in extensive inelastic deformation and crystalline rotation, and this was characterized by ductile failure modes and interfacial delamination. For edge-on packing orientations, brittle failure modes and film cracking were due to lower inelastic deformation and higher film stress in comparison with the face-on orientations. The higher crystallinity of P3HT and larger PCBM aggregates associated with larger domain sizes, strengthened the film and resulted in extensive film cracking. These predictions of ductile and brittle failure are consistent with experimental observations for P3HT:PCBM films. The proposed predictive framework can be used to improve organic film ductility and strength through the control of molecular packing orientations and microstructural mechanisms. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 896–907}, number={9}, journal={JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS}, author={Zhao, Bingxiao and Awartani, Omar and O'Connor, Brendan and Zikry, Mohammed A.}, year={2016}, month={May}, pages={896–907} }
 @article{brown_bond_zikry_2016, title={Microstructural Modeling of Coupled Electromagnetic-Thermo-Mechanical Response of Energetic Aggregates to Infrared Laser Radiation and Dynamic Fracture}, volume={1}, ISSN={["2059-8521"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85041287988&partnerID=MN8TOARS}, DOI={10.1557/adv.2015.56}, abstractNote={A dislocation-density based crystalline plasticity, a finite viscoelasticity, and a nonlinear finite-element formulation were used to study the high strain-rate failure of energetic crystalline aggregates. The energetic crystals of RDX (cyclotrimethylene trinitramine) with a polymer binder were subjected to high strain-rate tensile loading, and the predictions indicate that high localized stresses and stress gradients develop due to mismatches along crystalline-crystalline and crystalline-amorphous interfaces. These high-stress interfaces are sites for crack nucleation and propagation, and the predictions are used to show how the cracks nucleate and propagate.}, number={17}, journal={MRS ADVANCES}, author={Brown, J. A. and Bond, D. M. and Zikry, M. A.}, year={2016}, pages={1197–1202} }
 @article{wu_zikry_2016, title={Microstructural modeling of transgranular and intergranular fracture in crystalline materials with coincident site lattice grain-boundaries: Sigma 3 and Sigma 17b bicrystals}, volume={661}, ISSN={["1873-4936"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84960079801&partnerID=MN8TOARS}, DOI={10.1016/j.msea.2016.02.039}, abstractNote={The competing microstructural failure mechanisms of transgranular (TG) and intergranular (IG) fracture, in martensitic steel bicrystals with coincident site lattice (CSL) boundaries of Σ3 and Σ17b, have been investigated, using a dislocation-density-based crystalline plasticity formulation and a recently developed overlapping fracture method. A dislocation-density grain boundary (GB) interaction scheme was coupled within a dislocation-density based crystal plasticity formulation to investigate how different types of CSL GBs affect dislocation-density evolution, plastic deformation, dislocation pile-up formation, TG and IG fracture, and fracture toughness. The computational predictions indicate that the bicrystal, with a Σ3 boundary, transitioned from IG to TG fracture, with large dislocation density generation and plastic deformation on the TG fracture planes. Bicrystals with the Σ17b boundary failed due to intergranular fracture and rupture, with much lower, in comparison with the Σ3 boundary case, dislocation density generation and plastic deformation. These predictions, which are consistent with experimental observations, indicate that Σ3 boundary is resistant to IG fracture with a higher fracture toughness than the Σ17b boundary case. More significantly, the computational framework can potentially be used as a guideline for GB engineering for failure-resistant materials.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Wu, Q. and Zikry, M. A.}, year={2016}, month={Apr}, pages={32–39} }
 @article{ziaei_zikry_2016, title={The effects of twins on the large strain deformation and fracture of hexagonal close packed crystalline materials}, volume={120}, ISSN={["1873-2453"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84986587922&partnerID=MN8TOARS}, DOI={10.1016/j.actamat.2016.08.059}, abstractNote={We investigated how twin modes in hexagonal close packed materials can affect large inelastic strain behavior and fracture. We considered the two twin mode systems of (112¯1)[1¯1¯26] and (0001) [1¯1¯20] in zircaloy-2, with each mode having 24 unique twin systems. We then incorporated these twin and parent slip systems with a dislocation-density crystalline plasticity, a non-linear finite-element, and fracture framework that accounts for crack nucleation and propagation. We investigated how these twin modes affect the interrelated effects of crack nucleation and propagation, dislocation density and inelastic slip evolution, stress accumulation, and lattice rotation. The predictions indicate that twin modes significantly affect local deformation and fracture behavior, and, therefore, are essential for the accurate representation of behavior at different physical scales in heterogeneous crystalline hexagonal close packed systems.}, journal={ACTA MATERIALIA}, author={Ziaei, S. and Zikry, M. A.}, year={2016}, month={Nov}, pages={435–442} }
 @article{brown_zikry_2015, title={Behaviour of crystalline-amorphous interfaces in energetic aggregates subjected to coupled thermomechanical and laser loading}, volume={471}, ISSN={["1471-2946"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84956865216&partnerID=MN8TOARS}, DOI={10.1098/rspa.2015.0548}, abstractNote={The behaviour of energetic aggregates was investigated for quasi-static compression and high strain rate thermomechanical compression behaviour that is coupled to laser irradiation. A dislocation-density-based crystal plasticity formulation was used to represent energetic crystalline behaviour, a finite viscoelastic formulation was used for the polymer binder and a coupled electromagnetic (EM)–thermomechanical computational scheme was used to predict aggregate response. Aggregates with different crystal sizes were considered to account for physically representative energetic microstructures and to understand the effects of crystal–crystal and crystal–binder interactions. The presence of smaller embedded crystals in the binder ligaments inhibited viscous sliding, and resulted in global hardening of the aggregate, which led to large stress gradients, localized plasticity and dislocation-density accumulation. The embedded crystals also increased scattering of the EM wave within the binder ligaments and increased the localization of EM energy and laser heat generation. Geometrically, necessary dislocation densities and stress gradients were calculated to characterize how hardening at the binder interfaces can lead to strengthening or defect nucleation.}, number={2184}, journal={PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES}, author={Brown, Judith A. and Zikry, M. A.}, year={2015}, month={Dec} }
 @article{labarbera_zikry_2015, title={Dynamic fracture and local failure mechanisms in heterogeneous RDX-Estane energetic aggregates}, volume={50}, ISSN={["1573-4803"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84930277182&partnerID=MN8TOARS}, DOI={10.1007/s10853-015-9102-1}, number={16}, journal={JOURNAL OF MATERIALS SCIENCE}, author={LaBarbera, D. A. and Zikry, M. A.}, year={2015}, month={Aug}, pages={5549–5561} }
 @article{wu_zikry_2015, title={Dynamic fracture predictions of microstructural mechanisms and characteristics in martensitic steels}, volume={145}, ISSN={["1873-7315"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84937031196&partnerID=MN8TOARS}, DOI={10.1016/j.engfracmech.2015.06.002}, abstractNote={A dislocation-density-based multiple-slip crystalline plasticity formulation, and an overlapping fracture method were used to investigate the effects of carbide precipitates, M23C6, and martensitic block size on dynamic fracture in martensitic steels. The interrelated effects of dislocation-density evolution, orientation relations (ORs), adiabatic heating, and heat conduction on fracture behavior were investigated. Precipitates interfaces are shown to be the sites of crack nucleation due to dislocation-density impedance. Dislocation-densities are also shown to relieve tensile stresses and blunt crack propagation. These predictions indicate that the size refinement of martensitic blocks increases crack deflection at block/packet boundaries, which can significantly improve fracture toughness.}, journal={ENGINEERING FRACTURE MECHANICS}, author={Wu, Q. and Zikry, M. A.}, year={2015}, month={Aug}, pages={54–66} }
 @article{brown_zikry_2015, title={Effect of microstructure on the coupled electromagnetic-thermo-mechanical response of cyclotrimethylenetrinitramine-estane energetic aggregates to infrared laser radiation}, volume={118}, ISSN={["1089-7550"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84942532175&partnerID=MN8TOARS}, DOI={10.1063/1.4931379}, abstractNote={The coupled electromagnetic (EM)-thermo-mechanical response of cyclotrimethylenetrinitramine-estane energetic aggregates under laser irradiation and high strain rate loads has been investigated for various aggregate sizes and binder volume fractions. The cyclotrimethylenetrinitramine (RDX) crystals are modeled with a dislocation density-based crystalline plasticity formulation and the estane binder is modeled with finite viscoelasticity through a nonlinear finite element approach that couples EM wave propagation with laser heat absorption, thermal conduction, and inelastic deformation. Material property and local behavior mismatch at the crystal-binder interfaces resulted in geometric scattering of the EM wave, electric field and laser heating localization, high stress gradients, dislocation density, and crystalline shear slip accumulation. Viscous sliding in the binder was another energy dissipation mechanism that reduced stresses in aggregates with thicker binder ligaments and larger binder volume fractions. This investigation indicates the complex interactions between EM waves and mechanical behavior, for accurate predictions of laser irradiation of heterogeneous materials.}, number={12}, journal={JOURNAL OF APPLIED PHYSICS}, author={Brown, Judith A. and Zikry, M. A.}, year={2015}, month={Sep} }
 @article{labarbera_zikry_2015, title={Heterogeneous thermo-mechanical behavior and hot spot formation in RDX-estane energetic aggregates}, volume={62}, ISSN={["1879-2146"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84928274530&partnerID=MN8TOARS}, DOI={10.1016/j.ijsolstr.2015.02.007}, abstractNote={Hot spot formation has been investigated in energetic aggregates with a viscoelastic binder and crystalline grains that has been subjected to dynamic thermo-mechanical loading conditions. A dislocation-density based crystalline plasticity, finite viscoelasticity, and specialized finite-element formulations were used to predict hot spot formation due to dynamic thermo-mechanical loading conditions in RDX–estane energetic aggregates. The interrelated effects of grain boundary (GB) misorientations, porosity, grain morphology, dislocation densities, polymer binder relaxation, and crystal–binder interactions were coupled with adiabatic plasticity heating, thermal decomposition, viscous dissipation heating, and thermal conduction to analyze aggregate behavior and hot spot formation. The predictions indicate that hot spot formation occurs when temperatures become unbounded in localized regions at the peripheries of RDX crystals where RDX–estane interfacial incompatibilities result in crystal sliding and localized plastic deformation at RDX crystal edges and interfaces.}, journal={INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES}, author={LaBarbera, D. A. and Zikry, M. A.}, year={2015}, month={Jun}, pages={91–103} }
 @article{lam_zikry_2015, title={Identifying and controlling the behavior of gold nanoparticle-DNA superlattice systems}, volume={12}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84931297208&partnerID=MN8TOARS}, DOI={10.1166/jctn.2015.3955}, number={8}, journal={Journal of Computational and Theoretical Nanoscience}, author={Lam, L.M. and Zikry, M.A.}, year={2015}, pages={1761–1769} }
 @article{labarbera_zikry_2015, title={Interfacial effects on fracture nucleation and propagation in crystalline-amorphous energetic material systems}, volume={104}, ISSN={["1879-0801"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84927732379&partnerID=MN8TOARS}, DOI={10.1016/j.commatsci.2015.03.038}, abstractNote={Local failure modes, such as the nucleation and propagation of a pre-existing crack, have been investigated for energetic materials with a viscoelastic binder and crystalline grains subjected to dynamic thermal and mechanical loading conditions. A crystalline plasticity with dislocation density, finite viscoelasticity, dynamic fracture nucleation and propagation methods, and finite element methods were used to study crack nucleation and propagation due to dynamic thermal and mechanical loading conditions. The interrelated effects of dislocation densities, grain boundary (GB) misorientations, polymer binder relaxation, and interactions between crystal and binder were coupled to material thermal decomposition, adiabatic inelastic heating, viscous dissipation heating, and thermal conduction to analyze interfacial fracture behavior in RDX–estane systems. The predictions indicate that cracks propagated toward the binder and were arrested due to the viscous nature of the polymer binder and plasticity buildup. For low angle misorientations, the pre-existing crack propagated toward the binder with increasing crack tip speed until it reaches the binder, at which point the crack was arrested. For high angle misorientations, the crack propagated toward the binder and was arrested, adjacent to the binder, due to plastic deformation and lattice rotations. A secondary crack eventually nucleated and propagated to the interface, where it was arrested.}, journal={COMPUTATIONAL MATERIALS SCIENCE}, author={LaBarbera, D. A. and Zikry, M. A.}, year={2015}, month={Jun}, pages={10–22} }
 @book{shanthraj_zikry_2015, title={Microstructural behavior and fracture in crystalline materials: Overview}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84945340172&partnerID=MN8TOARS}, DOI={10.1007/978-1-4614-5589-9}, journal={Handbook of Damage Mechanics: Nano to Macro Scale for Materials and Structures}, author={Shanthraj, P. and Zikry, M.A.}, year={2015}, pages={419–452} }
 @article{lam_zikry_2015, title={Modeling and predicting the mechanical strength and stability of DNA-modified gold nanoparticle systems}, volume={12}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84964939547&partnerID=MN8TOARS}, DOI={10.1166/jctn.2015.4398}, number={11}, journal={Journal of Computational and Theoretical Nanoscience}, author={Lam, L.M. and Zikry, M.A.}, year={2015}, pages={4539–4548} }
 @article{ziaei_zikry_2015, title={Modeling the Effects of Dislocation-Density Interaction, Generation, and Recovery on the Behavior of HCP Materials}, volume={46A}, ISSN={["1543-1940"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84940718705&partnerID=MN8TOARS}, DOI={10.1007/s11661-014-2635-0}, number={10}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Ziaei, S. and Zikry, M. A.}, year={2015}, month={Oct}, pages={4478–4490} }
 @article{mailen_liu_dickey_zikry_genzer_2015, title={Modelling of shape memory polymer sheets that self-fold in response to localized heating}, volume={11}, ISSN={["1744-6848"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84943141129&partnerID=MN8TOARS}, DOI={10.1039/c5sm01681a}, abstractNote={We conduct a nonlinear finite element analysis (FEA) of the thermo-mechanical shrinking and self-folding behavior of pre-strained polystyrene polymer sheets.}, number={39}, journal={SOFT MATTER}, publisher={Royal Society of Chemistry (RSC)}, author={Mailen, Russell W. and Liu, Ying and Dickey, Michael D. and Zikry, Mohammed and Genzer, Jan}, year={2015}, pages={7827–7834} }
 @article{ziaei_wu_zikry_2015, title={Orientation relationships between coherent interfaces in hcp-fcc systems subjected to high strain-rate deformation and fracture modes}, volume={30}, ISSN={["2044-5326"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84939515483&partnerID=MN8TOARS}, DOI={10.1557/jmr.2015.207}, abstractNote={Abstract}, number={15}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Ziaei, Shoayb and Wu, Qifeng and Zikry, Mohammed A.}, year={2015}, month={Aug}, pages={2348–2359} }
 @article{wu_zikry_2015, title={Prediction of diffusion assisted hydrogen embrittlement failure in high strength martensitic steels}, volume={85}, ISSN={["1873-4782"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84943403130&partnerID=MN8TOARS}, DOI={10.1016/j.jmps.2015.08.010}, abstractNote={A stress assisted hydrogen diffusion transport model, a dislocation-density-based multiple-slip crystalline plasticity formulation, and an overlapping fracture method were used to investigate hydrogen diffusion and embrittlement in lath martensitic steels with distributions of M23C6 carbide precipitates. The formulation accounts for variant morphologies based on orientation relationships (ORs) that are uniquely inherent to lath martensitic microstructures. The interrelated effects of martensitic block and packet boundaries and carbide precipitates on hydrogen diffusion, hydrogen assisted crack nucleation and growth, are analyzed to characterize the competition between cleavage fracture and hydrogen diffusion assisted fracture along preferential microstructural fracture planes. Stresses along the three cleavage planes and the six hydrogen embrittlement fracture planes are monitored, such that crack nucleation and growth can nucleate along energetically favorable planes. High pressure gradients result in the accumulation of hydrogen, which embrittles martensite, and results in crack nucleation and growth along {110} planes. Cleavage fracture occurs along {100} planes when there is no significant hydrogen diffusion. The predictions indicate that hydrogen diffusion can suppress the emission and accumulation of dislocation density, and lead to fracture with low plastic strains.}, journal={JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS}, author={Wu, Q. and Zikry, M. A.}, year={2015}, month={Dec}, pages={143–159} }
 @article{zhao_zikry_2015, title={The effects of structural disorders and microstructural mechanisms on semi-crystalline P3HT behavior}, volume={57}, ISSN={["1873-2291"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84920446650&partnerID=MN8TOARS}, DOI={10.1016/j.polymer.2014.12.003}, abstractNote={Semiconducting conjugated polymers, such as P3HT, have applications for photovoltaic and flexible electronics. However, charge transport is sensitive to the mechanical behavior of the donor P3HT. A computational framework has, therefore, been used to identify the microstructural mechanisms, at different physical scales, that affect behavior. The approach accounts for the microstructure as an interrelated three-phase model that is physically representative of crystalline domains, an amorphous interphase, and tie-chain bridging regions. Based on our predictions, the face-on packing crystalline orientations had higher toughness in comparison with the edge-on packing orientations that had higher strengths due to local dislocation-density interaction mechanisms. The higher inelastic deformation, associated with face-on orientations, disrupted the conjugation structure in the crystalline phase, and this could affect charge. These predictions indicate that the behavior of P3HT polymers can be optimized by controlling the packing orientations, the crystallinity, the entangled chain density, and the tie chain interconnectivity.}, journal={POLYMER}, author={Zhao, Bingxiao and Zikry, M. A.}, year={2015}, month={Jan}, pages={1–11} }
 @article{webb_shin_peters_zikry_stan_chadderdon_selfridge_schultz_2014, title={Characterization of fatigue damage in adhesively bonded lap joints through dynamic, full-spectral interrogation of fiber Bragg grating sensors: 1. Experiments}, volume={23}, ISSN={["1361-665X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84892404653&partnerID=MN8TOARS}, DOI={10.1088/0964-1726/23/2/025016}, abstractNote={In this study we measure the in situ response of a fiber Bragg grating (FBG) sensor embedded in the adhesive layer of a single composite lap joint, subjected to harmonic excitation after fatigue loading. After a fully reversed cyclic fatigue loading is applied to the composite lap joint, the full-spectral response of the sensor is interrogated at 100 kHz during two loading conditions: with and without an added harmonic excitation. The full-spectral information avoided dynamic measurement errors often experienced using conventional peak wavelength and edge filtering techniques. The short-time Fourier transform (STFT) is computed for the extracted peak wavelength information to reveal time-dependent frequencies and amplitudes of the dynamic FBG sensor response. The dynamic response of the FBG sensor indicated a transition to strong nonlinear dynamic behavior as fatigue-induced damage progressed. The ability to measure the dynamic response of the lap joint through sensors embedded in the adhesive layer can provide in situ monitoring of the lap joint condition.}, number={2}, journal={SMART MATERIALS AND STRUCTURES}, author={Webb, S. and Shin, P. and Peters, K. and Zikry, M. A. and Stan, N. and Chadderdon, S. and Selfridge, R. and Schultz, S.}, year={2014}, month={Feb} }
 @article{webb_shin_peters_zikry_stan_chadderdon_selfridge_schultz_2014, title={Characterization of fatigue damage in adhesively bonded lap joints through dynamic, full-spectral interrogation of fiber Bragg grating sensors: 2. Simulations}, volume={23}, ISSN={["1361-665X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84892411813&partnerID=MN8TOARS}, DOI={10.1088/0964-1726/23/2/025017}, abstractNote={In this paper, we simulate the response of fiber Bragg grating (FBG) sensors embedded in the adhesive layer of a composite lap that is subjected to harmonic excitation. To simulate accumulated fatigue damage at the adhesive layer, two forms of numerical nonlinearities are introduced into the model: (1) progressive plastic deformation of the adhesive and (2) changing the boundary of an interfacial defect at the adhesive layer across the overlap shear area. The simulation results are compared with previous measurements of the dynamic, full-spectral response of such FBG sensors for condition monitoring of the lap joint. Short-time Fourier transforms (STFT) of the locally extracted axial strain time histories reveal a transition to nonlinear behavior of the composite lap joint by means of intermittent frequencies that were observed in the experimental measurements and are not associated with the external excitation. The simulation results verify that the nonlinear changes in measured dynamic FBG responses are due to the progression of damage in the lap joint.}, number={2}, journal={SMART MATERIALS AND STRUCTURES}, author={Webb, S. and Shin, P. and Peters, K. and Zikry, M. A. and Stan, N. and Chadderdon, S. and Selfridge, R. and Schultz, S.}, year={2014}, month={Feb} }
 @article{zikry_2014, title={Editorial}, volume={136}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84889836991&partnerID=MN8TOARS}, DOI={10.1115/1.4026012}, abstractNote={Dear Readers,I am honored to be named, the Editor in Chief for the ASME Journal of Engineering Materials and Technology. The journal has been in existence since 1973, and it is associated with the Materials Division of ASME. It has been providing top-quality research papers on contemporary issues of engineering materials and technology, for a broad spectrum of issues pertaining to experimental, computational, and theoretical investigations of the mechanical behavior of materials with a mechanics of materials perspective, at physical scales ranging from the nano to the macro for materials, such as metals, polymers, ceramics, composites, biomaterials, and nanostructured materials.I am indebted to the selfless service of all the previous editors, and especially, my predecessor, Professor Hussein Zbib, who have all guided the journal to the highest standards. The journal’s aim now is to continue to publish research of the highest quality and of lasting significance in areas related to engineering materials, mechanics of materials, and materials technology. The scope is broad, since it encompasses interdisciplinary research that spans fundamental knowledge, which is related to mechanics of materials, materials science, mathematics, and applied physics, and technological applications, which are related to engineering innovations and applications. The journal will include research articles, technical notes, book reviews, and special issues related to emerging areas.The content of the journal will, therefore, move to emphasize the multidisciplinary efforts needed to advance the field in areas related to materials development, experimental and computational analysis, and engineering innovation. Our aim, as an editorial board, in conjunction with the publishing team, is to establish the journal as the leading international forum for original scientific research with balanced contributions that combine theoretical, experimental, and computational investigations. We look forward to that challenge.}, number={1}, journal={Journal of Engineering Materials and Technology}, author={Zikry, M.}, year={2014} }
 @article{khanikar_liu_zikry_2014, title={Experimental and computational investigation of the dynamic behavior of Al-Cu-Li alloys}, volume={604}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84897871655&partnerID=MN8TOARS}, DOI={10.1016/j.msea.2014.02.089}, abstractNote={A dislocation-density based crystalline plasticity formulation, finite-element techniques, rational crystallographic orientation relations and a new fracture methodology were used to predict the failure modes associated with the high strain rate behavior of high strength Al–Cu–Li alloys. Widely used aluminum alloy 2195 (AA2195) was taken as the representative of Al–Cu–Li alloys. Experimental characterization using Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) were performed to gain insights on microstructural behavior. The alloy aggregate was modeled with representative microstructures that included precipitates, dispersed particles, and different grain boundary (GB) distributions. The new fracture methodology, based on overlapping elements and phantom nodes, was used with a fracture criteria specialized for fracture on different cleavage planes to investigate dynamic crack nucleation and growth. The compressive behavior of AA2195 under high strain rate loading was compared with that of Al–Cu alloy 2139 to further understand the behavior of the AA2195 with the more ductile AA2139. The predictions quantify how local microstructural effects, due to precipitates and dispersed particles, have a dominant effect on crack initiation and growth.}, journal={Materials Science & Engineering. A, Structural Materials: Properties, Microstructure and Processing}, author={Khanikar, P. and Liu, Y. and Zikry, Mohammed}, year={2014}, pages={67–77} }
 @article{webb_peters_zikry_stan_chadderdon_selfridge_schultz_2014, title={Fiber Bragg grating spectral features for structural health monitoring of composite structures}, volume={9157}, ISSN={["1996-756X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84903169877&partnerID=MN8TOARS}, DOI={10.1117/12.2059625}, abstractNote={We demonstrate the measurement of and applications for reflected spectral signatures obtained from FBG sen- sors in dynamic environments. Three uses of the spectral distortion measurements for monitoring of airframe structures are presented: the measurement of the dynamic response of a laminated plate to an impact event; the measurement of damage induced spectral distortion in a thin plate during vibration loading; and the measurement of the change in dynamic response of an adhesively bonded joint with the progression of fatigue damage.}, journal={23RD INTERNATIONAL CONFERENCE ON OPTICAL FIBRE SENSORS}, author={Webb, Sean and Peters, Kara and Zikry, Mohammed and Stan, Nikola and Chadderdon, Spencer and Selfridge, Richard and Schultz, Stephen}, year={2014} }
 @article{khanikar_zikry_2014, title={High strain-rate interfacial behavior of layered metallic composites}, volume={77}, ISSN={["1872-7743"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84904976514&partnerID=MN8TOARS}, DOI={10.1016/j.mechmat.2014.07.008}, abstractNote={The high strain-rate interfacial behavior of layered aluminum composite has been investigated. A dislocation-density based crystalline plasticity formulation, specialized finite-element techniques, rational crystallographic orientation relations, and a new fracture methodology for large scale plasticity been used. Two alloy layers, a high strength alloy, aluminum 2195, and an aluminum alloy 2139, with high toughness, were modeled with representative microstructures that included precipitates, dispersed particles, and different grain boundary (GB) distributions. The new fracture methodology, based on an overlapping element method and phantom nodes, along with a fracture criteria specialized for fracture on different cleavage planes is used to model interfacial delamination. Dislocation-density evolution significantly affects the delamination process, and this has a directly related to the strengthening, toughening, and failure of the layered composite. It is also shown that brittle alumina (Al2O3) platelets in the interface region played an important role in interfacial delamination and overall composite behavior.}, journal={MECHANICS OF MATERIALS}, author={Khanikar, Prasenjit and Zikry, M. A.}, year={2014}, month={Oct}, pages={52–66} }
 @article{stan_bailey_chadderdon_webb_zikry_peters_selfridge_schultz_2014, title={Increasing dynamic range of a fibre Bragg grating edge-filtering interrogator with a proportional control loop}, volume={25}, ISSN={["1361-6501"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84899634683&partnerID=MN8TOARS}, DOI={10.1088/0957-0233/25/6/065206}, abstractNote={We present a fibre Bragg grating (FBG) interrogator that uses a microcontroller board and a tunable optical filter in a proportional control loop to increase dynamic range and achieve high strain sensitivity. It is an edge-filtering interrogator with added proportional control loop that locks the operating wavelength to the mid-reflection point on the FBG spectrum. The interrogator separates low-frequency (LF) components of strain and measures them with extended dynamic range, while at the same time measuring high-frequency (HF) strain without loss in strain sensitivity. In this paper, we describe the implementation of the interrogator and analyse the characteristics of individual components, such as the speed and voltage resolution of the microcontroller and the tunable optical filter. We measure the performance of the proportional control loop at frequencies up to 1 kHz and characterize the system using control theory. We illustrate the limitation of the conventional interrogator to measure strains greater than 40 μϵ and demonstrate successful application of the proposed interrogator for simultaneous measurement of 450 μϵ LF strain at 50 Hz superimposed with 32 kHz HF strain.}, number={6}, journal={MEASUREMENT SCIENCE AND TECHNOLOGY}, author={Stan, Nikola and Bailey, D. C. and Chadderdon, S. L. and Webb, S. and Zikry, M. and Peters, K. J. and Selfridge, R. H. and Schultz, S. M.}, year={2014}, month={Jun} }
 @article{brown_labarbera_zikry_2014, title={Laser interaction effects of electromagnetic absorption and microstructural defects on hot-spot formation in RDX-PCTFE energetic aggregates}, volume={22}, ISSN={["1361-651X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84903137725&partnerID=MN8TOARS}, DOI={10.1088/0965-0393/22/5/055013}, abstractNote={Hot-spot formation in energetic aggregates subjected to dynamic pressure loading and laser irradiation has been investigated. Specialized finite-element techniques with a dislocation-density-based crystalline plasticity constitutive formulation and thermo-mechanical coupling of heat conduction, adiabatic heating, laser heating and thermal decomposition were used to predict hot-spot formation in RDX–polymer aggregates subjected to dynamic pressures and laser energies. The effects of the electromagnetic absorption coefficient coupled with void distribution and spacing, grain morphology, crystal–binder interactions and dislocation densities were analyzed to determine their influence on the time, location and mechanisms of hot-spot formation. Four different mechanisms for hot-spot initiation under dynamic laser and pressure loads were identified, which depend on the localization of plastic shear strain and laser heat absorption within the aggregate. The predictions indicate that hot-spot formation is accelerated by higher absorption coefficients and by localized plastic deformations that occur in areas of significant laser heating.}, number={5}, journal={MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING}, author={Brown, Judith A. and LaBarbera, Darrell A. and Zikry, Mohammed A.}, year={2014}, month={Jul} }
 @article{wu_zikry_2014, title={Microstructural modeling of crack nucleation and propagation in high strength martensitic steels}, volume={51}, ISSN={["1879-2146"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84923217972&partnerID=MN8TOARS}, DOI={10.1016/j.ijsolstr.2014.08.021}, abstractNote={A dislocation-density based multiple-slip crystalline plasticity formulation, a dislocation-density grain boundary (GB) interaction scheme, and an overlapping fracture method were used to investigate crack nucleation and propagation in martensitic steel with retained austenite for both quasi-static and dynamic loading conditions. The formulation accounts for variant morphologies, orientation relationships, and retained austenite that are uniquely inherent to lath martensitic microstructures. The interrelated effects of dislocation-density evolution ahead of crack front and the variant distribution of martensitic blocks on crack nucleation and propagation are investigated. It is shown that dislocation-density generation ahead of crack front can induce dislocation-density accumulations and plastic deformation that can blunt crack propagation. These predictions indicate that variant distribution of martensitic blocks can be optimized to mitigate and potentially inhibit material failure.}, number={25-26}, journal={INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES}, author={Wu, Q. and Zikry, M. A.}, year={2014}, month={Dec}, pages={4345–4356} }
 @article{lee_zikry_2014, title={Microstructurally induced computational and material instabilities}, volume={52}, ISSN={["1879-2154"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84888199883&partnerID=MN8TOARS}, DOI={10.1016/j.ijplas.2013.06.011}, abstractNote={Abstract A dislocation-density based finite strain crystal plasticity finite element model and an hourglass strain measure orthogonal to the linear velocity field were used to investigate microstructural effects on deformation and hourglass instability. An aluminum aggregate was modeled in quasi-static plane strain tension and compression, and the effects of the presence of manganese-based dispersed particles were investigated. Both local plastic deformation and the presence of these dispersed particles can trigger hourglass instabilities, which can be mistaken for deformation or failure modes. These hourglass modes occur due to the difference in the deformability of neighboring elements or regions and the associated energy modes associated with hourglassing, and the proposed computational methodology can be used to delineate between failure modes and numerical instabilities.}, journal={INTERNATIONAL JOURNAL OF PLASTICITY}, author={Lee, W. M. and Zikry, M. A.}, year={2014}, month={Jan}, pages={95–104} }
 @article{zhao_awartani_o’connor_zikry_2014, title={Modeling the mechanical behavior of P3HT/fullerene blends for photovoltaic applications}, volume={1628}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84919391709&partnerID=MN8TOARS}, DOI={10.1557/opl.2014.128}, abstractNote={ABSTRACT}, number={2}, journal={Journal of the Gilded Age and Progressive Era}, author={Zhao, B. and Awartani, O. and O’Connor, B.T. and Zikry, M.A.}, year={2014} }
 @article{khanikar_zikry_2014, title={Predictions of High Strain Rate Failure Modes in Layered Aluminum Composites}, volume={45A}, ISSN={["1543-1940"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84891630404&partnerID=MN8TOARS}, DOI={10.1007/s11661-013-2016-0}, number={1}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Khanikar, Prasenjit and Zikry, M. A.}, year={2014}, month={Jan}, pages={60–71} }
 @article{lee_mazzoleni_zikry_2013, title={Aerodynamic effects on the accuracy of an end-over-end kick of an American football}, volume={16}, ISSN={1369-7072 1460-2687}, url={http://dx.doi.org/10.1007/S12283-012-0110-Y}, DOI={10.1007/S12283-012-0110-Y}, number={2}, journal={Sports Engineering}, publisher={Springer Science and Business Media LLC}, author={Lee, W. M. and Mazzoleni, A. P. and Zikry, M. A.}, year={2013}, month={Feb}, pages={99–113} }
 @article{webb_shin_peters_zikry_chadderdon_stan_selfridge_schultz_2013, title={Characterization of fatigue damage in adhesively bonded lap joints through dynamic, full-spectral interrogation of fiber Bragg grating sensors}, volume={8693}, ISSN={["1996-756X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84878407243&partnerID=MN8TOARS}, DOI={10.1117/12.2010018}, abstractNote={In this study we evaluate the measurements of a fiber Bragg grating (FBG) sensor embedded at the adhesive layer of a single composite lap joint subjected to harmonic excitation after fatigue loading. After a fully-reversed cyclic fatigue loading is applied to the composite lap joint, the full spectral response of the sensor is interrogated in reflection at 100 kHz during two states: with and without an added harmonic excitation. The dynamic response of the FBG sensor indicates strong nonlinearities as damage progresses. The short-time Fourier transform (STFT) is computed for the extracted peak wavelength information to reveal time-dependent frequencies and amplitudes of the dynamic FBG sensor response. Pulse-phase thermography indicates a progression in defect size at the adhesive layer that strongly suggests non-uniform loading of the FBG sensor.}, journal={SMART SENSOR PHENOMENA, TECHNOLOGY, NETWORKS, AND SYSTEMS INTEGRATION 2013}, author={Webb, S. and Shin, P. and Peters, K. and Zikry, M. A. and Chadderdon, S. and Stan, N. and Selfridge, R. and Schultz, S.}, year={2013} }
 @inproceedings{webb_shin_peters_zikry_schultz_selfridge_2013, title={Characterization of fatigue damage in adhesively bonded lap joints through dynamic, full-spectral interrogation of fiber bragg grating sensors}, booktitle={Structural Health Monitoring 2013, Vols 1 and 2}, author={Webb, S. and Shin, P. and Peters, K. and Zikry, M. and Schultz, S. and Selfridge, R.}, year={2013}, pages={1953–1960} }
 @article{xu_rezvanian_zikry_2013, title={Electro-mechanical modeling of the piezoresistive response of carbon nanotube polymer composites}, volume={22}, ISSN={["1361-665X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84876921770&partnerID=MN8TOARS}, DOI={10.1088/0964-1726/22/5/055032}, abstractNote={A coupled electro-mechanical FE approach was developed to investigate the piezoresistive response of carbon nanotube polymer composites. Gauge factors (GFs) and resistance variations of CNT–polymer composite systems were obtained by coupling Maxwell equations to mechanical loads and deformations through initial piezoresistive coefficients of the CNTs, the epoxy, and the tunnel regions, for different arrangements, percolated paths, tunnel distances, and tensile, compressive, and bending loading conditions. A scaling relation between GFs and applied strains was obtained to understand how variations in loading conditions and CNT arrangements affect sensing capabilities and piezoresistive carbon nanotube polymer composite behavior. These variations in GFs were then used to understand how the coupled strains, stresses and current densities vary for aligned and percolated paths for the different loading conditions, CNT arrangements, and tunnel distances. For the percolated path under tensile loading conditions, elastic strains as high as 16% and electrical conductivities that were four orders in magnitude greater than the initial matrix conductivity were obtained. Results for the three loading conditions clearly demonstrate that electrical conductivity and sensing capabilities can be optimized as a function of percolation paths, tunneling distance, orientation, and loading conditions for piezoresistive applications with large elastic strains and conductivities.}, number={5}, journal={SMART MATERIALS AND STRUCTURES}, author={Xu, S. and Rezvanian, O. and Zikry, M. A.}, year={2013}, month={May} }
 @article{xu_rezvanian_zikry_2013, title={Electrothermomechanical Modeling and Analyses of Carbon Nanotube Polymer Composites}, volume={135}, ISSN={["1528-8889"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84888342251&partnerID=MN8TOARS}, DOI={10.1115/1.4023912}, abstractNote={A new finite element (FE) modeling method has been developed to investigate how the electrical-mechanical-thermal behavior of carbon nanotube (CNT)–reinforced polymer composites is affected by electron tunneling distances, volume fraction, and physically realistic tube aspect ratios. A representative CNT polymer composite conductive path was chosen from a percolation analysis to establish the three-dimensional (3D) computational finite-element (FE) approach. A specialized Maxwell FE formulation with a Fermi-based tunneling resistance was then used to obtain current density evolution for different CNT/polymer dispersions and tunneling distances. Analyses based on thermoelectrical and electrothermomechanical FE approaches were used to understand how CNT-epoxy composites behave under electrothermomechanical loading conditions.}, number={2}, journal={JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME}, author={Xu, S. and Rezvanian, O. and Zikry, M. A.}, year={2013}, month={Apr} }
 @article{pearson_labarbera_prabhugoud_peters_zikry_2013, title={Experimental and Computational Investigation of Low-Impact Velocity and Quasi-Static Failure of PMMA}, volume={53}, ISSN={["1741-2765"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84872276475&partnerID=MN8TOARS}, DOI={10.1007/s11340-012-9650-0}, number={1}, journal={EXPERIMENTAL MECHANICS}, author={Pearson, J. D. and LaBarbera, D. and Prabhugoud, M. and Peters, K. and Zikry, M. A.}, year={2013}, month={Jan}, pages={53–66} }
 @article{webb_peters_zikry_chadderdon_nikola_selfridge_schultz_2013, title={Full-Spectral Interrogation of Fiber Bragg Grating Sensors Exposed to Steady-State Vibration}, volume={53}, ISSN={["1741-2765"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84874796178&partnerID=MN8TOARS}, DOI={10.1007/s11340-012-9661-x}, number={4}, journal={EXPERIMENTAL MECHANICS}, author={Webb, S. and Peters, K. and Zikry, M. A. and Chadderdon, S. and Nikola, S. and Selfridge, R. and Schultz, S.}, year={2013}, month={Apr}, pages={513–530} }
 @inproceedings{stan_bailey_chadderdon_selfridge_schultz_webb_peters_zikry_2013, title={High dynamic range high sensitivity FBG interrogation}, volume={8694}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84878401441&partnerID=MN8TOARS}, DOI={10.1117/12.2009875}, abstractNote={We present a fiber Bragg grating (FBG) interrogation method using a micro-controller board and optical filter that achieves high strain sensitivity and high dynamic range. This interrogation method allows high sensitivity detection of ultrasonic waves superimposed on low-frequency (on the order of 100Hz) vibrations of arbitrary magnitude. One possible application is in-situ structural health monitoring of windmill blades exposed to strong winds by using FBG sensors for detection of ultrasonic waves. Interrogator operation is based on the edge filtering method using a broadband source, fiber Fabry-Perot filter and a micro-controller board which acts as a control feedback loop that locks the filter wavelength to the mid-reflection point on the FBG spectrum. Wavelength locking method allows high sensitivity for edge filtering of high-frequency waves, while the feedback signal is the measurement of low-frequency vibration with high dynamic range. The concept of the interrogator operation and different implementations are described and discussed with experimental results.}, booktitle={Proceedings of SPIE - The International Society for Optical Engineering}, author={Stan, N. and Bailey, D. and Chadderdon, S. and Selfridge, R.H. and Schultz, S.M. and Webb, S. and Peters, K.J. and Zikry, M.}, year={2013} }
 @inproceedings{labarbera_zikry_2013, title={Microstructural behavior of energetic crystalline aggregates}, volume={1526}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84900318964&partnerID=MN8TOARS}, DOI={10.1557/opl.2013.503}, abstractNote={ABSTRACT}, booktitle={Materials Research Society Symposium Proceedings}, author={Labarbera, D. and Zikry, M.A.}, year={2013}, pages={24–29} }
 @article{shanthraj_zikry_2013, title={Microstructurally induced fracture nucleation and propagation in martensitic steels}, volume={61}, ISSN={["0022-5096"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84874657104&partnerID=MN8TOARS}, DOI={10.1016/j.jmps.2012.11.006}, abstractNote={A dislocation-density grain boundary (GB) interaction scheme that is representative of dislocation-density transmission and blockage within GBs is developed and incorporated into a dislocation-density based multiple-slip crystalline plasticity framework for a detailed analysis of fracture nucleation and growth in martensitic steels. This formulation accounts for variant morphologies and orientation relationships (ORs) that are uniquely inherent to lath martensitic microstructures. Specialized finite-element (FE) methodologies using overlapping elements to represent evolving failure surfaces and microstructurally-based failure criteria for cleavage are then used to investigate the effects of martensitic variant distributions and ORs on the dominant dislocation-density mechanisms for the localization of plastic strains, and the initiation and propagation of fracture surfaces in martensitic microstructures subjected to quasi-static and dynamic strain-rates. The results indicate that the local dislocation-density behavior at the variant boundaries and the interiors influence dominant failure initiation and growth. A dislocation-density GB interaction, which is based on dislocation-density accumulation and transmission at variant boundaries, is developed and used to predict stress build-up or relaxation, and together with the orientation of the cleavage planes in relation to the lath morphology, intergranular and transgranular fracture modes can be determined.}, number={4}, journal={JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS}, author={Shanthraj, P. and Zikry, M. A.}, year={2013}, month={Apr}, pages={1091–1105} }
 @article{wu_shanthraj_zikry_2013, title={Modeling the heterogeneous effects of retained austenite on the behavior of martensitic high strength steels}, volume={184}, DOI={10.1007/978-3-319-04397-5_16}, number={1-2}, journal={International Journal of Fracture}, author={Wu, Q. and Shanthraj, P. and Zikry, Mohammed}, year={2013}, pages={241–252} }
 @article{wu_shanthraj_zikry_2013, title={Modeling the heterogeneous effects of retained austenite on the behavior of martensitic high strength steels}, volume={184}, ISSN={0376-9429 1573-2673}, url={http://dx.doi.org/10.1007/S10704-013-9879-3}, DOI={10.1007/S10704-013-9879-3}, number={1-2}, journal={International Journal of Fracture}, publisher={Springer Science and Business Media LLC}, author={Wu, Q. and Shanthraj, P. and Zikry, M. A.}, year={2013}, month={Sep}, pages={241–252} }
 @article{labarbera_zikry_2013, title={The effects of microstructural defects on hot spot formation in cyclotrimethylenetrinitramine-polychlorotrifluoroethylene energetic aggregates}, volume={113}, ISSN={["0021-8979"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84879877008&partnerID=MN8TOARS}, DOI={10.1063/1.4811684}, abstractNote={Shock initiation due to hot spot formation has been investigated in energetic aggregates subjected to dynamic thermo-mechanical loading conditions. A dislocation-density based crystalline plasticity and specialized finite-element formulations were used to predict hot spot formation due to dynamic thermo-mechanical loading conditions in cyclotrimethylenetrinitramine-polymer energetic aggregates. The effects of grain boundary misorientations, porosity, grain morphology, dislocation densities, and crystal-binder interactions were coupled with adiabatic plasticity heating, thermal decomposition, and dissipated heat to analyze hot spot formation. The predictions indicate that hot spot formation occurs when temperatures become unbounded in localized regions between voids. The time to hot spot formation decreases with increases in dynamic pressure loads, which is consistent with experimental results.}, number={24}, journal={JOURNAL OF APPLIED PHYSICS}, author={LaBarbera, D. A. and Zikry, M. A.}, year={2013}, month={Jun} }
 @article{shanthraj_zikry_2013, title={The effects of microstructure and morphology on fracture nucleation and propagation in martensitic steel alloys}, volume={58}, ISSN={["1872-7743"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84872336398&partnerID=MN8TOARS}, DOI={10.1016/j.mechmat.2012.11.010}, abstractNote={A dislocation-density based multiple-slip crystalline plasticity framework, which accounts for variant morphologies and orientation relationships (ORs) that are uniquely inherent to lath martensitic microstructures, and a dislocation-density grain boundary (GB) interaction scheme, which is based on dislocation-density transmission and blockage at variant boundaries, is developed and used to predict stress accumulation or relaxation at the variant interfaces. A microstructural failure criterion, which is based on resolving these stresses on martensitic cleavage planes, and specialized finite-element (FE) methodologies using overlapping elements to represent evolving fracture surfaces are used for a detailed analysis of fracture nucleation and intergranular and transgranular crack growth in martensitic steels. The effects of block and packet boundaries are investigated, and the results indicate that the orientation of the cleavage planes in relation to the slip planes and the lath morphology are the dominant factors that characterize specific failure modes. The block and packet sizes along the lath long direction are the key microstructural features the affect toughening mechanisms, such as crack arrest and deflection, and these mechanisms can be used to control the nucleation and propagation of different failure modes.}, journal={MECHANICS OF MATERIALS}, author={Shanthraj, P. and Zikry, M. A.}, year={2013}, month={Mar}, pages={110–122} }
 @inproceedings{mclaughlin_zikry_2013, title={The mechanics and stability of gold nanoparticle-oligo-ligand-DNA systems}, volume={1513}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84899757656&partnerID=MN8TOARS}, DOI={10.1557/opl.2013.501}, abstractNote={ABSTRACT}, booktitle={Materials Research Society Symposium Proceedings}, author={McLaughlin, L.A. and Zikry, M.A.}, year={2013}, pages={6–11} }
 @article{xu_rezvanian_peters_zikry_2013, title={The viability and limitations of percolation theory in modeling the electrical behavior of carbon nanotube-polymer composites}, volume={24}, ISSN={["1361-6528"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84875677113&partnerID=MN8TOARS}, DOI={10.1088/0957-4484/24/15/155706}, abstractNote={A new modeling method has been proposed to investigate how the electrical conductivity of carbon nanotube (CNT) reinforced polymer composites are affected by tunneling distance, volume fraction, and tube aspect ratios. A search algorithm and an electrical junction identification method was developed with a percolation approach to determine conductive paths for three-dimensional (3D) carbon nanotube arrangements and to account for electron tunneling effects. The predicted results are used to understand the limitations of percolation theory and experimental measurements and observations, and why percolation theory breaks down for specific CNT arrangements.}, number={15}, journal={NANOTECHNOLOGY}, author={Xu, S. and Rezvanian, O. and Peters, K. and Zikry, M. A.}, year={2013}, month={Apr} }
 @article{dongare_lamattina_irving_rajendran_zikry_brenner_2012, title={An angular-dependent embedded atom method (A-EAM) interatomic potential to model thermodynamic and mechanical behavior of Al/Si composite materials}, volume={20}, ISSN={0965-0393 1361-651X}, url={http://dx.doi.org/10.1088/0965-0393/20/3/035007}, DOI={10.1088/0965-0393/20/3/035007}, abstractNote={A new interatomic potential is developed for the Al/Si system in the formulation of the recently developed angular-dependent embedded atom method (A-EAM). The A-EAM is formulated by combining the embedded atom method potential for Al with the Stillinger–Weber potential for Si. The parameters of the Al/Si cross-interactions are fitted to reproduce the structural energetics of Al/Si bulk alloys determined based on the results of density functional theory calculations and the experimentally observed mixing behavior of the AlSi liquid alloy at high temperatures. The ability to investigate the thermodynamic properties of the Al/Si system is demonstrated by computing the binary phase diagram of the Al–Si system as predicted by the A-EAM potential and comparing with that obtained using experiments. The ability to study the mechanical behavior of the Al/Si composite systems is demonstrated by investigating the micromechanisms related to dynamic failure of the Al/Si nanocomposites using MD simulations.}, number={3}, journal={Modelling and Simulation in Materials Science and Engineering}, publisher={IOP Publishing}, author={Dongare, Avinash M and LaMattina, Bruce and Irving, Douglas L and Rajendran, Arunachalam M and Zikry, Mohammed A and Brenner, Donald W}, year={2012}, month={Feb}, pages={035007} }
 @article{shanthraj_zikry_2012, title={Dislocation-density mechanisms for void interactions in crystalline materials}, volume={34}, ISSN={["0749-6419"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84860330583&partnerID=MN8TOARS}, DOI={10.1016/j.ijplas.2012.01.008}, abstractNote={Dislocation-density based evolution formulations that are related to a heterogeneous microstructure and is representative of different crystalline interactions, have been developed and used to investigate the dominant dislocation density mechanisms for void interactions, localized plastic strains, failure paths and ligament damage in face centered cubic (f.c.c.) and body centered cubic (b.c.c.) crystalline materials. The balance between the generation and annihilation of dislocation-densities, through glissile and forest interactions at the slip system level is taken as the basis for the evolution of mobile and immobile dislocation densities. The evolution equations are coupled to a multiple-slip crystal plasticity formulation, and a framework is established that relates it to a general class of crystallographies and deformation modes. Specialized finite-element (FE) methodologies have then been used to characterize void interactions in f.c.c. and b.c.c. crystals at different orientations, to obtain a detailed understanding of the interrelated physical mechanisms that can result in ductile material failure. The results indicate that dislocation-density interaction mechanisms, such as dislocation-density junction formation and annihilation, can have significant effects on shear strain localization and void interaction behavior.}, journal={INTERNATIONAL JOURNAL OF PLASTICITY}, author={Shanthraj, P. and Zikry, M. A.}, year={2012}, month={Jul}, pages={154–163} }
 @article{lee_zikry_2012, title={Dispersed particle and triple junction interactions in aluminum alloys}, volume={535}, ISSN={["0921-5093"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84856525455&partnerID=MN8TOARS}, DOI={10.1016/j.msea.2011.12.081}, abstractNote={The interrelated effects of dispersed particle interfaces and grain-boundary (GB) misorientations on the dynamic compressive deformation of high strength aluminum alloys have been investigated using an eigenstrain-based formulation coupled with dislocation-density based crystalline plasticity and a microstructurally based finite element framework. This formulation, which accounts for the unrelaxed plastic strains associated with the interfacial behavior of dispersed particles, such as Orowan looping, was used to model an aluminum tri-crystal with different distributions of dispersed particles and GB misorientations. Slip was relatively homogeneous and associated with initially preferential slip planes for low angle random GB misorientations. Particle dispersion had a greater effect on the deformation behavior for the high angle random GB misorientation tri-crystal, with dislocation density generation at the particle–matrix interface resulting in localized particle-controlled shear banding, which can inhibit transgranular shear banding caused by the triple junctions. Larger dispersed particles led to higher stress concentrations at the triple junction and higher tensile pressures at the particle–matrix interfaces.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Lee, W. M. and Zikry, M. A.}, year={2012}, month={Feb}, pages={264–273} }
 @article{elkhodary_zikry_2012, title={Dynamic crack nucleation and propagation in polycrystalline aluminum aggregates subjected to large inelastic deformations}, volume={175}, ISSN={["0376-9429"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84862189305&partnerID=MN8TOARS}, DOI={10.1007/s10704-012-9705-3}, number={2}, journal={INTERNATIONAL JOURNAL OF FRACTURE}, author={Elkhodary, K. I. and Zikry, M. A.}, year={2012}, month={Jun}, pages={95–108} }
 @article{elkhodary_zikry_2012, title={Dynamic crack nucleation, propagation, and interactions with crystalline secondary phases in aluminum alloys subjected to large deformations}, volume={92}, ISSN={["1478-6443"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84868694045&partnerID=MN8TOARS}, DOI={10.1080/14786435.2012.700126}, abstractNote={The major objective of this work was to model within a continuum framework the dynamic nucleation and evolution of failure surfaces in aluminum alloys with complex microstructures, using a recently developed compatibility-based fracture criterion for large deformations. Computational analyses were conducted to understand how Mn-bearing dispersoids, Ω and θ′ precipitates affect dynamic fracture processes in an Al–Cu–Mg–Ag alloys (2139-Al). High strain-rate simulations were based on a rate-dependent dislocation-density-based crystalline plasticity formulation and a nonlinear explicit dynamic finite-element approach. Results indicate that the fracture criterion elucidated how dispersoids and precipitates have a dominant role in dynamic crack blunting, branching and arrest. Rationally orientated precipitates result in overall dynamic microstructural strengthening and enhanced uniformity of deformation. These precipitates, however, accelerated unstable crack propagation, and this is amplified in the presence of a pre-crack. In contrast, dispersoids decreased microstructural toughness and ductility, but greatly improved dynamic damage tolerance, especially in the presence of a pre-crack. It can also be predicted that low angle boundaries can change the propagation direction of ductile cracks, and contribute to damage tolerance without crack initiation. Collectively, rationally oriented precipitates and dispersoids can significantly improve the combined dynamic strength, toughness and damage tolerance of crystalline aluminum alloys.}, number={32}, journal={PHILOSOPHICAL MAGAZINE}, author={Elkhodary, K. I. and Zikry, M. A.}, year={2012}, pages={3920–3949} }
 @article{webb_peters_zikry_chadderdon_nikola_selfridge_schultz_2012, title={Full-spectral interrogation of fiber Bragg grating sensors for measurements of damage during steady-state vibration}, volume={8346}, ISSN={["1996-756X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84901266148&partnerID=MN8TOARS}, DOI={10.1117/12.915150}, abstractNote={In this study we evaluate the measurements of a fiber Bragg grating (FBG) sensor subjected to a non-uniform static strain state and simultaneously exposed to vibration loading. The full spectral response of the sensor is interrogated in reflection at 100 kHz during two loading cases: with and without an added vibration load spectrum. The static tensile loading is increased between each test, in order to increase the magnitude of the non-uniform strain field applied to the FBG sensor. During steady-state vibration, the behavior of the spectral shape of the FBG reflection varies depending on the extent of non-uniform strain. With high-speed full spectral interrogation, it is potentially possible to separate this vibration-induced spectral change from spectral distortions due to non-uniform strain. Such spectral distortion contains valuable information on the static damage state of the surrounding host material.}, journal={SMART SENSOR PHENOMENA, TECHNOLOGY, NETWORKS, AND SYSTEMS INTEGRATION 2012}, author={Webb, S. and Peters, K. and Zikry, M. A. and Chadderdon, S. and Nikola, S. and Selfridge, R. and Schultz, S.}, year={2012} }
 @inproceedings{webb_peters_zikry_chadderdon_stan_schultz_selfridge_2012, title={Full-spectral interrogation of fiber bragg grating sensors for damage identification}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84863888345&partnerID=MN8TOARS}, booktitle={International SAMPE Technical Conference}, author={Webb, S.C. and Peters, K.J. and Zikry, M.A. and Chadderdon, S. and Stan, N. and Schultz, S.M. and Selfridge, R.H.}, year={2012} }
 @article{lee_zikry_2012, title={High strain-rate modeling of the interfacial effects of dispersed particles in high strength aluminum alloys}, volume={49}, ISSN={["1879-2146"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84865721891&partnerID=MN8TOARS}, DOI={10.1016/j.ijsolstr.2012.07.003}, abstractNote={The interfacial effects of dispersed particles on the dynamic deformation of high strength aluminum alloys have been investigated using an eigenstrain-based formulation coupled with dislocation-density based crystalline plasticity and a microstructurally based finite element framework. This accounts for the unrelaxed plastic strains associated with the interfacial behavior of dispersed particles, such as Orowan looping. Particle spacing had a significant effect on the distribution of plastic shear slip, with localization occurring between the particles for smaller particle spacing. The eigenstress field associated with larger particles led to longer-range interaction of pressure fields, which can promote void coalescence for nucleated voids at the particle-matrix interface. Grain orientation also had a significant effect on the behavior associated with the particles, with plastic shear slip localizing at the particle-matrix interfaces for low angle grain-boundary (GB) misorientations, and at GBs and GB junctions for high angle GB misorientations.}, number={23-24}, journal={INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES}, author={Lee, W. M. and Zikry, M. A.}, year={2012}, month={Nov}, pages={3291–3300} }
 @inproceedings{stan_chadderdon_selfridge_schultz_webb_peters_zikry_2012, title={High-speed full-spectrum interrogation of Fiber Bragg Grating sensor application in reducing sensor strain sensitivity}, volume={8347}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84860822093&partnerID=MN8TOARS}, DOI={10.1117/12.914751}, abstractNote={We used high-speed full-spectrum interrogation of a Fiber Bragg Grating (FBG) sensor to measure dynamic strain in different sensor packages in real-time. In this effort we performed solenoid impact tests on a variety of sensor mounting structures made with FR4, steel, and carbon fiber composite materials. Full spectrum FBG interrogation at 40 kHz repetition rate was the key that allowed us to measure and compare dynamic strain in the structures, with measurement resolution on the sub-millisecond scale. With this interrogation method we were able to measure the full character of the dynamic strain including the strain non-uniformity and distribution manifested in peak-splitting and spectrum broadening. Results showed that the FR4 board with soft epoxy responded with a maximum dynamic strain on the order of 3000 micro-strain. Adding hard materials such as steel and graphite fiber composite reduced the strain about 7 times. However, the FR4 board mounted in a free-floating configuration using hard epoxy reduced the maximum strain to a value below the noise threshold of the full spectrum interrogation configuration. Here we proposed using edge detection method of FBG interrogation due to its increased strain sensitivity which enabled us to further analyze the critical results obtained by full spectrum interrogation. We also proposed using edge detection to measure sensor strain in real time for the purpose of filtering out the strain noise from useful signal. We will use the results and data obtained with both methods to analyze and enhance the performance of our electric field sensors in environments of high static and dynamic strain.}, booktitle={Proceedings of SPIE - The International Society for Optical Engineering}, author={Stan, N. and Chadderdon, S. and Selfridge, R.H. and Schultz, S.M. and Webb, S. and Peters, K.J. and Zikry, M.}, year={2012} }
 @inproceedings{xu_rezvanian_peters_zikry_2012, title={Microstructural modeling of electrical behavior in CNT polymer composites}, volume={1420}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84879398074&partnerID=MN8TOARS}, DOI={10.1557/opl.2012.504}, abstractNote={ABSTRACT}, booktitle={Materials Research Society Symposium Proceedings}, author={Xu, S. and Rezvanian, O. and Peters, K. and Zikry, M.A.}, year={2012}, pages={36–41} }
 @article{lee_zikry_2012, title={Modeling the interfacial plastic strain incompatibilities associated with dispersed particles in high strength aluminum alloys}, volume={60}, ISSN={["1359-6454"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84862802552&partnerID=MN8TOARS}, DOI={10.1016/j.actamat.2011.11.058}, abstractNote={A new formulation based on an eigenstrain representation of Orowan looping was developed, and was coupled with a dislocation density based crystalline plasticity formulation and a specialized finite element framework to model the unrelaxed plastic strain and interfacial behavior associated with dispersed particles in high strength aluminum alloys. This representation accounts for the increased stresses associated with Orowan looping at interfacial locations, where extra half-planes due to Orowan loops occur at opposite particle corners. Plastic relaxation of the Orowan loops was modeled using the incompatibility of the lattice rotations between the particles and the alloy matrix. The predictions indicate that the orientations and morphologies of the particles with respect to the most active slip plane are the critical factors in the relaxation of the eigenstrains associated with the loops.}, number={4}, journal={ACTA MATERIALIA}, author={Lee, W. M. and Zikry, M. A.}, year={2012}, month={Feb}, pages={1669–1679} }
 @article{shanthraj_zikry_2012, title={Optimal microstructures for martensitic steels}, volume={27}, ISSN={["2044-5326"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84862010206&partnerID=MN8TOARS}, DOI={10.1557/jmr.2012.127}, abstractNote={Abstract}, number={12}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Shanthraj, P. and Zikry, M. A.}, year={2012}, month={Jun}, pages={1598–1611} }
 @article{salem_lee_bodelot_ravichandran_zikry_2012, title={Quasi-Static and High-Strain-Rate Experimental Microstructural Investigation of a High-Strength Aluminum Alloy}, volume={43A}, ISSN={["1073-5623"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84862807927&partnerID=MN8TOARS}, DOI={10.1007/s11661-011-1064-6}, number={6}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Salem, H. G. and Lee, William M. and Bodelot, Laurence and Ravichandran, G. and Zikry, M. A.}, year={2012}, month={Jun}, pages={1895–1901} }
 @article{elkhodary_zikry_2011, title={A fracture criterion for finitely deforming crystalline solids-The dynamic fracture of single crystals}, volume={59}, ISSN={["0022-5096"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-80052335624&partnerID=MN8TOARS}, DOI={10.1016/j.jmps.2011.07.004}, abstractNote={The major objective of this work has been to develop, within a continuum framework, a microstructurally-based computational theory to investigate dynamic failure in metals. To model the nucleation and propagation of failure surfaces at the microstructural scale, under large deformations and dynamic loading conditions, general finite-deformation theory, as relating to the decomposition of the deformation gradient, was tailored to monitor displacement incompatibilities and fracture in crystalline solids subjected to large deformations. Based on this proposed decomposition, a general fracture criterion for finitely deforming crystals, using the integral law of incompatibility, was developed. The analyses indicate that this newly proposed fracture formulation and criterion can be validated with experimental results, and can be used to accurately predict brittle and ductile failure modes for the large deformation of single crystals. As part of the newly proposed decomposition of the deformation gradient, sub-problems can also be solved for lattice distortions, such as twinning and geometrically necessary dislocation (GND) densities. Accordingly, the interactions of GND densities with cracks were investigated for single crystals. GND densities were shown to form as loops for stationary crack tips, but no loops formed for propagating cracks.}, number={10}, journal={JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS}, author={Elkhodary, K. I. and Zikry, M. A.}, year={2011}, month={Oct}, pages={2007–2022} }
 @article{hatem_zikry_2011, title={A model for determining initial dislocation-densities associated with martensitic transformations}, volume={27}, ISSN={["0267-0836"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-80054886787&partnerID=MN8TOARS}, DOI={10.1179/1743284711y.0000000079}, abstractNote={ A three-dimensional multiple-slip dislocation-density-based crystal plasticity formulation, and specialised finite element formulations were used to determine the initial dislocation-densities associated with martensitic transformations in steel alloys. The analysis is based on modelling the shear part from the phenomenological theory of martensitic transformation to obtain both the transformation mobile and immobile dislocation-densities. The model was validated with experiments related to the transformation of lath martensite in high-strength low-alloying steels. }, number={10}, journal={MATERIALS SCIENCE AND TECHNOLOGY}, author={Hatem, T. M. and Zikry, M. A.}, year={2011}, month={Oct}, pages={1570–1573} }
 @article{rezvanian_zikry_2011, title={Continuum modeling of large-strain deformation modes in gold nanowires}, volume={26}, ISSN={["2044-5326"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84864699682&partnerID=MN8TOARS}, DOI={10.1557/jmr.2011.148}, abstractNote={Abstract}, number={17}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Rezvanian, Omid and Zikry, Mohammed A.}, year={2011}, month={Sep}, pages={2286–2292} }
 @article{elkhodary_lee_sun_brenner_zikry_2011, title={Deformation mechanisms of an Omega precipitate in a high-strength aluminum alloy subjected to high strain rates}, volume={26}, ISSN={["0884-2914"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-80054905299&partnerID=MN8TOARS}, DOI={10.1557/jmr.2010.29}, abstractNote={Abstract}, number={4}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Elkhodary, K. and Lee, W. and Sun, L. P. and Brenner, D. W. and Zikry, M. A.}, year={2011}, month={Feb}, pages={487–497} }
 @article{shanthraj_zikry_2011, title={Dislocation density evolution and interactions in crystalline materials}, volume={59}, ISSN={1359-6454}, url={http://dx.doi.org/10.1016/j.actamat.2011.08.041}, DOI={10.1016/j.actamat.2011.08.041}, abstractNote={Dislocation density-based evolution formulations that are related to a heterogeneous microstructure and are physically representative of different crystalline interactions have been developed. The balance between the generation and annihilation of dislocations, through glissile and forest interactions at the slip system level, is taken as the basis for the evolution of mobile and immobile dislocation densities. The evolution equations are coupled to a multiple slip crystal plasticity formulation, and a framework is established that relates it to a general class of crystallographies and deformation modes. Specialized finite element (FE) methodologies have then been used to investigate how certain dislocation density activities, such as dislocation density interactions and immobilization, are directly related to strain hardening and microstructure evolution. The predictions are validated with channel die compressed (CDC) experiments, and are consistent with inelastic deformation modes of fcc metals.}, number={20}, journal={Acta Materialia}, publisher={Elsevier BV}, author={Shanthraj, P. and Zikry, M.A.}, year={2011}, month={Dec}, pages={7695–7702} }
 @article{dongare_rajendran_lamattina_zikry_brenner_2011, title={Dynamic failure behavior of nanocrystalline Cu at atomic scales}, volume={24}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-80155206327&partnerID=MN8TOARS}, number={1}, journal={Computers, Materials and Continua}, author={Dongare, A.M. and Rajendran, A.M. and Lamattina, B. and Zikry, M.A. and Brenner, D.W.}, year={2011}, pages={43–60} }
 @article{shanthraj_rezvanian_zikry_2011, title={Electrothermomechanical Finite-Element Modeling of Metal Microcontacts in MEMS}, volume={20}, ISSN={["1941-0158"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79953737151&partnerID=MN8TOARS}, DOI={10.1109/jmems.2010.2100020}, abstractNote={Three-dimensional fractal representations of surface roughness are incorporated into a finite-element framework to obtain the electrothermomechanical behavior of ohmic contacts in radio frequency (RF) microelectromechanical systems (MEMS) switches. Fractal surfaces are generated from the Weierstrass-Mandelbrot function and are representatives of atomic force microscope surface roughness measurements of contact surfaces in fabricated RF MEMS switches with metal contacts. A specialized finite-element scheme is developed, which couples the thermomechanical asperity creep deformations with the electromechanical contact characteristics to obtain predictions of contact parameters and their evolution as a function of time and loading. A dislocation-density-based crystal plasticity framework is also used to investigate microstructure evolution at microcontacts and its effects on contact parameters. Using this approach, simulations are made to investigate how surface roughness, initial residual strains, and operating temperature can affect asperity contact behavior. Based on these predictions, tribological design guidelines can be obtained to increase the lifetime of low-contact-resistance RF MEMS switches by limiting stiction and electrical resistance increase.}, number={2}, journal={JOURNAL OF MICROELECTROMECHANICAL SYSTEMS}, author={Shanthraj, Pratheek and Rezvanian, Omid and Zikry, Mohammed A.}, year={2011}, month={Apr}, pages={371–382} }
 @article{webb_noevere_peters_zikry_vella_chadderdon_selfridge_schultz_2011, title={Full-spectral interrogation of fiber Bragg grating sensors for damage identification}, volume={7982}, ISSN={["1996-756X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79956068726&partnerID=MN8TOARS}, DOI={10.1117/12.881093}, abstractNote={In this study we evaluate the measurements of a fiber Bragg grating (FBG) sensor subjected to a non-uniform static strain state and simultaneously exposed to vibration loading. The full spectral response of the sensor is interrogated in reflection at 100 kHz during two loading cases: with and without an added vibration load spectrum. The static tensile loading is increased between each test, in order to increase the magnitude of the non-uniform strain field applied to the FBG sensor. The spectral distortion due to non-uniform strain is observed to change once the sensor is exposed to a non-transient 150 Hz vibration spectrum. With high-speed full spectral interrogation, it is potentially possible to separate this vibration-induced spectral change from spectral distortions due to non-uniform strain. Such spectral distortion contains valuable information on the static damage state of the surrounding host material.}, journal={SMART SENSOR PHENOMENA, TECHNOLOGY, NETWORKS, AND SYSTEMS 2011}, author={Webb, S. and Noevere, A. and Peters, K. and Zikry, M. A. and Vella, T. and Chadderdon, S. and Selfridge, R. and Schultz, S.}, year={2011} }
 @inproceedings{chadderdon_selfridge_schultz_webb_park_peters_zikry_2011, title={High-speed full-spectrum fiber Bragg gratings interrogator system and testing}, volume={7753}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79958006102&partnerID=MN8TOARS}, DOI={10.1117/12.885138}, abstractNote={This paper presents a high repetition rate fiber Bragg grating (FBG) interrogation system that is able to capture the entire reflection spectrum at a rate of up to 300 kHz. The system uses a high speed MEMS based tunable optical filter that is driven with a sinusoidal voltage. The time varying FBG reflection spectrum in transmitted through the tunable filter. The time varying signal is then mapped into time varying reflection spectra. This interrogation system is used during two dynamic strain tests, in which the reflection spectra are measured at a repetition rate of 100 kHz. The first test is the impact of a woven carbon composite and the second test is on an electromagnetic railgun.}, booktitle={Proceedings of SPIE - The International Society for Optical Engineering}, author={Chadderdon, S. and Selfridge, R. and Schultz, S. and Webb, S. and Park, C. and Peters, K. and Zikry, M.}, year={2011} }
 @inproceedings{pearson_zikry_2011, title={Indentation and contact mechanics of nanocrystalline diamond crystals: A hierarchical molecular dynamics and finite-element approach}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84872434507&partnerID=MN8TOARS}, DOI={10.2514/6.2011-1925}, abstractNote={Molecular dynamics (MD) and finite-element (FE) simulations of a nano-crystalline diamond (NCD) grain system subjected to indentation were undertaken to understand how contact behavior pertaining to the surface roughness of NCD crystals can be spanned from the molecular to the continuum scale. It is shown that if the same surface roughness morphology, grain orientations, and elastic properties are used for both MD and FE simulations, there is agreement between contact pressures for relatively low indentation loads and shallow substrates. It should be emphasized that the strong correlation between MD and FE methods can also be due to the lack of defect nucleation associated with the elastic deformation of the NCD system. These predictions can be used for a hierarchical computational framework to harness the advantages of both computational approaches. Inherent to this approach is representation of surface roughness and crystal orientation that is physically consistent for both computational approaches. Using the techniques presented herein, MD simulations of fluids and fluid solid interactions may be able to be accurately performed using computational fluid dynamics (CFD) and FE simulations if an appropriate set of translation rules can be found for converting MD models to CFD models. An initial analysis of the requirements to convert MD models to CFD is undertaken and a subset of the necessary rules is postulated.}, booktitle={Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference}, author={Pearson, J.D. and Zikry, M.A.}, year={2011} }
 @article{lee_zikry_2011, title={Microstructural Characterization of a High-Strength Aluminum Alloy Subjected to High Strain-Rate Impact}, volume={42A}, ISSN={["1543-1940"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79954431266&partnerID=MN8TOARS}, DOI={10.1007/s11661-010-0476-z}, number={5}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Lee, W. M. and Zikry, M. A.}, year={2011}, month={May}, pages={1215–1221} }
 @inproceedings{shanthraj_hatem_zikry_2011, title={Microstructural modeling of failure modes in martensitic steel alloys}, volume={1296}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84859022469&partnerID=MN8TOARS}, DOI={10.1557/opl.2011.1446}, abstractNote={ABSTRACT}, booktitle={Materials Research Society Symposium Proceedings}, author={Shanthraj, P. and Hatem, T.M. and Zikry, M.A.}, year={2011}, pages={56–61} }
 @article{shi_zikry_2011, title={Modeling of grain boundary transmission, emission, absorption and overall crystalline behavior in Sigma 1, Sigma 3, and Sigma 17b bicrystals}, volume={26}, ISSN={["0884-2914"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-81455159237&partnerID=MN8TOARS}, DOI={10.1557/jmr.2011.192}, abstractNote={Abstract}, number={14}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Shi, Jibin and Zikry, Mohammed A.}, year={2011}, month={Jul}, pages={1676–1687} }
 @inproceedings{xu_rezvanian_peters_zikry_2011, title={Tunneling effects and electrical conductivity of CNT polymer composites}, volume={1304}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84860133288&partnerID=MN8TOARS}, DOI={10.1557/opl.2011.606}, abstractNote={ABSTRACT}, booktitle={Materials Research Society Symposium Proceedings}, author={Xu, S. and Rezvanian, O. and Peters, K. and Zikry, M.A.}, year={2011}, pages={50–56} }
 @article{webb_peters_zikry_vella_chadderdon_selfridge_schultz_2011, title={Wavelength hopping due to spectral distortion in dynamic fiber Bragg grating sensor measurements}, volume={22}, ISSN={0957-0233 1361-6501}, url={http://dx.doi.org/10.1088/0957-0233/22/6/065301}, DOI={10.1088/0957-0233/22/6/065301}, abstractNote={We demonstrate the measurement of wavelength hopping in dynamic fiber Bragg grating (FBG) sensor measurements and its effect on the interpretation of the dynamic behavior of a composite laminate. Strain measurements are performed with FBG sensors embedded in laminates, subjected to low-velocity impacts, with data acquired using a commercial peak wavelength following controller and a high-speed full-spectral interrogator recently developed by the authors. The peak follower response is theoretically predicted from the full-spectral interrogator measurements. We demonstrate that dynamic wavelength hopping does occur, that it changes the apparent dynamic behavior of the composite and that it can be directly predicted from the dynamic spectral distortion. We also demonstrate that full-spectral data acquisition at speeds lower than those required to fully resolve the dynamic event creates apparent measurement errors due to wavelength hopping as well.}, number={6}, journal={Measurement Science and Technology}, publisher={IOP Publishing}, author={Webb, S and Peters, K and Zikry, M and Vella, T and Chadderdon, S and Selfridge, R and Schultz, S}, year={2011}, month={May}, pages={065301} }
 @article{propst_peters_zikry_schultz_kunzler_zhu_wirthlin_selfridge_2010, title={Assessment of damage in composite laminates through dynamic, full-spectral interrogation of fiber Bragg grating sensors}, volume={19}, ISSN={["0964-1726"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-74849118513&partnerID=MN8TOARS}, DOI={10.1088/0964-1726/19/1/015016}, abstractNote={In this study, we demonstrate the full-spectral interrogation of a fiber Bragg grating (FBG) sensor at 535 Hz. The sensor is embedded in a woven, graphite fiber–epoxy composite laminate subjected to multiple low-velocity impacts. The measurement of unique, time dependent spectral features from the FBG sensor permits classification of the laminate lifetime into five regimes. These damage regimes compare well with previous analysis of the same material system using combined global and local FBG sensor information. Observed transient spectral features include peak splitting, wide spectral broadening and a strong single peak at the end of the impact event. Such features could not be measured through peak wavelength interrogation of the FBG sensor. Cross-correlation of the measured spectra with the original embedded FBG spectrum permitted rapid visualization of average strains and the presence of transverse compressive strain on the optical fiber, but smeared out the details of the spectral profile.}, number={1}, journal={SMART MATERIALS AND STRUCTURES}, author={Propst, A. and Peters, K. and Zikry, M. A. and Schultz, S. and Kunzler, W. and Zhu, Z. and Wirthlin, M. and Selfridge, R.}, year={2010}, month={Jan} }
 @article{dongare_rajendran_lamattina_zikry_brenner_2010, title={Atomic scale studies of spall behavior in nanocrystalline Cu}, volume={108}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.3517827}, DOI={10.1063/1.3517827}, abstractNote={The micromechanisms related to ductile failure during dynamic loading of nanocrystalline Cu are investigated in a series of large-scale molecular dynamics simulations. Void nucleation, growth, and coalescence is studied for a nanocrystalline Cu system with an average grain size of 6 nm under conditions of impact of a shock piston with velocities of 250, 500, 750, and 1000 m/s and compared to that observed in single crystal copper. Higher impact velocities result in higher strain rates and higher values of spall strengths for the metal as well as nucleation of larger number of voids in smaller times. For the same impact velocity, the spall strength of the nanocrystalline metal, however, is lower than that for single crystal copper. The results obtained for void nucleation and growth in nanocrystalline Cu for various impact velocities and for single crystal copper [001] suggests two distinct stages of evolution of voids. The first stage (I) corresponds to the fast nucleation of voids followed by the second stage (II) attributed to growth and coalescence of voids. The first stage is found to be dependent on the microstructure of the system as well as the shock pressure/strain rate, whereas, the second stage of void growth is independent of the strain rate and microstructure of the system and dependent only on the number of voids nucleated.}, number={11}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Dongare, Avinash M. and Rajendran, Arunachalam M. and LaMattina, Bruce and Zikry, Mohammed A. and Brenner, Donald W.}, year={2010}, month={Dec}, pages={113518} }
 @article{dongare_rajendran_lamattina_brenner_zikry_2010, title={Atomic-Scale Study of Plastic-Yield Criterion in Nanocrystalline Cu at High Strain Rates}, volume={41A}, ISSN={["1073-5623"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77949270731&partnerID=MN8TOARS}, DOI={10.1007/s11661-009-0113-x}, number={2}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Dongare, A. M. and Rajendran, A. M. and Lamattina, B. and Brenner, D. W. and Zikry, M. A.}, year={2010}, month={Feb}, pages={523–531} }
 @article{hatem_zikry_2010, title={Deformation and failure of single-packets in martensitic steels}, volume={17}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78349278902&partnerID=MN8TOARS}, number={2}, journal={Computers, Materials and Continua}, author={Hatem, T.M. and Zikry, M.A.}, year={2010}, pages={127–147} }
 @inproceedings{elkhodary_lee_cheeseman_sun_brenner_zikry_2010, title={Deformation of precipitate platelets in high strength aluminum alloys under high strain-rate compression}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77952596072&partnerID=MN8TOARS}, booktitle={TMS Annual Meeting}, author={Elkhodary, K. and Lee, W. and Cheeseman, B. and Sun, L.P. and Brenner, D.W. and Zikry, M.A.}, year={2010}, pages={47–52} }
 @article{hatem_zikry_2010, title={Dynamic shear-strain localization and inclusion effects in lath martensitic steels subjected to high pressure loads}, volume={58}, ISSN={["1873-4782"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-80052492778&partnerID=MN8TOARS}, DOI={10.1016/j.jmps.2010.04.009}, abstractNote={A three-dimensional multiple-slip dislocation-density based crystalline formulation, specialized finite-element formulations, and specialized Voronoi tessellations adapted to martensitic orientations, were used to investigate shear–strain localization, and dislocation-density evolution in martensitic microstructures under dynamic compressive loading conditions. The formulation is based on accounting for variant morphologies and orientations, secondary-phase structures, and initial dislocations-densities that are uniquely inherent to martensitic microstructures. The effects of strain rate and inclusions on the evolution of shear–strain localization were investigated. The analysis indicates that variant morphology and orientations have a direct consequence on dislocation-density accumulation and inelastic localization in martensitic microstructures, and that lath directions, orientations, and arrangements are critical characteristics of high-strength martensitic dynamic behavior. It is shown that tensile hydrostatic pressure due to the unloading of the plastic waves at the free boundary and extensive shear–strain accumulation occurs at certain triple junctions. Furthermore, plastic shear-slip accumulation between inclusions and the surrounding martensitic matrix results in shear–strain localization and increases in the tensile hydrostatic pressure at critical locations, such as trip junctions.}, number={8}, journal={JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS}, author={Hatem, T. M. and Zikry, M. A.}, year={2010}, month={Aug}, pages={1057–1072} }
 @article{ingle_king_zikry_2010, title={Finite element analysis of barbed sutures in skin and tendon tissues}, volume={43}, ISSN={0021-9290}, url={http://dx.doi.org/10.1016/j.jbiomech.2009.11.012}, DOI={10.1016/j.jbiomech.2009.11.012}, abstractNote={Barbed surgical sutures are a new type of knotless suture that are currently being used clinically in cosmetic and plastic surgery procedures for faster healing and better cosmesis. Clinical studies are also underway to evaluate their performance in other deep tissue applications. However, little is known about their intrinsic mechanical behavior and their interactions with surrounding tissues. The primary objective of the current study was to analyze the mechanical behavior of barbed sutures using a finite element analysis approach. First, the effect of applying a point-pressure load to the tip of the barb and measuring its effect on barb displacement was studied. Second, the effect of an applied displacement to a barb anchored either in skin or tendon material for both the suture and the surrounding tissue. The results indicate that the flexibility of the barb can be increased or decreased by changing the barb geometry. It was concluded that the barb geometry and design need to be modified for use with different types of tissue. For example, in order to achieve the best mechanical anchoring with skin tissue the barb should be more flexible compared to the one designed to work with tendon tissue. The uniqueness of this study is that it is the first to establish a virtual prototyping and designing method for barbed sutures. For example, a new and improved virtual design of barb geometry is proposed and validated. It also provides the first report on how to develop a virtual bench top suture/tissue pullout testing environment.}, number={5}, journal={Journal of Biomechanics}, publisher={Elsevier BV}, author={Ingle, N.P. and King, M.W. and Zikry, M.A.}, year={2010}, month={Mar}, pages={879–886} }
 @article{vella_chadderdon_selfridge_schultz_webb_park_peters_zikry_2010, title={Full-spectrum interrogation of fiber Bragg gratings at 100 kHz for detection of impact loading}, volume={21}, ISSN={["1361-6501"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77958167493&partnerID=MN8TOARS}, DOI={10.1088/0957-0233/21/9/094009}, abstractNote={This paper explains key innovations that allow monitoring of detailed spectral features of an FBG in response to impact loading. The new system demonstrates capture of FBG spectral data at rates of 100 kHz. Rapid capture of the entire reflection spectrum at such high reading rates shows important features that are missed when using systems that merely track changes in the peak location of the spectrum. The update rate of 100 kHz allows resolution of features that occur on transient time scales as short as 10 µs. This paper gives a detailed description of the unique features of the apparatus and processes used to capture the data at such a rapid rate. Furthermore, we demonstrate this interrogation scheme on a composite laminate system during impact.}, number={9}, journal={MEASUREMENT SCIENCE AND TECHNOLOGY}, author={Vella, T. and Chadderdon, S. and Selfridge, R. and Schultz, S. and Webb, S. and Park, C. and Peters, K. and Zikry, M.}, year={2010}, month={Sep} }
 @inproceedings{chadderdon_vella_selfridge_schultz_webb_park_peters_zikry_2010, title={High-speed full-spectrum interrogation of fiber Bragg gratings for composite impact sensing}, volume={7648}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77953516554&partnerID=MN8TOARS}, DOI={10.1117/12.847662}, abstractNote={This paper presents a means for the high repetition rate interrogation of fiber Bragg gratings (FBG's). The new system highlights a method that allows a tradeoff between the full spectrum capture rate and the wavelength range and/or the spectral resolution of the technique. Rapid capture of the entire reflection spectrum at high interrogation rates shows important features that are missed when using methods that merely track changes in the peak location of the spectrum. The essential feature of the new system is that it incorporates a MEMs tunable filter driven by a variable frequency openloop sinusoidal source. The paper demonstrates the new system on a laminated composite system under impact loading.}, booktitle={Proceedings of SPIE - The International Society for Optical Engineering}, author={Chadderdon, S. and Vella, T. and Selfridge, R. and Schultz, S. and Webb, S. and Park, C. and Peters, K. and Zikry, M.}, year={2010} }
 @article{webb_peters_zikry_vella_chadderdon_selfridge_schultz_2010, title={Impact induced damage assessment in composite laminates through embedded fiber Bragg gratings}, volume={7648}, ISSN={["1996-756X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77953525959&partnerID=MN8TOARS}, DOI={10.1117/12.847543}, abstractNote={In this study we evaluate the measurements of fiber Bragg sensor spectra from a sensor embedded in a composite laminate subjected to multiple low velocity impacts. The full-spectral response of the sensor is interrogated in reflection at 100 kHz during the impact events. The measurement of the time dependent spectra features are compared with previous results obtained at a 534 Hz interrogation rate. With the increased interrogation rate, we can observe a smooth transition in the full-spectra response of the sensor between strikes and the presence of peak-splitting due to transverse compression from the beginning of the laminate lifetime. Finally, at the 100 kHz acquisition rate, it is possible to determine the maximum wavelength and accurately determine the duration of the impact event for all of the strikes.}, journal={SMART SENSOR PHENOMENA, TECHNOLOGY, NETWORKS, AND SYSTEMS 2010}, author={Webb, S. and Peters, K. and Zikry, M. A. and Vella, T. and Chadderdon, S. and Selfridge, R. and Schultz, S.}, year={2010} }
 @article{park_peters_zikry_haber_schultz_selfridge_2010, title={Peak wavelength interrogation of fiber Bragg grating sensors during impact events}, volume={19}, ISSN={["1361-665X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77949894501&partnerID=MN8TOARS}, DOI={10.1088/0964-1726/19/4/045015}, abstractNote={In this paper, we embed fiber Bragg grating (FBG) sensors in graphite fiber–epoxy woven composite laminates to detect evolving damage modes. The peak wavelengths of the FBG sensors are interrogated at 625 and 295 kHz, while the laminates are subjected to 11.0 J low-velocity impact events. It is demonstrated that 295 kHz interrogation is sufficient for accurately collecting the dynamic response of the sensors. The FBG sensors embedded at the laminate midplanes successfully reconstructed the global laminate response to impact. The maximum and full width at half-maximum (FWHM) for the relative strain histories demonstrated the same trends as the maximum and FWHM of the contact force histories measured from the impactor. More noise was present in the strain histories obtained from the FBG sensors than the contact force histories, as the embedded FBGs were sensitive to local perturbations in the stress state. The FBG sensors embedded below the midplane of the laminate were closer to the damage regions and measured complex strain histories. In one case, this strain history revealed the presence of delamination.}, number={4}, journal={SMART MATERIALS AND STRUCTURES}, author={Park, Chun and Peters, Kara and Zikry, Mohammed and Haber, Todd and Schultz, Stephen and Selfridge, Richard}, year={2010}, month={Apr} }
 @article{dongare_rajendran_lamattina_zikry_brenner_2010, title={Tension–compression asymmetry in nanocrystalline Cu: High strain rate vs. quasi-static deformation}, volume={49}, ISSN={0927-0256}, url={http://dx.doi.org/10.1016/j.commatsci.2010.05.004}, DOI={10.1016/j.commatsci.2010.05.004}, abstractNote={Large-scale molecular dynamics (MD) simulations are used to understand the yield behavior of nanocrystalline Ni and Cu with grain sizes ⩽10 nm at high strain rates. The calculated flow stress values at a strain rate of 109 s−1 suggest an asymmetry in the strength values in tension and compression with the nanocrystalline metal being stronger in compression than in tension. This tension–compression strength asymmetry is observed to decrease with a decrease in grain size of the nanocrystalline metal up to a grain size of 4 nm, after which, a further decrease in grain size results in an increase in the strength asymmetry. The effect of strain rate on the yield behavior of nanocrystalline metals as obtained from MD simulations is discussed and compared with that reported in the literature obtained by molecular statics simulations for quasi-static loading conditions.}, number={2}, journal={Computational Materials Science}, publisher={Elsevier BV}, author={Dongare, Avinash M. and Rajendran, Arunachalam M. and LaMattina, Bruce and Zikry, Mohammed A. and Brenner, Donald W.}, year={2010}, month={Aug}, pages={260–265} }
 @article{park_peters_zikry_2010, title={The Effects of Embedded Optical Fiber Density on the Impact Response and Lifetime of Laminated Composites}, volume={21}, ISSN={["1530-8138"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78650907528&partnerID=MN8TOARS}, DOI={10.1177/1045389x10390250}, abstractNote={ Graphite fiber/epoxy, two-dimensional woven composite laminates were fabricated with various densities of embedded optical fibers at the midplane. The specimens were subjected to multiple low-velocity impacts until failure, as the energy dissipated by the laminate and the maximum contact force were measured for each impact event. Cumulative probability distributions were calculated for each embedded optical fiber density, from which probability distribution functions in terms of embedded optical fiber density were extrapolated. At low fiber densities, the total energy dissipated by the specimen and the total maximum contact force over the lifetime of the specimen decreased rapidly with increasing optical fiber density. After a threshold embedded optical fiber density, the optical fibers dominated the failure mode of the laminate and the laminate lifetime, and the overall stiffness was not affected by the embedded optical fiber density. The obtained probability distribution functions could be applied for future optimization of embedded sensor placement for smart composite structures. }, number={18}, journal={JOURNAL OF INTELLIGENT MATERIAL SYSTEMS AND STRUCTURES}, author={Park, Chun and Peters, Kara and Zikry, Mohammed}, year={2010}, month={Dec}, pages={1819–1829} }
 @article{park_peters_zikry_2010, title={The Role of Embedded Sensors in Damage Assessment of Composite Laminates}, volume={7648}, ISSN={["0277-786X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77953489216&partnerID=MN8TOARS}, DOI={10.1117/12.847634}, abstractNote={Various densities of optical fibers are embedded into a total of eighty woven, graphite fiber-epoxy composite laminates, for which the response to low velocity impacts are evaluated. The goal of this work is to determine the role of hostsensor interaction on the lifetime of the host material system. The woven composites are subjected to multiple impacts at 14.5 J until perforation of the specimen. We obtain the energy dissipated by the laminate and the maximum contact force between the impactor laminate for each strike. From these experimental data we calculate the statistical distribution of the total energy dissipated at failure as a function of embedded optical fiber density. The total dissipated energy, a measure of the specimen lifetime, decreased with increasing embedded optical fiber density, however remained constant after a threshold density was reached. The total maximum contact force per specimen, a measure of the specimen stiffness, continued to decrease with the number of embedded optical fibers.}, journal={SMART SENSOR PHENOMENA, TECHNOLOGY, NETWORKS, AND SYSTEMS 2010}, author={Park, Chun and Peters, Kara and Zikry, Mohammed}, year={2010} }
 @inproceedings{elkhodary_lee_cheeseman_sun_brenner_zikry_2010, title={The effects of precipitates and Mn-bearing particles on the high strain-rate compression of high strength aluminum}, volume={1225}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79952052398&partnerID=MN8TOARS}, booktitle={Materials Research Society Symposium Proceedings}, author={Elkhodary, K. and Lee, W. and Cheeseman, B. and Sun, L. and Brenner, D. and Zikry, M.}, year={2010}, pages={19–23} }
 @inproceedings{rezvanian_zikry_2010, title={Thermo-mechanical modeling of RF MEMS devices}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-79957982395&partnerID=MN8TOARS}, DOI={10.1109/THETA.2010.5766380}, abstractNote={Time-dependent thermoelectromechanical behavior of metal contacts in microelectromechanical system (MEMS) devices and packaging is studied. The analysis relates the electrical constriction resistance to contact temperature and contact surface evolution over time, using a microcontact asperity creep model for metal microcontacts under continual applied or residual stresses. The effects of contact temperature on constriction resistance are investigated. This work provides guidance toward the rational design of microcontacts with enhanced reliabilities by better defining variables that control the electrical resistance at such microcontcats.}, booktitle={2010 3rd International Conference on Thermal Issues in Emerging Technologies, Theory and Applications - Proceedings, ThETA3 2010}, author={Rezvanian, O. and Zikry, M.A.}, year={2010}, pages={63–67} }
 @inproceedings{dongare_rajendran_lamattina_zikry_brenner_elert_furnish_anderson_proud_butler_2009, title={ATOMISTIC STUDIES OF VOID-GROWTH BASED YIELD CRITERIA IN SINGLE CRYSTAL CU AT HIGH STRAIN RATES}, volume={1195}, url={http://dx.doi.org/10.1063/1.3295254}, DOI={10.1063/1.3295254}, abstractNote={Dynamic fracture of ductile metals is attributed to the nucleation, growth, and coalescence of voids which eventually form the fracture surface. Large‐scale MD simulations are used to model void growth behavior in single crystal Cu at high strain rates. Yielding is studied for systems with various values of void fractions as well as combinations of loading conditions. The calculated yield surface of single crystal Cu for varying void fractions indicates the inability of traditional continuum models to predict void growth at high strain rates.}, publisher={AIP}, author={Dongare, A. M. and Rajendran, A. M. and LaMattina, B. and Zikry, M. A. and Brenner, D. W. and Elert, Mark and Furnish, Michael D. and Anderson, William W. and Proud, William G. and Butler, William T.}, year={2009}, pages={769–772} }
 @article{dongare_rajendran_lamattina_zikry_brenner_2009, title={Atomic scale simulations of ductile failure micromechanisms in nanocrystalline Cu at high strain rates}, volume={80}, ISSN={["1098-0121"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70349914381&partnerID=MN8TOARS}, DOI={10.1103/physrevb.80.104108}, abstractNote={The micromechanisms related to ductile failure during dynamic loading of nanocrystalline Cu are investigated in a series of large-scale molecular-dynamics MD simulations. Void nucleation, growth, and coalescence are studied for a nanocrystalline Cu system with an average grain size of 6 nm under conditions of uniaxial tensile strain and triaxial tensile strain at a strain rate of 10 8 s �1 . The MD simulations of deformation of the nanocrystalline system under conditions of triaxial tensile stress show random nucleation of voids at grain boundaries and/or triple point junctions. The initial shape of the voids is nonspherical due to growth of the voids along the grain boundaries. Void growth is observed to occur by the creation of a shell of disordered atoms around the voids and not by nucleation of dislocations from the void surface. Void coalescence occurs by the shearing of the disordered regions in between the voids. The nucleation and growth of voids result in the relaxation of tensile stresses, after which growth of the voids is slower. The slower growth is accompanied by recrystallization of the surrounding disordered regions resulting in near-spherical shapes of the voids.}, number={10}, journal={PHYSICAL REVIEW B}, author={Dongare, Avinash M. and Rajendran, Arunachalam M. and LaMattina, Bruce and Zikry, Mohammed A. and Brenner, Donald W.}, year={2009}, month={Sep} }
 @article{pearson_zikry_wahl_2009, title={Computational design of thin-film nanocomposite coatings for optimized stress and velocity accommodation response}, volume={267}, ISSN={["1873-2577"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-65949109936&partnerID=MN8TOARS}, DOI={10.1016/j.wear.2008.11.027}, abstractNote={The tailoring of thin-film coatings comprised of high strength nano-grained constituents is investigated by new microstructurally based finite-element techniques for applications related to the wear, durability, and performance of these coatings over a broad range of temperatures and loading conditions. These coatings are comprised of brittle phases, diamond-like carbon and partially stabilized zirconia and ductile constituents, such as gold and molybdenum. The effects of wear, contact transfer films, grain sizes and distributions, grain spacing and strength are used to determine the optimal thin-film coating compositions. Comparisons are made with experimental measurements pertaining to durability and wear for validation and for the development of design guidelines for thin-film nanocomposite coatings.}, number={5-8}, journal={WEAR}, author={Pearson, J. D. and Zikry, M. A. and Wahl, K.}, year={2009}, month={Jun}, pages={1137–1145} }
 @article{hatem_zikry_2009, title={Dislocation density crystalline plasticity modeling of lath martensitic microstructures in steel alloys}, volume={89}, ISSN={["1478-6443"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70449117497&partnerID=MN8TOARS}, DOI={10.1080/14786430903185999}, abstractNote={A three-dimensional multiple-slip dislocation density-based crystalline formulation, specialized finite-element formulations and Voronoi tessellations adapted to martensitic orientations were used to investigate large strain inelastic deformation modes and dislocation density evolution in martensitic microstructures. The formulation is based on accounting for variant morphologies and orientations, retained austenite and initial dislocation densities that are uniquely inherent to martensitic microstructures. The effects of parent austenite orientation and retained austenite were also investigated for heterogeneous fcc/bcc crystalline structures. Furthermore, the formulation was used to investigate microstructures mapped directly from SEM/EBSD images of martensitic steel alloys. The analysis indicates that variant morphology and orientations have a direct effect on dislocation density accumulation and inelastic localization in martensitic microstructures, and that lath directions, orientations and arrangements are critical characteristics of high strength martensitic deformation and behavior.}, number={33}, journal={PHILOSOPHICAL MAGAZINE}, author={Hatem, T. M. and Zikry, M. A.}, year={2009}, pages={3087–3109} }
 @inproceedings{propst_peters_zikry_kunzler_zhu_wirthlin_selfridge_schultz_2009, title={Dynamic, full-spectral interrogation of fiber bragg grating sensors for impact testing of composite laminates}, volume={7503}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70449404871&partnerID=MN8TOARS}, DOI={10.1117/12.835406}, abstractNote={This paper presents the full-spectral measurement of fiber Bragg grating sensor responses during impact testing of composite laminates. The sensors are embedded in carbon fiber/epoxy laminates which are subjected to multiple low velocity impacts until perforation of the laminate occurs. Applying a recently developed high-speed interrogator, the Bragg grating sensor interrogation is demonstrated at 534 Hz over a 14.9 nm bandwidth. The measurement of the transient response of the grating sensors during impact reveals unique spectral signatures that could not be detected through peak-wavelength monitoring or post-impact full-spectral scanning of the sensors, including local relaxation of the laminate.}, booktitle={Proceedings of SPIE - The International Society for Optical Engineering}, author={Propst, A. and Peters, K. and Zikry, M.A. and Kunzler, W. and Zhu, Z. and Wirthlin, M. and Selfridge, R. and Schultz, S.}, year={2009} }
 @article{sun_irving_zikry_brenner_2009, title={First-principles investigation of the structure and synergistic chemical bonding of Ag and Mg at the Al vertical bar Omega interface in a Al-Cu-Mg-Ag alloy}, volume={57}, ISSN={["1873-2453"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-65849380009&partnerID=MN8TOARS}, DOI={10.1016/j.actamat.2009.04.006}, abstractNote={Density functional theory was used to characterize the atomic structure and bonding of the Al | Ω interface in a Al–Cu–Mg–Ag alloy. The most stable interfacial structure was found to be connected by Al–Al bonds with a hexagonal Al lattice on the surface of the Ω phase sitting on the vacant hollow sites of the Al {1 1 1} matrix plane. The calculations predict that when substituted separately for Al at this interface, Ag and Mg do not enhance the interface stability through chemical bonding. Combining Ag and Mg, however, was found to chemically stabilize this interface, with the lowest-energy structure examined being a bi-layer with Ag atoms adjacent to the Al matrix and Mg adjacent to the Ω phase. This study provides an atomic arrangement for the interfacial bi-layer observed experimentally in this alloy.}, number={12}, journal={ACTA MATERIALIA}, author={Sun, Lipeng and Irving, Douglas L. and Zikry, Mohammed A. and Brenner, D. W.}, year={2009}, month={Jul}, pages={3522–3528} }
 @article{schultz_kunzler_zhu_wirthlin_selfridge_propst_zikry_peters_2009, title={Full-spectrum interrogation of fiber Bragg grating sensors for dynamic measurements in composite laminates}, volume={18}, ISSN={["1361-665X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70350668824&partnerID=MN8TOARS}, DOI={10.1088/0964-1726/18/11/115015}, abstractNote={This paper presents a new means for collecting fiber Bragg grating (FBG) data during drop-tower measurements used to assess damage to composite structures. The high repetition-rate collection process reveals transient features that cannot be resolved in quasi-static measurements. The experiments made at a repetition rate of about 500 Hz show that the detected FBG spectrum broadens for a short period of time and relaxes quickly to a narrower static state. Furthermore, this relaxation time increases dramatically as the strike count increases. The information gained by such measurements will enhance the ability to characterize and distinguish failure modes and predict the remaining lifetime in composite laminate structures.}, number={11}, journal={SMART MATERIALS AND STRUCTURES}, author={Schultz, S. and Kunzler, W. and Zhu, Z. and Wirthlin, M. and Selfridge, R. and Propst, A. and Zikry, M. and Peters, K.}, year={2009}, month={Nov} }
 @article{shi_zikry_2009, title={Grain size, grain boundary sliding, and grain boundary interaction effects on nanocrystalline behavior}, volume={520}, ISSN={["1873-4936"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-67650726010&partnerID=MN8TOARS}, DOI={10.1016/j.msea.2009.05.012}, abstractNote={A dislocation–density grain boundary (GB) interaction scheme, a GB misorientation dependent dislocation–density relation, and a grain boundary sliding (GBS) model are presented to account for the behavior of nanocrystalline aggregates with grain sizes ranging from 25 nm to 200 nm. These schemes are coupled to a dislocation–density multiple slip crystalline plasticity formulation and specialized finite element algorithms to predict the response of nanocrystalline aggregates. These schemes are based on slip system compatibility, local resolved shear stresses, and immobile and mobile dislocation–density evolution. A conservation law for dislocation–densities is used to balance dislocation–density absorption, transmission and emission from the GB. The relation between yield stresses and grain sizes is consistent with the Hall–Petch relation. The results also indicate that GB sliding and grain-size effects affect crack behavior by local dislocation–density and slip evolution at critical GBs. Furthermore, the predictions indicate that GBS increases with decreasing grain sizes, and results in lower normal stresses in critical locations. Hence, GBS may offset strength increases associated with decreases in grain size.}, number={1-2}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Shi, J. and Zikry, M. A.}, year={2009}, month={Sep}, pages={121–133} }
 @article{shi_zikry_2009, title={Grain-boundary interactions and orientation effects on crack behavior in polycrystalline aggregates}, volume={46}, ISSN={["1879-2146"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-69249219074&partnerID=MN8TOARS}, DOI={10.1016/j.ijsolstr.2009.07.019}, abstractNote={A dislocation-density grain–boundary interaction scheme has been developed to account for the interrelated dislocation-density interactions of emission, absorption and transmission in GB regions. The GB scheme is based on slip-system compatibility, local resolved shear stresses, and immobile and mobile dislocation-density accumulation at critical GB locations. To accurately represent dislocation-density evolution, a conservation law for dislocation-densities is used to balance dislocation-density absorption, transmission and emission from the GB. The behavior of f.c.c. polycrystalline copper, with different random low and high angle GBs, are investigated for different crack lengths. For aggregates with random low angle GBs, dislocation-density transmission dominates at the GBs, which can indicate that the low angle GB will not significantly change crack growth directions. For aggregates with random high angle GBs, extensive dislocation-density absorption and pile-ups occur. The high stresses associated with this behavior, along the GBs, can result in intergranular crack growth due to potential crack nucleation sites in the GB.}, number={21}, journal={INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES}, author={Shi, J. and Zikry, M. A.}, year={2009}, month={Oct}, pages={3914–3925} }
 @inproceedings{kunzler_zhu_wirthlin_selfridge_schultz_propst_peters_zikry_2009, title={High repetition-rate full-spectrum interrogation of FBG sensors for dynamic measurements in composite laminates}, volume={7293}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-66749184331&partnerID=MN8TOARS}, DOI={10.1117/12.816384}, abstractNote={This paper presents a new means for collecting fiber Bragg grating (FBG) data during drop tower measurements used to assess damage to composite structures. The high repetition-rate collection process reveals transient features that cannot be resolved in quasi-static measurements. The experiments made at a repetition rate of about 500 Hz show that the detected FBG spectrum broadens for a short period of time and relaxes quickly to a narrower static state. Furthermore, this relaxation time increases dramatically as the strike count increases. The information gained by such measurements will enhance the ability to characterize and distinguish failure modes and predict remaining lifetime in composite laminate structures.}, booktitle={Proceedings of SPIE - The International Society for Optical Engineering}, author={Kunzler, W. and Zhu, Z. and Wirthlin, M. and Selfridge, R. and Schultz, S. and Propst, A. and Peters, K. and Zikry, M.}, year={2009} }
 @article{garrett_peters_zikry_2009, title={In-situ impact-induced damage assessment of woven composite laminates through a fibre Bragg grating sensor network}, volume={113}, ISSN={["0001-9240"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-68349093775&partnerID=MN8TOARS}, DOI={10.1017/S0001924000003031}, abstractNote={Abstract}, number={1144}, journal={AERONAUTICAL JOURNAL}, author={Garrett, R. C. and Peters, K. J. and Zikry, M. A.}, year={2009}, month={Jun}, pages={357–370} }
 @article{rezvanian_zikry_2009, title={Inelastic contact behavior of crystalline asperities in rf MEMS devices}, volume={131}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77955373765&partnerID=MN8TOARS}, DOI={10.1115/1.3026545}, abstractNote={Microelectromechanical systems (MEMS), particularly those with radio frequency (rf) applications, have demonstrated significantly better performance over current electromechanical and solid-state technologies. Surface roughness and asperity microcontacts are critical factors that can affect contact behavior at scales ranging from the nano to the micro in MEMS devices. Recent investigations at the continuum level have underscored the importance of microstructural effects on the inelastic behavior of asperity microcontacts. Hence, a microstructurally based approach that accounts for the inhomogeneous deformation of the asperity microcontacts under cyclic loading and that is directly related to asperity physical scales and anisotropies can provide a detailed understanding of the deformation mechanisms associated with asperity microcontacts so that guidelines can be incorporated in the design and fabrication process to effectively size critical components and forces for significantly improved device durability and performance. A physically based microstructural representation of fcc crystalline materials that couples a multiple-slip crystal plasticity formulation to dislocation densities is used in a specialized finite-element modeling framework. The asperity model and the loading conditions are based on realistic service conditions consistent with rf MEMS with metallic normal contacts. The evolving microstructure, stress fields, contact width, hardness, residual effects, and the localized phenomena that can contribute to failure initiation and evolution in the flattening of single crystal gold asperity microcontacts are characterized for a loading-unloading cycle. It is shown that the nonuniform loading conditions due to asperity geometry and contact loading and the size effects due to asperity dimensions result in significant contribution of the geometrically necessary dislocation densities to stress, deformation, and microstructural evolution of crystalline asperities. This is not captured in modeling efforts based on von Mises continuum plasticity formulations. Residual strains and stresses are shown to develop during the cyclic loading. Localized tensile stress regions are shown to develop due to stress reversal and strain hardening during both loading and unloading regimes. Hardness predictions also indicate that nano-indentation hardness values of the contact material can overestimate the contact force in cases, where a rigid flat surface is pressed on a surface roughness asperity.}, number={1}, journal={Journal of Engineering Materials and Technology}, author={Rezvanian, O. and Zikry, Mohammed}, year={2009}, pages={0110021–01100210} }
 @article{elkhodary_sun_irving_brenner_ravichandran_zikry_2009, title={Integrated experimental, atomistic, and microstructurally based finite element investigation of the dynamic compressive behavior of 2139 aluminum}, volume={76}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77952634990&partnerID=MN8TOARS}, DOI={10.1115/1.3129769}, abstractNote={The objective of this study was to identify the microstructural mechanisms related to the high strength and ductile behavior of 2139-Al, and how dynamic conditions would affect the overall behavior of this alloy. Three interrelated approaches, which span a spectrum of spatial and temporal scales, were used: (i) The mechanical response was obtained using the split Hopkinson pressure bar, for strain-rates ranging from 1.0×10−3 s to 1.0×104 s−1. (ii) First principles density functional theory calculations were undertaken to characterize the structure of the interface and to better understand the role played by Ag in promoting the formation of the Ω phase for several Ω-Al interface structures. (iii) A specialized microstructurally based finite element analysis and a dislocation-density based multiple-slip formulation that accounts for an explicit crystallographic and morphological representation of Ω and θ′ precipitates and their rational orientation relations were conducted. The predictions from the microstructural finite element model indicated that the precipitates continue to harden and also act as physical barriers that impede the matrix from forming large connected zones of intense plastic strain. As the microstructural FE predictions indicated, and consistent with the experimental observations, the combined effects of θ′ and Ω, acting on different crystallographic orientations, enhance the strength and ductility, and reduce the susceptibility of 2139-Al to shear strain localization due to dynamic compressive loads.}, number={5}, journal={Journal of Applied Mechanics, Transactions ASME}, author={Elkhodary, K. and Sun, L. and Irving, D.L. and Brenner, D.W. and Ravichandran, G. and Zikry, Mohammed}, year={2009}, pages={1–9} }
 @article{pearson_zikry_wahl_2009, title={Microstructural modeling of adaptive nanocomposite coatings for durability and wear}, volume={266}, ISSN={["1873-2577"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-64749097639&partnerID=MN8TOARS}, DOI={10.1016/j.wear.2009.02.004}, abstractNote={Adaptive thin-film nanocomposite coatings comprised of crystalline ductile phases of gold and molybdenum disulfide, and brittle phases of diamond like carbon (DLC) and ytrria stabilized zirconia (YSZ) have been investigated by specialized microstructurally based finite-element techniques. One of the major objectives is to determine optimal crystalline and amorphous compositions and behavior related to wear and durability over a wide range of thermo-mechanical conditions. The interrelated effects of microstructural characteristics such as grain shapes and sizes, local material behavior due to interfacial stresses and strains, varying amorphous and crystalline compositions, and transfer film adhesion on coating behavior have been studied. The computational predictions, consistent with experimental observations, indicate specific interfacial regions between DLC and ductile metal inclusions are critical regions of stress and strain accumulation that can be precursors to material failure and wear. It is shown by varying the composition, resulting in tradeoffs between lubrication, toughness, and strength, the effects of these critical stresses and strains can be controlled for desired behavior. A mechanistic model to account for experimentally observed transfer film adhesion modes was also developed, and based on these results, it was shown that transfer film bonding has a significant impact on stress and wear behavior.}, number={9-10}, journal={WEAR}, author={Pearson, James D. and Zikry, Mohammed A. and Wahl, Kathryn J.}, year={2009}, month={Apr}, pages={1003–1012} }
 @article{ma_zikry_2009, title={Microstructural modeling of nanoidentational polycrsytalline gold with random high angle grain-boundaries}, volume={19}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-64649089133&partnerID=MN8TOARS}, number={1-2}, journal={Reviews on Advanced Materials Science}, author={Ma, J.B. and Zikry, M.A.}, year={2009}, pages={78–92} }
 @inproceedings{hatem_zikry_2009, title={Microstructural modelling of failure modes in crystalline materials}, volume={8}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84869835552&partnerID=MN8TOARS}, booktitle={12th International Conference on Fracture 2009, ICF-12}, author={Hatem, T.M. and Zikry, M.A.}, year={2009}, pages={5923–5932} }
 @article{hatem_zikry_2009, title={Modeling of Lath Martensitic Microstructures and Failure Evolution in Steel Alloys}, volume={131}, ISSN={["0094-4289"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77955251717&partnerID=MN8TOARS}, DOI={10.1115/1.3183780}, abstractNote={A multiple-slip dislocation-density-based crystalline formulation, specialized finite-element formulations, and Voronoi tessellations adapted to martensitic orientations were used to investigate dislocation-density activities and crack tip blunting in high strength martensitic steels. The formulation is based on accounting for variant morphologies and orientations, retained austenite, and initial dislocations densities that are uniquely inherent to martensitic microstructures. The effects of variant distributions and arrangements are investigated for different crack and void interaction distributions and arrangements. The analysis indicates that for certain orientations related to specific variant block arrangements, which correspond to random low angle orientations, cracks can be blunted by dislocation-density activities along transgranular planes. For other variant block arrangements, which correspond to random high angle orientations, sharp crack growth can occur due to dislocation activities along intergranular planes.}, number={4}, journal={JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME}, author={Hatem, T. M. and Zikry, M. A.}, year={2009}, month={Oct} }
 @article{ma_zikry_2009, title={Nanoindentation and microstructural evolution of polycrystalline gold}, volume={24}, ISSN={["2044-5326"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-63149171212&partnerID=MN8TOARS}, DOI={10.1557/jmr.2009.0133}, abstractNote={A finite-element (FE) microstructurally based dislocation density multiple-slip crystalline formulation that is coupled to molecular dynamic (MD) simulations has been used to predict how nanoindentation affects behavior in crystalline gold polycrystals at scales that span the molecular to the continuum level. Displacement profiles from MD simulations of nanoindentation were used to obtain scaling relations, which are based on indented depths, grain sizes, and grain aggregate distributions. These scaling relations are then used in a microstructurally based FE formulation that accounts for dislocation density evolution, crystalline structures, and grain sizes. This hierarchical methodology can be used to ascertain inelastic effects, such as shear-slip distribution, pressure accumulation, and dislocation density and slip-rate evolution at physical scales that are commensurate with ductile behavior at the microstructural scale.}, number={3}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Ma, Jeong Beom and Zikry, M. A.}, year={2009}, month={Mar}, pages={1093–1104} }
 @article{pearson_gao_zikry_harrison_2009, title={Nanoindentation of model diamond nanocomposites: Hierarchical molecular dynamics and finite-element simulations}, volume={47}, ISSN={["1879-0801"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70449134804&partnerID=MN8TOARS}, DOI={10.1016/j.commatsci.2009.06.007}, abstractNote={Complementary molecular dynamics (MD) and finite-element (FE) simulations of model diamond nanocomposites (MDN) subjected to nanoindentation were undertaken to understand how contact behavior pertaining to the surface morphology of MDN surfaces can be spanned from the molecular to the continuum scale. The MD simulations determined that the behavior inside the contact region is influenced by atomic-scale features on the tip and surface, indent location, grain tilt and roughness of the MDN surfaces. In addition, if the atomic-scale surface morphology is treated as a surface roughness within the FE simulations, the same grain orientations, and similar elastic properties are used for both MD and FE simulations, there is reasonable agreement between the contact pressures for relatively low indentation loads and shallow substrates. For larger loads, the contact pressures from the FE simulations deviate somewhat from the MD results near the center of the contact. The contact behavior for length scales that are prohibitive for MD models (e.g., deep substrates) was also examined using FE simulations. This allowed for a detailed investigation of how contact conditions and stick-slip events within the contact evolve as a function of contact pressure and continuum surface stresses.}, number={1}, journal={COMPUTATIONAL MATERIALS SCIENCE}, author={Pearson, James D. and Gao, Guangtu and Zikry, Mohammed A. and Harrison, Judith A.}, year={2009}, month={Nov}, pages={1–11} }
 @inproceedings{pan_dawson_krim_baker_pearson_zikry_vovoedin_2009, title={Nanoscale design of adaptive tribological coatings}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70349869620&partnerID=MN8TOARS}, booktitle={2008 Proceedings of the STLE/ASME International Joint Tribology Conference, IJTC 2008}, author={Pan, L. and Dawson, B. and Krim, J. and Baker, C. and Pearson, J. and Zikry, M. and Vovoedin, A.}, year={2009}, pages={65–67} }
 @article{krim_dawson_barefoot_pan_pearson_zikry_baker_voevodin_2009, title={Nanoscale design of adaptive tribological coatings for gold-ytrium based nanocomposites}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77749339040&partnerID=MN8TOARS}, DOI={10.1179/175158309X12586382418373}, abstractNote={Nanocomposites hold great promise for space and ambient applications on account of their ability to adapt to and exhibit low friction and wear rates in constantly varying environmental conditions. In order to explore the impact of nanocrystalline grain size and fractal scaling properties on tribological performance, the authors have performed experimental and theoretical studies examining nanotribological properties of gold–ytrium based nanocomposites. These include modelling the impact of grain size on film stress and wear attributes and the documentation of surface region grain size distributions. The authors’ modelling results associate smaller grain sizes with lower wear, consistent with experimental observations for the range of grain sizes studied. The findings show promise for nanoscale customisation of coatings so as to tailor them at the nanoscale in an application specific manner.}, number={4}, journal={Tribology - Materials, Surfaces and Interfaces}, author={Krim, J. and Dawson, B.D. and Barefoot, K. and Pan, L. and Pearson, J. and Zikry, M. and Baker, C. and Voevodin, A.}, year={2009}, pages={145–150} }
 @inproceedings{propst_garrett_park_peters_zikry_2009, title={Sensor networks for in-situ failure identification in woven composites}, volume={7293}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-66749128673&partnerID=MN8TOARS}, DOI={10.1117/12.815743}, abstractNote={This paper presents experimental measurements of the response of woven composite laminates to multiple low-velocity impacts. Damage initiation and progression occur at multiple physical and temporal scales in heterogeneous materials, including fiber breakage, matrix cracking, delamination and matrix relaxation. The sensor/interrogators were therefore chosen specifically to provide insight into the order and progression of different failure modes. Measurements of the contact force between the impactor and composite are measured throughout impact. Additionally, the dissipated energy per impact event is also calculated from the impactor velocity. Surface mounted and embedded fiber Bragg grating sensors are used for the measurement of the laminate response. Peak wavelength measurements are performed during impact at 1 kHz, while full-spectral scanning is performed at 5 Hz during relaxation period of the laminate immediately after impact and quasi-statically to measure post-impact residual strain states within the laminate. The results highlight the depth of information embedded within the FBG full-spectral data sensors, as well as the added insight to be gained from combined global-local measurements.}, booktitle={SMASIS 2009, vol 2}, author={Propst, A. and Garrett, R. and Park, C. and Peters, K. and Zikry, M.}, year={2009}, pages={477–485} }
 @inproceedings{park_propst_peters_zikry_2009, title={Sensor networks for in-situ failure identification in woven composites}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-77953777875&partnerID=MN8TOARS}, DOI={10.1115/SMASIS2009-1283}, abstractNote={This paper presents experimental measurements of the response of woven composite laminates to multiple low-velocity impacts. Damage initiation and progression occur at multiple physical and temporal scales in heterogeneous materials, including fiber breakage, matrix cracking, delamination and matrix relaxation. The sensor networks/interrogators were therefore chosen specifically to provide insight into the order and progression of different failure modes. Measurements of the contact force between the impactor and composite are measured throughout impact. Additionally, the dissipated energy per impact event is also calculated from the impactor velocity. Surface mounted and embedded fiber Bragg grating sensors are used for the measurement of the laminate response. Peak wavelength measurements are performed during impact at 1 kHz, while full-spectral scanning is performed at 5 Hz during relaxation period of the laminate immediately after impact and quasi-statically to measure post-impact residual strain states within the laminate. The results highlight the depth of information embedded within the FBG full-spectral data sensors, as well as the added insight to be gained from combined global-local measurements.}, booktitle={Proceedings of the ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems 2009, SMASIS2009}, author={Park, C. and Propst, A. and Peters, K. and Zikry, M.A.}, year={2009}, pages={477–485} }
 @article{hatem_zikry_2009, title={Shear pipe effects and dynamic shear-strain localization in martensitic steels}, volume={57}, ISSN={["1873-2453"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-67849128240&partnerID=MN8TOARS}, DOI={10.1016/j.actamat.2009.06.028}, abstractNote={A three-dimensional, multiple-slip, dislocation-density-based crystalline formulation, specialized finite-element formulations, and Voronoi tessellations adapted to martensitic orientations were used to investigate dislocation-density activities and shear-strain localization in high-strength martensitic steels under quasi-static and dynamic loading conditions. The formulation is based on accounting for variant morphologies and orientations, retained austenite, and initial dislocations densities that are uniquely inherent to martensitic microstructures. The effects of variant distributions and arrangements, loading directions, and microcracks on the evolution of shear-strain localization are investigated. The analysis indicates that shear-strain localization occurs due to slip-system compatibilities relative to the loading direction and the long direction of laths, which result in shear-strain accumulation. At specific triple junctions, rotation misalignments due to lattice and slip incompatibilities occur, and these incompatibilities are further exacerbated by the presence of defects, such as microcracks.}, number={15}, journal={ACTA MATERIALIA}, author={Hatem, T. M. and Zikry, M. A.}, year={2009}, month={Sep}, pages={4558–4567} }
 @article{brown_rezvanian_zikry_krim_2009, title={Temperature dependence of asperity contact and contact resistance in gold RF MEMS switches}, volume={19}, ISSN={0960-1317 1361-6439}, url={http://dx.doi.org/10.1088/0960-1317/19/2/025006}, DOI={10.1088/0960-1317/19/2/025006}, abstractNote={Experimental measurements and modeling predictions were obtained to characterize the electro-mechanical response of two different gold contact radio frequency microelectromechanical system (RF MEMS) switches due to variations in the temperature and applied contact voltage. A three-dimensional surface roughness profile from AFM measurements of the top contact surface of a sample RF MEMS switch was used to obtain modeling predictions of the time-dependent deformation of the asperity microcontacts, real areas of contact, number of asperity microcontacts and constriction resistance. The experimental data indicated a decrease in the overall resistance and a decrease in the creep mechanism at 77 K and 5.6 K when compared to measurements at 293 K. At 293 K, there is more contact area per unit time, and the resistance drop from the increase in real contact area dominates the resistance increase due to asperity heating. At 77 K, the creep rate is reduced, and fewer asperities are in contact. At 5.6 K, the change in contact area over time is small, and the contact resistance measurement is dominated by the Joule heating. The data presented and constriction resistance modeling for gold RF MEMS switches show that temperature plays a significant role in the creep deformation and heating of switch contacts.}, number={2}, journal={Journal of Micromechanics and Microengineering}, publisher={IOP Publishing}, author={Brown, C and Rezvanian, O and Zikry, M A and Krim, J}, year={2009}, month={Jan}, pages={025006} }
 @article{jawad_zikry_2009, title={The Effects of Grain-boundary Orientations on Failure Behavior in FCC Polycrystalline Systems}, volume={18}, ISSN={["1530-7921"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-65449169199&partnerID=MN8TOARS}, DOI={10.1177/1056789508097547}, abstractNote={ A multiple-slip rate-dependent crystalline constitutive formulation that is coupled to the evolutionary equations of mobile and immobile dislocation densities is used with specialized finite-element methodologies to obtain a detailed microstructural prediction of the inelastic deformation and interrelated physical mechanisms that affect different failure modes in f.c.c. crystalline materials. The effects of grain and grain-boundary (GB) orientations, grain shape and size, GB strength, and mechanical properties on the inelastic finite deformation and failure mode mechanisms in polycrystalline aggregates with Σ3 and Σ17b GBs have been investigated. Results from this study are consistent with experimental observations that microstructures with desired material properties, such as resistivity to crack nucleation, can be potentially achieved by the control of grain aggregate size and CSL GB orientations. Furthermore, it is also shown that transgranular failure modes can occur in aggregates with a high frequency of Σ3 GBs, whereas intergranular fracture modes can occur with a high frequency of Σ17b GBs. }, number={4}, journal={INTERNATIONAL JOURNAL OF DAMAGE MECHANICS}, author={Jawad, F. F. and Zikry, M. A.}, year={2009}, month={May}, pages={341–369} }
 @inproceedings{dongare_rajendran_lamattina_zikry_brenner_2008, title={Atomic scale simulations of orientation of loading axis on the growth of voids at the onset of ductile failure in single crystal Cu}, volume={1137}, url={http://dx.doi.org/10.1557/proc-1137-ee08-09-w10-09}, DOI={10.1557/proc-1137-ee08-09-w10-09}, booktitle={Materials Research Society Symposium Proceedings}, publisher={Materials Research Society}, author={Dongare, Avinash M. and Rajendran, Arunachalam and LaMattina, Bruce and Zikry, Mohammed and Brenner, Donald W.}, year={2008}, pages={162–167} }
 @inproceedings{propst_parker_capps_peters_zikry_2008, title={Damage monitoring in woven composites using fiber-Bragg grating sensors on multiple time scales}, volume={2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78149381666&partnerID=MN8TOARS}, DOI={10.1115/SMASIS2008-527}, abstractNote={Low-velocity impact events occurring over the span of a few milliseconds cause changes in composite structures through relaxation and delamination propagation which manifest themselves over the span of several seconds. Changes in embedded fiber Bragg grating sensor response allow the damage in the composite structure to be measured in lieu of simply analyzing the impact event itself. By observing the damage progression and subsequent failure of the sample, the sensor signal response can thus be used to predict the lifetime of the structure. In this paper, we expand previous sensor interrogation and damage identification methodologies by using scanning instrumentation capable of operating over multiple time scales. 2D woven composite specimens are subjected to multiple low velocity impacts while the fiber Bragg grating (FBG) sensor response is monitored in time scales of one millisecond to tens of seconds. A high frequency scanning spectrometer is used to determine the peak Bragg wavelength while scanning the FBG sensor at approximately 1 kHz during and immediately after the impact. Also, a high fidelity slow-scan laser source measures the quasi-static sensor response several seconds to minutes following the impact events. Features of the two measurement sets are used to identify the structural integrity of the laminate specimen after each impact event.}, booktitle={Proceedings of the ASME Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS2008}, author={Propst, A. and Parker, A. and Capps, Z. and Peters, K. and Zikry, M.A.}, year={2008}, pages={185–191} }
 @article{elkhodary_salem_zikry_2008, title={Equal channel angular pressing of canned 2124-Al compacts: Processing, experiments, and modeling}, volume={39A}, ISSN={["1073-5623"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-50149111309&partnerID=MN8TOARS}, DOI={10.1007/s11661-008-9541-2}, number={9}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Elkhodary, K. I. and Salem, H. G. and Zikry, M. A.}, year={2008}, month={Sep}, pages={2184–2192} }
 @inproceedings{elkhodary_lee_cheeseman_brenner_zikry_2008, title={High strain-rate behavior of high strength aluminum alloys}, volume={1137}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70450123718&partnerID=MN8TOARS}, booktitle={Materials Research Society Symposium Proceedings}, author={Elkhodary, K. and Lee, W. and Cheeseman, B. and Brenner, D.W. and Zikry, M.A.}, year={2008}, pages={143–148} }
 @inproceedings{garret_peters_zikry_2008, title={In-situ impact induced damage assessment of woven composite laminates through a FBG sensor network}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-62949086365&partnerID=MN8TOARS}, booktitle={Proceedings of the 4th European Workshop on Structural Health Monitoring}, author={Garret, R. and Peters, K. and Zikry, M.}, year={2008}, pages={825–832} }
 @article{rezvanian_zikry_rajendran_2008, title={Microstructural modeling in f.c.c. crystalline materials in a unified dislocation-density framework}, volume={494}, ISSN={["0921-5093"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-49849087562&partnerID=MN8TOARS}, DOI={10.1016/j.msea.2007.10.091}, abstractNote={A unified physically based microstructural representation of f.c.c. crystalline materials, has been developed such that evolving microstructural behavior at different physical scales can be accurately predicted. This microstructural framework is based on coupling a multiple-slip crystal plasticity formulation to three distinct dislocation densities, which pertain to statistically stored dislocations, geometrically necessary dislocations, and grain boundary dislocations. This interrelated dislocation-density formulation is then used with specialized finite-element modeling techniques to predict the evolving heterogeneous microstructure and the localized phenomena that can contribute to failure initiation as a function of inelastic deformation.}, number={1-2}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Rezvanian, O. and Zikry, M. A. and Rajendran, A. M.}, year={2008}, month={Oct}, pages={80–85} }
 @inproceedings{shi_zikry_hatem_2008, title={Microstructural modeling of failure in polycrystalline materials}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-56649102273&partnerID=MN8TOARS}, booktitle={Advances in Heterogeneous Material Mechanics 2008 - Proceedings of the 2nd International Conference on Heterogeneous Material Mechanics, ICHMM 2008}, author={Shi, J. and Zikry, M.A. and Hatem, T.M.}, year={2008}, pages={3–8} }
 @inproceedings{rezvanian_zikry_2008, title={Modeling of large strain deformation and failure modes in crystalline aggregates}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-51649122510&partnerID=MN8TOARS}, booktitle={TMS Annual Meeting}, author={Rezvanian, O. and Zikry, M.A.}, year={2008}, pages={129–134} }
 @inproceedings{crill_irving_padgett_zikry_brenner_2008, title={Modeling the Effect of Varying Electrical Voltage on the Plastic Deformation of a Single Asperity in Hot-Switched RF MEMS Contacts}, volume={1137}, url={http://dx.doi.org/10.1557/proc-1137-ee10-15}, DOI={10.1557/proc-1137-ee10-15}, booktitle={Materials Research Society Symposium Proceedings}, publisher={Materials Research Society}, author={Crill, John Wesley. and Irving, Douglas and Padgett, Cliff and Zikry, Mohommed and Brenner, Don}, year={2008}, pages={185–190} }
 @inproceedings{rezvanian_zikry_brown_krim_2008, title={RF MEMS behavior, surface roughness and asperity contact}, volume={1052}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-45849129829&partnerID=MN8TOARS}, booktitle={Materials Research Society Symposium Proceedings}, author={Rezvanian, O. and Zikry, M.A. and Brown, C. and Krim, J.}, year={2008}, pages={135–140} }
 @inproceedings{garrett_peters_zikry_2008, title={Sensor networks for in-situ failure identification in woven composites throughout impact}, volume={10 PART A}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-44349189093&partnerID=MN8TOARS}, DOI={10.1115/IMECE2007-42737}, abstractNote={In this study, the development of embedded fiber Bragg grating (FBG) sensor networks within composite materials is investigated. Various densities of optical fibers were embedded within two-dimensional woven composite laminates, and low-velocity impact damage responses were evaluated to determine the effects on the mechanical behavior of the laminates. The woven composites were subjected to multiple strikes at 2 m/s until perforation occurred, and the impactor position and acceleration were monitored throughout each event. From these measurements, we obtained dissipated energies and contact forces for specimens with and without embedded optical fibers. Cross sectional optical micrographs of the specimens were also used to determine the local effects of the embedded fibers on neighboring fibers and the surrounding matrix material, both before and after impact events. Multiple FBG sensors were serially multiplexed together to create a single fiber sensing network capable of monitoring damage for each impact event. Residual strain information was gathered through strain distributions along the FBG sensors to map out the near-field and far-field regions with respect to the impact location. The resulting data will be used to better monitor and predict damage in the composite system when combined with global response data from the laminate itself.}, booktitle={ASME International Mechanical Engineering Congress and Exposition, Proceedings}, author={Garrett, R. and Peters, K. and Zikry, M.A.}, year={2008}, pages={203–210} }
 @article{rezvanian_brown_zikry_kingon_krim_irving_brenner_2008, title={The role of creep in the time-dependent resistance of Ohmic gold contacts in radio frequency microelectromechanical system devices}, volume={104}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.2953072}, DOI={10.1063/1.2953072}, abstractNote={It is shown that measured and calculated time-dependent electrical resistances of closed gold Ohmic switches in radio frequency microelectromechanical system (rf-MEMS) devices are well described by a power law that can be derived from a single asperity creep model. The analysis reveals that the exponent and prefactor in the power law arise, respectively, from the coefficient relating creep rate to applied stress and the initial surface roughness. The analysis also shows that resistance plateaus are not, in fact, limiting resistances but rather result from the small coefficient in the power law. The model predicts that it will take a longer time for the contact resistance to attain a power law relation with each successive closing of the switch due to asperity blunting. Analysis of the first few seconds of the measured resistance for three successive openings and closings of one of the MEMS devices supports this prediction. This work thus provides guidance toward the rational design of Ohmic contacts with enhanced reliabilities by better defining variables that can be controlled through material selection, interface processing, and switch operation.}, number={2}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Rezvanian, O. and Brown, C. and Zikry, M. A. and Kingon, A. I. and Krim, J. and Irving, D. L. and Brenner, D. W.}, year={2008}, month={Jul}, pages={024513} }
 @inproceedings{zhao_dusche_zikry_chopra_ozturk_rozgonyi_2007, title={Correlation of local strain in a TEM sample and in the bulk for a recesses SiGe CMOS structure}, volume={6}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-45849110335&partnerID=MN8TOARS}, DOI={10.1149/1.2727384}, abstractNote={The strain distribution of a strained Si channel in a embedded SiGe PMOS test structure was investigated with experimental convergent beam electron diffraction (CBED) measurements and finite element (FE) calculations. The strain distribution both in a TEM sample and in the bulk sample was examined and correlated. It was found that the magnitude of the longitudinal strain, εx along the [-1,1,0] channel direction, is about 20% higher in the TEM sample than in the bulk; whereas the transverse strain, εy along [-1,-1,0] parallel to the TEM sample thinning direction, is tensile in the TEM sample due to the loss of constraints, while it is zero in the bulk. This combined approach can be sued to successfully explain data from other CBED studies of strained Si devices and is generally applicable for nano scale strain determination in advanced generation CMOS technology nodes.}, number={1}, booktitle={ECS Transactions}, author={Zhao, W. and Dusche, G. and Zikry, M.A. and Chopra, S. and Ozturk, M.C. and Rozgonyi, G.}, year={2007}, pages={23–30} }
 @article{pearson_zikry_prabhugoud_peters_2007, title={Global-local assessment of low-velocity impact damage in woven composites}, volume={41}, ISSN={["1530-793X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-35448962064&partnerID=MN8TOARS}, DOI={10.1177/0021998307078734}, abstractNote={ Global measurements from low-velocity impact experiments and local strain measurements from embedded and surface mounted optical fiber Bragg grating (FBG) sensors were used to obtain failure maps for two- and three dimensional woven composites. These maps delineated five distinct regimes spanning behavior from initial impact to complete penetration. Sensor and host damage were separated by signal intensity and the evolution of Bragg peaks due to repeated impact loads. The results indicate that a local-global framework can be used to monitor damage progression in different host materials, and hence it can be potentially used to mitigate damage. }, number={23}, journal={JOURNAL OF COMPOSITE MATERIALS}, author={Pearson, J. D. and Zikry, M. A. and Prabhugoud, M. and Peters, K.}, year={2007}, month={Dec}, pages={2759–2783} }
 @article{ma_zikry_ashamwi_brenner_2007, title={Hierarchical modeling of nanoindentation and microstructural evolution of face-centered cubic gold aggregates}, volume={22}, ISSN={["2044-5326"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33947268483&partnerID=MN8TOARS}, DOI={10.1557/JMR.2007.0076}, abstractNote={A hierarchical computational method has been developed and used with a finite-element microstructurally based dislocation density multiple-slip crystalline formulation to predict how nanoindentation affects behavior in face-centered cubic crystalline aggregates at scales that span the molecular to the continuum level. Displacement profiles from molecular dynamics simulations of nanoindentation were used to obtain scaling relations, which are based on indented depths, grain-sizes, and grain aggregate distributions. These scaling relations are then used to coarsen grains in a microstructurally based finite-element formulation that accounts for dislocation density evolution, crystalline structures, and grain-sizes. This computational approach was validated with a number of experimental measurements pertaining to single gold crystals. This hierarchical model provides a methodology to link molecular level simulations with a microstructurally based finite element method formulation that can be used to ascertain inelastic effects, such as shear-slip distribution, pressure accumulation, and dislocation density and slip-rate evolution at physical scales that are commensurate with ductile behavior at the microstructural scale.}, number={3}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Ma, Jeong Beom and Zikry, M. A. and Ashamwi, W. M. and Brenner, D. W.}, year={2007}, month={Mar}, pages={627–643} }
 @inproceedings{pearson_prabhugoud_zikry_peters_2007, title={In-situ failure identification in woven composites throughout impact}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-37349076591&partnerID=MN8TOARS}, DOI={10.1115/IMECE2006-15784}, abstractNote={In this study, measurements form low-impact velocity experiments including embedded and surface mounted optical fiber Bragg grating (FBG) sensors were used to obtain detailed information pertaining to damage progression in two-dimensional laminate woven composites. The woven composites were subjected to multiple strikes at 2m/s until perforation occurred, and the impactor position and acceleration were monitored throughout each event. From these measurements, we obtained dissipated energies and contact forces. The FBG sensors were embedded and surface mounted at different critical locations near penetration-induced damaged regions. These FBG sensors were used to obtain initial residual strains and axial and transverse strains that correspond to matrix cracking and delamination. The transmission and reflection spectra were continuously monitored throughout the loading cycles. They were used, in combination with the peak contact forces, to delineate repeatable sensor responses corresponding to material failure. From the FBG spectra, fiber and matrix damage were separated by an analysis based on signal intensity and the behavior of individual Bragg peaks as a function of evolving and repeated impact loads. This provided independent feedback on the integrity of the Bragg gratings which can serve to eliminate errors in the strain data such as due to sensor debonding or fracture. The critical indicators present in the sensor spectra for the mapping of these sensor failure modes are derived.}, booktitle={Proceedings of the Materials Division, The ASME Non-Destructive Evaluation Division and The ASME Pressure Vessels and Piping Division, 2006}, author={Pearson, J. and Prabhugoud, M. and Zikry, M. and Peters, K.}, year={2007}, pages={267–276} }
 @article{prabhugoud_peters_pearson_zikry_2007, title={Independent measurement of strain and sensor failure features in Bragg grating sensors through multiple mode coupling}, volume={135}, ISSN={["0924-4247"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34047170478&partnerID=MN8TOARS}, DOI={10.1016/j.sna.2006.08.021}, abstractNote={This article presents the interrelated measurements of Bragg reflection, cladding and radiation modes to obtain the applied strain and integrity of a short period Bragg grating sensor. While the Bragg reflection is known to be sensitive to applied strain, the relative strength of the cladding and radiation mode coupling is shown to be sensitive to damage such as debonding from the host structure. Furthermore, the length of the Bragg grating debonded from the surrounding medium is quantitatively related to the coupling to continuum radiation modes from the core mode. While the sensitivity of the radiation mode coupling to microcracking in the optical fiber is shown to be relatively low, maximum intensity measurements provide sufficient information on local fractures of the optical fiber. These results provide intelligent self-diagnostic capabilities within the Bragg grating sensor without additional measurements, and also permit the separate identification of sensor failure from the failure of the host structure.}, number={2}, journal={SENSORS AND ACTUATORS A-PHYSICAL}, author={Prabhugoud, Mohanraj and Peters, Kara and Pearson, James and Zikry, Mohammed A.}, year={2007}, month={Apr}, pages={433–442} }
 @inproceedings{pearson_zikry_peters_prabhugoud_2007, title={Local and global measurements of dynamic damage evolution in woven composite systems}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85076867871&partnerID=MN8TOARS}, booktitle={ICCM International Conferences on Composite Materials}, author={Pearson, J.D. and Zikry, M.A. and Peters, K.J. and Prabhugoud, M.}, year={2007} }
 @article{pearson_zikry_prabhugoud_peters_2007, title={Measurement of low velocity and quasi-static failure modes in PMMA}, volume={28}, ISSN={["0272-8397"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34250820545&partnerID=MN8TOARS}, DOI={10.1002/pc.20287}, abstractNote={Abstract}, number={3}, journal={POLYMER COMPOSITES}, author={Pearson, J. D. and Zikry, M. A. and Prabhugoud, M. and Peters, K.}, year={2007}, month={Jun}, pages={381–391} }
 @inproceedings{garrett_pearson_peters_zikry_2007, title={Optimization of fiber Bragg grating sensor configurations for in-situ failure identification in woven composites throughout impact}, volume={6529 PART 2}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-35549000969&partnerID=MN8TOARS}, DOI={10.1117/12.715216}, abstractNote={In this study, the development and optimization of embedded fiber Bragg grating (FBG) sensor networks within composite materials was investigated. Various densities of optical fibers were embedded within composite laminates, and low-velocity impact damage responses were evaluated to determine the effects on the mechanical behavior of the laminates. The woven composites were subjected to multiple strikes at 2 m/s until perforation occurred, and the impactor position and acceleration were monitored throughout each event. From these measurements, we obtained dissipated energies and contact forces for specimens with and without embedded optical fibers. Embedded fibers were interrogated with light to determine the degree to which light could pass through them for each density and arrangement. Cross sectional optical micrographs of the specimens were used to determine the local effects of the embedded fibers on neighboring fibers and the surrounding matrix material, both before and after impact events. Currently FBG sensors are being calibrated and prepared for embedment in specifically chosen configurations within the composite. They will be serially multiplexed together to create a single fiber sensing network capable of monitoring damage over a large area. Real time strain information will be gathered as future embedded laminates are subjected to impact events, and the resulting data will be used to better monitor and predict damage in the composite system.}, booktitle={Proceedings of SPIE - The International Society for Optical Engineering}, author={Garrett, R. and Pearson, J. and Peters, K. and Zikry, M.}, year={2007} }
 @article{zhao_duscher_rozgonyi_zikry_chopra_ozturk_2007, title={Quantitative nanoscale local strain profiling in embedded SiGe metal-oxide-semiconductor structures}, volume={90}, ISSN={["1077-3118"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34248361149&partnerID=MN8TOARS}, DOI={10.1063/1.2738188}, abstractNote={Mechanical strain by strain engineering has been widely used in Si metal-oxide-semiconductor field effect transistors. Experimental convergent beam electron diffraction (CBED) strain measurements and finite element calculations to quantitatively correlate the strain in the transmission electron microscope (TEM) sample with the actual device. It was found that the magnitude of the longitudinal strain, εx, along the channel direction, is about 20% higher in the TEM sample than in the real device. This combined approach can be used to explain data from other CBED studies of strained Si devices.}, number={19}, journal={APPLIED PHYSICS LETTERS}, author={Zhao, W. and Duscher, G. and Rozgonyi, G. and Zikry, M. A. and Chopra, S. and Ozturk, M. C.}, year={2007}, month={May} }
 @inproceedings{zhao_duscher_zikry_rozgonyi_2007, title={Reliable local strain characterization on Si/SiGe structures in biaxial tension}, volume={958}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34347252267&partnerID=MN8TOARS}, booktitle={Materials Research Society Symposium Proceedings}, author={Zhao, W. and Duscher, G. and Zikry, M.A. and Rozgonyi, G.}, year={2007}, pages={151–157} }
 @article{rezvanian_zikry_rajendran_2007, title={Statistically stored, geometrically necessary and grain boundary dislocation densities: microstructural representation and modelling}, volume={463}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-36348999315&partnerID=MN8TOARS}, DOI={10.1098/rspa.2007.0020}, abstractNote={A unified physically based microstructural representation of f.c.c. crystalline materials has been developed and implemented to investigate the microstructural behaviour of f.c.c. crystalline aggregates under inelastic deformations. The proposed framework is based on coupling a multiple-slip crystal plasticity formulation to three distinct dislocation densities, which pertain to statistically stored dislocations (SSDs), geometrically necessary dislocations (GNDs) and grain boundary dislocations. This interrelated dislocation density formulation is then coupled to a specialized finite element framework to study the evolving heterogeneous microstructure and the localized phenomena that can contribute to failure initiation as a function of inelastic crystalline deformation. The GND densities are used to understand where crystallographic, non-crystallographic and cellular microstructures form and the nature of their dislocation composition. The SSD densities are formulated to represent dislocation cell microstructures to obtain predictions related to the inhomogeneous distribution of SSDs. The effects of the lattice misorientations at the grain boundaries (GBs) have been included by accounting for the densities of the misfit dislocations at the GBs that accommodate these misorientations. By directly accounting for the misfit dislocations, the strength of the boundary regions can be more accurately represented to account for phenomena associated with the effects of the GB strength on intergranular deformation heterogeneities, stress localization and the nucleation of failure surfaces at critical regions, such as triple junctions.}, number={2087}, journal={Philosophical Transactions of the Royal Society of London. Series A, Mathematical, Physical and Engineering Sciences}, author={Rezvanian, O. and Zikry, Mohammed and Rajendran, A. M.}, year={2007}, pages={2833–2853} }
 @article{rezvanian_zikry_brown_krim_2007, title={Surface roughness, asperity contact and gold RFMEMS switch behavior}, volume={17}, ISSN={["1361-6439"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34748865043&partnerID=MN8TOARS}, DOI={10.1088/0960-1317/17/10/012}, abstractNote={Modeling predictions and experimental measurements were obtained to characterize the electro-mechanical response of radio frequency (RF) microelectromechanical (MEM) switches due to variations in surface roughness and finite asperity deformations. Three-dimensional surface roughness profiles were generated, based on a Weierstrass–Mandelbrot fractal representation, to match the measured roughness characteristics of contact bumps of manufactured RF MEMS switches. Contact asperity deformations due to applied contact pressures were then obtained by a creep constitutive formulation. The contact pressure is derived from the interrelated effects of roughness characteristics, material hardening and softening, temperature increases due to Joule heating and contact forces. This modeling framework was used to understand how contact resistance evolves due to changes in the real contact area, the number of asperities in contact, and the temperature and resistivity profiles at the contact points. The numerical predictions were qualitatively consistent with the experimental measurements and observations of how contact resistance evolves as a function of deformation time history. This study provides a framework that is based on integrated modeling and experimental measurements, which can be used in the design of reliable RF MEMS devices with extended life cycles.}, number={10}, journal={JOURNAL OF MICROMECHANICS AND MICROENGINEERING}, author={Rezvanian, O. and Zikry, M. A. and Brown, C. and Krim, J.}, year={2007}, month={Oct}, pages={2006–2015} }
 @inproceedings{pearson_zikry_rezvanian_2006, title={Computational modeling and design of adaptive thin-film composite coatings}, volume={977}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-41549101067&partnerID=MN8TOARS}, DOI={10.1557/proc-977-0977-ff08-10}, abstractNote={Abstract}, booktitle={Materials Research Society Symposium Proceedings}, author={Pearson, J.D. and Zikry, M.A. and Rezvanian, O.}, year={2006}, pages={85–90} }
 @inproceedings{pearson_prabhugoud_zikry_peters_2006, title={In-situ failure identification in woven composites throughout impact}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84920632313&partnerID=MN8TOARS}, booktitle={American Society of Mechanical Engineers, Materials Division (Publication) MD}, author={Pearson, J. and Prabhugoud, M. and Zikry, M. and Peters, K.}, year={2006} }
 @inproceedings{pearson_prabhugoud_zikry_peters_2006, title={In-situ failure identification in woven composites throughout impact using fiber bragg grating sensors}, volume={6174 II}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33745946683&partnerID=MN8TOARS}, DOI={10.1117/12.657989}, abstractNote={In this study, measurements from low-impact velocity experiments and surface mounted optical fiber Bragg grating (FBG) sensors were used to obtain detailed information pertaining to damage progression in two-dimensional laminate woven composites. The woven composites were subjected to multiple strikes at 2m/s until perforation occurred, and the impactor position and acceleration were monitored throughout each event. From these measurements, we obtained dissipated energies and contact forces. The FBG sensors were surface mounted at different critical locations near penetration-induced damaged regions. These FBG sensors were used to obtain initial residual strains and axial and transverse strains that correspond to matrix cracking and delamination. The transmission and the reflection spectra were continuously monitored throughout the loading cycles. They were used, in combination with the peak contact forces, to delineate repeatable sensor responses corresponding to material failure. From the FBG spectra, fiber and matrix damage were separated by an analysis based on the behavior of individual Bragg peaks as a function of evolving and repeated impact loads. This provided an independent feedback on the integrity of the Bragg gratings. Thus, potential sources of error such as sensor debonding were eliminated from the strain data throughout the measurements. A comparison by number of impact strikes and dissipated energies corresponding to material perforation indicates that these measurements can provide accurate failure strains.}, booktitle={Proceedings of SPIE - The International Society for Optical Engineering}, author={Pearson, J. and Prabhugoud, M. and Zikry, M. and Peters, K.}, year={2006} }
 @inproceedings{shi_zikry_hatem_2006, title={Inelastic behavior and grain-boundary effects in polycrystalline materials}, volume={978}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-41549160841&partnerID=MN8TOARS}, DOI={10.1557/proc-978-0978-gg12-07-ee08-07}, abstractNote={Abstract}, booktitle={Materials Research Society Symposium Proceedings}, author={Shi, J. and Zikry, M. and Hatem, T.M.}, year={2006}, pages={333–338} }
 @inproceedings{zhao_duscher_zikry_rozgonyi_2006, title={Local strain characterization on strained-Si/SiGe heterostructures with convergent beam electron diffraction and finite element simulation}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33846976714&partnerID=MN8TOARS}, DOI={10.1149/1.2355831}, abstractNote={We introduce a novel and reliable method to quantify local strain variation in microelectronic device structures based on convergent beam electron diffraction (CBED) and finite element (FE) calculation. The match of the finite element calculation results with the experimental data not only validated the parameters used for the finite element simulations, but also gives us insights into the origin of high order Laue zone (HOLZ) line splitting in a lattice-mismatched heterostructure. The 2D and 3D calculations showed that the residual strain measured from  clean  and sharp CBED patterns deviate from the initial strain. The effect of a SiO2 layer on the strain in a TEM sample was also investigated by FE simulation and we found that a SiO2 layer can suppress some of the elastic deformation making it possible to obtain  clean  and sharp CBED patterns. The here proposed novel method uses the elastic deformation to determine the initial strain in microelectronic devices structures by combining FE simulations and CBED patterns.}, number={7}, booktitle={ECS Transactions}, author={Zhao, W. and Duscher, G. and Zikry, M.A. and Rozgonyi, G.}, year={2006}, pages={333–338} }
 @article{baucom_zikry_rajendran_2006, title={Low-velocity impact damage accumulation in woven S2-glass composite systems}, volume={66}, ISSN={["1879-1050"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33747351080&partnerID=MN8TOARS}, DOI={10.1016/j.compscitech.2005.11.005}, abstractNote={The objective of this experimental investigation is to obtain a detailed understanding of damage accumulation in two-dimensional (2D) and three-dimensional (3D) woven glass-fiber-reinforced composite panels under repeated transverse drop-weight impact loading conditions. Measurements were obtained for impact force and energy dissipation. The radial spread of damage was smallest for the 2D laminates and largest for the 3D woven composites. The 3D composites had the greatest resistance to penetration and dissipated more total energy than the laminate system. This damage tolerance is due to unique energy absorption mechanisms, which involve the crimped portion of z-tows in the 3D composites. This is significant, since 3D architectures can provide both an inherent capability to dissipate energy over a large radial area and a greater perforation strength than comparable 2D laminate systems.}, number={10}, journal={COMPOSITES SCIENCE AND TECHNOLOGY}, author={Baucom, J. N. and Zikry, M. A. and Rajendran, A. M.}, year={2006}, month={Aug}, pages={1229–1238} }
 @inproceedings{rezvanian_zikry_rajendran_2006, title={Microstructural behavior and failure of FCC crystalline aggregates}, volume={976}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-41549153890&partnerID=MN8TOARS}, DOI={10.1557/proc-976-0976-ee02-02}, abstractNote={Abstract}, booktitle={Materials Research Society Symposium Proceedings}, author={Rezvanian, O. and Zikry, M.A. and Rajendran, A.M.}, year={2006}, pages={78–83} }
 @article{rezvanian_zikry_rajendran_2006, title={Microstructural modeling of grain subdivision and large strain inhomogeneous deformation modes in f.c.c. crystalline materials}, volume={38}, ISSN={["0167-6636"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33746933462&partnerID=MN8TOARS}, DOI={10.1016/j.mechmat.2005.12.006}, abstractNote={In this study, evolution equations related to a heterogeneous microstructure that is physically representative of the densities and dimensions of dislocation-cells and walls have been formulated and coupled to a multiple-slip crystal plasticity formulation. Specialized finite-element methodologies have then been used to investigate how an imbalance in shear-strain amplitudes can result in deformation band formation in a cube-oriented aluminum single crystal subjected to strains of up to 30% under rolling deformation. It has been shown that a change in the microstructural morphology from matrix to transition bands occurs as the dislocation-cell size increases with decreases in the stored dislocation density and as a function of slip-system structure and orientation. Comparisons with experimental measurements and observations clearly indicate that the transition and matrix bands can occur in cube orientations as a consequence of shear strain imbalance on active slip-systems.}, number={12}, journal={MECHANICS OF MATERIALS}, author={Rezvanian, O. and Zikry, M. A. and Rajendran, A. M.}, year={2006}, month={Dec}, pages={1159–1169} }
 @article{kameda_zikry_rajendran_2006, title={Modeling of grain-boundary effects and intergranular and transgranular failure in polycrystalline intermetallics}, volume={37A}, ISSN={["1073-5623"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33745933649&partnerID=MN8TOARS}, DOI={10.1007/BF02586131}, number={7}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE}, author={Kameda, T. and Zikry, M. A. and Rajendran, A. M.}, year={2006}, month={Jul}, pages={2107–2115} }
 @article{rajendran_ashmawi_zikry_2006, title={The modeling of the shock response of powdered ceramic materials}, volume={38}, ISSN={["1432-0924"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33646550239&partnerID=MN8TOARS}, DOI={10.1007/s00466-005-0712-3}, number={1}, journal={COMPUTATIONAL MECHANICS}, author={Rajendran, AM and Ashmawi, WM and Zikry, MA}, year={2006}, month={Jun}, pages={1–13} }
 @inproceedings{pearson_prabhugoud_zikry_peters_2005, title={Damage progression identification in woven composites with fiber bragg grating sensors}, volume={100 MD}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33645654612&partnerID=MN8TOARS}, DOI={10.1115/IMECE2005-80487}, abstractNote={In this study, measurements from low-impact velocity experiments including embedded and surface mounted optical fiber Bragg grating (FBG) sensors were used to obtain detailed information pertaining to damage progression in two-dimensional laminate woven composites. The woven composites were subjected to multiple strikes at 2m/s until perforation occurred, and the impactor position and acceleration were monitored throughout each event. From these measurements, we obtained dissipated energies and contact forces. The FBG sensors were embedded and surface mounted at different critical locations near penetration-induced damaged regions. These FBG sensors were used to obtain initial residual strains and axial and transverse strains that correspond to matrix cracking and delamination. The transmission and reflection spectra were continuously monitored throughout the loading cycles. They were used, in combination with the peak contact forces, to delineate repeatable sensor responses corresponding to material failure. From the FBG spectra, fiber and matrix damage were separated by an analysis based on signal intensity, the presence of cladding modes, and the behavior of individual Bragg peaks as a function of evolving and repeated impact loads. This provided an independent feedback on the integrity of the Bragg gratings. A comparison by number of impact strikes and dissipated energies corresponding to material perforation indicates that embedding these sensors did not affect the integrity of the woven systems and that these measurements can provide accurate failure strains.}, booktitle={American Society of Mechanical Engineers, Materials Division (Publication) MD}, author={Pearson, J. and Prabhugoud, M. and Zikry, M. and Peters, K.}, year={2005}, pages={49–57} }
 @inproceedings{pearson_prabhugoud_zikry_peters_sitar_davis_2005, title={Failure and damage identification in woven composites with fiber Bragg grating sensors}, volume={5765}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-25144476656&partnerID=MN8TOARS}, DOI={10.1117/12.599771}, abstractNote={In this study, measurements from low-impact velocity experiments and embedded and surface mounted optical fiber Bragg grating (FBG) sensors were used to obtain detailed information pertaining to damage progression in two-dimensional laminate woven composites. The woven composites were subjected to multiple strikes at 2m/s until perforation occurred, and the impactor position and acceleration were monitored throughout each event. From these measurements, we obtained dissipated energies and contact forces. The FBG sensors were embedded and surface mounted at different critical locations near penetration-induced damaged regions. These FBG sensors were used to obtain initial residual strains and axial and transverse strains that correspond to matrix cracking and delamination. The transmission and the reflection spectra were continuously monitored throughout the loading cycles. They were used, in combination with the peak contact forces, to delineate repeatable sensor responses corresponding to material failure. From the FBG spectra, fiber and matrix damage were separated by an analysis based on signal intensity, the presence of cladding modes, and the behavior of individual Bragg peaks as a function of evolving and repeated impact loads. This provided an independent feedback on the integrity of the Bragg gratings. A comparison by number of strikes and dissipated energies corresponding to material perforation indicates that embedding these sensors did not affect the integrity of the woven systems and that these measurements can provide accurate failure strains.}, number={PART 1}, booktitle={Proceedings of SPIE - The International Society for Optical Engineering}, author={Pearson, J. and Prabhugoud, M. and Zikry, M. and Peters, K. and Sitar, M. and Davis, L.}, year={2005}, pages={540–551} }
 @article{baucom_zikry_2005, title={Low-velocity impact damage progression in woven E-glass composite systems}, volume={36}, ISSN={["1878-5840"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-13844315208&partnerID=MN8TOARS}, DOI={10.1016/j.compositesa.2004.07.008}, abstractNote={The objective of this experimental study is to obtain a detailed understanding of the effects of reinforcement geometry on damage progression in woven composite panels under repeated drop-weight impact loading conditions. The composite systems included a 2D plain-woven laminate, a 3D orthogonally woven monolith, and a biaxially reinforced warp-knit. The radial spread of damage was smallest for the 2D laminates and largest for the 3D woven composites. The 3D composites had the greatest resistance to penetration and dissipated more total energy than the other systems. This is due to unique energy absorption mechanisms, which involve the crimped portion of z-tows in the 3D composites, and implies that failure can be controlled by manipulation of the properties of the z-tows. The 3D systems provide both an inherent capability to dissipate energy over a larger area and a greater perforation strength than other systems with comparable areal densities and fiber-volume-fractions.}, number={5}, journal={COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING}, author={Baucom, JN and Zikry, MA}, year={2005}, pages={658–664} }
 @inproceedings{ma_ashmawi_zikry_schall_brenner_2005, title={Modeling of nanoindentation and microstructural ductile behavior in metallic material systems}, volume={841}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-23844433619&partnerID=MN8TOARS}, booktitle={Materials Research Society Symposium Proceedings}, author={Ma, J.B. and Ashmawi, W. and Zikry, M.A. and Schall, D. and Brenner, D.W.}, year={2005}, pages={317–322} }
 @inproceedings{prabhugoud_pearson_peters_zikry_2005, title={Radiation and cladding modes as independent measurements of Bragg grating sensor integrity}, volume={5758}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-25144473506&partnerID=MN8TOARS}, DOI={10.1117/12.597782}, abstractNote={This article presents the use of Bragg reflection and cladding mode measurements to independently measure axial strain and the integrity of a Bragg grating sensor. While the Bragg reflection is known to be sensitive to applied strain, the cladding modes are shown to be sensitive to expected damage within the sensor such as microcracking and debonding from the host structure. This phenomenon allows the intelligent self-testing of the Bragg grating sensor without additional instrumentation and permits the separate identification of sensor failure from the failure of the host structure. The growth of cladding modes during degradation of a Bragg grating is experimentally demonstrated in controlled tension tests with different fiber-host interface conditions.}, booktitle={Proceedings of SPIE - The International Society for Optical Engineering}, author={Prabhugoud, M. and Pearson, J. and Peters, K. and Zikry, M.}, year={2005}, pages={440–450} }
 @article{badr_m.arif_sheikh_shuaib_khan_khan_tseng_zikry_2005, title={Theme issue on modeling of metal forming processes}, volume={30}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-32544458475&partnerID=MN8TOARS}, number={1 C}, journal={Arabian Journal for Science and Engineering}, author={Badr, H. and M.Arif, A.F. and Sheikh, A.K. and Shuaib, A.N. and Khan, Z. and Khan, A.S. and Tseng, A.A. and Zikry, M.A.}, year={2005} }
 @article{bahei-el-din_rajendran_zikry_2004, title={A micromechanical model for damage progression in woven composite systems}, volume={41}, ISSN={["1879-2146"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-1842484113&partnerID=MN8TOARS}, DOI={10.1016/j.ijsolstr.2003.12.006}, abstractNote={Damage progression in woven composites is modeled for multiscale analysis of structures. The proposed model is a representative volume element (RVE) of the woven material, derived from micrographs. In principle, it is applicable to any woven system with periodic fiber placement; however, the focus in this paper is on 3D weaves. The domain and boundary conditions of the RVE are selected such that the model can serve as a repository for predicting the overall behavior under general, multiaxial stress states. The overall response due to applied stress, or strain, and local damage is evaluated by a transformation field analysis (TFA) scheme. Damage mechanisms observed under quasi-static and impact loads are implemented. This includes matrix cracking, frictional sliding and debonding of the fiber bundles, and fiber rupture. The local stress components affected by the active damage modes are removed or reduced by superimposing a transformation stress field on the elastic field caused by the overall loads in the undamaged material. This results in a local stress field that is within the affordable local strength magnitudes, and an overall transformation stress, which modifies the elastic estimate. Implementation of the material model in quasi-static and dynamic finite element procedures is discussed, and examples, which illustrate the model capabilities, are presented.}, number={9-10}, journal={INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES}, author={Bahei-El-Din, YA and Rajendran, AM and Zikry, MA}, year={2004}, month={May}, pages={2307–2330} }
 @inproceedings{prabhugoud_pearson_peters_zikry_2004, title={Demonstration of failure identification methodology incorporating sensor degradation}, volume={5391}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-10044277158&partnerID=MN8TOARS}, DOI={10.1117/12.540093}, abstractNote={The long-term goal of this project is the development of embedded, optimally distributed, multi-scale sensing methodologies that can be integrated into material systems for failure identification in structural systems. The coupling of sensor data fusion with a three-dimensional predictive framework will provide insight and understanding of events that are difficult, if not impossible, in any experimental study, such as subsurface damage and crack nucleation in structural systems. The current work presents an experimental study of the survivability and degradation behavior of an optical fiber Bragg grating sensor, surface mounted on a woven fiber composite material system during multiple low velocity impacts. The results reveal that as sensor degradation occurs, additional coupling phenomena other than Bragg reflection are observed in the grating sensor. From these additional modes, information on the sensor/host bond and fiber degradation is obtained.}, booktitle={Proceedings of SPIE - The International Society for Optical Engineering}, author={Prabhugoud, M. and Pearson, J. and Peters, K. and Zikry, M.}, year={2004}, pages={107–116} }
 @article{baucom_zikry_qiu_2004, title={Dynamic and quasi-static failure evolution of 3D woven cellular composite systems}, volume={23}, ISSN={["0731-6844"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-1642443479&partnerID=MN8TOARS}, DOI={10.1177/0731684404032076}, abstractNote={ The effects of porosity on the impact response and perforation resistance of 3D woven carbon-fiber reinforced epoxy panels under impact by projectiles and under quasi-static three-point bending were experimentally investigated. The 3D cellular composite systems were fabricated by a new method, where porosity can be controlled. The porous samples absorbed a greater amount of specific energy than the nonporous samples. This may be due to the deflection of matrix cracks by the pores and the greater flexibility of the fibers to absorb energy through tensile straining. The quasi-static experiments also indicate that porosity may exhibit strength comparable to nonporous systems. }, number={5}, journal={JOURNAL OF REINFORCED PLASTICS AND COMPOSITES}, author={Baucom, JN and Zikry, MA and Qiu, Y}, year={2004}, pages={471–481} }
 @article{baucom_zikry_2004, title={Erratum: Evolution of failure mechanisms in 2D and 3D woven composite systems under quasi-static perforation (Journal of Composite Materials, 37, 18, (1651-1674) DOI: 10.1177/0021998304042170)}, volume={38}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-1842474470&partnerID=MN8TOARS}, DOI={10.1177/0021998304042170}, abstractNote={The authors also gratefully acknowledge the support of 3TEX. They provided the 2D and 3D composites with the desired layer and fiber combinations for this study. The 3D orthogonal composites were fabricated by the unique 3D weaving and fabrication processes developed by 3TEX. The support and advice of Drs. J. Singletary, M. Mohamed, and A. Bogdanovich of 3TEX, on different aspects of this study, have been invaluable.}, number={6}, journal={Journal of Composite Materials}, author={Baucom, J.N. and Zikry, M.A.}, year={2004}, pages={535} }
 @inproceedings{pearson_prabhugoud_zikry_peters_2004, title={Failure identification methodology for woven composites incorporating sensor degradation}, volume={99}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-19644380376&partnerID=MN8TOARS}, DOI={10.1115/IMECE2004-61802}, abstractNote={The long-term goal of this project is the development of embedded, optimally distributed, multi-scale sensing methodologies that can be integrated into material systems for failure identification in structural systems. The coupling of sensor data fusion with a three-dimensional predictive framework will provide insight and understanding of events that are difficult, if not impossible, in any experimental study, such as subsurface damage and crack nucleation in structural systems. The current work presents an experimental study of the survivability and degradation behavior of an optical fiber Bragg grating sensor, surface mounted on a woven fiber composite material system during multiple low velocity impacts. The results reveal that as sensor degradation occurs, additional coupling phenomena other than Bragg reflection are observed in the grating sensor. From these additional modes, information on the sensor/host bond and fiber degradation is obtained.}, booktitle={American Society of Mechanical Engineers, Materials Division (Publication) MD}, author={Pearson, J. and Prabhugoud, M. and Zikry, M. and Peters, K.}, year={2004}, pages={31–40} }
 @inproceedings{zikry_ashmawi_2004, title={Failure modes and grain-boundary effects in polycrystalline materials}, volume={819}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-5544263626&partnerID=MN8TOARS}, DOI={10.1557/proc-819-n1.3}, abstractNote={Abstract}, booktitle={Materials Research Society Symposium - Proceedings}, author={Zikry, M.A. and Ashmawi, W.M.}, year={2004}, pages={21–26} }
 @article{ashmawi_zikry_wang_reeber_2004, title={Modeling of residual stresses for thermally strained GaN/Al2O3 heterostructures}, volume={266}, ISSN={["1873-5002"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-2442603520&partnerID=MN8TOARS}, DOI={10.1016/j.jcrysgro.2004.02.105}, abstractNote={A finite element model and a specialized constitutive formulation were used to predict the evolving interfacial thermal mismatch stresses and strains in gallium nitride/alumina epitaxial layered systems. The constitutive formulation was based on having the coefficients of thermal expansion vary as a function of temperature for both material systems, which were assumed to be transversely isotropic. Different layer configurations were investigated, and it is shown that layer geometry is controlled by the evolution of induced thermal mismatch properties and residual stresses.}, number={4}, journal={JOURNAL OF CRYSTAL GROWTH}, author={Ashmawi, WM and Zikry, MA and Wang, K and Reeber, RR}, year={2004}, month={Jun}, pages={415–422} }
 @inproceedings{bahei-el-din_rajendran_zikry_2003, title={A material model for multi-scale analysis of textile composites}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0042012928&partnerID=MN8TOARS}, DOI={10.2514/6.2003-1476}, booktitle={Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference}, author={Bahei-El-Din, Y.A. and Rajendran, A.M. and Zikry, M.A.}, year={2003}, pages={685–690} }
 @article{baucom_zikry_2003, title={Evolution of failure mechanisms in 2D and 3D woven composite systems under quasi-static perforation}, volume={37}, ISSN={["1530-793X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0042793491&partnerID=MN8TOARS}, DOI={10.1177/0021998303035178}, abstractNote={ The effects of reinforcement geometry, in 2D and 3D woven fabric-reinforced composites, on the progression of damage and perforation failure at quasi-static loading rates (10-80 mm/s) are investigated. The broad classes of glass-fiber-reinforced systems that were examined include 2D plain-woven laminates, 3D orthogonally woven monolithic systems, and 3D orthogonally woven laminates. The experimental results indicate that the 3D laminates consistently had greater damage tolerance than the 2D laminates and the 3D monolithic composites. The enhanced damage tolerance of the 3D systems is due to unique energy absorption mechanisms, which involve the crimped portion of z-tows. }, number={18}, journal={JOURNAL OF COMPOSITE MATERIALS}, author={Baucom, JN and Zikry, MA}, year={2003}, pages={1651–1674} }
 @article{baucom_zikry_2003, title={Evolution of failure mechanisms in 2D and 3D woven composite systems under quasi-static perforation}, volume={37}, DOI={10.1177/002199803035178}, number={18}, journal={Journal of Composite Materials}, author={Baucom, J. N. and Zikry, Mohammed}, year={2003}, pages={1651–1674} }
 @article{ashmawi_zikry_2003, title={Grain boundary effects and void porosity evolution}, volume={35}, ISSN={["1872-7743"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0037339303&partnerID=MN8TOARS}, DOI={10.1016/S0167-6636(02)00269-7}, abstractNote={A multiple-slip dislocation-density based constitutive crystalline formulation that is coupled to a kinematic scheme that accounts for grain boundary (GB) interfacial interactions with dislocation densities, and an internal porosity formulation have been used to predict how void porosity is affected by GB interactions, such as dislocation-density pile-ups at GB interfaces, partial and total dislocation-density transmission from one grain to neighboring grains, and dislocation-density absorption within GBs. Void nucleation and growth is represented by a single scalar that is a function of total dislocation density, stress triaxiality, accumulated plastic strains, and temperature. The proposed methodology provides an understanding of how interactions at the GB interface scale affect overall macroscopic behavior due to the interrelated effects of GB orientations, the evolution of mobile and immobile dislocation densities, and porosity evolution, which occur at smaller physical scales. It is shown that the accumulation of pile-ups at GB interfaces and GB absorption at different GB regions are the triggering mechanisms that lead to porosity localization, and subsequently to void nucleation and growth.}, number={3-6}, journal={MECHANICS OF MATERIALS}, author={Ashmawi, WM and Zikry, MA}, year={2003}, pages={537–552} }
 @article{ashmawi_zikry_2003, title={Grain-boundary interfaces and void interactions in porous aggregates}, volume={83}, ISSN={["1478-6443"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0347592119&partnerID=MN8TOARS}, DOI={10.1080/14786430310001599423}, abstractNote={A multiple-slip dislocation-density-based formulation and computational schemes that are coupled to grain-boundary (GB) interfacial schemes and an internal porosity formulation are used to analyse the behaviour and interaction of different arrangements and geometries of explicit pairs of voids in a polycrystalline fcc aggregate. The GB regions are treated as regions with properties and topologies that are distinct from that of the grain bulk. The GB kinematic scheme accounts for dislocation density interactions with GBs, such as dislocation density impedance, blockage and GB absorption. These evolving interfacial conditions are monitored throughout the deformation history. The analysis indicated that void-to-void interactions result in dislocation density evolution and saturation and porosity localization that are intricately related to both dislocation density pile-ups and blockages at GB interfaces, and GB absorption within different GB regions.}, number={31-34}, journal={PHILOSOPHICAL MAGAZINE}, author={Ashmawi, WM and Zikry, MA}, year={2003}, pages={3917–3944} }
 @article{bahei-el-din_zikry_2003, title={Impact-induced deformation fields in 2D and 3D woven composites}, volume={63}, ISSN={["0266-3538"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0037403705&partnerID=MN8TOARS}, DOI={10.1016/S0266-3538(03)00021-6}, abstractNote={The deformation fields and kinematics of woven composite material systems, due to impact loads, were analyzed and characterized for various structural and load parameters. Target plates comprising of woven composites with 3D and 2D preforms were considered. Kinetic energies in the range of 18–39,000 J, due to projectile velocities in the range of 2–1000 m/s, were investigated. The impact problem model accounts for geometrical details of the flat target plates and the hemispherical projectile. Contact solutions at dissimilar surfaces were modeled with gap elements, and the solution of the nonlinear dynamic problem was obtained by the finite element method. In the present study, we investigated wave propagation effects, and how their spatial and temporal distribution is related to the evolution of multi-dimensional elastic fields and potential damage modes. Unit cells representative of the 2D and 3D woven composites were used to obtain estimates of the overall elastic moduli. It was found that the compression wave induced by impact reflected several times between the free surfaces of the target plate before fiber failure initiated, and that this was one of the major mechanisms leading to penetration. At low velocity impact, the deformations were similar to quasi-static bending deformation modes, and failure is predicted to be due to fiber breakage at the backside of the target plate. At higher impact velocities, wave propagation effects are more significant and lead to penetration at the impact face. For all material systems, localized shear damage in 3D woven systems and extensive shear delamination in 2D woven systems preceded complete penetration.}, number={7}, journal={COMPOSITES SCIENCE AND TECHNOLOGY}, author={Bahei-El-Din, YA and Zikry, MA}, year={2003}, month={May}, pages={923–942} }
 @article{bahei-el-din_zikry_rajendran_2003, title={Impact-induced deformation fields in 3D cellular woven composites}, volume={34}, ISSN={["1359-835X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0041631068&partnerID=MN8TOARS}, DOI={10.1016/S1359-835X(03)00143-X}, abstractNote={Abstract The deformation fields and kinematics of nonporous and porous three-dimensional (3D) woven composite material systems were analyzed and characterized under an incident impact energy of 560 J caused by a 78 g projectile at a velocity of 120 m/s. The analysis quantifies experimental observations of the effects of porosity on the impact resistance and behavior of 3D woven composites. The dynamic nonlinear impact solution was obtained by the finite element method, in which contact between the projectile and the target plate was modeled with gap elements. In the present study, we investigated the spatial and temporal evolution of multi-dimensional elastic fields and potential damage modes in the target plates. A unit cell, representative of the 3D woven composite, was used to obtain estimates of the overall elastic moduli. These estimates were then used with two material models to represent the porous system in the finite element analysis of the target plate. One material model, which had explicit geometrical distributions of 3D voids, was used in the impact region, and the other material model, which was based on a representation of smeared voids, was used in regions removed from the impact zone. The analysis indicates that wave propagation effects at the incident energy applied here are significant, and these effects can lead to projectile penetration at the impact face. Localized shear damage in the 3D woven system precedes penetration in both the nonporous and the porous systems. Experimental observations, which indicate that a porous system can dissipate more energy than the nonporous system before penetration, are found to be mainly attributed to the confinement of local damage fields, which emanate from the boundaries of the embedded voids.}, number={8}, journal={COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING}, author={Bahei-El-Din, YA and Zikry, MA and Rajendran, AM}, year={2003}, pages={765–778} }
 @article{ashmawi_zikry_2003, title={Single void morphological and grain-boundary effects on overall failure in FCC polycrystalline systems}, volume={343}, ISSN={["1873-4936"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0037465014&partnerID=MN8TOARS}, DOI={10.1016/s0921-5093(02)00325-8}, abstractNote={An investigation of how dislocation-density interactions, such as impedance, transmission, and absorption, with grain-boundaries (GBs) affect and control void growth and porosity evolution in F.C.C. aggregates has been conducted. A multiple-slip rate-dependent crystalline constitutive formulation that is coupled to the evolution of mobile and immobile dislocation-densities, a new internal porosity formulation for microvoid nucleation and growth, and specialized computational schemes have been developed to understand and quantify the interrelated effects of GB orientation, mobile and immobile dislocation-density evolution, and dislocation-density transmission and blockage on microvoid nucleation and growth. The effects of GB structure and orientation on ductile failure have been accounted for by the development of GB interfacial kinematic conditions that account for dislocation-density interactions with GBs, such as full and partial transmission, impedance, blockage, and absorption. Pile-ups and transmission regions are identified and monitored as the deformation and failure evolves. It is shown that mobile dislocation-density saturation, void size and shape, and dislocation-density interactions within the grains and the GBs are the interrelated triggering mechanisms that lead to porosity nucleation, growth, and localization.}, number={1-2}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Ashmawi, WM and Zikry, MA}, year={2003}, month={Feb}, pages={126–142} }
 @inproceedings{bahei-el-din_zikry_rajendran_2002, title={Deformation fields in woven composite plates under impact}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-78249232051&partnerID=MN8TOARS}, DOI={10.1115/IMECE2002-39482}, abstractNote={The deformation fields and kinematics of woven composite material systems due to impact loads are analyzed and characterized for various structural parameters. Target plates comprised of woven composites with 3D preforms are considered. The analysis examines fully consolidated as well as cellular systems and simulates actual experiments. Solution of the nonlinear dynamic/contact problem was obtained by a meso-mechanics based finite element model. The results quantify experimental observations, which reveal distinct behavior under impact among nonporous and porous systems. It was found that wave propagation effects at incident energies in the order of 500 J are significant and lead to penetration at the impact face. Localized shear damage in the 3D woven system precede penetration in both the nonporous and the porous systems. The porous system is capable of dissipating more energy prior to penetration due to containment of local damage, which emanates from the void boundaries, within subsurface locations.}, booktitle={ASME International Mechanical Engineering Congress and Exposition, Proceedings}, author={Bahei-El-Din, Y.A. and Zikry, M.A. and Rajendran, A.}, year={2002}, pages={41–45} }
 @article{garg_zikry_anderson_stepp_2002, title={Health monitoring and reliability of adaptive heterogeneous structures}, volume={1}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-1542359725&partnerID=MN8TOARS}, DOI={10.1177/147592170200100103}, abstractNote={ New adaptive structural systems comprised of optimal material combinations, innovative sensors and actuators, and control subsystems need to be developed and tailored for damage tolerant applications associated with severe loading conditions and harsh environments. In this position paper, fundamental considerations related to the modeling, design, and performance prediction of adaptive heterogeneous structures and benchmark laboratory experiments that would be needed for developing new and reliable sensor-integrated adaptive structures are discussed. Recent progress in these areas is discussed and new research directions that are needed and the barriers to be overcome to fulfill these objectives are proposed. One major challenge is to optimally integrate a variety of sensors and actuators in the context of health monitoring in order to enhance structural performance and reliability. The other major challenge is of scaling material and structural behavior from the micro- and meso-levels to the macro-level for full-scale adaptive structural system performance. }, number={1}, journal={Structural Health Monitoring}, author={Garg, D.P. and Zikry, M.A. and Anderson, G.L. and Stepp, D.}, year={2002}, pages={23–39} }
 @article{ashmawi_zikry_2002, title={Prediction of grain-boundary interfacial mechanisms in polycrystalline materials}, volume={124}, ISSN={["0094-4289"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0012448372&partnerID=MN8TOARS}, DOI={10.1115/1.1421611}, abstractNote={A multiple slip dislocation-density based crystalline formulation has been coupled to a kinematically based scheme that accounts for grain-boundary (GB) interfacial interactions with dislocation densities. Specialized finite-element formulations have been used to gain detailed understanding of the initiation and evolution of large inelastic deformation modes due to mechanisms that can result from dislocation-density pile-ups at GB interfaces, partial and total dislocation-density transmission from one grain to neighboring grains, and dislocation density absorption within GBs. These formulations provide a methodology that can be used to understand how interactions at the GB interface scale affect overall macroscopic behavior at different inelastic stages of deformation for polycrystalline aggregates due to the interrelated effects of GB orientations, the evolution of mobile and immobile dislocation-densities, slip system orientation, strain hardening, geometrical softening, geometric slip compatibility, and localized plastic strains. Criteria have been developed to identify and monitor the initiation and evolution of multiple regions where dislocation pile-ups at GBs, or partial and total dislocation density transmission through the GB, or absorption within the GB can occur. It is shown that the accurate prediction of these mechanisms is essential to understanding how interactions at GB interfaces affect and control overall material behavior.}, number={1}, journal={JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY-TRANSACTIONS OF THE ASME}, author={Ashmawi, WM and Zikry, MA}, year={2002}, month={Jan}, pages={88–96} }
 @article{garg_zikry_anderson_2001, title={Current and potential future research activities in adaptive structures: an ARO perspective}, volume={10}, ISSN={["1361-665X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0035417935&partnerID=MN8TOARS}, DOI={10.1088/0964-1726/10/4/304}, abstractNote={The Army Research Office (ARO) has been supporting projects focusing on basic research in the area of smart materials and adaptive structures over recent years. A major emphasis of the ARO's Structures and Dynamics Program has been on the theoretical, computational, and experimental analysis of smart structures and structural dynamics, damping, active control, and health monitoring as applied to rotorcraft, electromagnetic antenna structures, missiles, land vehicles, and weapon systems. The variety of research projects supported by the program have been primarily directed towards improving the ability to predict, control, and optimize the dynamic response of complex, multi-body deformable structures. The projects in the field of smart materials and adaptive structures have included multi-disciplinary research conducted by teams of several faculty members as well as research performed by individual investigators. This paper begins with a brief discussion of smart or active materials, i.e. materials having capabilities of sensing changes from the surrounding environment and actively responding to those inputs in an effective manner. Integrating these materials in structures makes them `smart', i.e. it provides them with the capability to respond to the external stimuli to compensate for undesired effects and/or to enhance the desired effects. The terms `active', `smart', `adaptive', and `intelligent' are frequently used interchangeably in this context. This discussion is followed by illustrations from several current ARO-sponsored research projects related to smart materials and adaptive structures. A summary of significant results based upon these investigations is given next. Finally, directions of potential future research in the smart materials and adaptive structures area are discussed.}, number={4}, journal={SMART MATERIALS AND STRUCTURES}, author={Garg, DP and Zikry, MA and Anderson, GL}, year={2001}, month={Aug}, pages={610–623} }
 @inproceedings{baucom_zikry_qiu_2001, title={Dynamic failure mechanisms in 3D cellular woven composite systems}, volume={248}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0242665316&partnerID=MN8TOARS}, booktitle={American Society of Mechanical Engineers, Applied Mechanics Division, AMD}, author={Baucom, J.N. and Zikry, M.A. and Qiu, Y.}, year={2001}, pages={117–123} }
 @article{qiu_xu_wang_zikry_mohamed_2001, title={Fabrication and characterization of three-dimensional cellular-matrix composites reinforced with woven carbon fabric}, volume={61}, ISSN={["0266-3538"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0035657722&partnerID=MN8TOARS}, DOI={10.1016/S0266-3538(01)00164-6}, abstractNote={A low-density three-dimensional cellular-matrix composite reinforced with woven carbon fabric (3DCMC), was fabricated by means of a pressure-quenching molding technique with nitrogen gas as the blowing agent. Epoxy resins in the interstices of yarns in the 3DCMC samples were vacated during the foaming process and needle shaped voids were also generated between fibers in yarns. The average density of the 3DCMC samples was about 103 kg/m3, and their density reduction was 28–37% compared with a regular matrix composite with the same preform. The 3DCMC has 32–42% higher specific tensile strength, 14–37% greater specific tensile modulus, a lower specific flexure strength but 35% higher specific tangent modulus in 3-point bending, a 30–40% higher specific impact energy absorption at an impact velocity around 120 m/s and a similar specific energy absorption at about 220 m/s. Meanwhile, the 3-point bending and impact test results of 3DCMC showed that they have different fracture mechanisms from that of 3DRMC.}, number={16}, journal={COMPOSITES SCIENCE AND TECHNOLOGY}, author={Qiu, YP and Xu, W and Wang, YJ and Zikry, MA and Mohamed, MH}, year={2001}, pages={2425–2435} }
 @inproceedings{baucom_zikry_2001, title={Impact-induced damage progression in 2-D and 3-D woven composite systems}, volume={66}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0242410454&partnerID=MN8TOARS}, booktitle={American Society of Mechanical Engineers, Aerospace Division (Publication) AD}, author={Baucom, J.N. and Zikry, M.A.}, year={2001}, pages={67–76} }
 @article{subhash_sulibhavi_zikry_2001, title={Influence of strain-rate on the uniaxial compressive behavior of 2-D braided textile composites}, volume={32}, ISSN={["1359-835X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0035501401&partnerID=MN8TOARS}, DOI={10.1016/S1359-835X(01)00011-2}, abstractNote={The uniaxial compressive stress–strain response and the associated observed micro-structural deformation mechanisms of three braided textile composite sheets were experimentally investigated at quasi-static and high-strain-rates. The compressive loads were applied in a direction perpendicular to the plane of the textile composites. For quasi-static loading, the three composites exhibited a non-linear elastic response followed by a load-drop at the on-set of matrix failure. With further increase in load, the axial and bias braids were stretched in the matrix damaged zones resulting in inelastic deformation at a constant stress level. Under high-strain-rate loading conditions, the yield strength increased upto 60%, and the overall stress did not unload as a function of strain. Composites with a greater number of lay-ups exhibited nonuniform deformation along the thickness direction in the form of shear fracture through several lay-ups.}, number={11}, journal={COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING}, author={Subhash, G and Sulibhavi, S and Zikry, MA}, year={2001}, pages={1583–1591} }
 @inproceedings{garg_zikry_anderson_stepp_2001, title={Reliable adaptive structures via sensor integration: Research and development issues}, volume={3}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85067322036&partnerID=MN8TOARS}, DOI={10.2514/6.2001-1440}, booktitle={19th AIAA Applied Aerodynamics Conference}, author={Garg, D.P. and Zikry, M.A. and Anderson, G.L. and Stepp, D.}, year={2001}, pages={1918–1926} }
 @article{garmestani_zikry_2001, title={Special issue on: "Inelastic Deformation and Failure" in honor of Professor E.W. Hart on his 80th birthday - Editorial}, volume={17}, ISSN={["0749-6419"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0034741804&partnerID=MN8TOARS}, DOI={10.1016/S0749-6419(00)00085-1}, number={10}, journal={INTERNATIONAL JOURNAL OF PLASTICITY}, author={Garmestani, H and Zikry, MA}, year={2001}, pages={1303–1304} }
 @article{orsini_zikry_2001, title={Void growth and interaction in crystalline materials}, volume={17}, ISSN={["1879-2154"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0034741808&partnerID=MN8TOARS}, DOI={10.1016/S0749-6419(00)00091-7}, abstractNote={An inelastic rate-dependent crystalline constitutive formulation and specialized computational schemes have been developed and used to obtain a detailed understanding of the interrelated physical mechanisms that can result in ductile material failure in rate-dependent porous crystalline materials subjected to finite inelastic deformations. The effects of void growth and interaction and specimen necking on material failure have been investigated for a single material cell, with a discrete cluster of four voids, where geometrical parameters have been varied to result in seven unique periodic and random void arrangements. The interrelated effects of void distribution and geometry, strain hardening, geometrical softening, localized plastic strains and slip-rates, and hydrostatic stresses on failure paths and ligament damage in face centered cubic (f.c.c.) crystalline materials have been studied. Results from this study are consistent with experimental observations that ductile failure can occur either due to void growth parallel to the stress axis, which results in void coalescence normal to the stress axis, or void interaction along bands, which are characterized by intense shear-strain localization and that intersect the free surface at regions of extensive specimen necking.}, number={10}, journal={INTERNATIONAL JOURNAL OF PLASTICITY}, author={Orsini, VC and Zikry, MA}, year={2001}, pages={1393–1417} }
 @inproceedings{baucom_zikry_qiu_2000, title={Control of failure evolution in 3D cellular woven composite systems}, volume={2000-G}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0242537027&partnerID=MN8TOARS}, DOI={10.1115/IMECE2000-2155}, abstractNote={Abstract}, booktitle={ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)}, author={Baucom, J.N. and Zikry, M.A. and Qiu, Y.}, year={2000}, pages={59–65} }
 @article{ashmawi_zikry_2000, title={Effects of grain boundaries and dislocation density evolution on large strain deformation modes in fcc crystalline materials}, volume={7}, ISSN={["0928-1045"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0033876739&partnerID=MN8TOARS}, DOI={10.1023/A:1008717428264}, number={1}, journal={JOURNAL OF COMPUTER-AIDED MATERIALS DESIGN}, author={Ashmawi, WM and Zikry, MA}, year={2000}, pages={55–62} }
 @article{zikry_pothier_baucom_2000, title={High strain-rate shear-strain localization in f.c.c. crystalline materials: a perturbation analysis}, volume={37}, ISSN={["0020-7683"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0345852386&partnerID=MN8TOARS}, DOI={10.1016/S0020-7683(99)00266-8}, abstractNote={A new perturbation formulation has been developed that is based on a rate-dependent crystalline plasticity constitutive formulation to investigate planar high strain-rate instabilities and shear-strain localization in face-centered cubic (f.c.c.) crystalline materials. This new formulation can account for strain-rate sensitivity values that range from rate-independent to highly rate-dependent values. Hence, accurate and detailed predictions of material instabilities and shear-strain localization can be obtained for high strain-rate deformations of crystalline materials that are rate-sensitive, such as f.c.c. materials. Critical instability parameters are obtained for deformation modes that account for the effects of strain-rate history, inertia, strain-hardening, wave number, and thermal and geometrical softening for applied strain-rates that range from 100 to 5000 s−1. Post-instability behavior and localization modes are monitored by tracking the rate of growth of stability parameters beyond the initial instability point. Results from these perturbation analyses are in good agreement with rate-independent limiting cases and high strain-rate experimental observations. The present study underscores the importance of characterizing material instabilities and shear-strain localization in terms of the competing softening and hardening mechanisms of the lattice structure.}, number={43}, journal={INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES}, author={Zikry, MA and Pothier, MR and Baucom, JN}, year={2000}, month={Oct}, pages={6177–6202} }
 @inproceedings{ashmawi_zikry_2000, title={Microstructurally induced ductile deformation mechanisms and grain-boundary effects in polycrystalline aggregates}, volume={578}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0033697993&partnerID=MN8TOARS}, booktitle={Materials Research Society Symposium - Proceedings}, author={Ashmawi, W.M. and Zikry, M.A.}, year={2000}, pages={339–344} }
 @article{flanagan_zikry_wall_el-shiekh_1999, title={An experimental investigation of high velocity impact and penetration failure modes in textile composites}, volume={33}, ISSN={["0021-9983"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0032668475&partnerID=MN8TOARS}, DOI={10.1177/002199839903301202}, abstractNote={ The dynamic failure evolution of textile composites, which were subjected to impact velocities up to 1100 m/s, was investigated. Specialized machines were used to fabricate composites from combinations of Spectra®, Kevlara®, and Twaron® fibers and two- and three-dimensionally woven, braided, and needle-punched nonwoven fabrics. This control of fabrication and processing enabled us to characterize response as a function of areal density, fabric finish, and consolidation techniques. Failure was categorized in terms of material layers, debris mass, matrix cracking, fiber failure, and shear-plugging. Results indicate that shear-plugging occurs at velocities corresponding to decreases in debris mass. }, number={12}, journal={JOURNAL OF COMPOSITE MATERIALS}, author={Flanagan, MP and Zikry, MA and Wall, JW and El-Shiekh, A}, year={1999}, pages={1080–1103} }
 @article{baucom_zikry_1999, title={Perturbation analysis of high strain-rate shear localization in BCC crystalline materials}, volume={137}, ISSN={["0001-5970"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0033316049&partnerID=MN8TOARS}, DOI={10.1007/BF01313148}, number={1-2}, journal={ACTA MECHANICA}, author={Baucom, JN and Zikry, MA}, year={1999}, pages={109–129} }
 @article{zikry_kameda_1998, title={Inelastic three dimensional high strain-rate dislocation density based analysis of grain-boundary effects and failure modes in ordered intermetallics}, volume={28}, ISSN={["0167-6636"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0032068356&partnerID=MN8TOARS}, DOI={10.1016/S0167-6636(97)00026-4}, abstractNote={A three dimensional dislocation density based multiple slip crystalline formulation and computational scheme are introduced for a detailed understanding and accurate characterization of interrelated failure mechanisms that may occur on different length scales in intermetallics subjected to high strain-rates. This constitutive framework accounts for the generation, trapping, interaction, and annihilation of mobile and immobile dislocations densities that are generally associated with finite strain high strain-rate plasticity in Ll 2 ordered intermetallics. Coincident site-lattice (CSL) and random grain boundaries (GBs) effects on intergranular and transgranular failure at triple junctions are investigated. Results from this study indicate that intergranular cracks can nucleate due to dislocation pile-ups along the GBs, and that transgranular failure occurs on slip-planes that intersect the GB.}, number={1-4}, journal={MECHANICS OF MATERIALS}, author={Zikry, MA and Kameda, T}, year={1998}, month={May}, pages={93–102} }
 @article{kameda_zikry_1998, title={Intergranular and transgranular crack growth at triple junction boundaries in ordered intermetallics}, volume={14}, ISSN={["0749-6419"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0032309910&partnerID=MN8TOARS}, DOI={10.1016/S0749-6419(98)00017-5}, abstractNote={Abstract Coincident site-lattice (CSL) and random grain boundaries (GBs) effects on intergranular and transgranular crack propagation paths in ordered intermetallics that are subjected to high rates of strain are investigated. A three dimensional dislocation density based multiple slip crystalline formulation and computational scheme are used for a detailed understanding and accurate characterization of interrelated deformation and failure mechanisms that can occur due to the generation, trapping, interaction, and annihilation of mobile and immobile dislocation densities that are generally associated with finite strain high strain-rate plasticity in L1 2 ordered intermetallics. Results from this study indicate that intergranular crack growth is along the GBs, normal to the stress-axis, and is due to the dominance of normal stresses in the crack-tip region. Transgranular crack growth is along slip-planes, and is due to the dominance of shear stresses in the crack-tip region.}, number={8}, journal={INTERNATIONAL JOURNAL OF PLASTICITY}, author={Kameda, T and Zikry, MA}, year={1998}, pages={689–702} }
 @article{zikry_garmestani_1998, title={Special issue: Deformation and failure modes in multiphase materials}, volume={14}, number={8}, journal={International Journal of Plasticity}, author={Zikry, M. A. and Garmestani, H.}, year={1998}, pages={671} }
 @article{kameda_zikry_1998, title={Three dimensional dislocation-based crystalline constitutive formulation for ordered intermetallics}, volume={38}, ISSN={["1359-6462"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0031599393&partnerID=MN8TOARS}, DOI={10.1016/s1359-6462(97)00512-5}, abstractNote={Materials developed with special surface architecture are shown here to be more resilient to the transient thermomechanical environments imposed by intermittent exposures to high heat flux thermal loading typical of long-pulse plasma transients. In an accompanying article, we present experimental results that show the relaxation of residual thermal stresses in micro-engineered W surfaces. A dislocation-based model is extended here within the framework of large deformation crystal plasticity. The model is applied to the deformation of single crystals, polycrystals, and micro-engineered surfaces composed of a uniform density of micro-pillars. The model is utilized to design tapered surface micro-pillar architecture, composed of a Re core and W coatings. Residual stresses generated by cyclic thermomechanical loading of these architectures show that the surface can be in a compressive stress state, following a short shakedown plasma exposure, thus mitigating surface fracture.}, number={4}, journal={SCRIPTA MATERIALIA}, author={Kameda, T and Zikry, MA}, year={1998}, month={Jan}, pages={631–636} }
 @article{zikry_kao_1997, title={Inelastic microstructural failure modes in crystalline materials: The Sigma 33a and Sigma 11 high angle grain boundaries}, volume={13}, ISSN={["0749-6419"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0030713244&partnerID=MN8TOARS}, DOI={10.1016/S0749-6419(97)80006-X}, abstractNote={The initiation and evolution of microstructurally induced failure mechanisms in crystalline materials with coincident site lattice (CSL) high angle grain boundaries (GBs) have been investigated. A constitutive formulation that couples a rate-dependent multiple-slip crystalline formulation, through internal variables, to evolutionary equations for the mobile and immobile dislocation densities, has been developed. This dislocation-density based constitutive formulation is used with specialized computational schemes to investigate failure modes in f.c.c. crystalline materials with Σ11 and Σ33a CSL GBs. The interrelated effects of mobile and immobile dislocation densities, lattice rotation, localized plastic slip, and high angle GB misorientations on the evolution of failure modes that can occur owing to dislocation pile-ups and slip-rate blockage and transmission at the GB have been investigated. Comparisons have been made with experimental results and observations, and results from this study are consistent with experimental observations that transgranular failure can occur owing to single dislocation pile-ups at the GB for the Σ11 and Σ33a CSL GBs.}, number={4}, journal={INTERNATIONAL JOURNAL OF PLASTICITY}, author={Zikry, MA and Kao, M}, year={1997}, pages={403–434} }
 @article{zikry_kao_1996, title={Dislocation based multiple-slip crystalline constitutive formulation for finite-strain plasticity}, volume={34}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0030129988&partnerID=MN8TOARS}, DOI={10.1016/1359-6462(95)00629-X}, abstractNote={Revisiting the classical topic of the strain hardening behaviour from a perspective of the analytical model based on the evolution of dislocation density with strain, we extended the capacity of the single internal variable model towards predicting necking instability and re-examined the grain size dependence of the flow stress. An excellent agreement is observed between the model predictions of the necking strain and stress and the results of tensile testing of nickel polycrystals with grain sizes varied from sub-micrometres to hundred micrometres. The pivotal significance of the dynamic recovery in the occurrence of necking has been analysed and emphasised in the context of the discussion on the effect of grain size on flow stress. The most interesting corollary of the analysis made is that not only the simple modelling of the dislocation density evolution, which can be traced back from the very early stage of plastic flow in materials with different grain sizes, can be used for realistic approximation of the stress-strain behaviour during homogeneous deformation under constant plastic strain rate, but also for predicting the onset of necking instability with high confidence.}, number={7}, journal={Scripta Materialia}, author={Zikry, M.A. and Kao, M.}, year={1996}, pages={1115–1121} }
 @article{zikry_kao_1996, title={Inelastic microstructural failure mechanisms in crystalline materials with high angle grain boundaries}, volume={44}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0030290888&partnerID=MN8TOARS}, DOI={10.1016/0022-5096(96)00049-X}, abstractNote={Microstructurally-induced failure mechanisms in crystalline materials with coincident site-lattice (CSL) high angle grain boundaries (GBs) have been investigated. A multiple-slip rate-dependent crystalline constitutive formulation that is coupled to the evolution of mobile and immobile dislocation densities and specialized computational schemes have been developed to obtain a detailed understanding of the interrelated physical mechanisms that result in material failure. A transmission scalar has also been introduced to investigate slip-rate transmission, blockage and incompatibility at the GB. The combined effects of high angle GB misorientation, mobile and immobile dislocation densities, strain hardening, geometrical softening, localized plastic strains, and slip-rate transmission and blockage on failure evolution in face centered cubic (f.c.c.) crystalline materials have been studied. Results from the present study are consistent with experimental observations that single dislocation pile-ups result in a transgranular failure mode for the ∑9 CSL GB, and that symmetric double dislocation pile-ups result in an intergranular failure mode for the ∑17b CSL GB.}, number={11}, journal={Journal of the Mechanics and Physics of Solids}, author={Zikry, M.A. and Kao, M.}, year={1996}, pages={1765–1798} }
 @inproceedings{zikry_kao_1995, title={Grain-boundary effects and failure mechanisms in crystalline materials}, volume={212}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0029427840&partnerID=MN8TOARS}, booktitle={American Society of Mechanical Engineers, Applied Mechanics Division, AMD}, author={Zikry, M.A. and Kao, M.}, year={1995}, pages={107–128} }
 @article{zikry_kao_1995, title={Large-scale crystal plasticity computations of microstructural failure modes}, volume={6}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0007616957&partnerID=MN8TOARS}, DOI={10.1016/0956-0521(95)00024-T}, abstractNote={Abstract A computational scheme is introduced for the integration of rate-dependent multiple-slip crystal plasticity constitutive relations. Fundamental issues of accuracy, stability, and stiffness that are intrinsically related to the evolution of microstructural failure modes in metallic crystals are addressed. An adaptive finite-element methodology is introduced to classify these characteristics. A nonlinear initial value system is derived to update the plastic deformation-rate tensor. An explicit method is used in non-stiff domains, where accuracy is required. If a time-step reduction is due to stability, a harbinger of numerical stiffness, the algorithm is automatically switched to an A-stable method. A stiffness ratio is defined to measure the eigenvalue dispersion of the system. The adaptability of the proposed algorithm for the solution of a class of inelastic constitutive relations is illustrated by investigating the influence of high angle grain boundary orientations on failure in face-centered cubic (f.c.c.) bicrystals. The effects of grain boundary misorientation, dislocation densities, strain hardening, and geometrical softening on failure evolution are investigated. This study underscores the importance of understanding the origin of numerical instabilities, such that these instabilities are not mistaken for inherent material instabilities.}, number={3}, journal={Computing Systems in Engineering}, author={Zikry, M.A. and Kao, M.}, year={1995}, pages={225–240} }
 @inproceedings{zikry_kao_1995, title={Microstructural failure mechanisms in crystalline materials}, volume={200}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0028994195&partnerID=MN8TOARS}, booktitle={American Society of Mechanical Engineers, Applied Mechanics Division, AMD}, author={Zikry, M.A. and Kao, M.}, year={1995}, pages={143–163} }
 @article{zikry_1994, title={An accurate and stable algorithm for high strain-rate finite strain plasticity}, volume={50}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0028762570&partnerID=MN8TOARS}, DOI={10.1016/0045-7949(94)90004-3}, abstractNote={A computational scheme is introduced for the integration of rate-dependent constitutive relations for the high strain-rate finite inelastic deformation and failure of metallic materials. Fundamental issues of accuracy, stability, and stiffness that are intrinsically related to the evolution of dynamic inelastic deformation and failure modes, such as shear-band formation, are addressed. Due to this evolution, accuracy, and stability characteristics of the constitutive relations change throughout the integration domain. Stiffness, a stability problem, may occur due to widely dispersed solution components that result from material instabilities. An adaptive methodology is introduced to classify these characteristics, and appropriate numerical methods were used. The current deformation configuration was updated by obtaining the current total deformation and the plastic deformation-rate tensors. The total deformation-rate tensor was obtained by an explicit finite element method. A nonlinear initial value problem is derived to update the plastic deformation-rate tensor. A combination of a fifth-order accurate explicit Runge-Kutta variable-step method and the A-stable backward Euler method were used to integrate this initial value system. The explicit method was used in nonstiff domains, where accuracy is required. If a time-step reduction was due to stability, a harbinger of numerical stiffness, the algorithm was automatically switched to the A-stable method. To distinguish a time-step reduction due to stability from one due to accuracy, a stiffness ratio is defined to measure the eigenvalue dispersion of the initial-value system. The adaptability of the proposed algorithm to a wide class of inelastic constitutive relations is illustrated by applications to crystal plasticity. This study underscores the importance of understanding the origin of numerical instabilities, such that these instabilities are not mistaken for inherent material instabilities.}, number={3}, journal={Computers and Structures}, author={Zikry, M.A.}, year={1994}, pages={337–350} }
 @article{zikry_1994, title={Dynamic void collapse and material failure mechanisms in metallic crystals}, volume={17}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0028397428&partnerID=MN8TOARS}, DOI={10.1016/0167-6636(94)90065-5}, abstractNote={The micromechanical failure mechanisms of compression-induced high strain-rate void collapse in monocrystalline copper are studied. A theoretical and a computational constitutive model are introduced to study the material failure mechanisms of shear-strain localization and cleavage fracture in monocrystalline fcc structures. An explicit dynamic finite-element algorithm is introduced for the integration of the numerically stiff micromechanical visco-plastic constitutive relations. The combined effects of strain hardening, strain-rate history, lattice rotation, and thermal softening on void collapse are investigated, and criteria for the formation of macroscopic shear-bands and tensile cracks formation are developed. The computed results are compared with experimental results and observations, and it is shown that the material failure mode is governed by the competition between the strengthening and the softening mechanisms of the crystalline structure. Shear bands may form, if the thermal and geometrical softening mechanisms of the crystal surmount the dynamic strain hardening and the strain-rate hardening of the crystal. An increase in the strain hardening and the strain-rate hardening of the crystal retards the formation of shear bands. Material failure, in this case, is due to the coupled effects of large stress concentrations and physically limiting values of plastic strain-rates, temperatures, resolved shear-stresses, and dislocation velocities near the tip of the collapsed void. These physically limiting values result in the homogeneous generation of dislocations and the local unloading of the stresses from compression to tension at the void tip. This opening mode of stress, at the void tip, in combination with the limiting values, can result in tensile cracks occurring normal to the compression stress axis.}, number={2-3}, journal={Mechanics of Materials}, author={Zikry, M.A.}, year={1994}, pages={273–288} }
 @inproceedings{zikry_kao_1994, title={High angle grain boundary effects and microstructural failure mechanisms in crystalline materials}, volume={42}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0028731415&partnerID=MN8TOARS}, booktitle={American Society of Mechanical Engineers, Aerospace Division (Publication) AD}, author={Zikry, M.A. and Kao, M.}, year={1994}, pages={71–101} }
 @inproceedings{zikry_1993, title={Failure modes in cubic crystalline materials}, volume={36}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0027853243&partnerID=MN8TOARS}, booktitle={American Society of Mechanical Engineers, Aerospace Division (Publication) AD}, author={Zikry, M.A.}, year={1993}, pages={199–210} }
 @inproceedings{zikry_1992, title={High strain-rate failure mechanisms in single crystals}, volume={132}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0026479668&partnerID=MN8TOARS}, booktitle={American Society of Mechanical Engineers, Applied Mechanics Division, AMD}, author={Zikry, M.A.}, year={1992}, pages={265–279} }
 @article{zikry_nemat-nasser_1990, title={High strain-rate localization and failure of crystalline materials}, volume={10}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-0025640233&partnerID=MN8TOARS}, DOI={10.1016/0167-6636(90)90044-G}, abstractNote={A theoretical and a computational model are introduced to study the micromechanical high strain-rate failure mechanisms of shear-strain localization in monocrystalline fcc structures. A theoretical framework for a constitutive model for the dynamic finite plastic deformation of rate-dependent single fcc crystals is developed. The micromechanics of plastic flow are based on a high strain-rate single crystal plasticity model and a visco-plastic power law. The single crystal is subjected to far-field dynamic tensile strain-rates ranging from 100/s to 2000/s. An explicit finite-element model is introduced for the integration of the numerically stiff visco-plastic constitutive relations. The total deformation rate tensor is obtained by the central difference explicit integration of the equations of motion. The plastic deformation rate tensor is obtained from the solution of an initial-value nonlinear problem for the resolved shear stresses. In time intervals when the differential equations for the resolved shear stresses are not numerically stiff, the initial-value problem is integrated by the explicit fifth-order Runge-Kutta adaptive time-step method. In time domains where the propagated error grows and the time-step must be restricted due to stability requirements, which is an indication of numerical stiffness, the initial-value problem is integrated by an A-stable method. To correctly differentiate time-step reductions due to stability, from time-step reductions due to accuracy, a stiffness ratio is defined. The present analysis corroborates experimental observations that high strain-rate shear-strain localization, in rate-dependent crystals, is a function of thermal and geometrical softening, overall strain-rates, strain hardening, strain-rate hardening, and strain-rate sensitivity.}, number={3}, journal={Mechanics of Materials}, author={Zikry, M.A. and Nemat-Nasser, S.}, year={1990}, pages={215–237} }