@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{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} }
 @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{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{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} }