@article{schoell_xi_west_hosemann_park_kenesei_almer_shayer_kaoumi_2022, title={Investigation of the fatigue crack behavior of 304 stainless steels using synchrotron X-ray tomography and diffraction: Influence of the martensite fraction and role of inclusions}, volume={188}, ISSN={["1873-4189"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85129349891&partnerID=MN8TOARS}, DOI={10.1016/j.matchar.2022.111903}, abstractNote={The effect of fatigue on the microstructure of four-point bend specimens of three variations of 304 stainless steels (Commercial 304, 304H, and 304 L) was investigated using synchrotron x-ray tomography and diffraction. X-ray tomography revealed the formation of the fatigue-induced microvoids and crack while the diffraction data was used to quantify the amount of deformation-induced martensite found after fatigue in all samples. Transmission electron microscopy evidenced the role of the precipitates/inclusions on the microvoid formation. It was found to depend on their chemical nature. The shape of the precipitates/inclusions was also found to have an effect on the microvoid shape.}, journal={MATERIALS CHARACTERIZATION}, author={Schoell, Ryan and Xi, Li and West, Harvey and Hosemann, Peter and Park, Jun-Sang and Kenesei, Peter and Almer, Jonathan and Shayer, Zeev and Kaoumi, Djamel}, year={2022}, month={Jun} }
 @article{rock_ledford_garcia-avila_west_miller_pankow_dehoff_horn_2021, title={The Influence of Powder Reuse on the Properties of Nickel Super Alloy ATI 718 (TM) in Laser Powder Bed Fusion Additive Manufacturing}, volume={52}, ISSN={["1543-1916"]}, DOI={10.1007/s11663-020-02040-2}, number={2}, journal={METALLURGICAL AND MATERIALS TRANSACTIONS B-PROCESS METALLURGY AND MATERIALS PROCESSING SCIENCE}, author={Rock, Christopher and Ledford, Christopher and Garcia-Avila, Matias and West, Harvey and Miller, Victoria M. and Pankow, Mark and Dehoff, Ryan and Horn, Tim}, year={2021}, month={Apr}, pages={676–688} }
 @article{rock_vadlakonda_figurskey_ledford_west_miller_pankow_daniels_horn_2020, title={Analysis of Self-Organized Patterned Surface Oxide Spots on Ejected Spatter Produced during Laser Powder Bed Fusion}, volume={35}, ISBN={2214-7810}, url={http://dx.doi.org/10.1016/j.addma.2020.101320}, DOI={10.1016/j.addma.2020.101320}, abstractNote={Spatter particles ejected from the melt pool after melting of 316 L stainless steel by laser powder bed fusion additive manufacturing (LPBF), were found to contain morphologies not observed in as-atomized 316 L powder. This spatter consisted of large, spherical particles, highly dendritic surfaces, particles with caps of accreted liquid, and agglomerations of multiple individual particles fixed together by liquid ligaments prior to solidification. The focus of this study is on an additional, unique spatter morphology consisting of larger, spherical particles with surface oxide spots exhibiting a wide distribution of surface configurations, including organized patterning. Spatter particles with organized surface oxide patterns were characterized for surface and internal particle features using multiple imaging techniques. The following observations are made: 1) spots resided at the spatter particle surface and did not significantly penetrate the interior, 2) the spot(s) were amorphous and rich in Silicon (Si)-Manganese (Mn)-Oxygen (O), 3) a two-part Chromium (Cr)-O rich layer exists between the particle and spot, 4) Cr-O rich morphological features were present at the top surface of the spots, 5) the spatter particle composition was consistent with 316 L but appeared to decrease in Si content into the spatter particle away from a spot, and 6) small Si-rich spherical particles existed within the spatter particle interior.}, journal={Additive Manufacturing}, publisher={Elsevier BV}, author={Rock, Christopher and Vadlakonda, Rashmi and Figurskey, Sullivan and Ledford, Christopher and West, Harvey and Miller, Victoria and Pankow, Mark and Daniels, Karen E. and Horn, Tim}, year={2020}, month={Oct}, pages={101320} }
 @article{mahbooba_thorsson_unosson_skoglund_west_horn_rock_vogli_harrysson_2018, title={Additive manufacturing of an iron-based bulk metallic glass larger than the critical casting thickness}, volume={11}, ISSN={["2352-9407"]}, DOI={10.1016/j.apmt.2018.02.011}, abstractNote={Fe-based bulk metallic glasses (BMG) are of increasing research interest, driven in part by a unique combination of mechanical, magnetic and chemical properties. However, the maximum thickness and geometry of BMGs achievable in traditional manufacturing processes is limited. This work examines the capabilities of laser based powder bed additive manufacturing (AM) to produce relatively large Fe-based bulk metallic glass specimens. AM fabricated specimens exceed the critical casting thickness of the material by a factor of 15 or more in all dimensions. Resulting microstructural and mechanical properties are reported. Despite decreasing quench effect with increasing build thickness, X-ray diffraction analysis suggests that a fully amorphous structure was maintained throughout the build. However, a low concentration of sparsely distributed nano-grain clusters was discovered using a high-resolution electron backscatter diffraction scan. The results pave the way for novel applications of metallic glasses achievable through appropriate material design and optimization of existing additive manufacturing processes.}, journal={APPLIED MATERIALS TODAY}, author={Mahbooba, Zaynab and Thorsson, Lena and Unosson, Mattias and Skoglund, Peter and West, Harvey and Horn, Timothy and Rock, Christopher and Vogli, Evelina and Harrysson, Ola}, year={2018}, month={Jun}, pages={264–269} }
 @inproceedings{xu_husain_west_yu_hopkins_2016, title={Development of an ultra-high density power chip on bus (PCoB) module}, url={https://www.lens.org/092-761-376-063-354}, DOI={10.1109/ecce.2016.7855040}, abstractNote={A traditional power module uses metal clad ceramic (e.g. DBC or DBA) bonded to a baseplate that creates a highly thermally resistive path, and wire bond interconnect that introduces substantial inductance and limits thermal management to single-sided cooling. This paper introduces a Power Chip on Bus (PCoB) power module approach that reduces parasitic inductance through an integrated power interconnect structure. The PCoB maximizes thermal performance by direct attaching power chips to the busbar, integrating the heatsink and busbar as one, and uses a dielectric fluid, such as air, for electrical isolation. This new power module topology features all planar interconnects and double-sided air cooling. Performance evaluations are carried out through comprehensive electrical and multi-physics simulation and thermal testing for a 1200V, 100A rated single-switch PCoB design. Fabrication and assembly processes are included. For the developed double-sided air-cooled module, 0.5°C/w thermal resistance and 8nH power loop parasitic inductance are achieved.}, note={\urlhttp://ieeexplore.ieee.org/document/7855040/}, booktitle={2016 ieee energy conversion congress and exposition (ecce)}, author={Xu, Y. and Husain, I. and West, H. and Yu, W. S. and Hopkins, Douglas C}, year={2016} }
 @article{mahbooba_west_harrysson_wojcieszynski_dehoff_nandwana_horn_2017, title={Effect of Hypoeutectic Boron Additions on the Grain Size and Mechanical Properties of Ti-6Al-4V Manufactured with Powder Bed Electron Beam Additive Manufacturing}, volume={69}, ISSN={["1543-1851"]}, DOI={10.1007/s11837-016-2210-9}, abstractNote={In additive manufacturing, microstructural control is feasible via processing parameter alteration. However, the window for parameter variation for certain materials, such as Ti-6Al-4V, is limited, and alternative methods must be employed to customize microstructures. Grain refinement and homogenization in cast titanium alloys has been demonstrated through the addition of hypoeutectic concentrations of boron. This work explores the influence of 0.00 wt.%, 0.25 wt.%, 0.50 wt.%, and 1.0 wt.% boron additions on the microstructure and bulk mechanical properties of Ti-6Al-4V samples fabricated in an Arcam A2 electron beam melting (EBM) system with commercial processing parameters for Ti-6Al-4V. Analyses of EBM fabricated Ti-6Al-4V + B indicate that the addition of 0.25–1.0 wt.% boron progressively refines the grain structure, and it improves hardness and elastic modulus. Despite a reduction in size, the β grain structure remained columnar as a result of directional heat transfer during EBM fabrication.}, number={3}, journal={JOM}, author={Mahbooba, Zaynab and West, Harvey and Harrysson, Ola and Wojcieszynski, Andrzej and Dehoff, Ryan and Nandwana, Peeyush and Horn, Timothy}, year={2017}, month={Mar}, pages={472–478} }
 @article{yang_harrysson_cormier_west_gong_stucker_2015, title={Additive Manufacturing of Metal Cellular Structures: Design and Fabrication}, volume={67}, ISSN={["1543-1851"]}, DOI={10.1007/s11837-015-1322-y}, number={3}, journal={JOM}, author={Yang, Li and Harrysson, Ola and Cormier, Denis and West, Harvey and Gong, Haijun and Stucker, Brent}, year={2015}, month={Mar}, pages={608–615} }
 @article{yang_harrysson_west_cormier_park_peters_2015, title={Low-energy drop weight performance of cellular sandwich panels}, volume={21}, ISSN={["1758-7670"]}, DOI={10.1108/rpj-08-2013-0083}, abstractNote={
               Purpose
                – The aim of this study is to perform a comparative study on sandwich structures with several types of three-dimensional (3D) reticulate cellular structural core designs for their low-energy impact absorption abilities using powder bed additive manufacturing methods. 3D reticulate cellular structures possess promising potentials in various applications with sandwich structure designs. One of the properties critical to the sandwich structures in applications, such as aerospace and automobile components, is the low-energy impact performance. 
            
            
               Design/methodology/approach
                – Sandwich samples of various designs, including re-entrant auxetic, rhombic, hexagonal and octahedral, were designed and fabricated via selective laser sintering (SLS) process using nylon 12 as material. Low-energy drop weight test was performed to evaluate the energy absorption of various designs. Tensile coupons were also produced using the same process to provide baseline material properties. The manufacturing issues such as geometrical accuracy and anisotropy effect as well as their effects on the performance of the structures were discussed. 
            
            
               Findings
                – In general, 3D reticulate cellular structures made by SLS process exhibit significantly different characteristics under low-energy drop weight impact compared to the regular extruded honeycomb sandwich panels. A hexagonal sandwich panel exhibits the largest compliance with the smallest energy absorption ability, and an octahedral sandwich panel exhibits high stiffness as well as good impact protection ability. Through a proper geometrical design, the re-entrant auxetic sandwich panels could achieve a combination of high energy absorption and low response force, making it especially attractive for low-impact protection applications. 
            
            
               Originality/value
                – There has been little work on the comparative study of the energy absorption of various 3D reticulate cellular structures to date. This work demonstrates the potential of 3D reticulate cellular structures as sandwich cores for different purposes. This work also demonstrates the possibility of controlling the performance of this type of sandwich structures via geometrical and process design of the cellular cores with powder bed additive manufacturing systems.
            }, number={4}, journal={RAPID PROTOTYPING JOURNAL}, author={Yang, Li and Harrysson, Ola A. and West, Harvey A., II and Cormier, Denis R. and Park, Chun and Peters, Kara}, year={2015}, pages={433–442} }
 @article{yang_harrysson_west_cormier_2015, title={Mechanical properties of 3D re-entrant honeycomb auxetic structures realized via additive manufacturing}, volume={69-70}, ISSN={["1879-2146"]}, DOI={10.1016/j.ijsolstr.2015.05.005}, abstractNote={In this work, an analytical model of a 3D re-entrant honeycomb auxetic cellular structure has been established based on both a large deflection beam model and a Timoshenko beam model. Analytical solutions for the modulus, Poisson’s ratios and yield strength of the cellular structure in all principal directions were obtained, which indicate a wide range of mechanical property control via geometrical designs. The results were compared with experimentation and finite element analysis, and it was verified that the analytical model provides a convenient and relatively accurate method in the prediction of the performance for the auxetic cellular structures once the manufacturing related factors are adequately incorporated into the model. It was also found that the model provides less accurate predictions when higher-order coupling effects such as warp locking becomes significant under lower structural symmetry.}, journal={INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES}, author={Yang, Li and Harrysson, Ola and West, Harvey and Cormier, Denis}, year={2015}, month={Sep}, pages={475–490} }
 @article{hasib_harrysson_west_2015, title={Powder Removal from Ti-6Al-4V Cellular Structures Fabricated via Electron Beam Melting}, volume={67}, ISSN={["1543-1851"]}, DOI={10.1007/s11837-015-1307-x}, abstractNote={Direct metal fabrication systems like electron beam melting (EBM) and direct metal laser sintering (also called selective laser melting) are gaining popularity. One reason is the design and fabrication freedom that these technologies offer over traditional processes. One specific feature that is of interest is mesh or lattice structures that can be produced using these powder-bed systems. One issue with the EBM process is that the powder trapped within the structure during the fabrication process is sintered and can be hard to remove as the mesh density increases. This is usually not an issue for the laser-based systems since most of them work at a low temperature and the sintering of the powder is less of an issue. Within the scope of this project, a chemical etching process was evaluated for sintered powder removal using three different cellular structures with varying mesh densities. All meshes were fabricated via EBM using Ti6Al4V powder. The results are promising, but the larger the structures, the more difficult it is to completely remove the sintered powder without affecting the integrity of the mesh structure.}, number={3}, journal={JOM}, author={Hasib, Hazman and Harrysson, Ola L. A. and West, Harvey A., II}, year={2015}, month={Mar}, pages={639–646} }
 @article{yang_harrysson_west_cormier_2012, title={Compressive properties of Ti-6Al-4V auxetic mesh structures made by electron beam melting}, volume={60}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2012.03.015}, abstractNote={In this current work, a Ti–6Al–4V 3-D re-entrant lattice auxetic structure is manufactured by the electron beam melting (EBM) process. Four different design configurations (two negative Poisson’s ratio values × two relative densities) were manufactured and tested under compressive stress. Two failure modes were observed whose occurrence appeared to be dependent on the ratio of vertical strut length to re-entrant strut length. A small deflection analytical model is presented that predicts yield strength and modulus for one type of design with good accuracy. Results also show that the re-entrant lattice structure possesses superior mechanical properties compared to regular foam structures. Limitations of the analytical model are also discussed.}, number={8}, journal={ACTA MATERIALIA}, author={Yang, Li and Harrysson, Ola and West, Harvey and Cormier, Denis}, year={2012}, month={May}, pages={3370–3379} }
 @article{yang_harrysson_west_cormier_2013, title={Modeling of uniaxial compression in a 3D periodic re-entrant lattice structure}, volume={48}, ISSN={["0022-2461"]}, DOI={10.1007/s10853-012-6892-2}, number={4}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Yang, Li and Harrysson, Ola and West, Harvey and Cormier, Denis}, year={2013}, month={Feb}, pages={1413–1422} }
 @article{yang_cormier_west_harrysson_knowlson_2012, title={Non-stochastic Ti-6Al-4V foam structures with negative Poisson's ratio}, volume={558}, ISSN={["1873-4936"]}, DOI={10.1016/j.msea.2012.08.053}, abstractNote={This paper details the design, fabrication, and testing of non-stochastic auxetic lattice lattice structures. All Ti–6Al–4V samples were created via the Electron Beam Melting (EBM) additive manufacturing process. It was found that the Poisson's ratio values significantly influence the mechanical properties of the structures. The bending properties of the auxetic samples were significantly higher than those of currently commercialized metal foams. The compressive strength was moderately higher than available metal foams. These results suggest that metallic auxetic structures have considerable promise for use in a variety of applications in which tradeoffs between mass and mechanical properties are crucial.}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Yang, Li and Cormier, Denis and West, Harvey and Harrysson, Ola and Knowlson, Kyle}, year={2012}, month={Dec}, pages={579–585} }
 @article{aman_west_cormier_2008, title={An evaluation of loose tenon joint strength}, volume={58}, number={3}, journal={Forest Products Journal}, author={Aman, R. L. and West, H. A. and Cormier, D. R.}, year={2008}, pages={61–64} }
 @article{cansizoglu_harrysson_west_cormier_mahale_2008, title={Applications of structural optimization in direct metal fabrication}, volume={14}, ISSN={["1355-2546"]}, DOI={10.1108/13552540810862082}, abstractNote={PurposeOptimization techniques can be used to design geometrically complex components with a wide variety of optimization criteria. However, such components have been very difficult and costly to produce. Layered fabrication technologies such as electron beam melting (EBM) open up new possibilities though. This paper seeks to investigate the integration of structural optimization and direct metal fabrication process.Design/methodology/approachMesh structures were designed, and optimization problems were defined to improve structural performance. Finite element analysis code in conjunction with nonlinear optimization routines were used in MATLAB. Element data were extracted from an STL‐file, and output structures from the optimization routine were manufactured using an EBM machine. Original and optimized structures were tested and compared.FindingsThere were discrepancies between the performance of the theoretical structures and the physical EBM structures due to the layered fabrication approach. A scaling factor was developed to account for the effect of layering on the material properties.Practical implicationsStructural optimization can be used to improve the performance of a design, and direct fabrication technologies can be used to realise these structures. However, designers must realize that fabricated structures are not identical to idealized CAD structures, hence material properties much be adjusted accordingly.Originality/valueIntegration of structural optimization and direct metal fabrication was reported in the paper. It shows the process from design through manufacturing with integrated analysis.}, number={2}, journal={RAPID PROTOTYPING JOURNAL}, author={Cansizoglu, Omer and Harrysson, Ola L. A. and West, Harvey A., II and Cormier, Denis R. and Mahale, Tushar}, year={2008}, pages={114–122} }
 @article{cansizoglu_harrysson_cormier_west_mahale_2008, title={Properties of Ti-6Al-4V non-stochastic lattice structures fabricated via electron beam melting}, volume={492}, ISSN={["0921-5093"]}, DOI={10.1016/j.msea.2008.04.002}, abstractNote={This paper addresses foams which are known as non-stochastic foams, lattice structures, or repeating open cell structure foams. The paper reports on preliminary research involving the design and fabrication of non-stochastic Ti–6Al–4V alloy structures using the electron beam melting (EBM) process. Non-stochastic structures of different cell sizes and densities were investigated. The structures were tested in compression and bending, and the results were compared to results from finite element analysis simulations. It was shown that the build angle and the build orientation affect the properties of the lattice structures. The average compressive strength of the lattice structures with a 10% relative density was 10 MPa, the flexural modulus was 200 MPa and the strength to density ration was 17. All the specimens were fabricated on the EBM A2 machine using a melt speed of 180 mm/s and a beam current of 2 mA. Future applications and FEA modeling were discussed in the paper.}, number={1-2}, journal={MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING}, author={Cansizoglu, O. and Harrysson, O. and Cormier, D. and West, H. and Mahale, T.}, year={2008}, month={Sep}, pages={468–474} }
 @article{harrysson_cansizoglu_marcellin-little_cormier_west_2008, title={Direct metal fabrication of titanium implants with tailored materials and mechanical properties using electron beam melting technology}, volume={28}, ISSN={["0928-4931"]}, DOI={10.1016/j.msec.2007.04.022}, abstractNote={The design of custom or tailored implant components has been the subject of research and development for decades. However, the economic feasibility of fabricating such components has proven to be a challenge. New direct metal fabrication technologies such as Electron Beam Melting (EBM) have opened up new possibilities. This paper discusses the design and fabrication of titanium implant components having tailored mechanical properties that mimic the stiffness of bone to reduce stress shielding and bone remodeling. Finite Element Analysis was used to design the tailored structures, and results were verified using mechanical testing.}, number={3}, journal={MATERIALS SCIENCE & ENGINEERING C-BIOMIMETIC AND SUPRAMOLECULAR SYSTEMS}, author={Harrysson, Ola L. A. and CansiZoglu, Omer and Marcellin-Little, Denis J. and Cormier, Denis R. and West, Harvey A., II}, year={2008}, month={Apr}, pages={366–373} }
 @article{cormier_harrysson_west_2004, title={Characterization of H13 steel produced via electron beam melting}, volume={10}, ISSN={["1355-2546"]}, DOI={10.1108/13552540410512516}, abstractNote={Electron beam melting (EBM) is a direct‐metal freeform fabrication technique in which a 4 kW electron beam is used to melt metal powder in a layer‐wise fashion. As this process is relatively new, there have not yet been any independently published studies on the H13 steel microstructural properties. This paper describes the EBM process and presents results of microstructural analyses on H13 tool steel processed via EBM.}, number={1}, journal={RAPID PROTOTYPING JOURNAL}, author={Cormier, D and Harrysson, A and West, H}, year={2004}, pages={35–41} }
 @misc{cormier_taylor_west_2001, title={Methods and apparatus for rapidly prototyping three-dimensional objects from a plurality of layers}, volume={6,324,438}, number={2001 Nov. 27}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Cormier, D. R. and Taylor, J. B. and West, Harvey A., II}, year={2001} }