The Experts below are selected from a list of 78 Experts worldwide ranked by ideXlab platform
Jing Zhang - One of the best experts on this subject based on the ideXlab platform.
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A multi-scale multi-physics modeling framework of laser powder bed fusion additive manufacturing process
Metal Powder Report, 2018Co-Authors: Jing Zhang, Weng Hoh Lee, Hyun Hee Choi, Linmin Wu, Yi Zhang, Yeon-gil JungAbstract:A longstanding challenge is to optimize additive manufacturing (AM) process in order to reduce AM Component failure due to excessive distortion and cracking. To address this challenge, a multi-scale physics-based modeling framework is presented to understand the interrelationship between AM processing parameters and resulting properties. In particular, a multi-scale approach, spanning from atomic, particle, to Component levels, is employed. The simulations of sintered material show that sintered particles have lower mechanical strengths than the bulk metal because of their porous structures. Higher heating rate leads to a higher mechanical strength due to accelerated sintering rates. The average temperature in the powder bed increases with higher laser power. The predicted distortion due to residual stress in the AM Fabricated Component is in good agreement with experimental measurements. In summary, the model framework provides a design tool to optimize the metal powder based additive manufacturing process.
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Finite element simulation and experimental validation of distortion and cracking failure phenomena in direct metal laser sintering Fabricated Component
Additive Manufacturing, 2017Co-Authors: Yi Zhang, Jing ZhangAbstract:A new one-way coupled thermal-mechanical finite element based model of direct metal laser sintering (DMLS) is developed to simulate the process, and predict distortion and cracking failure location in the Fabricated Components. The model takes into account the layer-by-layer additive manufacturing features, solidification and melting phenomena. The model is first validated using experimental data, then model is applied to a DMLS Fabricated Component. The study shows how the stress distribution at the support-solid interface is critical to contributing to cracking and distortion. During the DMLS process, thermal stress at the support-solid interface reaches its maximum during the printing process, particularly when the first solid layer is built above the support layer. This result suggests that cracking at the interface may occur during the printing process, which is consistent with experimental observation. Using a design parametric study, a thick and low-density porous layer is found to reduce residual stress and distortion in the built Component. The developed finite element model can be used to future design and optimize DMLS process.
Sudarsanam S. Babu - One of the best experts on this subject based on the ideXlab platform.
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Numerical modeling of heat-transfer and the influence of process parameters on tailoring the grain morphology of IN718 in electron beam additive manufacturing
Acta Materialia, 2016Co-Authors: Narendran Raghavan, Neil Carlson, Sreekanth Pannala, Michael M. Kirka, Ryan R. Dehoff, John Turner, Srdjan Simunovic, Sudarsanam S. BabuAbstract:The fabrication of 3-D parts from CAD models by additive manufacturing (AM) is a disruptive technology that is transforming the metal manufacturing industry. The correlation between solidification microstructure and mechanical properties has been well understood in the casting and welding processes over the years. This paper focuses on extending these principles to additive manufacturing to understand the transient phenomena of repeated melting and solidification during electron beam powder melting process to achieve site-specific microstructure control within a Fabricated Component. In this paper, we have developed a novel melt scan strategy for electron beam melting of nickel-base superalloy (Inconel 718) and also analyzed 3-D heat transfer conditions using a parallel numerical solidification code (Truchas) developed at Los Alamos National Laboratory. The spatial and temporal variations of temperature gradient (G) and growth velocity (R) at the liquid-solid interface of the melt pool were calculated as a function of electron beam parameters. By manipulating the relative number of voxels that lie in the columnar or equiaxed region, the crystallographic texture of the Components can be controlled to an extent. The analysis of the parameters provided optimum processing conditions that will result in columnar to equiaxed transition (CET) during the solidification. The results from the numerical simulations were validated by experimental processing and characterization thereby proving the potential of additive manufacturing process to achieve site-specific crystallographic texture control within a Fabricated Component.
Yi Zhang - One of the best experts on this subject based on the ideXlab platform.
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A multi-scale multi-physics modeling framework of laser powder bed fusion additive manufacturing process
Metal Powder Report, 2018Co-Authors: Jing Zhang, Weng Hoh Lee, Hyun Hee Choi, Linmin Wu, Yi Zhang, Yeon-gil JungAbstract:A longstanding challenge is to optimize additive manufacturing (AM) process in order to reduce AM Component failure due to excessive distortion and cracking. To address this challenge, a multi-scale physics-based modeling framework is presented to understand the interrelationship between AM processing parameters and resulting properties. In particular, a multi-scale approach, spanning from atomic, particle, to Component levels, is employed. The simulations of sintered material show that sintered particles have lower mechanical strengths than the bulk metal because of their porous structures. Higher heating rate leads to a higher mechanical strength due to accelerated sintering rates. The average temperature in the powder bed increases with higher laser power. The predicted distortion due to residual stress in the AM Fabricated Component is in good agreement with experimental measurements. In summary, the model framework provides a design tool to optimize the metal powder based additive manufacturing process.
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Finite element simulation and experimental validation of distortion and cracking failure phenomena in direct metal laser sintering Fabricated Component
Additive Manufacturing, 2017Co-Authors: Yi Zhang, Jing ZhangAbstract:A new one-way coupled thermal-mechanical finite element based model of direct metal laser sintering (DMLS) is developed to simulate the process, and predict distortion and cracking failure location in the Fabricated Components. The model takes into account the layer-by-layer additive manufacturing features, solidification and melting phenomena. The model is first validated using experimental data, then model is applied to a DMLS Fabricated Component. The study shows how the stress distribution at the support-solid interface is critical to contributing to cracking and distortion. During the DMLS process, thermal stress at the support-solid interface reaches its maximum during the printing process, particularly when the first solid layer is built above the support layer. This result suggests that cracking at the interface may occur during the printing process, which is consistent with experimental observation. Using a design parametric study, a thick and low-density porous layer is found to reduce residual stress and distortion in the built Component. The developed finite element model can be used to future design and optimize DMLS process.
Raghavan Srinivasan - One of the best experts on this subject based on the ideXlab platform.
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Effect of Laser Power and Scan Speed on Melt Pool Characteristics of Commercially Pure Titanium (CP-Ti)
Journal of Materials Engineering and Performance, 2017Co-Authors: Chandrakanth Kusuma, Alec Mian, Sazzad H. Ahmed, Raghavan SrinivasanAbstract:Selective laser melting (SLM) is an additive manufacturing technique that creates complex parts by selectively melting metal powder layer-by-layer using a laser. In SLM, the process parameters decide the quality of the Fabricated Component. In this study, single beads of commercially pure titanium (CP-Ti) were melted on a substrate of the same material using an in-house built SLM machine. Multiple combinations of laser power and scan speed were used for single bead fabrication, while the laser beam diameter and powder layer thickness were kept constant. This experimental study investigated the influence of laser power, scan speed, and laser energy density on the melt pool formation, surface morphology, geometry (width and height), and hardness of solidified beads. In addition, the observed unfavorable effect such as inconsistency in melt pool width formation is discussed. The results show that the quality, geometry, and hardness of solidified melt pool are significantly affected by laser power, scanning speed, and laser energy density. © 2017, ASM International.
Narendran Raghavan - One of the best experts on this subject based on the ideXlab platform.
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Numerical modeling of heat-transfer and the influence of process parameters on tailoring the grain morphology of IN718 in electron beam additive manufacturing
Acta Materialia, 2016Co-Authors: Narendran Raghavan, Neil Carlson, Sreekanth Pannala, Michael M. Kirka, Ryan R. Dehoff, John Turner, Srdjan Simunovic, Sudarsanam S. BabuAbstract:The fabrication of 3-D parts from CAD models by additive manufacturing (AM) is a disruptive technology that is transforming the metal manufacturing industry. The correlation between solidification microstructure and mechanical properties has been well understood in the casting and welding processes over the years. This paper focuses on extending these principles to additive manufacturing to understand the transient phenomena of repeated melting and solidification during electron beam powder melting process to achieve site-specific microstructure control within a Fabricated Component. In this paper, we have developed a novel melt scan strategy for electron beam melting of nickel-base superalloy (Inconel 718) and also analyzed 3-D heat transfer conditions using a parallel numerical solidification code (Truchas) developed at Los Alamos National Laboratory. The spatial and temporal variations of temperature gradient (G) and growth velocity (R) at the liquid-solid interface of the melt pool were calculated as a function of electron beam parameters. By manipulating the relative number of voxels that lie in the columnar or equiaxed region, the crystallographic texture of the Components can be controlled to an extent. The analysis of the parameters provided optimum processing conditions that will result in columnar to equiaxed transition (CET) during the solidification. The results from the numerical simulations were validated by experimental processing and characterization thereby proving the potential of additive manufacturing process to achieve site-specific crystallographic texture control within a Fabricated Component.
