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Open AccessArticle

Analytical Modeling of Residual Stress in Laser Powder Bed Fusion Considering Part’s Boundary Condition

1
Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
2
Department of Mechanical Engineering, National Cheng Kung University, Tainan City 701, Taiwan
*
Author to whom correspondence should be addressed.
Crystals 2020, 10(4), 337; https://doi.org/10.3390/cryst10040337
Received: 31 March 2020 / Revised: 21 April 2020 / Accepted: 21 April 2020 / Published: 24 April 2020
(This article belongs to the Special Issue Additive Manufacturing (AM) of Metallic Alloys)
Rapid and accurate prediction of residual stress in metal additive manufacturing processes is of great importance to guarantee the quality of the fabricated part to be used in a mission-critical application in the aerospace, automotive, and medical industries. Experimentations and numerical modeling of residual stress however are valuable but expensive and time-consuming. Thus, a fully coupled thermomechanical analytical model is proposed to predict residual stress of the additively manufactured parts rapidly and accurately. A moving point heat source approach is used to predict the temperature field by considering the effects of scan strategies, heat loss at part’s boundaries, and energy needed for solid-state phase transformation. Due to the high-temperature gradient in this process, the part experiences a high amount of thermal stress which may exceed the yield strength of the material. The thermal stress is obtained using Green’s function of stresses due to the point body load. The Johnson–Cook flow stress model is used to predict the yield surface of the part under repeated heating and cooling. As a result of the cyclic heating and cooling and the fact that the material is yielded, the residual stress build-up is precited using incremental plasticity and kinematic hardening behavior of the metal according to the property of volume invariance in plastic deformation in coupling with the equilibrium and compatibility conditions. Experimental measurement of residual stress was conducted using X-ray diffraction on the fabricated IN718 built via laser powder bed fusion to validate the proposed model. View Full-Text
Keywords: residual stress prediction; IN718; experimental measurement of residual stress; additive manufacturing residual stress prediction; IN718; experimental measurement of residual stress; additive manufacturing
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Mirkoohi, E.; Tran, H.-C.; Lo, Y.-L.; Chang, Y.-C.; Lin, H.-Y.; Liang, S.Y. Analytical Modeling of Residual Stress in Laser Powder Bed Fusion Considering Part’s Boundary Condition. Crystals 2020, 10, 337.

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