A new procedure for implementing the modified inherent strain method with improved accuracy in predicting both residual stress and deformation for laser powder bed fusion

Wen Dong, Xuan Liang, Qian Chen, Shawn Hinnebusch, Zekai Zhou, Albert C. To

Research output: Contribution to journalArticlepeer-review

60 Scopus citations

Abstract

As a metal additive manufacturing (AM) process, laser powder bed fusion (L-PBF) has been widely used to produce parts with complex geometries. The large thermal gradient caused by the fast, intense, and repeated laser scanning induces significant residual deformation and stress to the as-built parts, which increase manufacturing difficulty and geometrical inaccuracy as a result. The modified inherent strain (MIS) method exploiting multiscale process simulations was developed to simulate residual deformation accurately and efficiently. However, the existing procedure of implementing the MIS method is found to give inaccurate residual stress prediction. In this work, a new implementation procedure for the MIS method is proposed to improve the simulation accuracy of residual stress without degrading the residual deformation prediction. The new procedure concerns the application of inherent strains to the part-scale layer-by-layer finite element model to obtain residual stress and deformation field. While the existing implementation of the part-scale MIS model involves only mechanical properties at ambient temperature, the new procedure adds one more solution step employing mechanical properties at an elevated temperature determined from the inherent strain extraction step. Both numerical and experimental studies are conducted to validate the proposed new implementation procedure. It shows that by using the new procedure, the MIS-based simulation can predict both residual stress and deformation of as-built L-PBF metal parts with good accuracy.

Original languageEnglish
Article number102345
JournalAdditive Manufacturing
Volume47
DOIs
StatePublished - Nov 2021
Externally publishedYes

Funding

This research work is supported by the Department of Energy , Nuclear Energy University Program (NEUP Project 18-15251 ). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect those of the Department of Energy.

Keywords

  • Inherent strain
  • Laser powder bed fusion
  • Residual stress
  • Temperature-dependent material property

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