An efficient numerical model for predicting residual stress and strain in parts manufactured by laser powder bed fusion

Computational modeling of additively manufactured structures plays an increasingly important role in product design and optimization. For laser powder bed fusion processes, the accurate modeling of stress and distortion requires large amount of computational cost due to very localized heat input and evolving complex geometries. The current study takes advantage of a graphics processing unit accelerated explicit finite element analysis code and approximated heat conduction analysis to predict the macroscopic thermo-mechanical behavior in laser selective melting. Adjacent layers and tracks were lumped to reduce the number of time steps and elements in the finite element model. The effects of track and layer grouping on prediction accuracy and solution efficiency are investigated to provide a guidance for a cost-effective simulation. Thin-wall builds from Inconel alloy 625 (IN625) powders were simulated by applying the developed modeling approach to get the detailed residual stress and distortion at a computational speed 50 times higher than conventional approach. Under repeated heating and cooling cycles, a high tensile stress was produced near surfaces of a build due to a larger shrinkage on surface than that in central area. It is also shown that horizontal stresses concentrate near the root and top layers of the IN625 build. The predicted residual elastic strain distribution was validated by the experimental measurement using x-ray synchrotron diffraction.

Automated summary

Computational modeling is crucial in product design and optimization for additively manufactured structures, especially in laser powder bed fusion processes that involve complex geometries and localized heat input. This study utilized GPU-accelerated finite element analysis and approximated heat conduction analysis to predict thermo-mechanical behavior in laser selective melting. By grouping adjacent layers and tracks, the model efficiency was improved without compromising accuracy, allowing for cost-effective simulations. The developed approach allowed for faster computation of detailed residual stress and distortion in Inconel alloy 625 thin-wall builds compared to conventional methods.