Prediction of Residual Stress and Part Distortion in Selective Laser Melting

Selective laser melting (SLM) is widely used to make functional metal parts. The high-temperature process will produce large tensile residual stress (RS) which leads to part distortion and poor product performance. Traditional modeling approaches are not practical to predict residual stress and part distortion due to the exceedingly high computational cost. In this study, two efficient multiscale modeling methods have been developed to across microscale laser scan, mesoscale layer hatch, and macroscale part buildup for fast prediction of residual stress and part distortion. A concept of equivalent heat source has been developed from the microscale laser scan model. In the "stress-thread" method, the local residual stress field was predicted by the mesoscale layer hatch model using the equivalent heat source, then the residual stress field is imported, i.e.; "stress-thread", to the macroscale part buildup model to predict residual stress and part distortion. In the temperature-thread method, the powder-liquid-solid material transition has been incorporated. A body heat flux obtained from the microscale laser scan model is applied, i.e.; "temperature-thread", to the hatch layer. Then multiple hatches are sequentially "deposited" in the macroscale part buildup model with different scanning strategies. The predicted part distortions by both methods were compared and compared with the experimental data.