A segmented heat source for efficiently calculating the residual stresses in laser powder bed fusion process

Abstract

To improve the efficiency and accuracy of the numerical simulation for the laser powder bed fusion (LPBF) process, an optimized segmented heat source (OSHS) model is proposed in this work. The results show that the geometrical size and temperature distribution contour of the calculated cross-sectional molten pool are almost the same as those calculated by the moving heat source (MHS). Under the same mesh scheme, the calculation efficiency of the OSHS model improves about 9 times to that of the traditional MHS model. Moreover, the OSHS model can achieve stable calculations with the medium-size elements grid, which can reduce the required calculation time to one-third of the fine mesh scheme and achieve almost the same thermal-mechanical calculation result. This model was successfully applied on the simulation of the LPBF single layer multi-tracks thermal-mechanical numerical simulation. To verify the calculated results, the sample of the same size was prepared using 316L stainless steel by LPBF technology. The surface residual stress components of the as-built sample were measured by X-Ray Diffraction (XRD). The calculated residual stress curves were in good agreement with the measured results. The simulation and experimental results indicated that the primary surface residual stress component was the tensile stress along the laser scanning direction, which was about 280 MPa. The shear stress was concentrated at the corners of the as-built sample. Therefore, the OSHS model proposed in this work greatly improved the calculation efficiency and obtained very accurate results for the thermal-mechanical simulation of the LPBF process.