Numerical Analysis of Residual Stresses in Parts Produced by Selective Laser Melting Process

Abstract

Additive manufacturing (AM) of metallic components has received large attention in the last decade, particularly the selective laser melting (SLM) process, due to its ability to produce complex and customized parts. However, the high residual stresses generated by the thermal cycles can lead to significant distortions and ultimately to the part cracking. Therefore, several numerical simulation tools have been adopted to predict and mitigate the unwanted part distortion. This study presents a thermo-mechanical model able to simulate the SLM process, considering multitrack within a single powder layer. The finite element model considers the powder-liquid-solid phase changes, i.e. includes melting, solidification and cooling phenomena. The thermal analysis is based on the transient heat conduction problem, considering a volumetric moving heat source. The mechanical analysis is based in an elastoplastic constitutive law, which predicts the residual stresses through the strains induced by the thermal gradients. Both the thermal and the mechanical material properties are assumed as temperature dependent. The main goal of this study is to assess the effect of the scan strategy on the residual stresses generated in the built component. In this context, unidirectional and alternating scan strategies are compared in terms of thermal history and consequent residual stresses generated.