Residual stress modeling of PBF-LB

Sammanfattning

This thesis investigates the modeling of residual stress in laser powder bed fusion (PBF-LB) processes using AdditiveLab as a meso-scale simulation tool. The study aims to evaluate AdditiveLab as a process simulations tool for PBF-LB by repli cating experimentally verified simulations, specifically focusing on 316L stainless steel. A literature review of simulation techniques was conducted, followed by transient thermal and thermo-mechanical simulations, and validation of AdditiveLab’s simulations against experimentally verified models from the literature. The simulations analyzed the thermal distribution, the dimensions of the melt pool, and the development of residual stress. The findings indicate that, while the moving heat source can be modeled using AdditiveLab, limitations of the possible material modeling negatively impact the accuracy of the temperature distribution in meso-scale simulations. The primary limitation being the phase change model, in which the density of the metal powder can only be modeled as being equal to the solid metal density. Although all mesoscale modeling involves simplifications of complex physical phenomena, the assumption of powder properties leads to an overestimation of powder thermal inertia, leading to an overestimation of the melt-pool temperature and an underestimation of the melt-pool depth and width. This thesis discusses these limitations and their impact on predicting thermal behavior and stress development.