Simulation-based investigation of statistical fatigue strength of selective laser melted lightweight alloys

Selective laser melting (SLM) process is based on the powder-bed fusion principle, which is using high-energy laser beams. SLM process is characterized by producing very finely grained cellular and columnar dendritic microstructure in aluminum alloy AlSi12. Melt pool instabilities are a key factor in the formation of the pores and increasing of the porosity within the produced parts. Through this study, structural characteristics were investigated using two approaches crack propagation-based and plastic damage-based to isolate influences of microstructure and defects on the fatigue lifetime. The influence of platform heating during deposition on fatigue strength was studied. Platform heating was concluded to reduce the remnant porosity, and consequently, fatigue strength scatter. Fatigue lifetime calculation, which utilized crack propagation curves and weakest-link theory, was consistent at low-cycle fatigue experiments. However, damage monitoring in a load increase test led to a prediction of lifetimes, which is more relevant, as a Monte-Carlo simulation was applied for post-processing of local stress distribution. The difference was the consideration of damage in the pre-crack initiation phase in the plasticity-based approach of the load increase test