Parametric investigation of micro-pores coalescence in the microstructure of LPBF manufactured AISI 316 stainless steel under high cycle fatigue loading

Abstract

In this study, damage growth and load-carrying capacity of specimens made by laser powder bed fusion (LPBF) at various triaxial stresses have been evaluated by the damage mechanics approach, using the Chaboche-Lemaitre stress-based damage model and Lemaitre damage model based on equivalent plastic strain under high cycle fatigue (HCF) loading. In this regard, with the development of a parametric numerical model, the effect of stress triaxiality, external HCF loading, and micro-pore geometric parameters size on the damage growth and coalescence of two-void cluster embedded in representative volume element (RVE) have been investigated. The results show that increasing the triaxial stress from 0.5 to 2.1 leads to a severe decrease in ligament load carrying capacity and eventually voids coalescence through an increase in von Mises stress around the micro-pores. The results also indicate that a two-void cluster with a relative distance of less than 10 can be considered as a crack initiating site in the microstructure of LPBF components under HCF loading.