Quantitative analyses on geometric shape effect of microdefect on fatigue accumulation in 316L stainless steel

Geometric shapes of microdefects are closely associated with the local deformation potentially inducing crack initiation. The main goal of this attempt is to explore and quantitatively analyze the close link between varying shapes of microdefects and fatigue accumulation in 316L stainless steel. In the perspective of crystal plasticity finite element method (CPFEM), we systematically build representative volume element (RVE) models designated with three typical geometric shapes of microdefects including rectangle, circle and rhombus, aiming to quantitatively reveal the underlying mechanism of fatigue accumulation in the presence of defects. Results show that crack initiation from multiple sites around microdefects is more likely dependent of the geometric shape of microdefect, as well as the heterogenous property of microstructure. Statistical probability analyses indicate that, compared to rectangular and circular defects, rhombic microdefect results in a higher degree of deformation that is prone to crack initiation at critical location. These numerical findings are consistent with experimental observation, providing quantitative reference for the design of polycrystalline materials.