Extremely Low Cycle Fatigue Behavior of Additively Manufactured 17-4PH Stainless Steel

Steel structures survive seismic loading thanks to components capable of dissipating large amounts of energy through large deformations. Future optimizations of these components include complex free-form geometries that are difficult to fabricate with traditional casting processes. Additive manufacturing (AM) is an alternative for producing optimized free-form geometries. AM material contains significant differences in microstructural characteristics and mechanical behavior compared to its wrought counterparts. Research has been conducted to understand the effect of microscopic features in the high cycle fatigue (HCF) and low cycle fatigue (LCF) regimes. This study focuses on the behavior of 17-4 Precipitation Hardening (PH) stainless steel in the extremely low cycle fatigue (ELCF) regime where large plastic strains lead to ductile failure in few cycles (less than 100 cycles). The goal of this project is to develop strain-life curves for AM 17-4PH steels and provide a better understanding of behavior in the ELCF regime. This is accomplished through material fatigue testing and fractographic analysis.