Load Sequence Effects on Fatigue Behavior of AISI 304 Stainless Steel Under Nonproportional Multiaxial Variable Amplitude Loading

ABSTRACT A strain‐controlled low‐cycle nonproportional multiaxial loading test, including both constant amplitude and variable amplitude loading, was conducted on AISI 304 stainless steel to investigate the load sequence effect on fatigue behavior. Under constant amplitude loading, the cyclic stress response exhibited initial hardening, with additional hardening induced by nonproportional loading. Under variable amplitude loading, the load sequence effect did not alter the hardening behavior but had contrasting effects on fatigue life depending on the loading characteristics. In a high‐low loading, the stable stress amplitude during the low‐strain stage increased significantly, leading to a reduction in fatigue life. In contrast, in a low‐high loading, both the stress response and fatigue life remained unchanged. The load sequence effect under different loading conditions was analyzed in detail based on variations in stress amplitude and nonlinear damage accumulation. The fatigue life evaluation capabilities of various nonlinear damage accumulation models were compared with the linear damage model.