Multiaxial fatigue of 304L stainless steel notched member

This work investigates the multiaxial notch fatigue of 304L stainless steel at room temperature and evaluates the life predictions made by using a local stress-strain approach. Circumferentially notched bars were submitted to fully reversed axial, torsional, and 90 degrees out-of-phase nonproportional loading. The applied force and torque amplitudes resulted in fatigue lives ranging from 10(3) to 10(6) cycles. For selected specimens, strain gauges were placed at the notch root to investigate the cyclic plasticity behaviour. An initial cyclic softening was observed for all tests in which the evolution of notch strains was investigated. Strain gauge readings were also used to compare observed and simulated strain amplitudes obtained from elastic-plastic Finite Element Analyses (FEA) based on the Chaboche model. Notch root strains were overestimated by FEA possibly due to the non-Masing behaviour of 304L stainless steel. Fractographic analyses indicate that the failure mechanism depends on the loading condition and the loading amplitude, as previously observed for smooth specimens. Fatigue life predictions obtained combining FEA and the Smith-Watson-Topper and Fatemi-Socie critical plane criteria were conservative, highlighting the importance of an accurate description of the cyclic stress-strain behaviour of 304L stainless steel for fatigue analyses.