Stress-strain response and fatigue life of four metallic materials under asynchronous loadings: Experimental observations

In this work, axial-torsional fatigue tests were carried out on four materials: PA38-T6 aluminium alloy, E235 and E355 non-alloy steels and X5CrNi18.10 austenitic steel. Applied loadings included axial, torsional, in-phase, 90 degrees out-of-phase loading as well as several types of asynchronous loadings. All tests were strain-controlled. The results reported include the stress-strain response (hysteresis loops, equivalent stress histories and cyclic hardening/softening). Fatigue life has been studied taking into account the problem of the loadings' cycle definition. The results show that this type of loading cause high non-proportional hardening and strongly influence fatigue life. The materials' response was both path- and material-dependent.