Material dependence of multiaxial low cycle fatigue lives under non-proportional loading

This study discusses evaluation of material dependence of multiaxial low cycle fatigue to develop a suitable strain parameter for life estimation under non-proportional loading. It has been reported that fatigue lives are reduced accompanying an additional hardening under strain controlled non-proportional loading in which principal directions of stress and strain are changed in a cycle. Strain controlled multiaxial low cycle fatigue tests under proportional and non-proportional strain paths were carried out using hollow cylinder specimens of several materials. The reduction in low cycle fatigue life due to non-proportional loading is discussed relating to the additional cyclic hardening behaviors and its material dependence. Material constant, α, used in strain parameter for life estimation under non-proportional multiaxial low cycle fatigue is also discussed.