Life time assessment of an aluminum alloy under complex low cycle fatigue loading

This publication presents an expression for the equivalent strain based on fatigue tests under complex strain state. The respective aluminum alloy was tested under a very low number of cycles. The criterion uses the critical plane determined according to the material kind function. The determined equivalent amplitude for complex proportional and non-proportional loading states is included into the scatter band of the same coefficient for simple loading states. The model based on the proposal by Carpinteri for determination of the critical plane position under a complex strain state can be a useful tool for fatigue life assessment in the case of a very low number of cycles. The expression for the equivalent strain includes both the normal and shear strain histories on the critical plane with suitable weight functions. The determined equivalent amplitude for complex proportional and non-proportional loading states is also included into the scatter band of the same coefficient for simple loading states.