Cheng Guangxu

A new damage variable for low-cycle fatigue of metallic materials

Abstract Experimental results show that the inherent ductility in a material is deflected after cycle loading. Based on the concept of ductility deflection, a new fatigue damage variable D ψ for low-cycle fatigue is recommended in this paper. This new damage variable D ψ has definite physical meaning and can be measured with a simple experimental procedure. It can be connected directly with the usual mechanical properties of materials. D ψ increases slowly at the initial stage of cycle loading, but it increases rapidly after a definite cycle where the macroscale crack is formed. We define the turning point on the D ψ - N curve as the critical damage value D c ψ and its corresponding cycle number N is the fatigue life N f .