Continuum damage model of low-cycle fatigue and fatigue damage analysis of welded joint

We know from experimental phenomena that the ductility of materials decreases with increasing numbers of cycles in the process of cycle fatigue loading, from which a new fatigue damage variable D ψ based on the material ductility property is defined. Then a continuum damage mechanics model for low-cycle fatigue is derived from the new damage variable and is used to study the fatigue damage of welded joint. Damage evolution equations for the weld metal, heat-affected zone and base metal of 16MnR steel are obtained, respectively. The theoretical and experimental results show that the new damage variable D ψ has a definite physical meaning and can be measured by a simple procedure and it can be related to the mechanical property of material directly.