Damage mechanics-based approach to studying effects of overload on fatigue life of notched specimens

A continuum damage mechanics-based method is adopted to predict the fatigue life of notched specimens subjected to constant amplitude cyclic loading while containing single or multiple overloads. The residual stress and plastic damage induced by an overload are considered to be the main factors affecting the fatigue life of a specimen. The residual stress and plastic strain fields of a notched specimen are calculated using the elastic–plastic finite element method. The mean stress of the following cyclic loading is then varied by superimposing the residual stress. Meanwhile, the plastic damage is calculated based on the ductile damage model and accumulated into the total damage of the material. The quantitative effects of an overload on the damage evolution and the fatigue life are evaluated. Furthermore, the effects of the damage–overload ratio on the variation of the residual stress induced by an overload are investigated, and the effects of the occurrence time for a single overload and the occurrence frequency for multiple overloads are studied.