Continuum damage mechanics combined with the extended finite element method for the total life prediction of a metallic component

Fatigue is a major reason for the failure of components subjected to cyclic loadings, and the fatigue failure of components can be divided into two phases: crack initiation and crack propagation. In this study, continuum damage mechanics (CDM) combined with the extended finite element method (XFEM) is proposed to predict the total fatigue life of components, that is, the crack initiation life and propagation life. First, the damage-coupled elastic-plastic constitutive equations and fatigue damage evolution equations are derived to calculate the fatigue damage and to predict the crack initiation life of a material under cyclic loads. Second, according to the distribution of the damage field and trend of fatigue damage evolution, the criterion to judge the formation of crack initiation is proposed. Third, based on linear elastic fracture mechanics (LEFM) with XFEM, the crack propagation life is predicted. Then, fatigue crack initiation and propagation analysis for a specimen with a preset pit and for a fuselage structure with opening are conducted using the method described above. Finally, fatigue experiments are conducted to verify the proposed method, and the predicted total fatigue life and crack propagation path are in accordance with the experimental results.