High cycle and low cycle hybrid fatigue damage based on continuum damage mechanics

Based on the continuum damage mechanics (CMD) and irreversible thermodynamics framework, a damage evolution model was investigated under high cycle and low cycle fatigue, respectively, and a new damage model was developed for high cycle and low cycle hybrid fatigue. A user defined material subroutine (UMAT) was compiled and coupled to ABAQUS finite element analysis software. The simulation of high-low cycle fatigue damage and the prediction of crack initiation position and life of notched materials were carried out. Simultaneously, the influence of different high cycle and low cycle ratios on the crack initiation life was studied. The results reveal that the crack was easy to initiate at the stress concentration spot of the notched root. As the interaction of high cycle and low cycle damage was taken into account, the simulated results were more in accord with the practical situation. Meanwhile, the high cycle ratio would accelerate the crack initiation.