RATCHETING-FATIGUE INTERACTION OF ANNEALED 42CrMo STEEL AND ITS FAILURE MODEL

The uniaxial ratcheting behavior and the ratcheting-fatigue interaction of annealed 42CrMo steel were studied by tests at room temperature. The ratcheting and low-cycle fatigue (LCF) properties of the material were investigated in uniaxial cyclic stressing. It is shown that the ratcheting deformation produced in asymmetrical cyclic stressing decreases the fatigue life of the material, and that the LCF life of the material depends on the applied mean stress, stress amplitude, maximum stress and stress ratio. Based on the experimental results, a simple and reasonable failure model based on the applied maximum stress and stress ratio is constructed to simulate the fatigue life of the material in asymmetrical cyclic stressing. In the developed model, the effect of ratcheting on the failure life is addressed. The comparison with the experimental results shows that the model gives good predicted results for the fatigue life in asymmetrical cyclic stressing. All of the calculated fatigue lives are kept within the twice-error bounds.