Nonlinear Fatigue Life Prediction Based on Energy Damage Parameter Correction of Fatigue Driving Force

In view of the difficulty in determining the interaction factors between variable amplitude loadings in the fatigue driving force energy model, an improved nonlinear fatigue life prediction model was established, in which the interaction factors were modified by cyclic loading ratio and real-time fatigue damage degree respectively, considering the influence of loading sequence, loading interaction and fatigue damage degree on the damage accumulation rule under variable amplitude loading. Based on the energy criterion to determine the damage parameters, the variable amplitude loading stress ratio, loading cycle ratio and fatigue damage degree were introduced into the calculation of the interaction factor between loads. According to the test data of the welded joints of Q235B and aluminum alloy under multi-stage variable amplitude load, the predictive ability of the improved fatigue life prediction model was verified. Numerical results show that, under the action of variable amplitude load, the improved fatigue life prediction model can effectively predict the fatigue life of welded structures, which is closer to the test results than other models. The model contains only two conventional parameters that can be easily determined by experiments, and no additional parameters need to be introduced to facilitate the analysis and design of practical engineering structures. © 2020, Editorial Department of China Railway Science. All right reserved.