Multiaxial Fatigue Life Prediction Considering Additional Hardening Effects and Mean Stains

Considering the physical significance of crack formations and propagations under multiaxial loading conditions, a multiaxial equivalent linear fatigue life prediction model was proposed based on Miner rule and critical plane method. The ratio of cyclic yield stress to static yield stress was used to reflect the cyclic strengthening capacity of the materials, and the additional hardening factor was defined. The influences of phase differences and loading conditions on the non-proportional additional hardening effects were considered, and the mean strains under asymmetrical loadings were corrected. Multiaxial fatigue lifes of smooth and notched samples for five kind of materials were estimated by equivalent strain prediction model, maximum shear strain amplitude model and the proposed model, and the estimated results were compared with the testing results. The results show that the three models may achieve good effectiveness under proportional loadings, but the proposed model performs better than that of the other two models under non-proportional loadings. Meanwhile, it also verified that the proposed additional hardening factor may reflect the influences of phase differences and material properties on additional hardening effects. © 2020, China Mechanical Engineering Magazine Office. All right reserved.