考虑附加强化效应及平均应变的多轴疲劳寿命预估

考虑多轴加载条件下裂纹萌生和扩展的物理意义，将Miner理论与临界面法相结合提出了一种多轴等效线性疲劳寿命预估模型；将循环屈服应力与静态屈服应力的比值用来反映材料的循环强化能力，并定义了附加强化因子，考虑相位差及载荷条件对非比例附加强化效应的影响，对非对称加载下的平均应变进行了修正；利用等效应变预估模型、最大剪切应变幅模型及所提模型对5种材料的光滑及缺口试样多轴疲劳寿命进行了预估，并将预估结果与试验结果进行了对比分析，结果表明：比例加载时，3种模型都能获得较好的效果；非比例加载时，所提模型的预估效果要优于其他两种模型的预估效果。同时也验证了所提出的附加强化因子能够反映相位差及材料特性对附加强化效应的影响。

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.