Abstract In the presence of multiaxial fatigue loadings with multiple loading variables, fatigue behavior of material differs from those under in-phase (IP) multiaxial fatigue loadings. The co-existence of non-zero mean stress and phase angle could be extremely harmful to fatigue resistance of material. In this case, it is vital for researchers engaging in relative fields to put forward capable life prediction methods. In this study, the mechanical property of a TiAl alloy under combined tension-torsion (CTT) fatigue loadings is investigated through experiments. The applied fatigue load contains non-zero mean stress components as well as phase angle components. The fracture of specimen is observed by scanning electron microscope (SEM) to investigate the correspondence between multiaxial fatigue life and failure behavior. Susmel and Lazzarin's (S-L) fatigue criterion is critically reviewed to put forward a modification on its intrinsic drawback. In parallel, a correction factor is introduced to make the modified Wӧhler curve method (MWCM) feasible for multiaxial fatigue life prediction with multiple loading variables. Verified by experimental results of present work, the proposed method is of good accuracy compared with Matake method and McDiarmid method.

中文翻译：

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平均应力和相位角对 TiAl 合金多轴疲劳行为的影响：失效分析和寿命建模

摘要 在具有多个载荷变量的多轴疲劳载荷下，材料的疲劳行为不同于同相（IP）多轴疲劳载荷下的疲劳行为。非零平均应力和相位角的共存可能对材料的抗疲劳性极为有害。在这种情况下，对于从事相关领域的研究人员来说，提出有能力的寿命预测方法至关重要。在这项研究中，通过实验研究了 TiAl 合金在组合拉扭 (CTT) 疲劳载荷下的力学性能。施加的疲劳载荷包含非零平均应力分量以及相位角分量。通过扫描电子显微镜（SEM）观察试样的断裂，以研究多轴疲劳寿命与失效行为之间的对应关系。Susmel 和 Lazzarin' s (SL) 疲劳准则经过严格审查，以对其固有缺陷进行修改。同时，引入了一个修正因子，使修正的 Wӧhler 曲线方法 (MWCM) 可用于具有多个载荷变量的多轴疲劳寿命预测。通过目前工作的实验结果验证，该方法与Matake方法和McDiarmid方法相比具有良好的精度。