Fatigue failure mechanism of Ti60 titanium alloy under tension–torsion multiaxial loading in the very high cycle regime was studied first, and the results showed that the shear/axial stress ratio directly affects the failure mechanism. When the shear/axial stress ratio is relatively small, cracks tend to originate from the subsurface in single-point initiation mode, and the larger the shear/axial stress ratio, the more cracks tend to originate from the surface in multi-point initiation mode. Then, a pragmatic equivalent method for multiaxial to uniaxial load based on the law of shear/axial stress ratio on fatigue strength was proposed. Based on this method and uniaxial - curve, the fatigue lives of Ti60 specimens under shear/axial stress ratios of 1.37, 1.95, and 3.53 was predicted, and the experimental results showed that the prediction error is basically within a factor of 3.

中文翻译：

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基于剪切/轴向应力比有效因子的 Ti60 钛合金在极高循环状态下的多轴疲劳寿命预测

首先研究了Ti60钛合金在极高循环状态下拉扭多轴载荷下的疲劳失效机制，结果表明剪/轴应力比直接影响失效机制。当剪轴应力比较小时，裂纹倾向于以单点起裂模式从地下萌生，剪轴应力比越大，裂纹越倾向于以多点起裂模式从表面起源。 。然后，提出了一种基于剪/轴应力比疲劳强度定律的多轴到单轴载荷的实用等效方法。基于该方法和单轴曲线对Ti60试件在剪/轴应力比为1.37、1.95和3.53下的疲劳寿命进行了预测，实验结果表明预测误差基本在3倍以内。