With the improvement and success of the Theory of Critical Distances (TCD) in notch fatigue problems, the TCD, especially the Point Method (PM), combined with multiaxial fatigue criteria, has been used over the last few years to predict the fretting fatigue life. However, little attention is paid to the effect of different damage mechanisms, especially stress distribution, between the two conditions on the application of the PM. This paper aims to select a suitable path for the PM, considering various stress distributions, for the fretting fatigue life prediction of complete contacts. A new method is developed to select the suitable path of the PM for fretting fatigue life prediction. To validate the analysis, corresponding tests were carried out using an improved proving ring-like rig in a Ti-6Al-4V alloy. Predicted lives on all paths were calculated using the PM combined with different multiaxial fatigue criteria, without incorporating wear effects, and compared with experimental lives using an error bar graph. Results indicate that when the fretting wear is not considered, the minimum predicted life path is more suitable for the PM than the perpendicular and maximum predicted life paths. This suitable path is compared to the path selection in the uniaxial symmetric V-notch fatigue condition. Analysis shows that the conventional path (the notch bisector) of the PM produces the maximum predicted life for the notch fatigue condition. The cause of this different path selection of the PM in the two fatigue conditions is assumed to be the effect of the asymmetric stress distribution and fretting wear damage in the fretting fatigue condition.

中文翻译：

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微动疲劳寿命预测的点法研究

随着临界距离理论（TCD）在缺口疲劳问题中的改进和成功，TCD，特别是点法（PM），与多轴疲劳准则相结合，在过去几年中已被用于预测微动疲劳寿命。然而，很少有人关注两种条件之间不同损伤机制，特别是应力分布对粉末冶金应用的影响。本文旨在考虑各种应力分布，为粉末冶金选择合适的路径，以进行完全接触的微动疲劳寿命预测。开发了一种新方法来选择合适的粉末冶金路径进行微动疲劳寿命预测。为了验证分析结果，使用改进的 Ti-6Al-4V 合金环形试验装置进行了相应的测试。使用 PM 结合不同的多轴疲劳标准计算所有路径的预测寿命，不考虑磨损效应，并使用误差条形图与实验寿命进行比较。结果表明，当不考虑微动磨损时，最小预测寿命路径比垂直和最大预测寿命路径更适合永磁体。将这种合适的路径与单轴对称 V 型缺口疲劳条件下的路径选择进行比较。分析表明，粉末冶金的传统路径（缺口平分线）可产生缺口疲劳条件下的最大预测寿命。两种疲劳条件下 PM 路径选择不同的原因被认为是微动疲劳条件下应力分布不对称和微动磨损损伤的影响。