Abstract This paper presents the results of fatigue tests combined with conformal contact, non-conformal contact and simple fatigue carried out on Ti-6Al-4V sheet specimens under externally remote bending load. A special fretting fatigue test rig was proposed to focus on two different fretting modes fatigue test simultaneously between non-conformal contact and conformal contact. The test results showed that all the specimens failed at the conformal contact area under external bending load, although the contact stress was lower, residual stress was higher than that with non-conformal contact area. The reason for failure was radial fretting induced fatigue depending upon the nature of conformal geometry. The conformal geometric nature reversed the contact shear stress, accelerated the debris accumulation, redistributed the contact loading and exacerbated the crack nucleation conditions. The mechanisms of fretting fatigue crack formation, including crack nucleation and the three stages of crack propagation were discussed. Furthermore, among the four regions (fretting region, protrusion region, dark inner friction region and fracture region) on fractography, the protrusion region and dark inner friction region were special, rarely reported before. To explain the formation of the protrusion region, dark inner friction region, internal crack and stripped material on the fractography, a friction-based press-push-separate procedure interpretation was proposed. In addition, crack arresting effect exists in the propagation of fretting fatigue cracks due to compression loading on the contact surface with non-conformal contact.

中文翻译：

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Ti-6Al-4V合金共形接触微动、非共形接触微动和简单疲劳的裂纹行为

摘要 本文介绍了在外部远程弯曲载荷下对 Ti-6Al-4V 薄板试样进行的结合共形接触、非共形接触和简单疲劳的疲劳试验结果。提出了一种特殊的微动疲劳试验台，重点在非共形接触和共形接触之间同时进行两种不同的微动模式疲劳试验。试验结果表明，在外弯曲载荷作用下，所有试件均在保形接触区失效，虽然接触应力较低，但残余应力高于非保形接触区。失败的原因是径向微动引起的疲劳，这取决于共形几何的性质。共形几何性质逆转了接触剪应力，加速了碎屑堆积，重新分配接触载荷并加剧裂纹成核条件。讨论了微动疲劳裂纹的形成机制，包括裂纹形核和裂纹扩展的三个阶段。此外，在断口的四个区域（微动区、突出区、暗内摩擦区和断裂区）中，突出区和暗内摩擦区是特殊的，以前很少报道。为解释断口相上的突起区、暗内摩擦区、内部裂纹和剥落材料的形成，提出了基于摩擦的压-推-分离程序解释。此外，由于非共形接触接触面上的压缩载荷，微动疲劳裂纹的传播过程中存在止裂效应。