Co-Operative Research on Fatigue Failure at Contact Surface

为了阐明接触表面疲劳的机理，进行了双滚子试验、三维滚动接触试验(模拟钢轨与车轮的接触状态)、微动试验和重复压缩试验。通过两次滚压试验，得出以下结论：(1)表面粗糙度的粗糙度交互作用是产生滚动疲劳的最重要因素，即点蚀、微观点蚀和剥落。(2)磨合条件由粗糙度接触频率Naf控制，Naf由不同显微结构的高硬度轧辊与低硬度轧辊的任何一个位置接触的位置数决定，而Naf控制粗糙度接触的严重程度和滚动疲劳的发生。(3)严重粗糙接触下的滚动疲劳极限由发生磨合或不发生磨合的极限赫兹压力决定。(4)渗碳钢的微观点蚀为c…。更多地受到磨合发生极限的粗糙度的控制。通过微动试验，阐明了切向牵引力对接触疲劳的影响是由于宏观的几何条件或微观的粗糙接触促使三维接触中经常出现的拉应力而产生的。宏观几何三维接触(即模拟轮轨接触)中疲劳裂纹的产生和重复压缩试验证实了上述结论。齿轮试验和重复压缩试验还表明，固体颗粒，如齿轮油中含有的固体润滑剂颗粒，可能是应力集中的来源，因此应足够小。通过对裂纹的失效力学分析，对裂纹的扩展进行了预测。通过三维测量得到的粗糙度轮廓的互相关函数，可以判断粗糙度接触的磨合状况或严重程度。较少

In order to clarify the mechanism of surface fatigue in contact, two-roller test, three dimensional rolling contact test (simulated the contact condition of rail and wheel), fretting test and repetitive compression test were conducted. By two roller tests, following conclusions were obtained: (1) Asperity interaction of surface roughness is most important factor for occurrence of rolling fatigue, i. e., pitting, micro pitting and spalling. (2) In especial, the running-in condition is controlled by the asperity contact frequency Naf, defined by the number of contact positions of higher hardness roller with different microgeometries which are brought into contact with any one position of mating lower hardness roller, and Naf controls the severity of asperity contact and the occurrence of rolling fatigue. (3) The rolling fatigue limits under severe asperity contacts are determined by the limiting Hertzian pressure where running-in occurs or not. (4) Micro-Pitting of carburized steel are c … More ontrolled by the value of roughness which is limit of occurrence of running-in. By fretting tests, it was clarified that the tangential traction have an influence on the contact fatigue by promoting the occurrence of tensile stresses which always appear in three dimensional contacts, owing to macro geometrical condition or micro asperity contacts. The occurrences of fatigue cracks in the macro geometrical three dimensional contact (i. e. the simulated rail-and-wheel contact) and the repetitive compression tests certify above conclusion. The gear tests and the repetitive compression tests also showed that particles of solid, e. g. the particles of solid lubricants contained in gear oil, are possible to be the sources of stress concentrations, and therefore it should be small enough. By the analysis of cracking from the failure mechanics, the propagations of cracks were predicted. Furthermore, it was shown that the running-in condition or the severity of asperity contacts can be estimated from the cross-corelation function of roughness profile measured three-dimensionally. Less