The Tribological Effect of Mechanically Produced Micro-dents by a Micro Diamond Pyramid on Medium Carbon Steel Surfaces in Rolling-sliding Contact

In order to evaluate the effects of micro-pockets on the lubrication and the pitting durability of medium carbon steel surfaces, in the present paper, using the roller with a small number of micro-dents marked by a diamond pyramid whose total area was, to minimize the effect of work-hardening, set negligibly small compared to the contact area as the follower in a two-roller testing machine, the pitting durability was tested under poor lubrication conditions and/or severe loading levels. The results successfully demonstrate the effect of such micro-pockets on the pitting durability and scuffing resistance of surfaces in rolling-sliding contact.     

Jacobian-free Newton-Krylov subspace method with wavelet-based preconditioner for analysis of transient elastohydrodynamic lubrication problems with surface asperities

This paper presents an investigation into the effect of surface asperities on the over-rolling of bearing surfaces in transient elastohydrodynamic lubrication(EHL) line contact. The governing equations are discretized by the finite difference method. The resulting nonlinear system of algebraic equations is solved by the Jacobian-free Newtongeneralized minimal residual(GMRES) from the Krylov subspace method(KSM). The acceleration of the GMRES iteration is accomplished by a wavelet-based preconditioner.The profiles of the lubricant pressure and film thickness are obtained at each time step when the indented surface moves through the contact region. The prediction of pressure as a function of time provides an insight into the understanding of fatigue life of bearings.The analysis confirms the need for the time-dependent approach of EHL problems with surface asperities. This method requires less storage and yields an accurate solution with much coarser grids. It is stable, efficient, allows a larger time step, and covers a wide range of parameters of interest.     

弹流润滑条件下表面形貌对摩擦噪声的影响

研究了弹流润滑状态下表面形貌对摩擦噪声的影响.通过激光微加工方法在金属圆盘试件表面上制造了两种沟槽型织构表面形貌,在双盘摩擦磨损试验机上对不同表面形貌进行了摩擦噪声和摩擦特性试验,分析了线接触弹流润滑条件下不同工况和表面形貌影响摩擦噪声的机理,并结合有限元分析对结论加以验证.结果表明:载荷和转速的变化对线接触摩擦噪声有明显影响,由于线接触副工作在部分膜弹流润滑状态下,所以摩擦噪声的特性与干摩擦时类似,摩擦因数较大的表面会辐射出更强的摩擦噪声;特定结构的表面形貌能改善表面润滑特性,有效降低摩擦噪声声压级,沟槽型织构的存在可以打断接触区域应力分布,减轻接触面微凸体碰撞作用,从而降低了表面自激振动,同时合适的表面形貌结构也有利于润滑油膜的形成,减小了系统的摩擦能量,达到降低摩擦噪声的效果.     

The effect of aging during storage on the performance of a radial lip seal

Since aging is an inevitable phenomenon during storage of a radial lip seal, this study aims to investigate the effect of aging on the seal performance. An air oven aging test is conducted to produce aged rubber samples and seal products. An aging life prediction model is constructed to predict the equivalent material properties at any storage temperature. The material property parameters of aged rubber samples are measured in a uniaxial compression experiment. The pumping rate and friction torque of the seal are calculated through numerical simulation by using a mixed elastohydrodynamic lubrication (EHL) model. A bench test is used to verify the aging life prediction model and the simulation results of the EHL model. Finally, the verified EHL model is used to study how aging during storage affects the lip seal performance, as characterized by the leakage and friction torque.     

润滑脂纤维结构对弹流油膜影响的试验研究

采用光干涉技术对脂润滑弹流油膜进行测量,分析了粗细两种稠化剂纤维结构对润滑脂膜厚的影响.试验结果表明:粗纤维结构的润滑脂稠化剂连续性好,可在滚道上形成较厚沉积层,在新鲜供脂条件下其油膜厚度是细纤维润滑脂的2到5倍.在首次升速-降速过程中润滑膜厚呈现明显差异;而在升速-降速多次循环后,膜厚曲线趋向一致.     

摆动工况下有限长线接触弹流的实验研究

针对对数型凸度滚子,在自制的滚子接触光弹流试验装置上开展了摆动工况弹流的实验研究.在2种不同摆动频率下,测量了弹流润滑油膜厚度和形状.结果表明:在一定载荷范围内,对数凸型滚子弹流润滑状态下的油膜厚度沿轴向呈均匀分布.摆动工况下润滑油膜的变化受到楔形效应和挤压效应的共同作用;低频时卷吸速度变化较小,以挤压效应为主;高频时卷吸速度变化较大,楔形效应增强.在卷吸速度为零时,油膜被封入接触区内,高频时形成的凹陷更为明显.     

对数滚子的热弹流凸度量设计研究

基于最佳凸度量取值区间的概念,针对性能最优的对数轮廓滚子,提出了根据热弹流理论进行凸度设计的方法.使用该设计方法研究了对数滚子凸度量修正系数随工况参数的变化规律.定义了轴向膜厚分布系数和轴向压力分布系数,通过限制二者许用值的方法确保压力分布和膜厚分布的轴向均匀性,而轴向膜厚分布系数和轴向压力分布系数的许用值分别与最佳凸度量取值区间的下限和上限相对应.研究指出:轻载时凸度量修正系数的下限随载荷的增加而增加;重载时凸度量修正系数的下限随载荷的增加而趋于稳定,凸度量修正系数的上限随载荷的增加而增大;速度参数对最佳凸度量取值区间的影响不显著.     

粗糙度纹理对有限长线接触混合润滑影响

采用统一Reynolds方程建立有限长线接触混合润滑模型,研究横向、纵向和二维规则表面粗糙度的波长、幅值及工况变化对润滑影响.结果表明:波长、幅值与工况对三种表面粗糙度接触副的润滑影响类似;随着载荷增大,平均膜厚降低,摩擦系数、接触载荷比与接触面积比均增大;随着转速升高,平均膜厚增大,摩擦系数、接触载荷比与面积比均降低,其中摩擦系数随转速进一步增大而小幅升高.在润滑状态转换区域润滑特征参数变化显著,而其他润滑区域变化平缓.沿卷吸速度方向的压力与膜厚波动分布存在相位差,垂直方向则同相位;相同的工况和粗糙度参数时,纵向粗糙度分布更有利于接触润滑.     

表面波纹度对偏心轮-平面挺杆接触润滑性能的影响

本文采用数值分析方法研究了偏心轮-挺杆副的微热弹性流体动力润滑问题.分析中假设平面挺杆表面分布有余弦波纹,探讨了偏心距和余弦波波长对润滑油膜变化的影响.数值模拟计算结果表明:在偏心轮-挺杆副工作的一个周期里,表面波纹度的存在会导致油膜压力和温度上升.在不同的滑滚比条件下,表面波纹的弹性变形程度不同.在两表面反向运动的半个周期内,随偏心距的增加,滑滚比也增加,导致表面波纹的变形程度降低.在两表面反向运动的半个周期内,波纹的弹性变形程度受“温度-黏度楔”机理的控制.     

滑动表面卷吸速度为零时的热弹流润滑分析

提出了接触处两表面等速反向运动的圆柱间在一定条件下赤存在足够厚的稳态热弹流膜,此时固体表面呈现中凹状、且凹陷深度随勒荷的增加而增大,随表面速度的增加而减小。