Study on mechanical environments and tribo-failures at the operating surfaces of mechanical elements

提出了一种直接接触非定常混合弹流润滑的数值分析方法。为了使分析成为可能，区分了接触区的三种状态，即流体动力成膜、直接接触区和空化区，并分别应用了不同的方程。在流体动力成膜区，用弹性方程代替雷诺方程作为直接接触区的控制方程。不仅要掌握压力和油膜厚度，而且要掌握计算区域内各点的油量，并用来确定点的状态和控制方程。将该数值计算方法应用于有直接接触的混合弹流润滑情况，对滚道反复微滑引起的滚珠轴承假褐化磨损进行了实验研究，考察了几种工况和润滑对轴承使用寿命的影响。用电阻法测量了油膜的形成状态，发现其寿命取决于油膜的形成状态。滚道粗糙度会影响滚动轴承在振动状态下的油膜形成状态和寿命，在双滚子机上进行了点蚀试验研究。每隔适当的加载周期将试验辊表面记录在录像带上，并通过倒转时间从运行的早期状态跟踪长期运行后观察到的明显的点蚀裂纹。研究发现，润滑油的塑性流动方向和流变性对润滑油的性能有显著影响。

A numerical method of analysis for unsteady mixed elastohydrodynamic lubrication with direct contacts was developed. In order to make the analysis possible, three states of the contacting regions are distinguished, I.e., the hydrodynamic-film-formation, the direct contact and the cavitation regions, to which different equations are applied, respectively. in place of Reynolds equation applied to the hydrodynamic-film-formation region, elasticity equation is used as the governing equation of the direct-contact region. Not only pressure and film-thickness, but also the oil mass quantity at each point in the calculation region are always grasped and used to decided the state of the point and the governing equation. This numerical calculation method was applied to the cases where mixed elastohydrodynamic lubrication with direct contacts occurred.Experimental study on false brinelling of ball bearings, which is identified as fretting wear caused by repeated microslip in raceways, has been conducted in oscillatory motion in order to investigate the effect of several operating conditions and lubrication on the service life. The state of oil-film formation was measured with the electric resistance method, and it was found that the life depends on the state of oil-film formation. The roughness of raceways can affect the state of oil-film formation and the life of ball bearings in oscillatory motion.Experimental study on pitting has been conducted using two-roller machine. The surface of test rollers were recorded in video tape at every adequate loading cycles and evident pitting cracks observed after a long running were followed from an early state of running by reversing the time. The influences of the plastic flow direction and the rheological properties of lubricating oils were recognized significantly.