Liquid/Solid Transition Lubrication in Hertzian Contacts

(1)在滚动接触处观测到的最小膜厚以格林伍德图的形式绘制。在VE（粘弹性）和EP（弹塑性）凝固范围内，形成较大的厚度。这些厚度曲线的上半部分受到Houpert定义的PR（压电粘性刚性）范围边界的限制。(2)与矿物油相比，牵引油的轴承寿命与膜参数关系不大，呈现出随着膜参数的增加轴承寿命增加的一般特征。(3)具有较大压力-粘度系数和较高牵引力系数的牵引油在轴承工作条件下容易凝固。(4)对于推力球轴承，固化膜的优点很少被认识到。它们缩短轴承寿命，增加摩擦和工作温度。这与固化膜的体积模量有关。(5)牵引油的缺点是由于推力球轴承的恶劣运行条件，这是强烈的影响存在的旋转力矩。(6)牵引油固化后的油膜易碎。脆性表现出与体模量相反的关系。通过测量低温下凝固温度与失效温度之间的温差来估算。(7)通过外部加热提高工作温度，轴承寿命迅速缩短，因为压力-粘度系数的乘积和平均接触压力大大降低到低于临界值25，即保持弹塑性状态所必需的。

(1) The observed minimum film thickness at a rolling contact is plotted in the form of the Greenwood diagram. In the solidification ranges VE (Viscoelastic) and EP (Elastic-Plastic) larger thickness is formed. The upper parts of these thickness curves are limited by the boundary of the PR (Piezoviscous rigid) range defined by Houpert.(2) In the case of traction oils bearing life is hardly related with the film parameter in contrast to mineral oils, which show a general feature that bearing life increases with increasing film parameter.(3) Traction oils having larger pressure-viscosity coefficients and higher coefficients of traction are easily solidified under the operating conditions of bearings.(4) In the case of thrust ball bearings the merit of the solidified films is rather little recognized. They shorten bearing life, increase friction and operating temperature. These facts are related with bulk moduli of solidified films.(5) Demerits of traction oils are attributed to severe operating conditions of thrust ball bearings, which are strongly affected by the presence of spin moment.(6) The solidified oil films of traction oils easily cause breakdown owing to their brittle nature. The brittleness shows a relation reversed to the bulk modulus. It is estimated by measuring the temperature difference between solidified and failure temperature at lowering temperatures.(7) By raising operating temperatures by external heating bearing life is rapidly shortened as the product of the pressure-viscosity coefficient and the average contact pressure is reduced considerably lower than the critical value 25, i.e. necessary to maintain the elastic plastic state.