Abstract This article presents a numerical analysis of elastohydrodynamic lubrication (EHL) with grease in point contacts to predict the grease film thickness at low speeds, which can increase with decreasing speed and exceed the base oil film thickness by orders of magnitude. The grease film thickness is obtained by solving the EHL problem, taking grease flow as a single-phase flow with a non-Newtonian viscosity. The continuity equation for thickener is derived, taking grease flow as a two-phase flow of base oil and thickener and the network structure of the thickener as both a porous medium and a non-Newtonian fluid. The flow rate of the thickener network is obtained as the grease flow rate subtracted by the Darcy flow rate of the base oil. The thickener concentration is obtained by solving the continuity equation for the thickener. Numerical results show that the increase in film thickness at low speeds is due to an increase in the equivalent viscosity in the inlet of the contact, which is due to a decrease in the shear rate and an increase in the thickener concentration. At low speeds, base oil is more easily squeezed out of the inlet of the contact than the thickener network, which leads to an increase in the thickener concentration, because the shear stress due to the Newtonian flow of base oil decreases with decreasing the shear rate, whereas the yield stress of the thickener network is independent of the shear rate. A reasonable agreement between the numerical and experimental results validates the present model.

中文翻译：

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点接触弹性流体动力润滑中脂膜厚度和增稠剂浓度的数值分析

摘要 本文对点接触润滑脂的弹性流体动力润滑 (EHL) 进行数值分析，以预测低速下的润滑脂膜厚度，该厚度会随着速度降低而增加，并超过基础油膜厚度几个数量级。脂膜厚度是通过求解 EHL 问题得到的，将润滑脂流动视为具有非牛顿粘度的单相流动。推导了稠化剂的连续性方程，将润滑脂流视为基础油和稠化剂的两相流，稠化剂的网络结构既是多孔介质又是非牛顿流体。增稠剂网络的流量是用润滑脂流量减去基础油的达西流量得到的。增稠剂浓度通过求解增稠剂的连续性方程获得。数值结果表明，低速时膜厚的增加是由于接触入口处等效粘度的增加，这是由于剪切速率的降低和增稠剂浓度的增加。在低速下，基础油比增稠剂网络更容易从接触入口挤出，这导致增稠剂浓度增加，因为基础油牛顿流动引起的剪切应力随着剪切速率的降低而减小，而增稠剂网络的屈服应力与剪切速率无关。数值和实验结果之间的合理一致性验证了本模型。这是由于剪切速率的降低和增稠剂浓度的增加。在低速下，基础油比增稠剂网络更容易从接触入口挤出，这导致增稠剂浓度增加，因为基础油牛顿流动引起的剪切应力随着剪切速率的降低而减小，而增稠剂网络的屈服应力与剪切速率无关。数值和实验结果之间的合理一致性验证了本模型。这是由于剪切速率的降低和增稠剂浓度的增加。在低速下，基础油比增稠剂网络更容易从接触入口挤出，这导致增稠剂浓度增加，因为基础油牛顿流动引起的剪切应力随着剪切速率的降低而减小，而增稠剂网络的屈服应力与剪切速率无关。数值和实验结果之间的合理一致性验证了本模型。因为基础油的牛顿流动引起的剪切应力随着剪切速率的降低而减小，而增稠剂网络的屈服应力与剪切速率无关。数值和实验结果之间的合理一致性验证了本模型。因为基础油的牛顿流动引起的剪切应力随着剪切速率的降低而减小，而增稠剂网络的屈服应力与剪切速率无关。数值和实验结果之间的合理一致性验证了本模型。