Zhao Bin, Xu Hanzhang, Lu Xiqun
College of Power and Energy Engineering, Harbin Engineering University, Harbin 150001, China.
Materials (Basel). 2019 Jul 26;12(15):2388. doi: 10.3390/ma12152388.
Sliding between asperities occurs inevitably in the friction pair, which affects the efficiency and reliability in both lubricated and non-lubricated conditions. In this work, the contact parameters in the coated asperity sliding process are studied, and the universal expressions of the average contact force and the friction coefficient are obtained. The effect of the interference between asperities, the material and geometrical parameters including the Young's modulus ratio and yield strength ratio of the coating and substrate, and the hardening exponent and thickness of the coating on the average contact forces and friction coefficient is considered. It shows both normal and tangential contact forces increase with the increasing interference, increasing Young's modulus ratio, decreasing yield strength ratio, and decreasing coating thickness; while the trend is different for the effect of the hardening exponent of the coating. The normal force increases and the tangential force decreases as the hardening exponent increases. Based on this, the influence of these parameters on the effective friction coefficient is obtained further. It reveals that the friction coefficient increases as the interference and Young's modulus ratio enlarge and decreases as the yield strength ratio, the coating's hardening exponent, and thickness increase. The universal expressions for the contact force and friction coefficient in the sliding process are obtained. This work might give some useful results to help choose the optimum coatings for specific substrates to reduce friction in cases where the asperity contact exists, especially in the focused field of the journal bearing in the marine engine under poor lubrication conditions.
在摩擦副中，微凸体之间的滑动不可避免地会发生，这会影响润滑和非润滑条件下的效率和可靠性。在这项工作中，研究了涂层微凸体滑动过程中的接触参数，并获得了平均接触力和摩擦系数的通用表达式。考虑了微凸体之间的干涉、材料和几何参数（包括涂层和基体的杨氏模量比和屈服强度比）以及涂层的硬化指数和厚度对平均接触力和摩擦系数的影响。结果表明，法向和切向接触力均随着干涉的增加、杨氏模量比的增加、屈服强度比的降低以及涂层厚度的减小而增大；而涂层硬化指数的影响趋势则不同。随着硬化指数的增加，法向力增大而切向力减小。基于此，进一步得到了这些参数对有效摩擦系数的影响。结果表明，摩擦系数随着干涉和杨氏模量比的增大而增大，随着屈服强度比、涂层硬化指数和厚度的增加而减小。得到了滑动过程中接触力和摩擦系数的通用表达式。这项工作可能会给出一些有用的结果，有助于为特定基体选择最佳涂层，以在存在微凸体接触的情况下减少摩擦，特别是在船舶发动机中润滑条件较差的滑动轴承这一重点领域。
