As a vital component in the valve train of internal combustion engines (ICEs), the cam/tappet pair undergoes high mechanical and thermal loads and usually works in a mixed and boundary lubrication regime. This leads to considerable friction loss and severe surface wear. Currently, the applications of diamond-like carbon (DLC) coatings for automotive components are becoming a promising strategy to reduce the friction and lower the wear. However, the practical performance of the coating is related to many factors, including friction coefficient, thermal properties, load conditions, and surface topography. In order to investigate these factors and successively improve the fuel efficiency and durability of the cam/tappet pair, a comprehensive multi-physics analytical model considering the mechanical, thermal and tribological properties of DLC coatings is established in this paper. Simulations are carried out for the coated as well as the uncoated cam/tappet conjunctions with different roughness at various ambient temperatures. The results show that both the fluid and asperity contact friction for the coated cam/tappet conjunction are significantly reduced due to their favourable characteristics. As a result, the friction loss of the coated cam/tappet pair is noticeably lower by almost 40% than that of the uncoated, despite a slightly higher asperity contact. In addition, the wear resistance of DLC coatings is also impressive, although the wear condition becomes progressively more severe with the increasing ambient temperature. Moreover, the roughness has complex effects on the friction and wear under different conditions.

中文翻译：

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不同条件下凸轮/气门副上表面涂层减摩和耐磨性的综合数值研究

作为内燃机（ICE）气门机构中的重要组成部分，凸轮/气门副承受很高的机械和热负荷，通常在混合和边界润滑状态下工作。这导致相当大的摩擦损失和严重的表面磨损。当前，在汽车部件中使用类金刚石碳（DLC）涂层正成为减少摩擦和降低磨损的有前途的策略。但是，涂层的实际性能与许多因素有关，包括摩擦系数，热性能，负载条件和表面形貌。为了研究这些因素并依次提高凸轮/气门副的燃油效率和耐用性，我们综合考虑了机械，本文建立了DLC涂层的热学和摩擦学性能。在不同的环境温度下，对具有不同粗糙度的涂层以及未涂层的凸轮/ tappet接头进行了仿真。结果表明，由于涂层的凸轮/止推接头的良好特性，它们的流体和粗糙接触摩擦都大大降低了。结果，尽管粗糙接触略微高一些，但涂覆的凸轮/ t子对的摩擦损失比未涂覆的凸轮//子对的摩擦损失明显降低了近40％。此外，DLC涂层的耐磨性也令人印象深刻，尽管随着环境温度的升高，其磨损条件变得越来越严重。而且，粗糙度在不同条件下对摩擦和磨损具有复杂的影响。