Investigation of Distribution and Structure of Surface Textures on Improving Tribological Properties of an Engine

The elastic hydrodynamic lubrication (EHL) region of the crankpin bearing (CB) not only creates the high friction force due to the solid asperity contact but also reduces the CB’s lubrication effectiveness. To improve the CB’s tribological properties, the partial textures (PT) designed on the EHL region are proposed. Based on a new hydrodynamic approach combined between the CB’s lubrication model and the slider-crank-mechanism (SCM) dynamics model, the distribution density of spherical dimples (SDs) and different structures of the SDs, circular-cylindrical dimples (CCDs), square-cylindrical dimples (SCDs), and wedge-shaped dimples (WSDs) are then simulated and assessed for their effectiveness on improving CB’s tribological properties, respectively. The oil film pressure (p), friction force (F _f), and friction coefficient (μ) of the CB are selected as the evaluation indexes. Research results show that the SDs of the PT designed on the EHL region has better performance than the SDs of the full textures (FT) designed over the bearing surface. Additionally, under the same simulation conditions of the PT, the performance of the SDs on improving CB’s tribological properties is also better than other textures of CCDs, SCDs, and WSDs. Particularly, the maximum values of both the p and F _f of the SDs with the distribution density of n′ = 4 and m′ = 6 are remarkably improved by {1.1% and 6.3%} compared to the FT with the distribution density of n = 12 and m = 6; and {14.5% and 15.0%} in comparison without textures on the bearing surface, respectively. Accordingly, the application of the SDs of PT on the bearing surface is not only simple in the design process but also can improve better the tribological properties and enhance the durability of the CB in comparison with both the FT and without textures on the bearing surface, and this is the innovation of the article. In addition, the design process of PT on a part of the bearing surface also can save cost, machining time, and economic efficiency better than the design process of FT on over the bearing surface.