Effect Of Dimples On Tribological Performances Of Palallel Surfaces And Their Improvements For Performances Of An Engine Bearing

Poor working conditions result in frequent lubrication failures for theconnecting-rod bearing in a working engine, such as high frictional power, prematurewear, fatigue, lubricant cavitation and so on. One of main reasons is that theconnecting-rod bearing can not provide enough load-carrying capacity to balance thebig reciprocating inertia force of the connecting-rod.With development of micro-machining, the surface texturing is paid close attentionto due to its ability to improve performances for tribological pairs. Researches availableshow that the appropriate design of the surface textures can increase the load-carryingcapacity of tribological pairs, and reduce their friction.This paper is supported by the national natural science foundation for Effect ofSurface Dimple on High-power Engine Connecting Rod Bearing TribologicalPerformances (project no.50975297), which explores how to use the surface texture toimprove tribological performances of the connecting-rod, mainly including theload-carrying capacity, friction force, friction coefficient and stress for the enginebearing.First, take an example of a dimple, effects of dimple’s geometric sizes ontribological performances of parallel dimpled surfaces are analyzed with fluid-structureinteraction method, including the load-carrying capacity, friction force, frictioncoefficient and surface stress of the bearing. Numerical results show that the tribologicalperformances can be improved significantly with varied geometric sizes of dimples. Thefluctuation of the surface stress can be reduced through decreased dimple depth, and themaximum stress decreases with decreased dimple width.Then, numerical models of engine bearing with dimples are established based onmultiphase flow theories, and are analyzed with CFD method. Influences of the variedposition of dimples on the tribological performances for the bearing are investigated.The study shows that the tribological performances for the bearing are affectedsignificantly by the varied position of the dimple, and the optimum dimple position isfound to lie where the maximum film pressure of the bearing appears.After these, the finite element model of the engine bearing is estabished withfluid-solid interaction technique, and further effects of the dimple on static stresses forthe engine bearing are studied. The simulation results show that the dimples can reduce the maximum static stresses. Finally, effects of dimples on transient performances forthe connecting-rod are simulated based on the inertia release method. It is found thatdimple effect on dynamic stresses of the connecting-rod body can almost be neglected.