Research On Friction Properties Of Micro-grooves Surface Textures

In today's world context of low-carbon economy, improving efficiency and reducing emissions are prerequisites of economic development. So, there is a growing concern over a wide range of mechanical equipment friction, wear and lubrication issues. Surface texture technology, which can reduce friction and wear, improve the lubrication performance, enhance load-carrying capability, is slowly coming into view and gradually becomes a significant method to resolve friction issues. Micro-grooves as a kind of surface textures have the most potential value for industry applications due to its easy processing and low price. In this thesis, both experiments and numerical analysis are employed to research the tribological properties of micro-grooves-type surface texture under reciprocating motion and to present a mechanism of friction reduction. That will provide the basis for the design of desirable surface micro-grooves and further expand its range of industrial applications. In this paper, photolithography combined with electrolytic etching process was used to fabricate micro-grooves on the plane surface of upper specimen which made of boron-copper alloy cast iron.The tribological experiments were carried out to evaluate the influence of micro-grooves in face-to-face condition using a reciprocating friction and wear test rig. Some factors were investigated by testing the average of friction coefficient in whole stroke under varied load and crank speed to understand the law of friction reduction, including width, depth, cover ratio and direction. Finite-element analysis method was used to simulate the friction situation when micro-grooves existed on surfaces. Stress distribution of micro-grooves in solid contact was analyzed by ANSYS soft. Pressure distribution and flow of lubricant oil were analyzed by FLUENT soft. The friction reduction mechanisms of micro-grooves were summarized by the consideration of experiment results and analysis results.Results of this study showed that: the groove width, depth, area rate and direction significantly influenced the tribology performance. Only the micro-grooves of appropriate parameters were able to play a role in reducing friction. The direction was the most significant factor, because mechanism was varied in different directions.This paper also analyzed and summarized the friction reduction mechanisms of micro-grooves-type surface texture:1. 90°grooves (the grooves perpendicular to the sliding direction) caused low friction coefficient due to load-bearing capacity in condition of hydrodynamic lubrication.2. 0°grooves (the grooves parallel to the sliding direction) decreased deformation and contact on surfaces due to its advantage of refrain from stress concentration in condition of solid contact. 3. 0°grooves exhibited remarkable effect of lubricant supply from grooves to interior continuously under the action of pressure difference.4. 45°grooves gave the best results of friction reduction in all experimental conditions due to the combined action of all positive mechanism.