Investigation on surface morphology and tribological property generated by vibration assisted strengthening on aviation spherical plain bearings

Abstract

The extreme and complex working conditions require aviation spherical plain bearings not only to have high machining accuracy and low surface roughness, but also to possess high surface microhardness and lubricant retaining capability. This paper presents a vibration assisted strengthening approach to achieving the synergistic effects of the surface property-improving and appearance-improving. The research attempts to answer how vibration assisted strengthening technique can improve the surface tribological properties of aviation spherical plain bearing components particularly in light of proposing the flat-headed asperity distribution model and the corresponding elastic–plastic contact modelling for the special processed surface morphology. Subsequently, the models are corroborated by the experimental results of characterizing the surface morphology produced by vibration assisted strengthening with different parameters such as rolling times and rolling static force. The surface tribological properties of spherical plain bearing specimens were studied by employing the UMT-TriboLab platform. The theoretical analysis and experimental results indicate that the surface asperities of spherical plain bearing components processed with repeated high frequency strikes present a flat-headed distribution but not Gauss distribution. It characterizes with a marked majority of produced small asperities with similar height, which is beneficial to frictional couple contacts and a lot of original valleys retaining lubricants. The processing technique contributes to increasing the surface microhardness by 20% and decreasing the surface roughness from about Ra 0.4 µm to below Ra 0.1 µm. The ball-on-flat friction tests demonstrate that both the special flat-headed surface structure and the elevated microhardness can attribute the improvement of tribological properties and wear resistance performance of spherical plain bearings.