Wetting and Spreading Behaviors of Lubricant Oil Droplets on Inner Ring Textured Surface of Ball Bearing

In high-speed mechanical systems, angular contact ball bearings are key transmission components, its performance directly affects the stability and lifespan of entire machinery. Oil-air lubrication is the main lubricate way for angular contact ball bearings, however, due to the centrifugal force, it’s difficult for lubricant oil to maintain on the inner ringway of bearing, resulting in low lubrication efficiency of bearing. In recent years, the continuous advancement of microfabrication technology make it more convenient and efficient to machine concave texture through material removal, and surface texture has become an effective means to improve the lubrication state of friction pairs. In this study surface texture was designed in the inner ringway of bearings, based on VOF theory, a three-dimensional numerical model was established for analyzing the wetting and spreading behaviors of lubricant oil droplets on textured surface of bearing inner ringway. The spreading and wetting characteristics of lubricant oil droplets on conventional and textured inner ring raceways were compared and analyzed, and its mechanism and influence factors are further explored. Dynamic oil droplet monitoring system and contact angle measurement platform were established, and the contact angle of oil droplets on the textured surface and the dynamic spreading process of oil droplets on the textured surface were measured through experiments. The experimental results were compared with the numerical analysis results to verify the correctness of the numerical analysis method. The results indicated that texture can reduce the contact angle of lubricant oil on the raceway surface, increase the spreading length and area on the inner raceway, and improve the wettability of the raceway surface. On the rotating surface of the inner raceway, the texture played a storage and retention role in the diffusion of lubricating oil, increasing the amount and diffusion area of lubricating oil on the inner raceway, which was conducive to forming a more stable oil film and improving bearing lubrication. The texture could decrease contact angular of lubricant oil, increase the spreading length and area on inner raceways, and improve wettability of raceway surface. On rotating surface of inner raceway, texture played a storage and retention role in the spreading of lubricant oil, it increases quantity and spreading area of lubricant oil on inner raceway, which was conducive to forming a more stable oil film and improving bearing lubrication. The higher bearing speed, the smaller texture spacing and lubricant oil viscosity, and the higher initial velocity of oil droplets, result in the larger spreading area of lubricant oil on the rotating raceway surface. As the increase of texture depth, the spreading area of oil droplets first increased and then decreased, 40 μm is the optimal value of texture depth. This study had some reference value for texture designing and lubrication efficiency enhancement of angular contact ball bearings.