Scuffing Failure of Ball Bearing Based on Thermal- Elasto-Hydrodynamic Lubrication Method

The extreme operating conditions such as high speed, heavy load, and oil starvation led to lubrication failures such as pitting and scuffing for mechanical components. Most of the studies, however, focused on scuffing failure of gears. Although there were few studies on the scuffing failure research and judgment criterion for rolling bearings, they did not consider the starved lubrication effect. For this reason, a thermal-elasto-hydrodynamic lubrication (TEHL) scuffing analysis model for ball bearings was established, based on which the distribution of its temperature safety factor and film thickness safety factor reflecting scuffing degree in the calculation domain were obtained numerically through non-Newtonian lubrication equations. In doing so, a method to judge the scuffing failure of ball bearing considering the oil starvation lubrication effect was proposed. This method comprehensively considers the influence of the temperature and film thickness of the raceway and the rolling element, which can not only judge whether there exists a scuffing of contact pair, but also judge the specific area where scuffing occurs and scuffing degree. Considering the centrifugal effect of ball bearing in high-speed operation conditions, the present study was conducted taking an example of the point contact pair between the most heavily loaded bearing roller and its outer raceway. Then, the scuffing analysis model of the bearing considering the effect of oil starvation was established based on TEHL model. In order to verify the model, the temperature of the contact pair and film thickness under the oil starvation condition were verified by comparing them with the corresponding results from the literature. Further, the simulated film thickness was verified through experiment data of the ball disk. After this, the contact load of the roller and entrainment velocity of lubricant were firstly obtained using the quasi static analysis method for ball bearings. Meanwhile, Fast Fourier Transform method was applied to accelerate the contact deform calculation. To obtain the film pressure and fraction film content, the Reynolds equation considering the oil starvation effect and non-Newtonian fluid effect which was solved through Jacobi linear iteration method and Elrod algorithm, and the temperature distributions of the rolling element, raceway and its lubricating oil film were solved by the chase-after method. Based on the obtained film thickness and temperature field distribution, the film thickness safety factor and temperature safety factor representing the whole contact area were introduced. Then, the intersection of the two areas with safety factors less than 1.0 was obtained as the scuffing failure area between the ball and the raceway. Compared with the previous scuffing failure criterion, the proposed method comprehensively considered the influence of lubrication film and contacting solid temperature, and determined the specific scuffing failure area of ball bearing. Finally, effects of varied inlet film thickness, applied radial load and inner race speed on the scuffing failure of ball bearing were analyzed. The numerical results show that the risk of scuffing failure of the bearing increases with the decrease of inlet film thickness and increments in the radial load and inner ring speed. The proposed scuffing judgment criterion can accurately analyze scuffing area and its degree of ball bearings, and therefore guide scuffing analyses and accurate designs for this and other kinds of bearings under extreme operating conditions.