Study On Tribological Properties Of Liners For Spherical Plain Bearings

Self-lubricating spherical plain bearings are widely used in aerospace, railway locomotives and other areas. The main factor of affecting the life for spherical plain bearings is the tribological properties of liners. The failure mechanism of liners is the main challenge for engineering development in high frequency and heavy load conditions. Therefore, according to the actual operating conditions of spherical plain bearings, the friction and wear behaviors for two liners of copper grid and polytetrafluoroethylene (PTFE) fabric were investigated. Dry sliding tests were carried out in the swivel motion direction, using homemade spherical plain bearings tribo-tester. Through many tests and analysis, the effects of high oscillating frequency and heavy load on the tribological properties of liners for spherical plain bearings were studied. The distribution of equivalent stress of two kinds of liners for spherical plain bearings and the variation of equivalent stress with contact pressure were analyzed. The main research works are as follows:Based on the measuring of friction coefficient and wear depth, a method of online testing friction temperature was designed, and the real-time surface friction temperature was measured.The influence of the oscillating frequency and contact pressure on the liners for spherical plain bearings were analyzed and studied systematically by the experiments. At the same time, the relationship between pv value and the tribological properties of liners was discussed. The trends of friction coefficient, wear depth and friction temperature with oscillating frequency and contact pressure were described. The effect of friction temperature on liner was discussed. Furthermore, the best working conditions for different spherical plain bearings were proposed.The worn surface morphology of liners for spherical plain bearings was analyzed, with the help of 3D non-contact profiler, SEM, EDS and XRD. The wear mechanisms of liners under different conditions were explored. The transforming processes of wear mechanism for liners under different conditions were stated. According to the effects of different bearing materials, adhesive type and bonding process on the tribological properties, the best outer race material and adhesive type were established.The distribution of equivalent stress of copper grid liner and fabric liner was analyzed by finite element method software and the greatest equivalent stress of bearings was obtained. The wear phenomena during the experiment were verified by these analysis data. Moreover, the variation of equivalent stress with contact pressure was discussed.By changing the sphere diameter of spherical plain bearing, the effect of structure on the distribution of stress for bearings was analyzed. The trend of equivalent stress with the changing of sphere diameter was obtained.