A spherical-coordinate grease lubrication model for wear evolution of miter gate bottom pivot bearings

The bottom pivot (spherical bearing and pintle) of miter gates operates under low-speed, ultra-heavy load conditions, where wear is unavoidable. Recent hydraulic projects have adopted grease injection to improve lubrication, yet the absence of models tailored to spherical friction pairs limits understanding of its mechanism and effectiveness. To address this, a non-Newtonian grease lubrication model in spherical coordinates, coupled with bearing elastic deformation, is developed to simulate mixed elastohydrodynamic conditions. Wear evolution is investigated with dry friction as a reference. Long-term tests on a scaled pivot rig demonstrate that grease lubrication reduces the maximum wear depth by approximately 39.5% after 16000 cycles and provides substantial protection to the lateral surface. Close agreement between simulated and experimental results for both wear distribution and depth validates the proposed model. It is important to note that grease lubrication can inhibit the formation of solid lubricant transfer films. Therefore, periodic maintenance is essential during long-term operation to prevent friction pair performance deterioration once the grease degrades and the protective transfer film becomes insufficient.