The mixed lubrication calculation of low-modulus polymer considering surface forces

Abstract Low-modulus polymers show excellent friction reduction via hydration-based surface modification, yet the strong coupling between surface forces and elastic deformation causes persistent convergence failures in mixed lubrication calculations. This study develops a numerical framework considering surface forces for such systems, derives a sufficient convergence condition for surface force iteration, resolves the computational difficulties, and analyzes how elastic modulus and hydration repulsion affect surface forces. Validation on UHMWPE-sapphire tribopairs confirms surface forces fully avoid asperity contact at low sliding velocities, with results consistent with experiments. A critical load-bearing criterion is further proposed. These analyses and results establish a foundation for advanced numerical simulations of complex water-lubricated conditions and provide theoretical insights for designing water-lubricated polymer components such as bearings and artificial joints.