Mixed elastohydrodynamic lubrication of transversely isotropic coatings in impact motion

In modern engineering applications, the performance and longevity of mechanical systems are critically influenced by the lubrication behavior of coatings under dynamic loading conditions. In this work, a mixed elastohydrodynamic lubrication (EHL) model for transversely isotropic coatings undergoing impact motion is developed. The set of explicit analytical formulas of the elastic field for transversely isotropic coating is derived. This model concurrently accounts for factors such as entrainment velocity, sudden squeeze effects, the non- Newtonian characteristics of the lubricant, and the transverse isotropy of the coating. The accuracy of the proposed model is validated through comparisons with existing literature. A detailed analysis is conducted to investigate how lubrication properties evolve during impact motion, focusing on the interplay between entrainment velocity, coating thickness, and the five elastic constants of the coating. Simulation results indicate that an abrupt load impact leads to two peak fluctuations in the maximum surface pressure when the lubricant conditions are optimal. Furthermore, the five elastic constants significantly influence the impact process, suggesting that the selection of coatings with appropriate elastic constants can mitigate the effects of impact.