Generalized MEMT-Field Reynolds Equation With Application to Electric Polarization in Lubrication

Abstract

Abstract. Lubricants used in electrically powered machinery, such as electric vehicles (EVs) and wind turbines, operate under complex mechanical, electric, magnetic, and thermal (MEMT) environments that can significantly affect lubrication performance. Capturing these coupled interactions requires a multifield lubrication theory capable of accurately describing lubricant behavior. In this study, we completed the generalized MEMT-field Reynolds equation with details for incorporating electric and magnetic forces arising from interactions between external fields and different lubricant components. These components are classified as free charged species, electric dipoles, and magnetic dipoles, each contributing distinct force terms such as Lorentz, polarization, magnetization, and torque-induced forces. A unified formulation of electric and magnetic body forces is developed to encompass these interactions, thereby broadening the applicability of the MEMT-field Reynolds equation to a wide range of field-lubricant systems. Numerical models are constructed to analyze the role of electric polarization on both infinitely long and finite-length journal bearings. The simulations show that polarization increases pressure buildup, load-carrying capacity, and friction force while reducing the coefficient of friction. Under typical EV operating conditions, these effects are pronounced in low-viscosity, high-dielectric-constant fluids such as water, but negligible in common base oils with higher viscosity and lower dielectric constants. Overall, this work not only provides a detailed modeling framework for MEMT-field lubrication but also practical insights into lubricant selection and system design for electromagnetic mechanical applications.