Modified Reynolds Equation for Non-Newtonian Fluid With Rheological Model in Frequency Domain

Abstract

The purpose of this paper is to provide a lubrication equation for non-Newtonian fluid. Three nonlinear functions instead of common power law model are used to describe non-Newtonian properties more completely. They are shear dependent viscosity, first normal stress difference and stress relaxation. After the coordinate conversion which is needed for the lubricant film thickness variation, the functions are involved in the modified Reynolds equation and show their effects on the lubrication results. As the principle factor in lubrication, viscosity is expressed by a first order transfer function in frequency domain. Its variation process is described by the function’s amplitude frequency response curve, which is validated by rheological experiment. Numerical results of the modified Reynolds equation show that non-Newtonian lubricant’s load capacity is not always higher or lower than Newtonian lubricant’s, and non-Newtonian lubricant has flatter pressure profile at high working speed.