Influence of Harmonic Surface Roughness on the Fatigue Life of Elastohydrodynamic Lubricated Contacts

Abstract

In recent years, owing to the increase in transmitted power, increase in temperature, and decrease in viscosity, elastohydrodynamic lubricated (EHL) contact conditions have become extremely severe. Consequently, roughness and surface features become increasingly important when compared with the lubricant film thickness, which can induce wear. Moreover, local pressure variations increasingly cause surface-induced fatigue. Therefore, the understanding of roughness behaviour in EHL contact performance has become important.

Three decades ago, a widely used tool to predict contact performance was proposed by Dawson and Tallian. It is based on the central film thickness to composite roughness (h³/σ) ratio. However, engineering fatigue life models require the stress level and the stressed volume to study the contact life reduction, and neither can be extracted directly from the h³/σ ratio.

This article extends the amplitude reduction analysis. It proposes a new dimensionless parameter including central film thickness, roughness wavelength, and amplitude. It is shown that the pressure fluctuations depend solely on this parameter and that the fatigue life depends mainly on this parameter.