Factors Affecting Surface Roughness Measurement Results, and the Impact on Predicted Life of Elastohydrodynamic Lubricated Rolling-Element Bearings

Abstract

This work investigates the sensitivity of the surface roughness lubricant life adjustment factor for rolling-element bearings to variations in measured roughness. Roughness measurement results using different values of stylus tip dimension and short wavelength cutoff filter were obtained for several bearing raceway surfaces and used as the inputs for a lubricant life adjustment factor based on the lambda ratio—the ratio of elastohydrodynamic lubrication (EHL) film thickness to the composite surface roughness. The effect on predicted bearing life is shown to be significant. As one means of verification of surface roughness measurements, an ISO type D random/repeating precision roughness specimen was also investigated and shown to have excellent sensitivity to stylus tip dimension, demonstrating its effectiveness as a tool for assessment of stylus radius and condition.

Stylus tip radius and wear estimation using the Rsk or the Rp and Rv parameter of a sine wave (Type C1) standard

“…The stylus tip radius affects typical surface topography parameters such as Ra, Rq, Rp, Rv and Rt in turned, milled, bored and honed samples to a limited, though often significant, extent [3,4]. The effect of tip size on the Ra-parameter can be significant for rectangular profiles [5] as well as for type D specimens with Ra-values<0.1 mm [6]. The determination of stylus wear is essential to prevent unexpected measurement errors and damage to the surface.…”