Effect of Molecular Weight Distribution of Mineral Oils on Life of Thrust Ball Bearings

Abstract

In order to investigate the effect of molecular weight distributions of mineral oils on bearing life, the authors carried out systematic tests using thrust ball bearings, type 51104. Besides the general trend of increasing life with viscosity, blended oils characterized by wide-ranged molecular weight distributions exhibited longer life compared with base oils with narrow-ranged distributions corresponding to the same viscosity grade. These results were obtained by estimating states of oil film and oxide film formations, and furthermore, by measuring coefficients of friction, oil temperatures, and viscosity at the glass transition points.