Fundamental Study on the Use of the Unisteel Bearing Tester to Differentiate Driveline Lubricant Additive Performance

Abstract

The impact of driveline lubricants on rolling element bearing fatigue has been an important concern for many years. The recent emphasis on improved drivetrain efficiency has further heightened interest in the impact of lubricants on bearing life. A number of laboratory roller bearing test machines have been used to qualify lubricants for automotive applications. Included in these is the Unisteel Rolling Fatigue Testing Machine. We herein present results from an experimental matrix of driveline additives tested using a Unisteel test procedure. Statistical analysis of the cycles to pitting failure suggests that there was no difference in calculated bearing fatigue life between additive families taken as a group. Failure analysis of the end-of-test bearings suggests that the observed fatigue lives were primarily governed by poor surface finish on a flat test specimen commonly used to increase contact stress in accelerated Unisteel bearing fatigue test procedures.

Keywords

• bearing fatigue
• pitting
• unisteel
• ball bearing
• transmission fluid
• gear oil
• lubricant