Diagnosis of Bearing Defects Using a Heterodyning Ultrasound Detector

Abstract

A single row ball bearing was presented to the Failure Analysis Lab because of noise and perceived roughness during low speed operation. The bearing was analyzed using a heterodyning ultrasound detector. Discrete sources of intermittent noise were detected. A quasi-static determination of the friction coefficient of the bearing was made. Contamination by hard foreign objects was suspected. The bearings were solvent washed, and particles of aluminum were recovered. The size of these particles was related to the static friction coefficient of the bearing. The cleaned bearings were retested and found to have residual friction related to microscopic defects caused by inclusions and voids in the races and balls. A generalized theory was formulated to account for the relation between noise and static friction.