Eddy Current Sizing of Case Depth in Bearing Components

Abstract

Encircling eddy current coil techniques are being used for the nondestructive evaluation of case depth in bearing components (Figure 1). These techniques, because of their ability to measure only bulk properties in test specimens, lack the necessary spatial resolution to detect local variations in case depth leading to eddy current imaging of the case depth. Further development in this area requires the knowledge of eddy current properties as a function of depth from the raceway (i.e. rolling contact surface). This paper describes the experimental determination of magnetic permeability and electrical conductivity of induction hardened case and unhardened core of a tapered roller bearing cup.