Bearing Ball Property Estimation using Multi-frequency Eddy-current Testing.

The quality of steel balls influences the accuracy, motion performance and service life of the rolling bearing. The eddy-current testing technique plays an important role in the measurement of bearing ball properties, including radius, electrical conductivity and relative magnetic permeability. In this study, an estimation method of bearing ball properties is proposed using the multi-frequency eddy-current testing technique. The estimation method optimizes the least squares problem between the measured and calculated coil inductance spectra through the modified Newton-Raphson algorithm. In addition, the combination of bearing ball properties to be estimated is evaluated by employing sensitivity analysis. The effectiveness of the proposed method has been evaluated by numerical simulation and experiments measuring bearing balls with various properties.