METHOD AND APPARATUS FOR THE DETECTION OF ANOMALIES IN ROTATING MEMBERS

摘要

A detector operable to detect cracks in a rotating member generates an alternating eddy current in the rotating member with an external coil surrounding the rotating member. A pick-up coil senses changes in the magnetic field of the eddy current due to a crack. The frequency of the excitation current is very much lower than the frequency of rotation of the rotating member and a plurality of samples are taken for each degree location. The output signal of the pick-up coil is comprised of both the crack indicative component and a residual or induced magnetism component. The signal is processed so as to extract the desired crack indicative component.