Noncontact Damage Detection of a Rotating Shaft Using the Magnetostrictive Effect

The objective of this investigation is to develop a cost-effective noncontact diagnostic method for rotating shafts in operation. Unlike most existing diagnostic methods developed for rotating shafts, longitudinal stress waves are used and processed for damage assessment. For the non-contact measurement of stress waves in rotating shafts, we propose to use magnetostrictive effect. Shaft rotations inevitably accompany lateral vibrations; thus the effects of the vibrations on the measurement accuracy of the sensor are studied to verify the validity of the magnetostrictive effect application to rotating shafts. For damage location estimation, we use the continuous wavelet transform of the measured wave signals. In particular, we propose to adopt the real-valued Gaussian wavelets as the mother wavelet in order to pinpoint accurately the arrival time of the reflected wave from a crack. Several case studies are considered to show the effectiveness of the present diagnostic method.