An experimental study of crack detection in a rotating shaft

Abstract

This thesis investigated the dynamic characteristics of a rotating shaft by using modal experimental method and an experimental model has been developed for crack detection. -- In this study, an imitation crack, which simulates the characteristic of a transverse crack, in the middle span of a rotating shaft, is designed and the rotating shaft experiment setup is made up. Experiments are carried out in different crack parameters and different size rotors in forward and backward rotation. -- It is found that the natural frequency of the rotating shaft decreases and frequency response amplitude increases with increasing crack parameter. The maximum difference of natural frequency between cracked and uncracked shaft is 14.7%, and the maximum difference of frequency response amplitude with a crack is 4 times as high as that without crack. It is also found that the rotating shaft in backward rotation has the same vibration response as that in forward rotation. -- The experiment results show that the critical speed of the rotating shaft is sensitive to cracks. Therefore, the method may be used in industrial application for detection crack in rotating shafts.