Detection and localization of multiple cracks in a stepped shaft

The presence of a crack in a shaft causes a slope discontinuity in the elastic line of the shaft. There are crack detection techniques, available in the literature, exploiting the slope discontinuity arising because of the crack in the shaft. Steps present in a shaft are expected to interfere with the results obtained through these identification techniques based upon slope discontinuity. It would be even more difficult to identify a crack if it is near a step as both the step and the crack will cause slope discontinuities. A multi‐crack identification technique has been developed (Singh S. K. and Tiwari R. (2010). Mech. Machine Theory 45, 1813–1827; Singh S. K., Tiwari R. and Talukdar S. (2009). IUTAM Proc. in Recent Trends in Rotor Dynamics, March 23–26, IIT Delhi, India) which uses shaft‐forced responses at several frequencies to identify the number of cracks and their locations over the shaft. The algorithm uses normalization of quadratic coefficients obtained from measured responses of a cracked shaft and from simulated responses of the intact shaft for detecting the slope discontinuity. In the present work, the effect of steps in the shaft on crack identification has been analysed. Cracks are assumed to be both near the step and far from the step. The identification algorithm works well for both the simulation cases.