Crack detection near the ends of a beam using wavelet transform and high resolution beam deflection measurement

Abstract

Wavelet based crack detection has certain limitations such as, border distortion near the ends of a signal and the requirement of high measurement resolution. Border distortion restricts the crack detection near the ends of a beam. Detecting crack near the fixed end is critical as it faces the highest bending stresses. High measurement resolution is required for better localization of cracks and also to shrink the border distortion zone. In the present work, the effect of measurement resolution and wavelet scale on the border distortion is studied. Suitable wavelet scale is selected based on crack localization and smoothness of wavelet coefficients. The effect of measurement resolution on signal extension using isomorphism is presented. Photographic method is used to obtain the high resolution measurement of the beam deflection. The algorithm is tested for the detection of a crack in the border distortion zone. Also, the detection of two simultaneous cracks in the beam is presented.