Detection of the location and size of cracks in the multiple cracked beam by spatial wavelet based approach

Abstract

This paper presents a technique for structure damage detection based on spatial wavelet analysis. The innovation of the proposed paper is that both the positions and depths of multi-cracks can be estimated from spatial wavelet based method. First, the mode shapes of free vibration and natural frequencies of the multiple cracked beams are obtained. The crack type is open crack and is represented as a rotational spring. Then the mode shapes are analysed by wavelet transformation to get the positions of the cracks. When the positions of the cracks have been known from the plot of wavelet coefficients, the natural frequencies can be used to predict the depth of the cracks through the characteristic equation. If the number of cracks is n, the first n natural frequencies are used to predict the depth of the cracks. It is observed that the positions and depths of the cracks can be predicted with acceptable precision even though there are many cracks in the beam.