Crack Detection and Quantification in Beams Using Wavelets

Abstract:  A new method has been proposed to detect the location and also to quantify the crack using the deflection response of the damaged beams alone. The deflection is measured at a particular point for various locations of a concentrated load on the beam. This static deflection profile is used as the input signal for wavelet (Symlet) analysis. Due to variation in deflection at some points, compared to their adjacent points, peaks are seen in the wavelet coefficient (WC) plot. These peak points are identified as damage points along the length of the beam. The peaks can also be seen at sensor point and supports. These can be eliminated by performing wavelet analysis for the deflection profile measured at another point. In a real damaged structure, it is very difficult to measure deflection at several points, as a large amount of instrumentation needs to be installed to measure the response. This practical difficulty can be avoided by minimizing the number of measuring points in the field as explained in the present work. A parametric study has been carried out by varying the damage, location of damage, intensity of load, flexural rigidity, and length of the beam. It has been observed that the WCs change with variations in damage, location of damage, intensity of load, flexural rigidity, and length of the beam. A generalized curve has been proposed to quantify the damage in a fixed beam by taking envelop of all maximum WCs of the deflection response measured at damage points.