Damage Detection in Structural Beams Using Model Strain Energy Method and Wavelet Transform Approach

Abstract

Damage identification method of surface cracks in beams using strain energy method and its spatial wavelet transform is investigated in this paper. Experimental modal analysis (EMA) is conducted on a aluminium cantilever beam to obtain the mode shapes before and after damage under a fixed-free boundary condition by Laser Doppler Vibrometer (LDV). A small perturbation is created by using Electro Discharge Machine (EDM) and simulated crack by separation of nodes at the crack location in beams. The purpose of the study is to present damage index method and spatial wavelet transform approaches to identify the location and quantification of surface crack in beam structure. A finite element analysis (FEA) is also performed to access this approaches and illustrate a attainable process for the experimental work. First, the displacement mode shapes obtained from the intact and damaged beams which are used to obtain strain energy ratio of the beam before and after damage and then these spatially distributed signals are analyzed by wavelet transformation. Good correlation between FEA and EMA results is obtained. Both methods damage index (DI) and wavelet transform (WT) successfully identify the location of surface crack in the aluminium beam. it is also demonstrated that the location and quantification of single and multi cracks can be detected by this methods