Damage detection on beam structures based on fractal theory and wavelet packet transform

Abstract

Summary Anew damage identificationmethodbasedonFractal theoryandwaveletpacket transform is presented in the paper. The damage identification method utilize frequency-based domain message, time-based domain message and space based domain message effectively. NeXT method were first employed to reduce loading effect of random vibration measured from structures and then the vibration sinal were decomposed into the certain level wavelet packet components. For every time array of wavelet packet component then need to calculate the mean FD values as the ultimated FD values to reduce noiseeffect. The location of damage in the beam can be determined by the dramatic fluctuation appearing on contour of estimated FD and the extent of the damage can be estimated by FD-based damage index of δ. As a validation, the proposed method is applied to detect damage in a simply supported beam by numerical study. The successful detection of the damage in the beam demonstrates that the method is capable of assessing both the location and size of the damage. Noise stress testsare also carried out to demonstrate the robustness of the method under the influence of noise by considering all the information of every wavelet packet component synthetically.