damage detection in pipes using vibration mode shapes and wavelet analysis

today piping systems play a crucial role in different industries. since pipes usually experience internal surface damages, damage detection in the pipes, using traditional inspection methods, is not possible. therefore, finding an effective method for detecting internal damages in the pipes seems important. the primary goal of this paper is to demonstrate the effectiveness of using the wavelet transform to detect and localize the internal damages in the pipes. one advantage of using the wavelet transform is that this method requires only one static or dynamic response of the damaged structure, while no information about the intact structure is needed. in this paper, vibration mode shapes of the damaged structure are obtained using the abaqus numerical modeling software package, and then the wavelet analysis has been applied to detect and localize the changes in the mode shapes. the damages have been modeled as a local reduction in the thickness of the pipe and three different damage scenarios have been investigated. the continuous wavelet transform using biorthogonal wavelet is used to get the spatially distributed wavelet coefficients. meanwhile, a multiple-mode damage indicator based on the squared residual of the wavelet coefficients along spatial locations is proposed and its performance has been investigated via several numerical examples.