Guided wave technique is an efficient method for monitoring structural integrity by detecting and forecasting possible damages in\r\ndistributed pipe networks. Efficient detection depends on appropriate selection of guided wave modes as well as signal processing\r\ntechniques. Fourier analysis and wavelet analysis are two popular signal processing techniques that provide a flexible set of tools\r\nfor solving various fundamental problems in science and engineering. In this paper, effective ways of using Fourier and Wavelet\r\nanalyses on guided wave signals for detecting defects in steel pipes are discussed for different boundary conditions. This research\r\ninvestigates the effectiveness of Fourier transforms and Wavelet analysis in detecting defects in steel pipes. Cylindrical Guided\r\nwaves are generated by piezo-electric transducers and propagated through the pipe wall boundaries in a pitch-catch system. Fourier\r\ntransforms of received signals give information regarding the propagating guided wave modes which helps in detecting defects by\r\nselecting appropriate modes that are affected by the presence of defects. Continuous wavelet coefficients are found to be sensitive\r\nto defects. Several types of mother wavelet functions such as Daubechies, Symlet, and Meyer have been used for the continuous\r\nwavelet transform to investigate the most suitable wavelet function for defect detection. This research also investigates the effect of\r\ndifferent boundary conditions on wavelet transforms for different mother wavelet functions.
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