Piezoelectric-based degradation assessment of a pipe using Fourier and wavelet analyses

One of the most important issues in today's oil and gas industry is the access to an effective and reliable damage-detection system for health monitoring of pipeline systems. Vibration-based damage-detection systems have been contemplated in the past with varying success. This article demonstrates the effectiveness of a series of coupled mathematical/engineering approaches that are used to detect damage in pipes, reliably and accurately. The proposed health-monitoring methodology is based on monitoring the vibration response of pipes using piezoelectric sensors. Finite element analysis is used to simulate the response of a healthy pipe, as well as pipes with various size damage. The degradations (defects) have been assumed to exist on the pipes in the form of local corrosion, simulated by reducing the wall thickness in various areas around the circumference of pipes. Fast Fourier transformation (FFT), FFT integration, wavelet transformation (WT), and wavelet packet transformation (WPT) methods are used to examine the pipe's dynamic response to an impacting force. Novel "Damage indices" expressions are developed based on the evaluation of vibration-signal-induced energies. As it will be seen, the damage indices can effectively establish the existence of defects. Moreover, the energy indices can distinguish the differences among various size defects. It was observed that all the approaches considered could essentially establish the existence of the defects with good accuracy; however, incorporation of the WT and WPT energy components yielded a more precise identification of damage in the pipes examined.