LAUSR

Abstract Ultrasonic guided wave based non-destructive testing is an effective method to inspect defects in long-distance pipe structures. This paper proposes a novel defect detection approach for the pipes using stochastic resonance of Duffing oscillator and ultrasonic guided waves. Stochastic resonance can improve the signal-to-noise ratio (SNR) in the output signal, because it can enhance the periodic component while attenuate the noise components. A detection system is first developed based on Duffing oscillator. The echo signal between the incident signal and end echo is used as the input to the Duffing oscillator, and the normalized power spectrum of the output signal is calculated to obtain the SNR of the output signal. The SNR curve is shown versus the change of the damping ratio value. When stochastic resonance occurs, the SNR is at the peak, corresponding to the optimal value of damping ratio. With the optimal damping ratio value, the power spectrum of the output signal from the Duffing oscillator is used to detect the characteristic frequency. If there is a distinct characteristic frequency with the same excitation frequency as the guided wave excitation signal, it can be concluded that there is a defect in the pipe. Both numerical simulations and experimental studies are conducted to investigate the accuracy and effectiveness of the proposed approach in defect detection in pipes. The detection results demonstrate that the proposed approach can significantly enhance the sensitivity of using weak guided wave signals for minor defect detection in pipe structures.