EXPERIMENTAL STUDIES ON ULTRASONIC GUIDED WAVE INSPECTION USING DUFFING SYSTEM

摘要

In order to improve the sensitivity of small crack detection using ultrasonic guided wave, a novel method of weak signal detection based on dynamics of Duffing equation that is sensitive to the guided wave and has strong immunity to the noise is proposed. The theory that the Duffing system has strong immunity to the noise is proved using the mathematical principle. The propagation of guided wave in 3m-in-length steel pipe is measured experimentally, and the measured signals are introduced to the Duffing inspection system. The experimental results show that the Lyapunov exponents of Duffing system can effectively identify small defect echo and has strong immunity to the noise simultaneously. The motion states of Duffing system can transform from periodic attractor to chaotic attractor if inputting measured guided wave signal and the symbol of maximum Lyapunov exponents is also changed. The proposed method though observing dynamical behavior of Duffing System can be used to detect weak guided wave signal with strong noise.