基于Lyapunov指数的管道超声导波小缺陷定位实验研究

Tests for datecting crack locations in a pipe with ultrasonic guided wave based on Lyapunov exponent

为了提高超声导波检测长距离管道中小缺陷的检测灵敏度,提出了基于杜芬方程最大Lyapunov指数的超声导波损伤定位方法。依据管道超声导波实测信号的采样频率、中心频率以及杜芬方程特性,设置检测系统参数,将待测信号作为杜芬方程外策动力扰动项输入杜芬方程中。通过比较杜芬系统在无信号输入和输入实测导波信号后,最大Lyapunov指数随策动力幅值F的变化,确定可用于识别导波信号的F值。利用移动窗函数给出了缺陷超声导波的波到时刻识别方法,从而给出了缺陷定位方法。实验研究表明,利用最大Lyapunov指数可有效提高超声导波的检测灵敏度。

In order to improve the detection sensitivity of small detection method based on the maximum Lyapunov exponent of a Duffing crack locations in long distance system was proposed. According frequency and center frequency of the measured ultrasonic guided wave signals and the characteristics of a pipes, a novel to the sampling Duffing chaotic oscillator, the parameters of the detection system were set up. The guided wave signals to be tested were input into Duffing equation as the external driving force＇s turbulent term. Comparing the curve of the maximum Lyapunov exponent of the Duffing system varying with the driving force amplitude F without a turbulent term and that with the measured guided wave signals as the turbulent term, the appropriate value of F used to detect the guided wave was determined. Then a time- moving window function was constructed to locate the crack by moving the window along the measured signals. The experimental results showed that the maximum Lyapunov exponent can effectively improve the sensitivity of small crack detection.