为了实现特种管道在高温、高压、辐射等特殊环境下管壁厚度的非均匀性检测, 提出一种基于微分算法的管道壁厚激光超声测量及特征信号处理方法。采用脉冲激光激励和激光干涉探测的激光超声方法, 实验测得管道试件的宽频带激光超声信号。采用数字平均算法对宽带激光超声信号进行去噪处理, 提高原始激光超声信号的信噪比。采用微分算法对激光超声信号进行特征提取处理, 得到表征管壁厚度的激光超声特征信号。根据管道材料声速和激光超声传播时间反演计算得到管道试件的壁厚值, 管壁厚度测量值与实际值的误差小于5%。研究表明, 基于微分算法的管道壁厚激光超声测量及特征信号处理方法具有良好的信噪比、准确的信号特征量和较高的测量精度, 可用于管道壁厚的在线实时检测以及因腐蚀、应力引起的管道壁厚不均匀性检测。

In view of the nonuniformity of pipe wall thickness of the special pipe under special environments such as high temperature, high pressure, radiation, and others, a method for laser ultrasonic measurement and thickness feature signals processing based on the differential algorithm was proposed. The laser ultrasonic method was adopted with pulse laser excitation and laser interference detection for the experimental measurement of broad-band laser ultrasonic signals of the test piece of pipe. Then the broad-band laser ultrasonic signals were de-noised by average algorithm in order to increase the signal to noise ratio of the original laser ultrasonic signals. Furthermore, the feature of the de-noised ultrasonic signals was extracted by differential algorithm, outputting the laser ultrasonic feature signals of pipe wall thickness. According to the sound velocity of pipe material and the laser ultrasonic transit time, the thickness values for the test piece of pipe wall were deduced. The error between the measured and actual thicknesses was less than 5%. The result shows that the processing method for thickness feature signals based on differential algorithm can provide favorable signal to noise ratio, accurate signal feature quantity and higher measurement accuracy, thus can be used for online real-time measurement of wall thickness of pipe and the thickness nonuniformity leaded by erosion and stress.