空气耦合超声检测中脉冲压缩方法的参数选优

多种脉冲压缩方法已成为提高空气耦合超声检测信号信噪比(SNR)的有效手段,而实际使用中面临如何选取合适参数以获得更好压缩效果的问题.基于脉冲压缩技术的基本原理及其在超声检测中的实现,建立了具备超声信号脉冲压缩实时处理的空气耦合超声检测系统.使用窄带空气耦合超声换能器分别就线性调频、非线性调频及相位编码脉冲压缩方法的关键参数对压缩效果的影响开展了实验研究,获得了脉冲压缩参数选取准则.最后以模拟缺陷的蜂窝夹芯复合材料试样为对象,验证了参数选优后的脉冲压缩方法在空气耦合超声检测中的应用效果.

Parameter optimization of pulse compression method in air-coupled ultrasonic testing

A variety of pulse compression methods are viewed as viable solutions to improve the signal to noise ratio (SNR) of received signal in air-coupled ultrasonic testing. However, the use of corresponding method to realistic inspection is faced with problem of optimal parameter selection to get better compression effect. Based on the basic principle of pulse compression method and its implementation in ultrasonic testing, an air-coupled ultrasonic testing system with function of real-time pulse compression processing of ultrasonic signal was established. The impact of key parameters of linear frequency modulation, nonlinear frequency modulation and phase coded pulse compression method on compression effect in narrow-band air-coupled ultrasonic transducer was analyzed, respectively, and then the optimal parameter selection criteria was acquired. Finally, the corresponding pulse compression method of optimized parameters was verified in air-coupled ultrasonic inspection of a honeycomb sandwich composite sample with simulated defects.