改进的非线性调频脉冲压缩方法在空气耦合超声检测中的应用

为解决空气耦合超声检测中信号微弱、信噪比低的问题,在应用线性调频脉冲压缩方法的基础上,研究非线性调频脉冲压缩方法及改进后的方法在空气耦合超声检测中应用。介绍非线性调频脉冲压缩方法的基本原理,针对超声检测中实际应用的特殊性,分析换能器频带特性对脉冲压缩效果的影响,试验研究改进的非线性脉冲压缩方法对空气耦合超声换能器接收信号的影响以及脉冲压缩方法对提高信噪比的实际效果,通过空气耦合超声C扫描检测系统,对玻璃纤维复合材料试样进行成像检测试验。试验结果表明,改进的非线性调频脉冲压缩方法可有效提高脉冲压缩效果,有利于改善空气耦合超声检测的效果。

Application of Non-linear Frequency-modulation Based Pulse Compression in Air-coupled Ultrasonic Testing

Effective signal processing technology should be used to improve signal-to-noise ratio in air-coupled ultrasonic testing,because of feeble signal and low signal-to-noise ratio.Pulse compression with non-linear frequency modulation is applied in air-coupled ultrasonic testing,based on the research of pulse compression with linear frequency modulation,some improved method are presented.Principle of non-linear frequency modulation pulse compression is introduced.The effect of frequency characteristic of transducers is analyzed,because of the particularity of ultrasonic testing process.The affecting of stimulating mode to ultrasonic signal and pulse compression to signal-to-noise ratio are researched by comparing experiment results.The imaging testing experiment of fiberglass composite sample is accomplished with air-coupled ultrasonic C-scan testing system.Experiment results indicated that the pulse compression with non-linear frequency modulation is effective to improve the effect of pulse compression,and enhance the effect of air-coupled ultrasonic testing.