基于时频分析的奥氏体焊缝超声检测信号处理

Signal processing in ultrasonic test of austenitic welds based on time-frequency analysis

对奥氏体焊缝超声检测信号处理方法进行了研究.提出一种基于匹配追踪和小波变换两种时频分析方法的信号处理方法,分别从能量和频率的角度区分缺陷信息和材料散射噪声,提高超声检测回波的信噪比.为了验证此方法的有效性,建立了超声检测试验系统,对53 mm厚焊缝试块进行检测试验,采集了含有大量材料噪声的实际检测信号.选用sym8小波包原子库对信号进行匹配追踪分解,提取前18个时频原子,利用sym8小波函数对提取的信号进行小波分析,用低频系数重建原信号.结果表明,此方法能够有效抑制材料噪声,明显增强缺陷信息.

Signal processing in ultrasonic test of austenitic welds was studied.Based on time-frequency analysis,a comprehensive signal processing method was proposed,which was a combination of matching pursuit and wavelet analysis.This method distinguishes flaw information and material noise from a point of energy and frequency,respectively,and improves the SNR of the ultrasonic echo signal.To verify the effectiveness of the method,an ultrasonic test system was established.Test experiment was carried out with a 53 mm thick weld specimen,and a signal with large amount of material noise was acquired.The noised signal was processed by the proposed method.The first 18 time-frequency atoms were extracted by matching pursuit with sym8 wavelet packet dictionary,the extracted signal was analyzed by sym8 wavelet decomposition and reconstructed with low frequency coefficients.The result shows that the material noise is reduced effectively and the flaw echo signal is enhanced significantly.