基于小波包分解的不锈钢焊缝超声TOFD检测信号及缺陷信号提取

Defect Signal Extraction on Ultrasonic TOFD Testing Signal of Stainless Steel Weld Based on Wavelet Packet Decomposition

奥氏体不锈钢焊缝超声检测时的信号受噪声和衰减的影响容易发生误判或漏检。将超声TOFD检测技术应用于不锈钢焊缝的检测中,利用小波包分解技术对检测信号深入分析,获得缺陷信号和噪声信号在时频域上的分布特征。结果表明:不锈钢焊缝的超声TOFD检测信号受焊缝结构噪声的干扰较大,通过小波包分解技术能够提取缺陷的衍射波特征,提高缺陷检测信号的信噪比及分辨率。

Ultrasonic testing signal of stainless steel weld is liable to be misjudged by its serious noise and attenuation.Ultrasonic Time of Flight Diffraction technique(Ultrasonic-TOFD)is one of the most effective weld test method and adopted in testing the weld of stainless steel in the research.The testing signal is analyzed to investigate the time-frequency characteristics of defect signal based on Wavelet Packet Decomposition(WPD).The results show that ultrasonic-TOFD signal of stainless steel weld is interfered by various noises such as electrical noise and structural noise,however,the diffraction characteristics of defect in testing signal can be extracted by use of WPD method,and the signal to noise performance and resolution is able to be enhanced in time domain.