小波变换在超声探伤仪检测回波处理中的应用

Application of Wavelet Transform to the Testing Echo Processing of Ultrasonic Flaw Detector

超声检测时探伤仪的电噪声和被检粗晶材料的散射噪声严重影响检测回波的信噪比。研究小波变换软阈值去噪方法在超声检测回波处理中的应用。在分析仪器电噪声、材料散射噪声和缺陷回波的小波变换特性的基础上 ,提出一种用一个尺度间变化的门限阈值来抑制噪声回波的小波变换系数再重构检测回波的方法提高信噪比。距离 -波幅 -当量曲线测定实验结果表明 ,该方法具有很好的去噪效果 ,处理后的回波损失小 。

The electrical noise of instrument and scattering noise from coarse grain material inspected have serious adverse effect to the signal to noise ratio of testing echo of ultrasonic flaw detector in inspection. The application of de noising by soft thresholding on wavelet transform to ultrasonic detection echo is discussed. According to the characteristics of electrical noise, scattering noise and flaw echo wavelet transform on the different scale, we present an algorithm that wavelet transform coefficients of noise are filtered by changing threshold on the different scale and reconstruct the detection echo in order to enhance signal to noise ratio. The experimental results of AVG curve measuring show that the new method is more effective, the defect is detected more easily, and the echo processed has slight distortion, it can ensure the accuracy of quantitative inspection.