基于混凝土缺陷超声检测的合成孔径聚焦成像

Synthetic Aperture Focusing Imaging for Ultrasonic Testing of Concrete Defects

由于混凝土的随机性,超声波在混凝土中传播伴随着强烈的衰减、反射以及散射作用,回波信号信噪比低,带有损伤信息的有效反射信号同背景噪声混叠畸变。传统超声信号处理难以识别缺陷的具体信息,本文引入了频域合成孔径聚焦算法对超声回波数据进行成像处理,并开展了对混凝土空洞缺陷的数值模拟和试验研究,采用道内平衡处理方法,对混凝土深部信号进行了增强处理,提高了缺陷回波的质量,对多次自发自收数据进行了频域合成孔径成像处理,空洞缺陷的绕射波被收敛,提高了100 kHz超声波的检测成像效果;同时预制了双空洞混凝土试件,使用宽频带窄脉冲探头进行现场混凝土空洞缺陷超声波检测试验,结果与数值模拟结果基本吻合,证明了合成孔径聚焦技术能够使混凝土缺陷的绕射波得到了很好的收敛,有效提高了小孔径超声波探头的分辨率。

Due to the randomness of concrete,the ultrasonic waves propagate in concrete with strong attenuation,reflection,and scattering effects,the SNR(signal to noise ratio)of echo signal is low and the effective reflected signal with damage information is distorted by background noise.Traditional ultrasonic signal processing is difficult to identify the specific information of defects.This article introduces the frequency domain synthetic aperture focusing algorithm to image the ultrasonic echo data picture.Numerical simulation and experimental research on concrete cavity defects are carried out at the same time.The trace equalization method is used to enhance the deep signal of concrete,which improves the quality of defect echoes.Using frequency domain synthetic aperture imaging on multiple self-excited and self-receiving data,the imaging effect of ultrasound detection is significantly improved.The double-cavity concrete specimens were prefabricated to conduct the field test with a broadband narrow pulse probe.The results were basically consistent with the numerical simulation results.It is proved that synthetic aperture focusing technology can make the diffraction wave of defects converge well and effectively improve the resolution of small aperture ultrasonic probe.