微小缺陷回波信号的成像方法研究

Research on Imaging Method of Micro Defect Echo Signal

针对金属中微小缺陷在超声检测时回波信号较弱,利用时域回波信号对微小缺陷试块进行C扫描成像时图像噪声较大且信噪比较低的问题,借鉴医学超声影像领域中的背散射积分诊断技术,提出了一种通过计算缺陷回波信号的功率谱(PSD)和频域背散射积分(IBS)来表征微小缺陷的方法。在使用IBS对试块进行成像后发现成像的信噪比较时域成像有显著的提高,但图像出现了明显的网格化。对此提出了使用频域背散射补偿积分(IBSC)和频域背散射全宽带积分(IBSF)成像的两种改进降噪方法。实验结果表明,这两种改进的成像方法均能在保持成像具有较高信噪比的条件下抑制图像的网格化,但IBSC的计算量远小于IBSF,更适用于金属中微小缺陷的成像检测。

In order to solve the problem that the echo signal of micro defects in metal is weak in ultrasonic testing,and the image noise is large and the signal-to-noise ratio is low when using the time domain echo signal for C-scan imaging of micro defects,the integrated backscatter diagnosis technology in the field of medical ultrasonic imaging is used for reference,a method of characterizing micro defects by calculating power spectral density(PSD)and integrated backscattering(IBS)of defect echo signal is proposed.After using IBS to image the test block,it is found that the signal-to-noise ratio of time domain imaging is significantly improved,but the image appears obvious gridding.For this reason,two improved noise reduction methods,frequency domain back scattering compensation integration(IBSC)and frequency domain back scattering full broadband integration(IBSF),are proposed.The experimental results show that the two improved imaging methods can suppress the gridding of the image while maintaining a high signal-to-noise ratio.However,the computation of IBSC is much less than that of IBSF,and it is more suitable for the imaging detection of small defects in metal.