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针对水浸超声检测常用缺陷定量方法存在成本高或缺陷定量误差较大的问题,提出一种将原始检测数据经频域合成孔径聚焦技术(FSAFT)处理后再运用半波高法进行缺陷定量评价(FSAFT-DQM)的新方法。建立了水浸超声点聚焦探头FSAFT成像方法,制备了横通孔和平底孔试样,开展了FSAFT-DQM缺陷定量评价试验研究。试验结果表明:FSAFTDQM缺陷定量精度受检测深度影响不明显;当扫描步距不大于探头中心频率对应的半波长时,与半波高法相比,平底孔试样FSAFT-DQM缺陷定量误差由71.9%降低到10.0%以内;扫描步距在探头中心频率对应的半波长到波长之间时,图像频域插值算法将平底孔试样FSAFTDQM缺陷定量误差由17.2%降低到5.6%。研究结果表明:FSAFT-DQM能有效提高缺陷定量精度。
Aiming at the problems of high cost and large quantitative error of defects in ultrasonic testing of water immersion, this paper proposes a method of quantitatively evaluating the defects by using half-wave height method after the original detection data is processed by FSIF (Frequency Synthetic Aperture Focusing) FSAFT-DQM). The FSAFT imaging method of water immersion ultrasonic point focusing probe was established and horizontal through hole and flat bottom hole samples were prepared. The quantitative evaluation test of FSAFT-DQM defect was carried out. The experimental results show that the quantitative accuracy of the FSAFTDQM defect is insignificantly affected by the depth of detection. When the scanning step is not more than half the wavelength corresponding to the center frequency of the probe, the quantitative error of the FSAFT-DQM defect is reduced from 71.9% To 10.0%. When the scanning step is between the half wavelength and the wavelength corresponding to the center frequency of the probe, the image frequency domain interpolation algorithm reduces the quantitative error of the FSAFTDQM defect of the flat bottom hole sample from 17.2% to 5.6%. The results show that: FSAFT-DQM can effectively improve the quantitative accuracy of defects.