合成孔径聚焦在水浸超声缺陷定量中的应用

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：FSAFT-DQM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FSAFT-DQM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。

Application of synthetic aperture focusing technique to defect quantification for immersion ultrasonic testing

Among the common defect quantification methods for immersion ultrasonic testing, some are high cost while others have relatively large quantitative error. Given the problem, a new 6 dB drop defect quantification method based on frequency domain synthetic aperture focusing technique (FSAFT-DQM) was studied. The FSAFT imaging method for spherically focused transducer used by immersion ultrasonic testing was established. Experiments conducted on specimens containing either circular cylindrical cavities or flat bottom hole show that defect depth has little effect on FSAFT-DQM's accuracy; compared with 6 dB drop method, flat bottom hole's quantitative error of FSAFT-DQM drops from 71.9% to within 10.0% with step length below half-wavelength of transducer's center frequency and the error decreases from 17.2% to 5.6% by image interpolation algorithm with step length between half-wavelength and wavelength. The research results show that FSAFT-DQM improves the precision of defect quantification effectively.