The shallow subsurface defects are difficult to be identified and quantified by ultrasonic time-of-flight diffraction(TOFD)due to the low resolution induced by pulse width and beam spreading.In this paper,Sparse-SAFT ...The shallow subsurface defects are difficult to be identified and quantified by ultrasonic time-of-flight diffraction(TOFD)due to the low resolution induced by pulse width and beam spreading.In this paper,Sparse-SAFT is proposed to improve the time resolution and lateral resolution in TOFD imaging by combining sparse deconvolution and synthetic aperture focusing technique(SAFT).The mathematical model in the frequency domain is established based on the l1 and l2 norm constraints,and the optimization problem is solved for enhancing time resolution.On this basis,SAFT is employed to improve lateral resolution by delay-and-sum beamforming.The simulated and experimental results indicate that the lateral wave and tip-diffracted waves can be decoupled with Sparse-SAFT.The shallow subsurface defects with a height of 3.0 mm at the depth of 3.0 mm were detected quantitatively,and the relative measurement errors of flaw heights and depths were no more than 10.3%.Compared to conventional SAFT,the time resolution and lateral resolution are enhanced by 72.5 and 56%with Sparse-SAFT,respectively.Finally,the proposed method is also suitable for improving resolution to detect the defects beyond dead zone.展开更多
针对薄壁堆焊结构裂纹类缺陷定位、定量检测的需要,引入TOFD（time of flight diffraction）超声检测系统进行了堆焊层缺陷的检测方法研究。研究了裂纹类缺陷超声衍射时差法的检测特征,分析了不同角度探头和不同探头间距对近表面裂纹类...针对薄壁堆焊结构裂纹类缺陷定位、定量检测的需要,引入TOFD（time of flight diffraction）超声检测系统进行了堆焊层缺陷的检测方法研究。研究了裂纹类缺陷超声衍射时差法的检测特征,分析了不同角度探头和不同探头间距对近表面裂纹类缺陷检测结果的影响。研究结果表明,TOFD法可以检测到堆焊层表面下3~10mm内的垂直裂纹,结合A扫描信号和B、D扫描图像的特征,能够有效地对裂纹状缺陷进行识别、定位和定量,为堆焊质量评价提供可靠准确的依据。展开更多
基金National Key Research and Development Program of China(Grant No.2019YFA0709003)National Natural Science Foundation of China(Grant No.51905079)Liaoning Revitalization Talents Program(Grant No.XLYC1902082).
文摘The shallow subsurface defects are difficult to be identified and quantified by ultrasonic time-of-flight diffraction(TOFD)due to the low resolution induced by pulse width and beam spreading.In this paper,Sparse-SAFT is proposed to improve the time resolution and lateral resolution in TOFD imaging by combining sparse deconvolution and synthetic aperture focusing technique(SAFT).The mathematical model in the frequency domain is established based on the l1 and l2 norm constraints,and the optimization problem is solved for enhancing time resolution.On this basis,SAFT is employed to improve lateral resolution by delay-and-sum beamforming.The simulated and experimental results indicate that the lateral wave and tip-diffracted waves can be decoupled with Sparse-SAFT.The shallow subsurface defects with a height of 3.0 mm at the depth of 3.0 mm were detected quantitatively,and the relative measurement errors of flaw heights and depths were no more than 10.3%.Compared to conventional SAFT,the time resolution and lateral resolution are enhanced by 72.5 and 56%with Sparse-SAFT,respectively.Finally,the proposed method is also suitable for improving resolution to detect the defects beyond dead zone.
文摘针对薄壁堆焊结构裂纹类缺陷定位、定量检测的需要,引入TOFD（time of flight diffraction）超声检测系统进行了堆焊层缺陷的检测方法研究。研究了裂纹类缺陷超声衍射时差法的检测特征,分析了不同角度探头和不同探头间距对近表面裂纹类缺陷检测结果的影响。研究结果表明,TOFD法可以检测到堆焊层表面下3~10mm内的垂直裂纹,结合A扫描信号和B、D扫描图像的特征,能够有效地对裂纹状缺陷进行识别、定位和定量,为堆焊质量评价提供可靠准确的依据。
