中文摘要：

针对在使用超声衍射时差技术检测焊缝时,对于薄壁试件、近表面或尺寸较小的缺陷,各回波波形之间容易发生重叠和给波达时间的测量带来困难的问题,基于Gabor函数,对传统的正交匹配追踪算法的优化进行了研究,建立了超声TOFD检测信号特征信号库。利用波形的相似性从特征信号库中选择了与检测信号相匹配的最优原子,实现了重叠信号分离以及检测信号稀疏化,设计了超声TOFD实验系统,并对带有人工缺陷的试块进行了相关实验验证。研究结果表明,该技术能够有效分离重叠信号并精确测量超声波波达时间,缺陷测量误差小于0.28 mm。

英文摘要：

Aiming at the problem that using Time of Flight Diffraction（ TOFD） was difficult to measure the arrival time of ultrasonic signals of welds and overlapping between echo waveforms of thin-wall specimens,near-surface defects and small size defects,optimization of traditional orthogonal matching pursuit（ OMP） was studied and the characteristic signals library of ultrasonic TOFD detection signals were built based on the Gabor function. Separation and rarefaction of overlapped detection signals were implemented by using the similarities of waveforms to choose the best matching Gabor atoms from characteristic signals library. An ultrasonic experimental system was established to do the confirmatory tests of artificialspecimens. The results indicate that the arrival time of ultrasonic signal is measured accurately and the overlapped signals is separated with errors of less than 0. 28 mm.