Separation method for overlapping TOFD signals based on improved orthogonal matching pursuit
LIU Kun1, LUO Fuxing2, YANG Keji3, YU Gang3
(1.Tianjin Pipe Group Corporation, Tianjin 300301, China; 2.Hangzhou Zheda Jingyi Electromechanical Technology Corporation Limited, Hangzhou 311121, China; 3.Institute of Modern Manufacture Engineering, Zhejiang University, Hangzhou 310027, China)
 

Abstract: 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.
Key words: TOFD; overlapping signals; arrival time; orthogonal matching pursuit; sparse technique