Defect detection in thin plates by ultrasonic lamb wave techniques (original) (raw)

In the present study, the numerical method was investigated for drawing the dispersion and displacement curves of ultrasonic lamb wave, propagated in Aluminum thin plate. Two ultrasonic lamb wave techniques, pulse-echo (a1 mode emitter) and emission (s1 mode emitter), were used for interpretation of notch defects with depths of 10%, 30% and 60% of plate thickness. Thickness of plate was 2 mm and the nominal center frequency of transducers was 2 MHz. It was observed that these techniques are sensitive to evaluate defects, especially in short probe to defect distances. Also, it was found that amplitude analysis can give some qualitative information about defects depth by using Distance-Amplitude-Correction curves, but it was not sometime repeatable. In this respect, pulse echo method showed better sensitivity of amplitude to defects depth variation.