Integrity evaluation of pipe welding zones using wavelet transforms, and specific sensitivities based on SH-EMAT pulse-echo method

Pipes in facilities contain lots of welding zones and requires automated ultrasonic inspection. An electromagnetic acoustic transducer (EMAT) can be usefully applied in an automated ultrasonic inspection system. In this study, shear horizontal waves (SH-waves) generated by EMAT were implemented for the inspection of pipe welding zones. In analyzing of SH-EMAT signals, wavelet transforms were useful to extract key information. The intensity of the directly transmitted signal was used as a reference signal. A ratio of the reflected signal to the reference was proposed as the specific sensitivity. The sizes of defects were evaluated quantitatively using the specific sensitivity.