半円形状コイルを用いた点集束型電磁超音波センサのスリット欠陥検出能の評価

抄録

We developed shear vertical (SV)-wave point-focusing electromagnetic acoustic transducer (PF-EMAT) using semicircular coils for the purpose of detecting stress corrosion cracking (SCC) on the inner surface of stainless steel pipes, and slit-defect detectability and its dependence on the angle of the EMAT to a defect were evaluated. Slit defects were made on the bottom surface of a SUS304 stainless-steel plate of 20 mm thickness. Length, width, and depth of defects were 0.5 mm, 10.0 mm, and 0.05-2.95 mm, respectively. Slit defects were detected by using a handmade PF-EMAT, and relationship between the defect depth and echo height was evaluated. Then, change in the echo height with incident angle of SV waves to a defect was evaluated by rotating the PF-EMAT. From these results, it was confirmed that the PF-EMAT has high slit defect detectability and it is less sensitive to the angle of the PF-EMAT to defects.