抄録
This study aims to evaluate position and size of corrosion on a steel plate using low-frequency So mode Lamb waves. Some dome-shaped artificial defects with diameter of 4 mm to 30 mm and depth of 2.7 mm to 5.1 mm on 6-mm-thick carbon steel plate were machined. Low-frequency So mode lamb wave whose amplitude profile along thickness of a plate has a uniform was generated by striking a distal plane of a plate with a rectangular type longitudinal PZT transmitter. We can detect the defect with 4 mm diameter and 2.7 mm depth and also detect aligned defects with separation distance of 100 mm individually. Distance to the defects from the transmitter could be estimated from arrival times of reflected wave by the defects and calculated velocity of So mode lamb wave. Wave amplitude reflected by the defects that was normalized by amplitude of wave reflected by an opposite edge to incident point was almost proportional to cross-sectional area of the defects
