Fast remaining thickness measurement using a laser source scanning technique

Abstract

Fast remaining thickness measurement using Lamb wave is presented for the purpose of maintenance of large structures like oil storage tanks and pipe networks. This study used a laser ultrasonic source to perform a high resolution remote scanning over aluminum plates with grooved and circular defects that were modeled on corrosions in plate-like structures. The antisymmetric A0 and symmetric S0 modes of Lamb wave were used to obtain information of the plate thickness from amplitude distributions over the scanned areas on plates. The amplitude distributions of A0 mode provide better thickness distributions that those of S0 modes for grooved defects. For plates with circular defects, the amplitude distributions did not agree well with the thickness distribution due to the refraction around the defects, defect images were seen in both modes. Especially in the amplitude distribution of S0 mode, the defect images for the circular defect were clearly obtained. © 2012 The Japan Institute of Metals.