Lamb wave-based experimental and numerical studies for detection and sizing of corrosion damage in metallic plates

Abstract

Lamb waves are ultrasonic-guided waves with applications in inspection and monitoring of plate-like structures. These waves can be used for detecting, locating, and sizing of defects. In this paper, a new method is proposed for in situ measurement of the location and size of circle-like corrosion defects in thin plates. A novel technique for omnidirectional generation of Lamb waves is also proposed. The probe is placed on at least three different points around the defect and the arrival times of reflected echoes are measured. An algorithm then estimates the location and size of the defect based on the arrival times of reflected echoes. A finite element model is also developed for modeling the process and studying various aspects of the method. The proposed method is then tested on an aluminum plate. The center location and radius of a 5-mm hole in a 0.5-mm thick aluminum plate is estimated with uncertainties of ±1 mm (1%) and ±0.25 mm (5%), respectively. Various aspects of the proposed method are discussed, and uncertainties in measurements are estimated. Effectiveness of the proposed method is also assessed by sizing actual corrosion defects. The proposed method is fast, flexible, and portable and shows better accuracy in comparison to similar existing methods.