Weld Root Crack Detection in Metal Plates Using Nonlinear Higher-Order Lamb Waves in Lamé Mode

Abstract

This paper proposes a method for weld root crack detection in metal plates using nonlinear ultrasonic methods. Second harmonic components of Lamb waves are generated during propagation, which makes it difficult to distinguish them from second harmonic components generated by the nonlinear vibrations of cracks. Therefore, the Lamé mode is employed to suppress unnecessary second harmonic components. Additionally, higher-order modes, which are more likely to be generated than the fundamental modes, are selected. In the case of higher-order Lamé mode Lamb waves, the second harmonic amplitude in the defect area is suppressed by approximately 10 dB compared with conventional S0 and A0 mode Lamb waves.