Nonlinear ultrasonic detection of partially closed cracks in metal plates using static component of lamb waves

This paper presents physical and experimental studies of the static component of Lamb waves (SCLWs) induced by partially closed cracks. The generation mechanism of SCLWs was investigated according to the nonlinear interaction between Lamb waves and partially closed cracks with various lengths, widths and orientation angles in finite element simulations. It was found that the SCLWs are more sensitive to the crack length, width and orientation angle as compared with the second harmonic Lamb waves. Fatigue crack evolution was further experimentally detected in aluminum alloy plates using SCLWs. Consistent with the simulation results, the acoustic nonlinearity parameter increases monotonically with increasing fatigue crack length. We show that the SCLWs are sensitive to partially closed cracks and can serve as a potential method to quantitatively evaluate the evolution of partially closed crack in metal plates. The findings of this study pave the way for the detection of partially closed crack using SCLWs in the field of nondestructive evaluation and structural health monitoring.