Nonlinear ultrasonic detection of closed cracks in metal plates with phase-velocity mismatching

In this paper, nonlinear Lamb waves with phase-velocity mismatching are proposed to detect accurately closed cracks by excluding the intrinsic material nonlinearity. Simulations and experimental studies were conducted to analyze double frequency Lamb waves (DFLWs) induced by the closed cracks and the intrinsic material nonlinearity. The results show that DFLWs induced by the material nonlinearity are negligible as compared with that caused by the contact acoustic nonlinearity (CAN) of the closed cracks. The closed cracks can be accurately detected using the proposed method, and the acoustic nonlinearity parameter increases monotonically with the crack evolution. The findings of this study provide a feasible method for detection and characterization of closed cracks.

Automated summary

In this paper, a method for accurately detecting closed cracks using nonlinear Lamb waves with phase-velocity mismatching is proposed, which excludes the intrinsic material nonlinearity. Simulations and experimental studies were conducted to analyze the double frequency Lamb waves induced by the closed cracks and the intrinsic material nonlinearity. The results show that the double frequency Lamb waves induced by material nonlinearity are negligible compared to those caused by the contact acoustic nonlinearity of the closed cracks. The proposed method can accurately detect closed cracks, and the acoustic nonlinearity parameter increases monotonically with crack evolution. The findings of this study provide a feasible method for the detection and characterization of closed cracks.