Ultrasonic nonlinear response of micro plastic damage on aluminum alloy plate with varying thickness

Abstract

Abstract A plate with varying thickness (PWVT) is a common structure in engineering and the demand for its early damage detection is strong. In this paper, the distribution of plastic strain in PWVT subjected to uniaxial tension was studied and it proposed that the nonlinear parameter distributed linearly. Based on this assumption the wave equation in damaged PWVT was solved and the model of ultrasonic nonlinear response was established. The model showed that when the plastic deformation kept constant, A 2/A 1 2 increased quadratically with propagation and when the propagation distance kept constant, A 2/A 1 2 was proportional to the plastic deformation level. A 2/A 1 2 carried the damage information of PWVT. A detection platform was built in simulation and laboratory respectively to investigate the ultrasonic nonlinearity in damaged PWVT. The simulation and experimental results were in good agreement with the model, which indicated that the model could accurately describe the behavior of ultrasound propagating in PWVT.