Ultrasonic Nonlinearity Evaluation of the Cracked Interface

This paper derives a novel analytical solution for acoustic nonlinearity evaluation of the cracked interface. When microcracks exist at the interface, the tensile and compressive effective moduli of the cracked interface are considered to be different. It is clearly shown that the tension and compression elastic asymmetry can result in acoustic nonlinearity. In addition, numerical simulations using the finite element method are conducted to validate the theoretical solution. It is shown that numerical results agree well with the analytical solution. Finally, two factors affecting acoustic nonlinearity are studied based on the analytical solution. One is the tension and compression elastic asymmetry and another is the frequency of incident wave. Different from acoustic nonlinearity parameter of the general second harmonics, it is found that acoustic nonlinearity parameter is a function of two factors.