Abstract: A micromechanical model of rough surface for an interface between two solids is presented to evaluate the acoustic properties during loading and unloading cycle. By theoretical description of the micromechanics of rough, contacting surfaces under static normal loads, the relationship between the topographic parameters of the rough surface and the acoustic response of pressure interface are established. Ultrasonic experiments are performed on three different interfaces formed by aluminum surfaces with different levels of roughness. The ultrasonic transmission coefficient from the interface is measured during loading and unloading cycles as a function of pressure, from which the ultrasonic interfacial contact stiffness and nonlinear coefficient are obtained. It is shown that the nonlinear coefficient is more sensitive to contact variation of interface under low loads. The topographic parameters of interface parameters are obtained by fitting measured transmission coefficients using nonlinear least squared minimization method. Using obtained parameters, the acoustic properties of interface are calculated. The theoretical acoustic properties are agreed well with the experimental results, and it is demonstrating the capability of the micromechanical model of rough surface in predicting the ultrasonic responses of imperfect interfaces.

Key words: Interfacial stiffness, Micromechanical model, Nonlinear ultrasonic, Non-perfection interface