Quantitative determination of nonlinear binding forces by ultrasonic technique

A quantitative determination of binding forces is very difficult. There exist several models based on a macroscopic description of the interface binding forces. The ansatz we use is the microscopic description of the interface binding forces. Because the interface is created by tow surfaces the interface binding force is given by the derivative of the potential energy versus distance relation for surfaces. We can show that a narrowband ultrasonic wave transmitting the interface is modulated by the characteristic binding force versus distance relation of the interface. In particular higher harmonics of the base frequency are generated. The magnitude of the higher harmonics depends on the strength of the binding forces and on the displacement of the interface caused by the incident ultrasonic wave. Applications of this new technique will be demonstrated by different composite materials.