Nonlinear reflection of surface acoustic waves from contact lines

We present the results of an experimental investigation of nonlinear processes accompanying the interaction of surface acoustic waves (SAWs) with real cracking defects and contact lines. The dynamic characteristics of the nonlinear reflection of higher harmonics are presented. It is shown that the third harmonic generation has a pronounced threshold character, the dynamic characteristics exhibit hysteresis, and the efficiency of nonlinear response depends on the duration of SAW action on the defect. The results lead to a conclusion that the nonlinear reflection of SAWs from a contact line provides an adequate model of reflection from a real cracking defect.