A probability model for ultrasonic nonlinear effects of rough contact interface

A piece-wise uniform probability distribution model for ultrasonic wave interaction with rough contact interfaces is proposed.Combined with microscopic geometric characteristics of rough contact interfaces,a piece-wise uniform probability function is utilized to describe variation of the contact interface stiffness,as a result the acoustic signal modulated by roughness and relative motion of the surfaces is obtained.Higher harmonics generation and threshold phenomena of the rough contact interface made up of aluminum alloy samples are observed,and the relationship between normalized nonlinearity parameter and pressure loaded on the rough interface of the different roughness is measured.The experimental data is consistent to the theoretical prediction,which demonstrates the piece-wise uniform probability distribution model can well predict the variation of nonlinearity parameter.This model may provide a theoretical foundation for further study on the nonlinear acoustic technique to evaluate mechanical properties of rough contact interface.