Theoretical Study of Effective Parameters in the Friction Reduction by Ultrasonic Vibrations in Solid Surfaces

Ultrasonic vibrations are used in many fields to reduce friction forces. In this paper, the reasons for reducing friction in solid surfaces are investigated using the friction model of Dahl and the elastic-plastic contact model. Based on the theoretical model, four parameters: relative velocity, contact surface, the distance between surfaces, and Young modulus, are effective in the frictional force reduction. This study is validated using experimental tests. The results showed that the effects of oscillations of the relative velocity and changes of contact surfaces on the friction reduction are 51% and 12%, respectively. The minimum effect, among the factors, was related to the Young modulus with a value of 1%. The reason for the force reduction is the nonlinear behavior of the contact surface, contact stiffness, and the friction force functions. Moreover, fluctuations in their input parameters cause an asymmetric oscillation in the value of those functions. This feature changes these functions’ average value and reduces the friction forces.