Ultrasonic determination of real contact area of randomly rough surfaces in elastoplastic contact

Abstract

Micromechanical characterization of interfacial properties of non-conforming rough surfaces in contact was performed by a method based on ultrasonic waves. The method to estimate the interfacial properties is based on ultrasonic spectroscopy of signals reflected from the interface. Ultrasonic results are complemented with probabilistic contact mechanics to model the normal and tangential interfacial stiffness (K$_{N}$ and K$_{T})$ constants for different degrees of closure. The results show that a single set of stiffness constants K$_{N}$ and K$_{T}$ is sufficient to describe the dynamic response of the interface independently of the incident angle of the ultrasonic waves. Plastic deformation of the rough interface is studied using the same ultrasonic method. Experimental results indicate that the hysteretic effect observed by repetitive loading cycles is an indication of plastic deformation at the asperity summits with greater height values. The phenomenon is explained using micromechanical and probabilistic models. The results show the possibility of using the method to estimate the interfacial stiffness, presence of plastic deformation, and the real contact area, which in the past have been impossible to measure accurately.