The use of reflected Rayleigh waves to study rough contact interfaces

Ultrasonic reflectometry is commonly used in the field of tribology. Bulk waves that travel through a component are reflected from an interface and can be used to measure parameters such as contact stress and lubricant film thickness. This paper presents the development of a novel ultrasonic technique using Rayleigh waves that propagate along the surface of a component. An analytical model is first proposed to explain the interaction of Rayleigh waves with a contact interface. When contact parameters change, so does the amplitude of the reflected Rayleigh wave. From the reflected waves, it is possible to simultaneously predict both normal and tangential interface stiffness. Experiments have been conducted to show how the reflected waves change as cyclic loading is applied and the roughness of the contact interface varied. Results have shown there is good agreement between experimental data and analytical predictions. Potential application of this study includes the remote monitoring of sealing components such as o-rings or radial lip seals.