Relaxation Tribometry: A Generic Method to Identify the Nature of Contact Forces

Abstract

Recent years have witnessed the development of so-called relaxation tribometers, the free oscillation of which is altered by the presence of frictional stresses within the contact. So far, analysis of such oscillations has been restricted to the shape of their decaying envelope, to identify in particular solid or viscous friction components. Here, we present a more general expression of the forces possibly acting within the contact, and retain six possible, physically relevant terms. Two of them, which had never been proposed in the context of relaxation tribometry, only affect the oscillation frequency, not the amplitude of the signal. We demonstrate that each of those six terms has a unique signature in the time-evolution of the oscillation, which allows efficient identification of their respective weights in any experimental signal. We illustrate our methodology on a PDMS sphere/glass plate torsional contact.

Oscillatory tribometry: transition from static to kinetic friction

“…Various approaches such as atomic force microscopy (AFM) [29][30][31], optical measurements [32][33][34][35] and relaxation tribology [36][37][38] have been employed to study the transition from static to kinetic friction.…”

Contact Mechanics Perspective of Tribology

“…First, asperity models in which the contact interface is divided into well-defined microjunctions actually carrying the normal and tangential loads applied to the contacting solids (Braun and Röder, 2002;Ciavarella et al, 2006;Violano and Afferrante, 2019). Each microjunction is ascribed a set of individual properties (e.g., its height, radius of curvature or friction coefficient) necessary to apply some assumed behavior laws [e.g., any contact or friction law (Le Bot et al, 2019)] when submitted to an external stimulus. The macroscopic behavior of the interface is then the emerging, collective response of the population of microjunctions (Trømborg et al, 2014;Braun and Peyrard, 2018;Costagliola et al, 2018).…”