Multiphysics of Tribocontacts

Abstract

The complex processes involved in the dry friction between two bodies are not yet fully understood. Towards an improved understanding of the associated tribological phenomena, the authors combine their skills and expertise in the respective fields of tribological experimentation, modeling, and simulation, as well as topological and chemical surface analyses. The aim of this research is more accurate predictions of the tribological behavior of minimal friction material mixtures. In order to improve the technical understanding of high-load tribological contacts (in which wear debris significantly influences the contact situation), a great volume and variety of research is necessary. The authors have devised a "vertically integrated" research approach towards addressing the myriad interdependent phenomena associated with such investigations. MethodsThe authors at the Institute of Dynamics and Vibrations have made several contributions towards the understanding of highload tribological contacts. For example, they have advanced the understanding of the influence of "patch dynamics" on the tribological behavior of high-load tribological contacts. They have also developed dynamic models of the coefficient of friction, which are capable of accurately representing complex behavior using simple mathematics [1]. They have developed various cellular automata towards the precise computation of tribological effects in a realistic 3-D model of a friction material mixture, and also towards efficiently simulating the tribological contact between a full-scale brake pad and disc [2].Multiple tribometers have been developed at the Institute of Dynamics and Vibrations which are capable of investigating high-load tribological contacts. These devices precisely measure the input and reaction forces very close to the tribological contact. Many other quantities are also measured, such as the temperatures of the two friction bodies, acoustic signals, and environmental conditions. An example of resulting friction and temperature measurements is shown in Figure 1. Furthermore, one of the tribometers is equipped with a built-in topography measurement station. Using this, quasi in situ photographs and measurements of the friction material's topography can be automatically made throughout the measurement procedure [3].The Institute of Surface Technology has performed various types of investigations into tribological systems, with a focus on surface technology and tribochemistry. They have developed methods for actively adjusting the friction and wear behavior of tribological contacts through the use of various coatings and thermal treatments, and analyzed the results based on the chemical composition of the associated surfaces [4]. By optimizing plasma nitriding treatments, they have improved the wear resistance of mechanical parts under tribological loads [5]. Recently, this institute has developed methods for optimizing chemical analyses of friction materials, particularly at the tribological boundary layer. As shown in Figure 2, this involv...