Engineering applications often contain lubricated (sub)systems. If a sufficiently thick layer is formed in such systems, contacting surfaces can be separated from each other (e.g., gear teeth, full lubrication in plain bearings). This Is known as hydrodynamic lubrication and ensures that no wear occurs in these systems. In most cases, however, modern systems operate in the mixed lubrication range, so that there is direct contact between the surfaces, or their asperities and they are exposed to a large part of the load. Without appropriate countermeasures, this leads to wear and a shortened service life. A suitable countermeasure is, for example, the use of anti-wear-additives. These are chemical substances that are added to the lubricants to prevent wear (of the base material) even in the case of direct surface contact. This is possible because, when used correctly, the additives form a protective layer known as tribofilm. This layer is worn away by shear stress but can be renewed by chemical or physical processes. For contacts operating in the mixed lubrication regime, the balance between the rate of layer degradation and the rate of layer renewal is critical to wear protection. The theory of Rabinowicz is used to study the wear of the tribofilm and the theory of Eyring is used to study the renewal of the tribofilm.

The project will develop a simulation scheme that simulates both wear and regeneration of the tribofilm. The different influencing parameters (e.g., mechanical properties, type of additive, etc.) should be variable in order to be able to calculate arbitrary systems and configurations and to allow application to real systems. The experimental investigations in the macroscopic range to verify the simulation results and to provide surface data are carried out by the Department for Machine Design and Tribology at Leibniz Universität Hannover. The complementary molecular dynamic simulations in the microscopic range to determine the mechanical properties are carried out by the Department of Microsystems Engineering at the Albert-Ludwigs-Universität of Freiburg. 

Project carrier: Deutsche Forschungsgemeinschaft

Project head: Prof. Dr. Valentin L. Popov

Executive research assistant: M.Sc. Henning Burger