Prof. Dr.-Ing habil. G.P. Ostermeyer
Head of Institute of Dynamics and Vibrations, Technische Universität Braunschweig, Germany
From Coulomb to Dynamic Friction Laws in Brakes
For centuries, Coulomb's law of friction has been used as a first approximation for friction. A static friction process is assumed to characterize the dissipation. Especially in brakes, these conditions are not given. In recent decades, highly complex dynamic processes have been found in the friction boundary layer in brakes, which explain many of the friction properties of brakes that are abnormal in Coulomb's sense. Here, novel friction descriptions provide an entry point into the analytical description of friction linings to optimize friction, wear, and even emission properties. The brake industry uses highly complex simulation programs to design its products. Very close attention is paid to the geometry of the brake, but not to the dynamic properties of brake friction. This often leads to very inaccurate simulation results. In this work, possibilities are shown how friction can be described more precisely and how such dynamic friction laws can be used in simulation programs.
He studied mathematics. His doctorate was on theoretical physics and his habilitation on mechanical engineering. He worked as research employee at Volkswagen AG and holds 30 years a full professorship first on friction physics in Berlin and then on dynamics and vibration in the same named institute of the university of Braunschweig. He received several times the Allan M. Lang Award, the Lloyd L. Withrow Award, and in 2015 the Dan Mahanna Achievement Award. He had several invited professorships in University of Linz, Austria and invited Professorships in University of Kremenchuk, Ukraine. He is member of the Advisory Board of Asia Brake, SAE Brake Colloquium and member of the Steering Board of Eurobrake and the International Friction Forum. In 2022 he was retired. He still works in the research of the university but too as a consultant for Friction, Wear and Emissions of Brakes
Prof. Dr. Peter Filip
Professor, Department of Mechanical Engineering and Energy Progresses Southern Illinois University at Carbondale, Carbondale, Illinois, USA
On Friction Layer and Performance of Friction Brake
Friction brakes were used in different industries including transportation sector extensively for centuries and they underwent considerable changes dictated by technical needs and legal limitations. Despite the very successful recent effort towards regenerative braking, the friction brakes remain a very important operation and safety requiring component today. Their performance (friction level and stability, wear, noise generation and environmental/health related aspects), however, is still not fully understand. As friction in brakes is always accompanied with formation of friction (surface) layer, having often different chemistry, microstructure and properties when compared to the bulk materials rubbing against each other, the friction layer contributes considerably to the performance characteristics of brakes. This contribution will address fundamental knowledge about friction layers typically formed in the currently used automotive and aircraft brake composites. Their role in friction performance will be discussed and demonstrated using selected “real life” examples. This discussion shall help designers, developers, and brake materials manufacturers to make “educated decisions” when addressing new needs related to current and future brake performance.
Professor Filip works and teaches in the areas of friction science, nanotechnology, materials engineering, and biomaterials at several institutions in the US, Europe and Asia. He served as Director of the NSF sponsored Center for Advanced Friction Studies, consultant, and expert witness, co-authored more than 500 scientific publications, graduated over 100 students, and performed research sponsored by 89 industrial partners and seven governmental agencies in US, Europe and Asia. He serves on numerous committees such as the ASTM and SAE International Standardization Committees, Eurobrake and SAE Brake Colloquium. Dr. Filip delivered 29 invited/keynote lectures and received numerous international awards. Currently, he co-organizes and chairs materials sessions at SAE and Eurobrake meetings, International Forum on Sliding Friction and Vibration, and serves as the Past Chair of the Wear of Materials Congress.
Prof. Dr. Ken Nakano
Professor Yokohama National University, Japan
Virtual damping generated by friction vector rotation
Stick-slip is the typical friction-induced instability appearing in various sliding systems, often caused by the velocity-weakening friction (i.e., the negative dependence of the friction force on the slip velocity). In the 2010s, Nakano and his colleagues theoretically found that in a single-degree-of-freedom sliding system, the in-plane angular misalignment generates positive damping, providing a design-based method to stabilize sliding systems. This novel stabilization method, which needs no additional devices for suppression, has been confirmed experimentally [see: https://youtu.be/Swwa3dO3MuE], and applications to several mechanical systems have been examined. In this lecture, we see that the virtual damping due to the in-plane misalignment is generated by the friction vector rotation, which is invisible from the conventional front view but visible from the top view.
He is a full professor at the Faculty of Environment and Information Sciences of Yokohama National University. He studied aeronautics and astronautics at the University of Tokyo (1988-1997) and obtained his doctorate from the University of Tokyo (1997). He worked as an assistant professor at the Department of Mechanical Engineering of Saitama University (1997-2000). After working as an associate professor at the Department of Mechanical Engineering of Yokohama National University (2000-2015), he obtained a full professorship at Yokohama National University (2015). His areas of interest include tribo-physics (e.g., origins of friction), tribo-dynamics (e.g., instabilities in tribosystems), and tribo-informatics (e.g., tactile sensations). In 2015, by the Japan Society of Mechanical Engineers (JSME), he was awarded the JSME Medal for Outstanding Paper on friction-induced vibration.
Prof. Dr. Ho Jang
Professor Korea University, Seoul, South Korea
A materials perspective on brake emission
Particulate matter emitted during brake applications originates from fine wear particles released at the sliding interface between brake pads and a disc. Therefore, the wear modes of the pads and a disc, which are determined by the ingredients in the friction material and microstructure of the disc, play a significant role in the concentration and size distribution of the brake-induced airborne particles. In this presentation, the effect of the ingredients in the friction materials on brake emission is informed with the suggestions to reduce brake emission based on experimental evidence. A considerable effect of the disc properties on brake emission is also demonstrated based on the brake emission test results obtained at moderate and elevated temperatures. Our studies indicate that the size distribution of the contact plateaus on the pad surface plays a vital role in determining the concentration and size distribution of the brake-induced airborne particles.
He is a Professor of Materials Science and Engineering and a Director of the Friction Materials Research Center (FMRC) at Korea University. He has performed friction materials studies for more than 30 years and published 85 SCI papers on the friction and wear of brake friction materials and discs. He carried out more than 30 research projects to improve the brake performance of the vehicle for vehicle manufacturers and friction material companies using his fundamental understanding of friction and vibration at the sliding interface. He is currently a member of the advisory board of Asia Brake, SAE Brake Colloquium, and a member of the steering committee of the International Friction Forum. In 2018, he was awarded the Dan Mahannah Achievement Award from SAE International for distinction and significant contributions to the brake and friction material industries.
Prof. Dr. Philippe DUFRÉNOY
University of Lille
Identification of key parameters of braking emissions by model-experience dialogue
Braking emissions, whether noise or particles, are generally approached from the point of view of their reduction by means of material or component solutions or by adding reduction or collection systems.
The point of view proposed here is to apprehend these emissions by their source using a description of the tribological system and the tribological circuit. The aim is to describe the physical mechanisms involved at different scales and to identify the key parameters acting on these emissions. This identification is achieved by highly instrumented experiments, coupled with modeling. The parameters identified are associated with the pair of materials used, but also with the braking system and the modalities of use (history effect).
Philippe Dufrenoy is Professor of Mechanics and Engineering at the University of Lille in France. He manages a research team of 30 people dedicated to tribology at the Laboratory of Multiscale and Multiphysics Mechanics in Lille. This team deals with theoretical and application aspects of friction-induced mechanisms, with a focus on the physical couplings involved in tribology. Numerous partnerships have been set up for braking applications in the automotive and railway sectors.
He has published more than 50 research papers in the field of tribology, dedicated to frictional braking, wheel-rail contact and blade-casing interactions in turbojet. He was co-founder of the EUROBRAKE conference in 2012 starting from the JEF conference in France and associating with other countries.