Other Symposia

Graphite is a well-known solid lubricant that has been studied for decades. At low loads, graphite’s lubricity depends on humidity. Classical models like e.g. the adsorption model explains this by molecular water films on graphite leading to defect passivation and easy sliding of counter bodies. To explore the humidity dependence and validate the adsorption model for high loads, a commercial graphite solid lubricant was studied using microtribometry ^[1]. Even at very high contact pressures, a high and low friction regime is observed - depending on humidity. Transmission electron microscopy reveals transformation of the polycrystalline graphite lubricant into turbostratic carbon after high and even after low load (50 MPa) sliding. Quantum molecular dynamics simulations relate high friction and wear to cold welding and shear-induced formation of turbostratic carbon, while low friction originates in molecular water films on surfaces. The combined experiments and simulations lead to a novel, generalized adsorption model including turbostratic carbon formation.

[1] C. Morstein, A. Klemenz, M. Dienwiebel, M. Moseler, Nature Comm. 13, 2022

Martin Dienwiebel studied Physics at the University Dortmund and the Rheinischen Friedrich-Wilhelms University Bonn. He conducted his diploma research at the Forschungszentrum Jülich using low-temperature scanning tunneling microscopy. He performed his doctoral research with Joost Frenken at the Institute for Atomic and molecular Physics in Amsterdam, the Kamerlingh Onnes Laboratory in Leiden and the Tokyo Institute of Technology. Martin Dienwiebel obtained his PhD 2003 at Leiden University on the topic "Superlubricity of Graphite".

Afterwards he worked in the Tribology department of IAVF Antriebstechnik AG. 2008 he received an Emmy-Noether grant of the Deutsche Forschungsgemeinschaft and set up a junior research group at the Karlsruhe Institute for Technology and the Fraunhofer Institute for Mechanics of Materials IWM. 2011 obtained his habilitation from KIT and 2016 he took a Heisenberg-Professur for Applied Nanotribology.

Lubricants are used to reduce friction and wear in machines, saving billions of dollars worldwide in energy and breakdown costs, and lowering CO₂ emissions. Today, most lubricants are made from hydrocarbons derived from crude oil, which is a finite resource and alternative bio-based lubricants are being widely investigated. CO₂ emissions from current lubricants (due to their manufacture and waste disposal) are calculated we find that CO₂ emissions from the production and disposal of lubricants are at least 100 times lower than the CO₂ emissions from the energy used in those machines. It is also shown that the most effective way to make lubricants more sustainable is to extend lubricant oil drain intervals and collect used oil and re-refine it to make base oil for re-use. Methods that lubricant companies are using to reduce CO₂ emissions during lubricant manufacture and how they are packaged are also discussed.

After a degree in Physics and a PhD in Applied Physics and Electronics, Ian Taylor worked for Plessey Research from 1988-1991 and then joined Shell in 1991. He mainly worked in tribology and lubrication research whilst at Shell and was global technology manager for Shell's Lubrication Science team from 2006 to 2012. His research focussed on energy efficient lubricants, and he managed Shell's University research links in tribology from the mid 1990's to 2020 working closely with various Universities including Leeds, York, Southampton, Imperial College, MIT and Tsinghua University. His research has resulted in over 70 papers on tribology in peer reviewed scientific journals. Ian has been a Visiting Professor at the University of Central Lancashire since 2020. Ian is a Fellow of the Institute of Physics and also of the STLE. He received the Tribology Silver Medal from the Institution of Mechanical Engineers in 2020.

Understanding of the film thickness formation provided by lubricant available at the EHD contact inlet is well known at present stage. Contrary, there is a limited knowledge about mechanisms responsible for lubricant replenishment in real bearing under operation. This is a point where simulation of elastohydrodynamic contact in standard ball-on-disk devices could not necessarily be example of conditions in real bearings. Main reason is direction of inertial forces and conformity of the EHD contact. Film thickness and starvation severity between classical ball-on-disk and newly designed ball-on-ring test rig are compared in this study with the use of the fluorescence technique. Use of fluorescence technique allows to separately observe grease constituents and identify the operating conditions where are individual constituents most important. Low speed operation is usually dominated by thickener acting as lubricant while high speed region is mostly supported by bleeding oil.

David Kostal studied at Brno University of Technology since 2005 and is specialized researcher in the field of Tribology since 2009. Start of his research in this field was focused on the starved elastohydrodynamic lubrication and is currently focused to grease lubrication. He uses mostly experimental approach to study the lubrication phenomena with focus on the colorimetric interferometry and fluorescence microscopy. His last research topics are separate observation of the grease constituents with the use of different fluorescence dyes. Another part of his work is focused on space tribology where he helps in designing tribological components, testing and inspection of the space mechanism and components. He is also experienced in mechanical and optical design of complex tribological test rigs for research purposes and testing of the components.

The JAST Technical committee on grease was established in 1970 with the main purpose of researching lubricating grease for rolling bearings, and this year marks the 53rd anniversary of its founding.

Currently, this committee is one of the industry-academia collaborative research groups of the Japanese Society of Tribologists (JAST), consisting of 4 academic experts and 14 company representatives, and is active at regular quarterly meetings.

Based on the 50th Anniversary Commemorative Journal of the Grease Research Group published in February 2020, this paper introduces a part of the activity history over the past 53 years and reports on the recent activities of the research group.

Junichi Imai joined Kyodo Yushi Co., Ltd. in 1995 and has been engaged in research and development of grease. So far, he has developed a wide range of products for automotive and various bearings. Currently Executive Officer of Tecnical Headquarter and General Manager of Grease Technology Department. He became a member of The JAST Technical committee on grease in 1998, and has served as chief examiner since 2022.

The German government has passed a bill to further develop the greenhouse gas reduction quota and many other countries are doing the same. As a result, more and more customers are asking about the carbon footprint of our products. The carbon footprint is divided into three groups: Scope 1 includes the direct release of climate-damaging gases within the company. Scope 2 includes the indirect release of climate-damaging gases by energy suppliers, and finally Scope 3 includes the indirect release of climate-damaging gases in the upstream and downstream supply chain. Reducing Scope 3 helps customers achieve their sustainability goals.

We call this part of the footprint ""handprint"" and this is where tribology plays a major role. Virtually all dynamic sealing systems have a much larger handprint than the rest of the footprint. Tribological optimization of the dynamic sealing system can drastically reduce the footprint of a product and thus contribute to the customers sustainability goals.

This paper presents the footprint scheme and shows examples where optimized tribology delivers a large handprint compared to scope 1 and 2 of the sealing system footprint.

Engineer at Freudenberg Sealing Technologies GmbH & Co. KG (FST)
April 2000 - May 2001: Head of R&D in the Lead Center Oil Seals.
May 2001-2010: Head of Main Department Automotive Sealing/Testing in the Technical Development Center and INNOVATIONCENTER.
2011 – 2012: Director Advanced Product Engineering Global Oil Seals in FST
2012 – 2013: Director Advanced Product Engineering Europe
2013 – 2014: Director Global Strategic Product Development
Since 2015: Vice President Technology & Innovation

Other:
April 1997: PhD (Doktor-Ingenieur) at Institute of Machine Components, University of Stuttgart.
Since 2005: Assistant Professor in Sealing Technology at the University of Kaiserslautern.
Since 2015: Professor in Sealing Technology at the University of Kaiserslautern

Lubrication of hip and knee joint replacements attracted increased attention in the past two decades. The motivation was in a limited knowledge of lubrication processes which eventually influence implant wear rate, the persisting drawback of artificial joints. Recent investigations introduced various experimental approaches consisting of different model configurations (ball-on-disc, ball-in-cup and others) while adopting various experimental methods (electrical resistance, optical interferometry, fluorescent microscopy). We learnt a lot about the lubrication regimes of implants, the development of film thickness, the dependence of the lubricating layer on speed, load, material, implant geometry or synovial fluid composition, protein adsorption onto surfaces and the interaction of synovial fluid constituents. However, there are still many challenges ahead that should motivate us towards further development of joint replacements. Specifically, there is a lack of knowledge on lubrication mechanisms considering the modern tribological trends, such as the application of coating (DLC, 2D coatings, polymers) and surface texturing, which have the potential to bring a breakthrough in implant design.

Dr. David Nečas completed his master's in 2012 at Brno University of Technology. After that, he started his PhD in the area of biotribology of artificial joints and was awarded a PhD degree in 2016. In 2021 he became an associated professor in the field of Design and Process Engineering. He lectures in both bachelor and master study programmes, focusing on Machine Design, Analytical Projects and Biomechanic Systems courses. His research activities cover a broad field of biotribology, including the investigation of artificial joints, frictional behaviour of cartilage, biotribology of the eye, fascia and teeth. He is also interested in modern trends towards improved biotribological performance of implants, such as surface texturing or coating. He cooperates with several international institutions worldwide and has a special long-term connection with universities in Japan. In 2018, he was awarded a JSPS postdoctoral fellowship and spent seven months at Kyushu University.

Tribo-chemical processes leading to the formation of transfer layer during friction the High Power Impulse Magnetron Sputtering (HiPIMS) W-C:H coatings against steel balls were investigated experimentally and theoretically in humid air, dry nitrogen, hydrogen and in vacuum. In humid air, the localized tribo-chemical reactions driven by flash temperatures resulted in rapid formation of a transfer layer on the ball. Transfer layers always consisted of disordered hydrogenated graphitic carbon, ferrotungstite and and some single tungsten and iron oxides. The tribo-chemical reactions necessary for their formation involve decomposition of WC into carbon and tungsten, oxidation of tungsten and adjacent iron, water vapor dissociation and carbon hydrogenation. These reactions were successfuly corroborated by thermo-dynamical calculations based on the minimization of Gibb’s free energy. Thus, the coefficient of friction (COF) would be controlled by the amount of carbon and level of its hydrogenation. In dry nitrogen, dominat reaction would be WC decomposition whereas in hydrogen atmosphere, carbon hydrogenation would control phases in transfer layer and COF. In vacuum, friction will be affected by the presence of ductile W and Fe resulting from WC and FeOxWO3 decomposition.

Assoc. Prof. F. Lofaj is a senior researcher at IMR SAS in Kosice, Slovakia. His research interests include PVD technologies for hard coatings and related nanoindentation and tribology as well as relationships microstructure- mechanical properties of bulk ceramic materials and hard coatings. He spent three years at JFCC, Nagoya, Japan, working on creep in silicon nitride. He is an author and co-author of more than 116 publications and his H index is 20.

Various machine elements operate under conditions of mixed lubrication where load is shared between direct asperity contact and elastohydrodynamic lubricating film. In this regime, mean film thickness is often lower than initial surface roughness that is being deformed in the contact. Hence, there is an ongoing challenge in precise prediction of transition to mixed lubrication. In classical theory, the increase of friction from full EHL regime corresponds to the first direct contact between surface asperities. To further extend the knowledge it is necessary to simultaneously measure thin lubricating film and friction. This contribution presents recent findings for real rough surfaces. Film thickness is bellow smooth surface prediction and friction increases before initial solid contact in early phase of mixed lubrication.

Dr. Petr Šperka took his Ph.D. degree in mechanical engineering from Brno University of Technology, Czech Republic in 2011. His current position is an assistant professor and head of Lubrication Fundamentals Section at Tribology Group, Institute of Machine and Industrial Design, Faculty of Mechanical Engineering, Brno University of Technology. His research areas cover the boundary, mixed and elastohydrodynamic lubrication, roughness effect, and lubricant rheology. He received Maurice Godet Award in 2009 and Captain Alfred E. Hunt Award in 2017.

Towards a carbon-neutral society, fuel for internal combustion engines is also becoming carbon-neutral. The trends and changes in these fuels and friction loss reduction research are introduced.

Assistant at Musashi Institute of Technology in 1996, professor in 2012, and director of the Engine Research Center at the Research Institute of Tokyo City University in 2015. His specialties are engine tribology and hydrogen engine research.