Golden Age of Tribology?

Recently, a paper titled “Is Tribology Approaching Its Golden Age? Grand Challenges in Engineering Education and Tribological Research” appeared in Frontiers | Tribology journal.  The author, Valentin Popov, Professor at TU Berlin, puts forward and discusses two fundamental problems of the current state of tribology.

The first one is why “in spite of its obvious importance, the subject of tribology has relatively low visibility in the engineering community and among the general public.”

The second one is identification of the problem of third body as still the central one in the current tribological research and its major current challenge.

As for the first problem, the author’s hypothesis is that the low visibility of tribology is at least partly due to its poor “availability”. In other words, there are practically no simple methods or concepts having high predictive power for tribological problem-solving. He compares the complexity of structural mechanics and contact mechanics and observes that while both are generic parts of any system and as such “equally important”, the structural mechanics has some basics which are available for any undergraduate student while the contact mechanics not. The theory of beams is such basic theory which is both simple and instructive and therefore has become part of any engineering curriculum. Contact mechanics, on the contrary, is formulated in form of integral equations which are tractable only by experienced researchers. In opinion of Professor Popov, in contact mechanics, a role similar to the theory of beams can play the solution found by Schubert in 1942 (more known as “Sneddon solution” due to highly cited paper of Sneddon from 1965). Initially invented for non-adhesive normal contact, recently the Schubert’ solution has been generalized to a great variety of related problems, including tangential contact, adhesive contact, contact with viscoelastic bodies and contacts of functionally graded materials. The author concludes that now it is on time to integrate this “mechanics of joints” into engineering curricula. This would ensure both adequate tribology education and public awareness of the field. This can be considered as the main educational challenge in tribology at present.

The main challenge in the field of research, the author sees in the third body-problem. He writes: “To exaggerate somewhat, understanding friction means understanding the third body.”  He sketches a possible approach to this complicated problem:  “On the empirical level it could be a combination of non-equilibrium thermodynamics of surface layers, similar to the framework used in Bryant et al. (2008) and kinetics of formation and wear of the surface layers similar to the works of Ostermeyer and Müller (2006). For example, it is generally recognized that in lubricated contacts the wear process is controlled by formation and wearing out of the boundary lubrication layer build trough mechanochemical reactions of additives with the surfaces. The wear process of this boundary layer could be described in the general framework suggested in 1958 by Rabinowicz (1995) and confirmed by direct quasimolecular simulations in Aghababaei et al. (2016). This concept is a generic and robust approach as it basically says that the wear particles can appear if the stored elastic energy is sufficient for their formation. The process of wear particle initiation has to be completed by mechanics of wear debris in the gap between two bodies and the transport of wear particles. The latter could be described using a macroscopic empirical framework similar to Schargott (2009). The reverse process of the layer deposition can be described using the classical concept of mechanically activated thermal processes (Spikes, 2018) which was validated experimentally also for the particular process of additive deposition (Gosvami et al., 2015)….”

Overall, Professor Popov provides in the paper a number of arguments why in his opinion the near future of tribology will be a “golden age”. “Contact mechanics and tribology expand to qualitatively new fields of applications, which are at the forefront of the global development trends of technology and society, in particular micro- and nanotechnology as well as biology and medicine. At the same time, tribology developed experimental methods, theoretical concepts, and numerical tools allowing effectively mastering the seemingly complicated physics and mechanics of interconnections.“

Further information: Popov VL (2018), Is Tribology Approaching Its Golden Age? Grand Challenges in Engineering Education and Tribological Research. Front. Mech. Eng. 4:16. https://doi.org/10.3389/fmech.2018.00016

The article by Professor Popov was also cited by Professor Ciavarella from Politecnico di Bari, on his blog page.