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Kenneth Langstreth Johnson. 19 March 1925 — 21 September 2015

Mike Ciavarella's picture

I strongly recommend reading these two papers about the recent loss of Ken L Johnson, FRS, Timoshenko Medallist, Gold Tribology Medal, who died the day of my 45th birthday, exactly twice as old.

Rod Smith Biographical Memoirs of Fellows of the Royal Society · August 2016 Kenneth Langstreth Johnson. 19 March 1925 — 21 September 2015 DOI: 10.1098/rsbm.2016.0012   

Hills, D. A., Nowell, D., & Barber, J. R. (2016). KL Johnson and contact mechanics. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 0954406216634121.

 

 

I must say my career has been strongly influenced by him, because of his Contact Mechanics book, because of his papers, but mostly because when he told me "this problem really is an enigma", then I could not resist thinking that if it was an enigma for the "man" KLJ, then it really must have been a really challenging problem worth spending weeks and months thinking hard about it, in search of "fame"!   

I was lucky enough to meet the "man" various times, but still not enough, and certainly he was already quite old: the first time I comunicated perhaps was when I wrote the "Contact Mechanics" review paper with Jim Barber in IJSS. I remember it was a useful excercise (in those days, I would write emails to many authors to ask them for printed copies of their papers to be sent by post --- how strange this may sound in the days where illegal web sites have all the PDF you can download and hope for!).

Ken was very complimentary then "to have covered such wide range of topics", and it was a useful discussion with Jim Barber especially about roughness --- we came to the conclusion that Archard model was already "fractal", and we found that the contact area is itself a fractal, so very disilluded we concluded that it was paradoxical and without much engineering sense:  in about the same time, Persson, perhaps smarter than us, provided a very similar result but he forgot to mention that this was nonsense!

Persson had more success because it was for Gaussian surfaces, which is the same reason the Greenwood-Williamson model was successful in 1966, despite already in the 1940 some russian authors had solved the same problem, but with less realistic distribution of heights.

I have then met KLJ a few times to discuss rolling contact fatigue, and he got me interested in ratchetting, on which I wrote a couple of papers, but then I realized that the problem was really "solved" to the extent it could be easily done.  

He then motivated me to adhesion and JKR, but only much later I got into that area, that is very recently.

Another "enigma" he suggested was the "roaring rails" enigma, short pitch corrugation on which he could not explain the wavelength. I have perhaps given some ideas, but unfortunately again I have moved out of that area when I realized I couldn't make more easy progress.

In other words, although KLJ has often "distracted" me with perhaps problems which were considered "old" by then, and I should have worried more about funding, I do not regret having worked on these problems.  What I regret is that I met the man too late, I could not work with him when he was very active in his best years, when he was arguably one of the best mechanicians in the world, and certainly "Contact Mechanics man".

I was lucky enough of course to work with David Hills and Jim Barber, two of his close friends, and also others, like Jim Greenwood who is still very active after co-authoring I don't know how many important papers with KLJ.

In one of the last occasions I meet KLJ, it was a NSF workshop where he showed his very first experiments on Mindlin contacts, which were still of interest in 2010 for the community of joints mechanics, where damping produced by friction is still an "enigma"!

He was wonderful in every respect, engineer, scientist, scholar, gentleman, family man. 

 

 

References

Ciavarella, M., & Monno, F. (2010). A comparison of multiaxial fatigue criteria as applied to rolling contact fatigue. Tribology International, 43(11), 2139-2144.

Ponter, A. R. S., Afferrante, L., & Ciavarella, M. (2004). A note on Merwin’s measurements of forward flow in rolling contact. Wear, 256(3), 321-328.

Barber, J. R., & Ciavarella, M. (2000). Contact mechanics. International Journal of solids and structures, 37(1), 29-43.

Ciavarella, M., & Barber, J. (2008). Influence of longitudinal creepage and wheel inertia on short-pitch corrugation: a resonance-free mechanism to explain the roaring rail phenomenon. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 222(3), 171-181. 

Afferrante, L., & Ciavarella, M. (2009). Corrugation models and the roaring rails enigma: a simple analytical contact mechanics model based on a perturbation of Carter’s solution. Journal of Mechanics of Materials and Structures, 4(2), 191-209.

Ciavarella, M., Demelio, G., Barber, J. R., & Jang, Y. H. (2000, February). Linear elastic contact of the Weierstrass profile. In Proceedings of the Royal Society of London A: Mathematical, Physical and Engineering Sciences (Vol. 456, No. 1994, pp. 387-405). The Royal Society.

Afferrante, L., & Ciavarella, M. (2009). Short-pitch rail corrugation: A possible resonance-free regime as a step forward to explain the “enigma”?. Wear, 266(9), 934-944.

Afferrante, L., Ciavarella, M., Dell'Orco, M., & Demelio, G. (2011). Rolling cylinder on an elastic half-plane with harmonic oscillations in normal force and rotational speed. Part II: energy dissipation receptances and example calculations of corrugation in the short-pitch range. International Journal of Mechanical Sciences, 53(11), 1000-1007.

 

 

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