Elastohydrodynamic film thickness of soft EHL contacts using optical interferometry

Marx, Nigel; Guegan, Johan; Spikes, H. A.

doi:10.1016/j.triboint.2016.03.020

Cited by 67 publications

(56 citation statements)

References 36 publications

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“…The testing conditions employed in this study were borderline between piezoviscous-elastic and isoviscous-elastic lubrication. Therefore, the oil film thickness calculations give almost the same results irrespective of using the equations for piezoviscous-elastic [43] or isoviscous-elastic lubrication [44,45]. The calculated values of approximately 0.2 for Lambda ratios entail that both PAO 50% and 100% tests operated in the boundary lubrication regime.…”

Section: Tribological Testsmentioning

confidence: 54%

Effect of Lubrication on Friction and Wear Properties of PEEK with Steel Counterparts

et al. 2019

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Poly-Ether-Ether-Ketone (PEEK) has been widely used for tribological applications with steel counterparts because of its superior mechanical and self-lubricating properties. Fluid lubrication has the potential to further improve the performance of PEEK/steel contacts but its effect has been shown to depend on the operating conditions. To elucidate these aspects and establish the mechanism of fluid lubrication, the friction and wear properties of the PEEK/steel contacts in both dry and poly-α-olefin (PAO) lubricated conditions were investigated by tribological tests and surface analytical techniques. The nanoindentation measurements showed that lubrication with PAO had a softening effect on the wear track of PEEK, but no correlation was established with the wear of PEEK. The tribological behavior, for both dry and lubricated contacts, was correlated with the thickness of PEEK transfer films on the steel counterparts. The thickness of these films, as determined by Electron Probe Micro Analysis (EPMA) and X-ray Photoelectron Spectroscopy (XPS), was controlled by the rates of their formation and removal and depended on the operating conditions. Moreover, lubrication with PAO inhibited not only the formation but also the removal of PEEK transfer films. This study thus sheds light on the mechanism of fluid lubrication of the PEEK/steel contacts.

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Section: Tribological Testsmentioning

confidence: 54%

Effect of Lubrication on Friction and Wear Properties of PEEK with Steel Counterparts

et al. 2019

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“…This indicated that the lubricating film thickness is given by H c = 5.08g e 0.67 (a simplified version of Hamrock's expression which neglects the ellipticity parameter because the contacts are spherical), and that if the lubricating film was thick enough then the experiment would fall under soft-elastohydrodynamic lubrication (EHL), also termed Isoviscous Elastic (IE). 48 A plot of the film thickness versus load for the various experimental conditions is shown in Fig. S3 (ESI †), showing that under all circumstances during this set of experiments the theoretical film thickness is <0.25 nm, the approximate diameter of a water molecule, and at least an order of magnitude less than the surface roughness.…”

Section: Frictional Force At the Nanoscale For Hard-soft (Bsg-pdms) Cmentioning

confidence: 86%

“…Before continuing with a detailed analysis of friction mechanisms, we must be certain that our assumption of being in the boundary regime is correct, as this soft-contact AFM-FFM experiment is many orders of magnitude away from macro-scale measurements. Firstly, the approach by Esfahanian and Hamrock 47 (and more recently by Marx et al 48 ) was used to determine the full film liquid lubrication regime. This method takes into account the reduced radius (R′), reduced modulus (E′), load (W, in the range 1 nN to 200 nN), mean sliding velocity (u, 0.5-200 µm s −1 ), lubricant viscosity (water, η = 8.9 × 10 −4 Pa s) and lubricant pressure-viscosity coefficient (water, λ = 0.713 GPa −1 or 7.13 × 10 −10 Pa −1 ) calculated by fitting the Barus equation: η P = η o e λP to a plot of viscosity vs. pressure, where η o is the viscosity under standard conditions.…”

Section: Frictional Force At the Nanoscale For Hard-soft (Bsg-pdms) Cmentioning

confidence: 99%

Friction between soft contacts at nanoscale on uncoated and protein-coated surfaces

et al. 2021

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“…Under high contact pressures the lubricant starts behaving as a "solid material", i.e., the steel surface deforms elastically around the lubricant, at the edges of the contact. With this technique EHL films in "soft" contacts with polymethylmethacrylate and polyurethane have also been measured [18].…”

Section: Lubrication To Combat Frictionmentioning

confidence: 99%

How tribology has been helping us to advance and to survive

Stachowiak

2017

Friction

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Movement between contacting surfaces ranges from macro to micro scales, from the movement of continental plates and glaciers to the locomotion of animals and insects. Surface topographies, lubricant layers, contaminants, operating conditions, and others control it, i.e., this movement depends on the tribological characteristics of a system. Before the industrial revolution, friction and wear were controlled by the application of animal fat or oil. During the industrial revolution, with the introduction of trains and other machinery, the operating conditions at the contacting surfaces changed dramatically. New bearings were designed and built and simple lubrication measures were no longer satisfactory. It became critical to understand the lubrication mechanisms involved. During that period, solid theoretical foundations, leading to the development of new technologies, were laid. The field of tribology had gained a significant prominence, i.e., it became clear that without advancements in tribology the technological progress would be limited. It was no longer necessary to build oversized ship bearings hoping that they would work. The ship or automobile bearings could now be optimized and their behavior predicted. By the middle of the 20th century, lubrication mechanisms in nonconformal contacts, i.e., in gears, rolling contact bearings, cams and tappets, etc., were also finally understood.Today, we face new challenges such as sustainability, climate change and gradual degradation of the environment. Problems of providing enough food, clean water and sufficient energy to the human population to pursue a civilized life still remain largely unsolved. These challenges require new solutions and innovative approaches. As the humanity progresses, tribology continue to make vital contributions in addressing the demands for advanced technological developments, resulting in, for example, reducing the fuel consumption and greenhouse gases emission, increasing machine durability and improving the quality of life through artificial implants, among the others.Keywords: tribology; friction; lubrication and wear Tribology as part of our livesIn our everyday life we take many things for granted. It never occurs to us to pause and think why our hands or feet provide a perfect grip on most of the surfaces. We rarely think why sharks swim so fast or why geckos can walk on glass surface even when upside down. We expect spacecraft or satellites that we send to explore our solar system and beyond to operate smoothly even after many months or years of being idle. We expect that our trains and aircraft would stop exactly at the designated places at train stations and airports. When hopping into a car we don't think twice about the material used for the car seats. We don't think often why the tectonic plates or glaciers move with apparent ease. These seemingly diverse problems, and many others, are of great interest and research focus of tribologists. Tribology has helped us to discover not only the underlying mechanisms involved...

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Elastohydrodynamic film thickness of soft EHL contacts using optical interferometry

Cited by 67 publications

References 36 publications

Effect of Lubrication on Friction and Wear Properties of PEEK with Steel Counterparts

Effect of Lubrication on Friction and Wear Properties of PEEK with Steel Counterparts

Friction between soft contacts at nanoscale on uncoated and protein-coated surfaces

How tribology has been helping us to advance and to survive

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