The Development of a Spacer Layer Imaging Method (SLIM) for Mapping Elastohydrodynamic Contacts

Three different lubricating greases and their bleed and base oils were compared in terms of film thickness in a ball-on-disc test rig through optical interferometry. The theoretical values calculated according to Hamrock's equation are in close agreement with the base oil film thickness measurements, which validates the selected experimental methodology.The grease and bleed oil film thickness under fully flooded lubrication conditions presented quite similar behaviour and levels. Therefore, the grease film thickness under full film conditions might be predicted using their bleed oil properties, namely the viscosity and pressure-viscosity coefficient. The base and bleed oil lubricant parameter LP are proportional to the measured film thickness.A relationship between grease and the corresponding bleed oil film thickness was evidenced.

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“…Details of this technique have been reported elsewhere [17][18][19] and only a brief description will be given here.…”

Section: Experimental Apparatusmentioning

confidence: 99%

“…The method to translate the optical phase difference map into film thickness is described by several authors, see for example [19][20][21]. The method used here is the Lab-method described by Hartl et al [21].…”

Section: Experimental Apparatusmentioning

confidence: 99%

Film thickness in a ball-on-disc contact lubricated with greases, bleed oils and base oils

Cousseau

Björling

Graça

et al. 2012

Tribology International

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“…The application of an additional solid spacer layer combined with spectrometric analysis of the light reflected from the contact provided a significant improvement and allowed for the measurement and mapping of very thin lubricant films, down to 10 nm [20,21]. With this new technology it appeared that observations and thickness measurements of boundary films might be within the reach.…”

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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“…As the traditional optical interference technique has been limited by weak resolution (visible thickness must be bigger than 1/4 wavelength) [45], great effort has been made to develop techniques with higher resolution and precision to study film formation mechanisms and characteristics at the nanometer scale during lubrication processes [46,47]. These include the space layer imaging technique [48][49][50][51][52], relative optical interference intensity (ROII) approach [53][54][55][56][57] and so on. The existing interference techniques can detect lubricant film thinner than 1 nm between two surfaces.…”

Section: Survey Of Investigation Methodsmentioning

confidence: 99%

Progress in experimental study of aqueous lubrication

Zhang

Liu

2012

Chin. Sci. Bull.

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Aqueous lubrication is commonly regarded as friendly to the environment. We review current knowledge of the behaviors and mechanisms of aqueous lubrication. Major methods for investigating aqueous lubrication are addressed. We describe studies on both friction and film formation performance of various water-based lubricants. Additionally, we discuss possible underlying mechanisms of aqueous lubrication. Attention is also drawn to continuing topics of investigation and some unsolved problems. [20][21][22], and aqueous lubrication [23][24][25]. Aqueous solutions are drawing attention because of their ecological advantages, fire-resistance, high thermal conductivity, nontoxicity, accessibility, biodegradability, environmental friendliness, and good solvency. However, water-based solutions have several disadvantages as lubricants, such as corrosiveness, vaporization and non-viscosity [26,27]. In the past several decades, aqueous fluids have been extensively used as lubricants in metal working processes, food processing, biological systems etc. Since petroleum will be exhausted within 50 years, aqueous fluids will have wide application in many industrial fields. Thus, research on aqueous fluids has become an important branch of tribology. Use of water-based lubrication in engineering can be traced back to about 2400 BC, when people used water as a lubricant in transporting statues in Egypt [28]. Meanwhile, water-based liquids have always been excellent lubricants in mammalian joints such as knees or hips, with friction coefficients μ< 0.002 [29,30]. Till now this ultra-low friction has not been well emulated in human-made aqueous systems. In contrast to oils and organic solvents, water has many unique properties due to the polarity of its molecules, which makes aqueous lubrication much more complicated than traditional lubrication with oils.Many studies have revealed both the characteristics and mechanisms of aqueous lubricants, with a wide variety of dimensions, conditions and application areas. In spite of the great efforts of both experimentalists and theorists, the study of aqueous lubrication still faces big challenges. As mentioned above, human-made systems seldom emulate natural lubrication well enough for practical use. Major efforts have been made to reduce the friction force of aqueous solutions between two solid surfaces and enhance the film formation ability at the same time. Nanotechnology has made much progress in revealing the underlying mechanisms and behaviors of materials at the nanometer-scale, especially the behaviors of atoms and molecules [31][32][33]. However, the mechanisms of aqueous lubrication are still not well known because of the diversity and complexity of aqueous solutions. This paper presents a general review of research on aqueous lubrication.

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The Development of a Spacer Layer Imaging Method (SLIM) for Mapping Elastohydrodynamic Contacts

Cited by 212 publications

References 12 publications

Film thickness in a ball-on-disc contact lubricated with greases, bleed oils and base oils

Film thickness in a ball-on-disc contact lubricated with greases, bleed oils and base oils

How tribology has been helping us to advance and to survive

Progress in experimental study of aqueous lubrication

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