Wear map a of severe and mild wear modes of ceramics, and SEM images and profiles b of severe and mild wear surfaces. Wear map a of coating delamination and SEM image b 1 of a sliding pin on Al 2 O 3 coating, delaminated wear particles b 2 and delaminating coating b 3.
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The observed linear relationship on log-log scale described by. The mild wear in Fig. It is shown and confirmed in the previous articles of water lubrication, N 2 -gas lubrication and tribo-coated In lubrication that the thin tribo-layer plays the key role in protecting the contact surfaces and reducing friction and wear. Therefore its mechanical and chemical properties, microstructure and formation mechanism become main subjects to understand for better control of friction and wear.
It is clear from this observation that a tribo-layer is not formed by simple chemical reaction and film growth. Microscopic mechanical mixing of chemical elements and tribo-chemical reaction may take place to form a tribo-layer like one in Fig. Similar discussion would be available for tribo-layers observed in Figs. In the case of hydrodynamic lubrication, load is supported by the hydrodynamic pressure in liquid or gas film between two moving surfaces and friction is generated as the flow resistance of liquid or gas between the surfaces.
In other cases of contact of solids, load is supported at micro asperity contacts which are deformed elastically and plastically under the combined effect of load and friction and are finally fractured to form wear particles. The theoretical curve in the figure is calculated by a plastic model and theory of slip line field. It is important to know that any model for lubrication or wear should consider the change of contact area A , which is called as Junction-growth, caused by plastic deformation in contact region before gross sliding. Static friction is observed at the last stage of the junction-growth as the termination of deformation and the separation of contact.
When friction force F is gradually increased at an elastic contact between a circle and flat under the load W in Fig. Micro-slip initiation and propagation at the contact area before reaching to the observation of static friction coefficient. The micro-slip region is enlarged by slip propagation caused by the further increase in F. Figure 52 b shows the effect of small two inclusions at the center of contact region, where micro-slips are introduced around them before the introduction along the circular periphery.
It is obvious in the figure that the level of coverage of micro-slip region on the contact area at the same friction force is quite different each other and the value of static friction coefficient is also very different as the result. The observations in Figs. Junction-growth at one contact between micro asperities shown in Fig.
Tribology covers the fields of friction, wear and lubrication which exist all around in nature and human society. The demand of controlling them at high level has been increased very rapidly in the past one hundred years.
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Some achievements made by the authors are described in this paper and summarized as follows;. The oil whip phenomenon is clarified theoretically for the first time in the world. Stable operation of an arbitrarily high speed rotary shaft supported by journal bearings can be made by the theory. The dynamic anti-earthquake design method of rotary shaft-bearing systems is first proposed to avoid sudden oil whip generation by a large disturbance such as an earthquake.
Large contributions to the theoretical and experimental analyses of temperature rise and turbulence in lubricating films are also made. The high potential of water lubrication of ceramics for practical use is shown experimentally, and main part of lubrication mechanism is made clear. It promises a new lubrication method with nitrogen gas by forming lubricous tribo-layer.
Thin tribo-layer of the thickness around nm is confirmed to play a key role for the reduction of friction and wear. Wear maps are proposed for classifying various wear modes and the importance of tribo-layer formation is shown. The mechanisms of junction-growth at the plastic contact of asperities and micro-slip propagation at the elastic contact area are shown experimentally and theoretically to understand static friction.
Yukio Hori was born in and graduated from the University of Tokyo in He was Lecturer —, Associate Professor — and then Professor of Mechanical Engineering —88 at the same university. He performed pioneering work on the stability of a rotary shaft supported by oil film bearings, especially on oil whip or self-excited vibrations of the shaft. Oil whip had been barriers to increase in speed of rotary machines or growth of output of rotary machines such as electric generators for many years.
He published since then many papers related to oil whip. Among others, he first discussed the possibility of oil whip being triggered by earthquake. He also made important contributions to theoretical and experimental analyses of temperature rise and turbulence in fluid films in high speed bearings and seals.
Although not included in this paper, his work also covers a variety of fields such as rheology of molten high-polymers and mechanical properties of solid high-polymers. Koji Kato was born in and graduated from Tohoku University in He received Degree of Doctor in from the same university at the Department of Mechanical Engineering. He was promoted to professor in the same department in and worked there as head of Tribology Laboratory until his retirement on 31 March He has been professor at Nihon University and professor emeritus of Tohoku University since April His research field has been fundamentals and applications of tribology where he wrote more than reviewed papers on international journals and co-authored 14 books published by international publishers.
He gave 68 invited lectures at international conferences on tribology, ceramics, coatings, materials, machineries etc. He received 4 best paper awards from 3 Japanese and 1 American academic journals of societies. National Center for Biotechnology Information , U. Find articles by Yukio Hori.
Find articles by Koji Kato. Author information Article notes Copyright and License information Disclaimer. Received Mar 25; Accepted May This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract In high speed rotating machines such as turbines and generators, vibrations of a rotating shaft often hinder the smooth operation of the machine or even cause failure.
Its definition is as follows: Tribology is the science and technology of interacting surfaces in relative motion and of the practices related thereto. Hydrodynamic lubrication Hori, one of the authors, has been interested in various problems in the hydrodynamic lubrication such as stability of rotating shafts in journal bearings, 1 , 2 foil bearings, 3 sinusoidal squeeze films, 4 heat generation 5 , 6 and turbulence 7 in the lubricating films. Stability of a rotating shaft in journal bearings 2.
Oil whip In high speed rotating machines such as turbines and generators, vibrations of a rotating shaft often hinder the smooth operation of the machine or even cause failure. Open in a separate window. Oil whip theory Newkirk and Taylor regarded oil whip as a resonant vibration caused by the oil circulation in the oil film. Equations of motion By using the oil film force in the previous section, the equations of motion of a rotating shaft supported by journal bearings can be derived and dynamic characteristics of the rotating shaft can thereby be analyzed.
A disk with mass m is attached to the shaft at the center. Both ends of the shaft are supported by journal bearings of the same specification.
Stability limits It is not easy to discuss the stability of the shaft by the equation of motion of the previous section, because of nonlinearity of the oil film forces P x and P y. Occurrence of oil whip — Hysteresis — As described in the previous section, the stability criterion for small vibrations and that for large vibrations whirling are different. Seismic effect on oil whip Although there has been much research on earthquake-resistant design of structures such as buildings, there is very little on that of machines, including rotating machines.
Response of a rotor and a journal to sinusoidal external forces. Chaos in rotor-bearing systems If an imbalance of a rotor and a bearing load are changed variously while it is running in the hysteresis domain, it has been shown that all kinds of rotor responses can occur, e. Hydrodynamic lubrication in high speed bearings 2. Heat generation and temperature rise Heat generation in the oil film and the accompanying temperature rise are the most important factors in bearings, especially in high speed bearings. Temperature distribution in the middle section of a bearing metal.
Temperature distribution at the middle cross section of an oil film. Lubrication of ceramics with water, nitrogen and indium Modern machineries are generally made of metal alloys, and their sliding or rolling elements are lubricated with mineral oils which protect metallic surfaces against corrosion and form oil film to separate mating surfaces by the hydrodynamic effect of oil between surfaces. Water lubrication 3. The effect of surface texture on friction and load carrying capacity In water lubrication of ceramics, the water film thickness at the contact interface is briefly estimated as below nm.
Mechanisms of water lubrication A thin water film of the thickness in nano-meter scale should work theoretically in hydrodynamic lubrication when contact surfaces have roughness values smaller than the value of film thickness and the amount of deformation of contact surfaces is within the limit for keeping water film hydrodynamically. Nitrogen lubrication 3. Indium lubrication 3. Mechanism of lubrication by tribo-coating of indium As shown in Fig. Wear 4. Generation of wear and formation of tribo-layer Wear of solids takes place at any contact surfaces in friction by generating wear particles and tribo-layers accompanied by the change of microscopic morphology of surfaces in contact.
Wear modes, wear maps and wear models of materials 4. Metallic materials Recognition of wear modes of adhesive, abrasive, flow, fatigue, corrosive and melt shown in Fig. Discussion on tribo-layer It is shown and confirmed in the previous articles of water lubrication, N 2 -gas lubrication and tribo-coated In lubrication that the thin tribo-layer plays the key role in protecting the contact surfaces and reducing friction and wear. Static friction 5. Junction-growth and static friction at contact of asperities In the case of hydrodynamic lubrication, load is supported by the hydrodynamic pressure in liquid or gas film between two moving surfaces and friction is generated as the flow resistance of liquid or gas between the surfaces.
Contact shape effect on static friction When friction force F is gradually increased at an elastic contact between a circle and flat under the load W in Fig. Summary Tribology covers the fields of friction, wear and lubrication which exist all around in nature and human society.
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Looks like you are currently in Finland but have requested a page in the United States site. Would you like to change to the United States site? Michael M. Khonsari , E. Richard Booser. Applications of tribology are widespread in industries ranging from aerospace, marine and automotive to power, process, petrochemical and construction.
With world-renowned expert co-authors from academia and industry, Applied Tribology: Lubrication and Bearing Design, 3rd Edition provides a balance of application and theory with numerous illustrative examples. The book provides clear and up-to-date presentation of working principles of lubrication, friction and wear in vital mechanical components, such as bearings, seals and gears. The third edition has expanded coverage of friction and wear and contact mechanics with updated topics based on new developments in the field.
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