File Name: applied tribology bearing design and lubrication .zip
Khonsari and E. The Second Edition of the Applied Tribology was published nearly a decade ago. Since then, the book has been adopted for courses in many universities as it has served as the basis for many short courses and lectures in industries.
Tribology is the science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of friction , lubrication , and wear.
Tribology is the study of the science and technology of interacting surfaces in relative motion and encompasses the study and application of friction, wear, lubrication and related design aspects. To further understand tribology, it is important to understand the definitions behind friction, wear and lubrication.
Friction is the resistance to relative motion between two bodies in contact. It is not a material property but a system property. Scientists believe it occurs due to the electromagnetic attraction between charged particles in two surfaces that are touching. There are several types of friction, including:. Friction is not considered a fundamental force. It is a non-conservative force meaning that work done against friction is path dependent.
Wear is the gradual removal, damaging or displacement of material at solid surfaces. When it comes to wear, the common types are:. Given the various types, tribology also illustrates how Wear can undergo many changes in time or undergo changes in operational conditions.
Lubrication is the control of friction and wear by introducing a friction-reducing film between moving surfaces in contact.
This film, aka lubricant, can be a solid, fluid or plastic substance with oil and grease being the most common. Lubricants have several functions, including reducing friction, preventing wear, protecting equipment from corrosion, controlling temperature and contamination, transmitting power and providing a fluid seal.
When it comes to lubrication, there are three different types referred to as regimes: boundary, mixed and full film. Boundary lubrication exists where there are frequent starts and stops, and also where shock-loading conditions are present. For example, some oils contain additives — such as extreme pressure EP or anti-wear AW — to help protect surfaces in case full films cannot be recognized due to load, speed or other factors.
Full-film lubrication exists in two forms: hydrodynamic and elastohydrodynamic. Hydrodynamic lubrication HL occurs when two surfaces in sliding motion are fully separated by a film of fluid. Elastohydrodynamic lubrication EHL is very similar to HL but occurs when the surfaces are in a rolling motion relative to each other.
This results in greater pressure on the film. As with boundary lubrication, mixed lubrication might also contain additives to create a protective layer on the metal. There are several fundamental concepts in Tribology, such as Tribosystem, Tribofilm and Stribeck Curve. It is essential for tribologists to understand Tribological Systems as it allows them to create and execute Tribological Tests.
Another important element of the Tribosystem revolves around the use of Tribological Coatings, as it relates to ferrous and non-ferrous materials. For example, a diamond-like carbon DLC or hydrocarbon coating might be applied to a component or components for reducing friction and protecting against wear. Physical vapor deposition PVD coating is another example and involves producing a thin coating by subjecting material from a condensed phase to a vapor phase, resulting in a thin film condensed phase.
This is different than chemical vapor deposition CVD which produces high-performance solid materials under vacuum. Other Tribological Coatings include:. Tribofilm, or Tribofilms, are films produced on surfaces and play an integral part in reducing or minimizing Friction and Wear in lubricated systems.
It is named after Richard Stribeck, a German mechanical engineer, who first described the concept in This graph showcases how the generation of lubricant films are critical in the reduction of friction and wear of machine parts. Jost, a British mechanical engineer, coined the term in the March 9, Jost Report. Jost is considered the founder of the discipline of Tribology and from his report, a greater spotlight was placed on the subject.
It called for the establishment of Institutes of Tribology, along with the publication of a handbook on tribo-design and engineering. It was at this conference where failures were discussed, particularly in broken steel mill machinery and equipment.
Shortly after publication of the Jost Report , the Committee on Tribology was formally established on September 26, and was charged with several duties, including:. Tribology has since become an interdisciplinary area linked with biology, chemistry, engineering, materials science, mathematics and physics.
Historically, tribology is applied to the most common rolling or sliding components, which are bearings, gears, cams, brakes and seals.
This early focus on enhancing operation and extending the life of industrial machinery has evolved into other applications where it has made a major impact on a variety of applications. When it comes to research, tribology ranges from macro to nano scales. While it was traditionally concentrated on transport and manufacturing sectors, it has grown more diversified over the decades and can be divided into the following fields:.
As the name suggests, Classical Tribology focuses on friction and wear in machine elements — rolling-element bearings, gears, plain bearings, brakes, clutches, wheels, etc. With Biotribology, research focuses on lubrication in biological systems such as human hip and knee joints. Green Tribology, which was also introduced by Peter H. Jost, looks at minimizing the environmental impact, including ways to reduce tribological losses by using technologies with minimal impact on the environment.
With Geotribology, the focus is on studying friction, wear and lubrication of geological systems such as faults and glaciers Wikipedia. As a new facet of Tribology, Geotribology is gaining momentum in the scientific world particularly in its abilities to analyze fault slips. With the development and commercialization of microelectromechanical systems MEMS and nanoelectromechanical systems NEMS , the field of Nanotribology has emerged as a strong focus. This particular application studies tribological phenomena at a nanoscopic scale, which refers to structures with a length scale applicable to nanotechnology.
With Computational Tribology, the aim is modeling the behavior of tribological systems by combining several disciplines such as contact mechanics i. Space Tribology looks at tribological systems with the ability to operate under the harsh environmental conditions of outer space, particularly due to extreme temperature fluctuations. Open System Tribology studies tribological systems exposed to and affected by the natural environment.
In the beginning, Tribology and Tribology research was focused on the design and effective lubrication of machine components such as bearings. Traditional applications, which fall under Classical Tribology, highlight the importance of tribology as it pertains to the sliding surfaces in most mechanical components, which are critical to energy efficiency and maximum life expectancy of those components.
Within the transportation industry, traditional tribology research focused on reliability but in more modern times, the focus has shifted towards energy consumption and increased efficiency, resulting in more complex lubricants. For example, Tribology can reduce carbon dioxide emissions by increasing energy efficiency.
In addition to the transportation industry, tribology has played a vital role in the manufacturing sector, particularly in metal-forming operations. Understanding tribology in manufacturing is important as it can increase productivity while reducing costs. Two other sectors where tribology has significant importance is power generation and residential.
The importance of tribology has only increased over time. Still awaiting further action, H. Lubrication and tribology go hand in hand.
The use of lubricants dates back to images from ancient civilizations in China and Egypt showing the application of lubricants to reduce friction from dragging heavy stones used in building.
Lubricants are used to separate two sliding surfaces, minimizing direct surface contact and reducing tool wear and power requirements.
Lubricants also conduct heat and contaminants away from the interface. The majority of lubricants are liquids, composed of oil and additives; but, some lubricants are gases and solids. Before selecting the proper lubricant, the tribological system needs to be identified. These identifying markers, or parameters, include the type of motion, speed, temperatures, load and operating environment. Type of motion is the first parameter of the tribological system. As discussed, EHL is a type of HL where significant elastic deformation of the surface takes place, drastically altering the shape and thickness of the separating lubricant film Tribonet.
In some cases, the motion is a combination of sliding and rolling, which occurs in certain rolling-element bearings, such as tapered roller bearing. The second parameter of the tribological system is speed, which can be divided into three categories: fast, moderate and slow. In determining the ranges for speed categories, it is essential to know the Stribeck curve and how to calculate it. As stated, the Stribeck Curve is a graph that shows how friction in fluid-lubricated contacts is a non-linear function of lubricant viscosity, entrainment velocity and contact load.
By knowing the speed of the contact, the proper lubricant can be selected to reduce friction. Temperature is the third tribological parameter and a vital one as all lubricants have specific temperature ranges for optimal performance and effectiveness. Due to its chemistries, some lubricants operate within a broad temperature range, while others perform optimally at lower temperatures. Next on the list is the load, which is an important component affecting the lubricant requirement.
If there is a light load, a lubricant designed to minimize fluid friction — while still providing metal-to-metal friction protection — would be needed since the application is sensitive to frictional torque.
Adversely, if there is a heavily loaded application, one would need to select a lubricant containing specific additives to protect against extreme wear, galling and pitting. The final parameter is the operating environment. If the tribosystem is operating in an environment subject to moisture or water, the required lubricant needs to be resistant to water washout or contamination, as well as provide good anti-corrosion properties.
When the application exists in an environment containing chemical liquids and vapors, the required lubricant must be resistant to these chemicals and vapors. After identifying the system and its parameters, the tribo-engineer or lubrication engineer employs different lubricant chemistries to determine the optimal lubricant for the application. In addition to choosing lubricants based on chemistry, the tribo-engineer also needs to analyze the application based on the tribological system, which includes an analysis on speed factors, elastohydrodynamic EHD lubrication, bearing-life calculations, extreme-pressure lubrication, emergency lubrication and other special application requirements.
In the past and even today , testing tribological properties of materials involved building entire systems to run specialized tests such as field tests, bench tests, component tests and model tests. Model tests, for example, allow for film thickness, friction and wear measurements to be conducted. Other tests include electrical and interferometry methods, the pin-on-disc test, the twin disc test, a reciprocating test and a rotary tribotest.
Tribology testing should always be designed and carried out to meet a defined need, and it is essential as it results in vital information regarding any failure mechanisms of mechanical components.
A Tribologist is a student of, or expert in, the field of Tribology. Leonardo da Vinci is one of earliest and most famous Tribologists for his studies on the laws of friction. Peter H. Those involved in the development, maintenance, and continual improvement of lubrication programs are Tribologists by extension. Toggle navigation Toggle search. Magazine Subscribe Today! Current Issue Archive Advertise. There are several types of friction, including: Static Friction, which occurs when two objects are not moving relative to each other i.
Tribology and Lubrication Lubrication is the control of friction and wear by introducing a friction-reducing film between moving surfaces in contact.
Kennedy, F. April 1, April ; 2 : The primary focus of this book is the application of tribology to the design and analysis of bearings and related mechanical components. In order to make the book more useful to a wide audience, the authors attempted to maintain a balance between theory and practical application.
Insightful working knowledge of friction, lubrication, and wear in machines. Applications of tribology are widespread in industries ranging from.
Students should prepare by organizing questions in advance. The instructor will introduce the current applications of modern fluid film bearings. Lecture material and topics.
Detailed study and review of published works dating from to Comments and comparisons made on findings and ease of use for each. Design guide study summarised in outline form showing relationships and interdependencies of dimensions and parameters. Some previous design recommendations difficult to use owing to errors, ambiguous use of symbols and undefined terms. Terms are frequently interchanged without definition, sometimes in the same paper. Work indicated that more evaluation and practical study may be needed for full study. Guideline approach useful for busy designers to help lead understanding through more detailed works available.
The interdisciplinary nature of tribology encompasses knowledge drawn from disciplines such as mechanical engineering, materials science, chemistry and physics. The interaction between these different fields of knowledge to achieve the final result, the control of friction and wear, is reviewed in this volume. This interdisciplinary approach has proven to be a very successful way of analysing friction and wear problems. In many cases tribology is viewed as an inaccessible subject which does not produce useful answers. In this volume the authors redress this problem by providing a comprehensive treatment of the subject. A basic feature of the book is the emphasis on describing various concepts in an accessible manner for the benefit of non-specialists. This principle is applied from the beginning of the book, where the reader is introduced to the fundamental concept of tribology.
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Kennedy, F. April 1, April ; 2 : The primary focus of this book is the application of tribology to the design and analysis of bearings and related mechanical components.
Kennedy, F. April 1,
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Applied Tribology Bearing Design and Lubrication — Applications of tribology are widespread in industries ranging from aerospace, marine and automotive to power, process, petrochemical and construction.