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Author: Alexis Bonetto
Publisher:
ISBN:
Category :
Languages : fr
Pages : 209
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Book Description
La fatigue de surface est aujourd'hui la principale cause de défaillances des roulements. Ce type de fatigue peut se développer du simple fait de la rugosité des surfaces mais est exacerbée par la présence de défauts de surface tels que les indents. La gestion de la pollution des lubrifiants, à l'origine de l'indentation des surfaces, est très coûteuse et ne peut être parfaite puisque la pollution est à la fois présente dans les huiles neuves, générée de manière continue par les systèmes lubrifiés et introduite lors des opérations sur le système. En conséquence, les huiles charrient systématiquement des particules d'origines variées qui sont amenées dans les contacts par les systèmes de lubrification. Au passage entre les surfaces, les particules sont écrasées et indentent les surfaces, créant ainsi des défauts qui seront les sites privilégiés d'amorçage de fatigue au cours des cycles de fonctionnement suivants. Ne pouvant se prémunir de l'indentation des surfaces, une bonne compréhension des mécanismes d'indentation et de fatigue sur indent est nécessaire pour garantir la fiabilité des roulements ainsi que pour réduire les coûts liés à leur maintenance. Au cours de cette thèse, un modèle éléments finis « couplé Euler-Lagrange » est développé pour reproduire le processus d'indentation réel des roulements et en étudier les effets. Dans un second temps, la fatigue des surfaces est étudiée par l'emploi de critères de fatigue issus de la littérature dans le cadre d'un contact sec. Enfin, l'effet du lubrifiant est ajouté par la mise en place d'un solveur multigrilles permettant la résolution du problème EHD transitoire.
Author: Alexis Bonetto
Publisher:
ISBN:
Category :
Languages : fr
Pages : 209
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Book Description
La fatigue de surface est aujourd'hui la principale cause de défaillances des roulements. Ce type de fatigue peut se développer du simple fait de la rugosité des surfaces mais est exacerbée par la présence de défauts de surface tels que les indents. La gestion de la pollution des lubrifiants, à l'origine de l'indentation des surfaces, est très coûteuse et ne peut être parfaite puisque la pollution est à la fois présente dans les huiles neuves, générée de manière continue par les systèmes lubrifiés et introduite lors des opérations sur le système. En conséquence, les huiles charrient systématiquement des particules d'origines variées qui sont amenées dans les contacts par les systèmes de lubrification. Au passage entre les surfaces, les particules sont écrasées et indentent les surfaces, créant ainsi des défauts qui seront les sites privilégiés d'amorçage de fatigue au cours des cycles de fonctionnement suivants. Ne pouvant se prémunir de l'indentation des surfaces, une bonne compréhension des mécanismes d'indentation et de fatigue sur indent est nécessaire pour garantir la fiabilité des roulements ainsi que pour réduire les coûts liés à leur maintenance. Au cours de cette thèse, un modèle éléments finis « couplé Euler-Lagrange » est développé pour reproduire le processus d'indentation réel des roulements et en étudier les effets. Dans un second temps, la fatigue des surfaces est étudiée par l'emploi de critères de fatigue issus de la littérature dans le cadre d'un contact sec. Enfin, l'effet du lubrifiant est ajouté par la mise en place d'un solveur multigrilles permettant la résolution du problème EHD transitoire.
Author: Emmanuel Tonicello
Publisher:
ISBN:
Category :
Languages : fr
Pages : 0
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Book Description
Le 32CrMoV13 nitruré est un matériau à gradient de propriétés utilisé pour la réalisation de bagues de roulements aéronautiques. Il présente l'avantage d'être dur en surface et ductile à cœur, facilitant ainsi la lutte contre les effets de la pollution des contacts par les lubrifiants. De plus, afin d'améliorer les performances des roulements, la tendance est à l'utilisation de céramique (nitrure de silicium Si3N4) pour les éléments roulants à la place de l'acier (M50). Ainsi, le travail de thèse proposé ici est l'étude du comportement en fatigue de contact en présence d'indentations pour deux couples de matériaux (32CrMoV13 nitruré / M50 et 32CrMoV13 nitruré / Si3N4). Ce comportement est principalement orienté en terme de durée de vie du contact indenté par l'intermédiaire d'un critère d'amorçage de fissures. Une étude des propriétés mécaniques du 32CrMoV13 nitruré, nécessaires à l'application du critère, a été réalisée. La loi d'écrouissage et l'ouverture micro-plastique cyclique de la couche nitrurée du 32CrMoV13 nitruré ont été identifiées. Puis, par l'intermédiaire de défauts géométrique de type trous cylindriques, les propriétés d'amorçage de fissures ont été étudiées lors d'essais de compression uniaxiale. Le comportement en fatigue de contact en présence d'indentations a été étudié sur machine bi-disques. Ces essais ont permis de caractériser la différence de comportement du 32CrMoV13 nitruré, et indenté, dans un contact acier / acier et acier / céramique. L'effet du glissement a notamment été mis en évidence. Ces études expérimentales ont été couplées avec des simulations numériques afin d'étalonner le modèle physique d'amorçage de fissures et d'en valider sa bonne représentativité. En conclusion un modèle de prédiction de durée de vie en fatigue de roulement a été proposé. Il est particulièrement adapté aux cas où des contraintes résiduelles sont présentes, par exemple suite à l'indentation des surfaces. Le modèle s'appuie sur la caractérisation mécanique des couches traitées thermo-chimiquement de l'acier 32CrMoV13 nitruré.
Author: British Standards Institute Staff
Publisher:
ISBN: 9780580437397
Category :
Languages : en
Pages : 50
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Book Description
Rolling bearings, Bearings, Damage, Appearance, Defects, Wear, Failure (mechanical), Failure analysis, Terminology, Quality control
Author: Robert K. Flitney
Publisher: Elsevier
ISBN: 008099413X
Category : Science
Languages : en
Pages : 648
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Book Description
Seals and Sealing Handbook, Sixth Edition provides comprehensive coverage of sealing technology, bringing together information on all aspects of this area to enable you to make the right sealing choice. This includes detailed coverage on the seals applicable to static, rotary and reciprocating applications, the best materials to use in your sealing systems, and the legislature and regulations that may impact your sealing choices.Updated in line with current trends this updated reference provides the theory necessary for you to select the most appropriate seals for the job and with its 'Failure Guide', the factors to consider should anything go wrong. Building on the practical, stepped approach of its predecessor, Seals and Sealing Handbook, 6th Edition remains an essential reference for any engineer or designer who uses seals in their work. - A comprehensive reference covering a broad range of seal types for all situations, to ensure that you are able to select the most appropriate seal for any given task - Includes supporting case studies and a unique 'Failure Guide' to help you troubleshoot if things go wrong - New edition includes the most up-to-date information on sealing technology, making it an essential reference for anyone who uses seals in their work
Author: A. Sethuramiah
Publisher: Elsevier
ISBN: 0128007842
Category : Technology & Engineering
Languages : en
Pages : 242
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Book Description
Modeling of Chemical Wear is a one-stop resource for students, researchers and professionals seeking quick and effective tribological evaluations of environmentally friendly and energy efficient products.This book considers optimizing additive combinations by proper methodology, bridging the gap between theory and practice. It defines effective approaches to evaluate antiwear chemical additives commonly used in industry, enhancing the mapping ability of their performance to reduce the extent of full scale evaluations. - Provides full coverage of tribology in four concise chapters, including lubricants and additives and up-and-coming nano-level tribology - Offers effective empirical modelling of chemical wear, along with computer programs relevant to industry standards to help you improve your test methods - Outlines effective methodology for optimization of additive packages, relevant to the present search for eco-friendly combinations
Author: Viktor P. Astakhov
Publisher: Elsevier
ISBN: 0080466850
Category : Technology & Engineering
Languages : en
Pages : 451
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Book Description
Tribology of Metal Cutting deals with the emerging field of studies known as Metal Cutting Tribology. Tribology is defined as the science and technology of interactive surfaces moving relative each other. It concentrates on contact physics and mechanics of moving interfaces that generally involve energy dissipation. This book summarizes the available information on metal cutting tribology with a critical review of work done in the past. The book covers the complete system of metal cutting testing. In particular, it presents, explains and exemplifies a breakthrough concept of the physical resource of the cutting tool. It also describes the cutting system physical efficiency and its practical assessment via analysis of the energy partition in the cutting system. Specialists in the field of metal cutting will find information on how to apply the major principles of metal cutting tribology, or, in other words, how to make the metal cutting tribology to be useful at various levels of applications. The book discusses other novel concepts and principles in the tribology of metal cutting such as the energy partition in the cutting system; versatile metrics of cutting tool wear; optimal cutting temperature and its use in the optimization of the cutting process; the physical concept of cutting tool resource; and embrittlement action. This book is intended for a broad range of readers such as metal cutting tool, cutting insert, and process designers; manufacturing engineers involved in continuous process improvement; research workers who are active or intend to become active in the field; and senior undergraduate and graduate students of manufacturing. · Introduces the cutting system physical efficiency and its practical assessment via analysis of the energy partition in the cutting system.· Presents, explains and exemplifies a breakthrough concept of the physical resource of the cutting tool.· Covers the complete system of metal cutting testing.
Author: George K. Nikas
Publisher:
ISBN: 9788130803777
Category :
Languages : en
Pages : 314
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Book Description
The knowledge gained from studies on friction, lubrication and wear of contacting surfaces (three terms collectively known as tribology) is met in every branch of engineering. Tribology is a multidisciplinary science involving mechanical engineering, materials and lubrication science, physics, and chemistry. Tribological principles are normally used in characterising the mechanical behaviour of surfaces in relative motion. This involves a very large number of applications ranging in size from the nano-scale (molecular and nano-tribology) to the macro-scale (bearings, tyres, rock drills, etc.). Friction, lubrication and wear are inherent characteristics of the physical world regardless of scale. From the intermolecular forces holding a gecko s feet on a vertical wall to the tractive forces at the contact patches of aircraft tyres; from the lubricating film at the rolling contact of a ball on a rolling-bearing raceway to the soft magma supporting tectonic plates of the earth; from the erosion of human teeth from toothpaste particles to the particle erosion of turbine blades; such diverse phenomena can be described and analysed in tribological terms. Every type of machinery includes parts affected by friction, lubrication, and wear. Therefore, the role of tribology in machine operation and reliability is a major one. As a result, the effect of tribology to modern world economy, even though unknown to the majority of the population, is crucial. Although the effect on the economy has been quantified and found to represent a significant proportion of the gross domestic product of economically advanced countries, the true effect pertaining to the development of technologically advanced products is far greater and not immediately obvious. There are several good books on tribology covering the fundamental theory and various applications. However, technology is progressing at an immense pace and engineering norms are quickly outdated. This book is based on the collective experience of some of the world s top experts on friction, lubrication and wear. It presents recent developments in the field of tribology and its contributors are equally divided among theoreticians and experimentalists. Furthermore, some chapters contain new theory and results, which, in the editor s experience, is at the frontier of research. The topics covered in the eight chapters of this book include thin-film lubrication from a theoretical perspective, a critical review of rolling-bearing life-prediction models, a review of Laser Surface Texturing, a proposed unification of friction and wear via thermodynamic principles, the role of tribofilms in concentrated contacts from a materials-science perspective, transient phenomena in elastohydrodynamic lubrication from an experimental point of view, a theoretical assessment of the Stribeck curve in lubricated contacts, and, finally, a thorough presentation of modelling and adhesion problems of microelectromechanical systems (MEMS) and miniature devices. Chapter 1 by Professor Szeri is an in-depth discussion of the thin-film lubrication theory referring to hydrodynamic and elastohydrodynamic lubrication. Professor Szeri (University of Delaware, USA), a well-known author with many decades of research experience, attempts to define the limits of the classical Reynolds theory of lubrication in both laminar and turbulent flows of liquids and gases. He discusses the continuity limitation of the classical theory in terms of film thickness, wall slip, and the Reynolds number. He reaches to quantitative conclusions on the validity of the film continuity assumption and the necessity to use the full Navier-Stokes equations or first principles in some applications for which the Reynolds theory is inaccurate. Chapter 2 by Dr. Zaretsky is a critical evaluation of the main models proposed for the prediction of the fatigue lives of rolling-element bearings, comprising the past and present ISO standards. Those models have been adopted by major bearing manufacturers such as SKF and include the classical work of Palmgren, Weibull, Lundberg, Ioannides, Harris, and Zaretsky. Dr Zaretsky, a Chief Engineer of NASA and Adjunct Professor at Case Western Reserve University (USA), is an authority on bearing life prediction. In his comprehensive tutorial, which is suitable both to experts and non-experts on this topic, he explains the advantages and disadvantages of the various models from a theoretical point of view, and includes a selection of endurance test results to compare the relative accuracy of the theoretical models. Among Dr Zaretsky s conclusions is that the load-life exponent (10/3) used in the ANSI/ABMA and ISO standards to predict rolling bearing life is not reflective of modern rolling bearings and actually underestimates bearing lives. Chapter 3 by Professor Etsion is a review of Laser Surface Texturing (LST). Surface texturing of tribological, mechanical components, has emerged in the last decade as a viable option of surface engineering resulting in significant improvements in load capacity, wear resistance, reduction of friction etc. Professor Etsion (Chair in Fluid Mechanics and Heat Transfer, Technion Israel Institute of Technology) is one of the most recognised experts on the topic of surface texturing. In his review of the LST, he outlines the technique and discusses the potential of this technology in various engineering applications, including automotive (piston rings), bearings, seals, magnetic storage devices (hard disk sliders and magnetic tapes), and others. Chapter 4 by Professor Bryant is rather unique in the literature. Professor Bryant, a professor in the University of Texas at Austin (USA) and the Editor of the Journal of Tribology of the American Society of Mechanical Engineers, attempts to unify friction and wear via thermodynamic principles, focusing on the dissipative processes found at sliding interfaces. He presents a review of friction and wear mechanisms, and relates them in terms of their associated thermodynamics, energy losses and entropy produced by common dissipative processes. He shows that the expressions for entropy generation in dissipative processes operative at a sliding interface, which are common to both friction and wear, could result in unified friction and wear models. Chapter 5 by Professors Jacobson and Hogmark provides an overview of the role of tribofilms on surfaces in sliding contacts. The authors, both professors of materials science and tribology at Uppsala University in Sweden, have several decades of research experience on such topics. Through illustrative examples based on real applications, they show that tribologically induced surface modifications result in the creation of surface layers or tribofilms ranging in thickness from a few nanometres to tens of micrometres. The surface modifications include topographical changes, formation of micro-cracks, material phase transformations, formation of oxides, formation of solid films by reaction with lubricant additives, material transfer from the counter surface, etc. It is such tribofilms that actually dominate the contact properties between sliding solids in terms of friction and wear and not the original materials. Chapter 6 by Dr. Glovnea, Reader in the School of Engineering and Design at Sussex University in England, presents a review of recent experimental research on non-steady-state elastohydrodynamic lubrication, including transient loading, sudden variation of entrainment speed and variation of micro-geometry. His study is relevant to all industrial machinery involving lubricated contacts and susceptible to vibrations or normal operation involving load and speed variations. Dr Glovnea, who has spent several years studying such phenomena in the Tribology Group of Imperial College London, shows how transient conditions and various parameters affect (normally sub-micrometre) elastohydrodynamic films, their thickness distribution and overall cohesion. It is thus possible to assess the risk of contact damage from film thinning or collapse. Chapter 7 by Professor Khonsari (Louisiana State University, USA) and Dr. Booser, both well-respected researchers in the tribology community and authors of best-selling tribology books, deals with the different lubrication regimes met in contacts at relatively low sliding speeds. These are related via the so-called Stribeck curve, which demonstrates the transition from boundary lubrication at the start-up of motion to mixed lubrication as the speed is increased, and on to full-film lubrication at higher speeds. The review covers issues pertaining to roughness asperity interactions (particularly in the mixed lubrication regime), wear, stick-slip phenomena, and the effects of lubricant additives. Chapter 8 by Dr. Xue (Analog Devices, Inc., USA) and Professor Polycarpou (University of Illinois at Urbana-Champaign, USA) covers microelectromechanical systems (MEMS) from an experimental and theoretical point of view. The authors have extensive experience in this research field and are focused on the problem of adhesion or stiction of MEMS and miniature devices, which reduces their reliability and hinders their advancement and wider commercialisation. They develop an experimentally validated, adhesive-contact model, which is valid for a wide range of adhesion parameter values, covering the practical range of application of MEMS and other miniature devices. The editor embarked on this project in June 2007 and invited eminent tribologists to make contributions on specific topics based on the editor s plans for the book. The project was completed in about 18 months before the manuscripts were sent to the publisher. The editor is grateful to the authors/contributors of this book for their cooperation and patience throughout the lengthy process of communication, chapter editing, and book compilation. The editor is also grateful to the expert reviewers (see the list of reviewers) who kindly reviewed the chapters, one chapter each reviewer. Finally, the editor would like to thank the publisher, Research Signpost, for the original invitation and kind assistance.
Author:
Publisher: University Science Press
ISBN: 9789381159613
Category :
Languages : en
Pages : 0
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Book Description
Author: J. J. C. Hoo
Publisher: ASTM International
ISBN: 9780803102897
Category : Technology & Engineering
Languages : en
Pages : 232
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Book Description
Author: Taisho Hasegawa
Publisher:
ISBN: 9781604569124
Category : Mechanical wear
Languages : en
Pages : 0
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Book Description
Tribology is the science and technology of interacting surfaces in relative motion. It includes the study and application of the principles of friction, lubrication and wear. The study of tribology is commonly applied in bearing design but extends into almost all other aspects of modern technology, even to such unlikely areas as hair conditioners and cosmetics such as lipstick, powders and lip-gloss. Any product where one material slides or rubs over another is affected by complex tribological interactions, whether lubricated like hip implants and other artificial prosthesis or unlubricated as in high temperature sliding wear in which conventional lubricants can not be used but in which the formation of compacted oxide layer glazes have been observed to protect against wear. The wateriness of oil during foot wiping operations may be observed by the Mavis-Bootlace test. Outcomes are typically modelled in the 4-Litre-Poulner hypothesis. Tribology plays an important role in manufacturing. In metal-forming operations, friction increases tool wear and the power required to work a piece. This results in increased costs due to more frequent tool replacement, loss of tolerance as tool dimensions shift, and greater forces are required to shape a piece. A layer of lubricant which eliminates surface contact virtually eliminates tool wear and decreases needed power by one third. This book presents the latest research in the field from around the globe.
