Rheological Effects on Friction in Elastohydrodynamic Lubrication


Book Description

An analytical and experimental investigation is presented of the friction in a rolling and sliding elastohydrodynamic lubricated contact. The rheological behavior of the lubricant is described in terms of two viscoelastic models. These models represent the separate effects of non-Newtonian behavior and the transient response of the fluid. A unified description of the non-Newtonian shear rate dependence of the viscosity is presented as a new hyperbolic liquid model. The transient response of viscosity, following the rapid pressure rise encountered in the contact, is described by a compressional viscoelastic model of the volume response of a liquid to an applied pressure step. The resulting momentum and energy equations are solved by an iterative numerical technique, and a friction coefficient is calculated. The experimental study was performed, with two synthetic paraffinic lubricants, to verify the friction predictions of the analysis. The values of friction coefficient from theory and experiment are in close agreement.




High Pressure Rheology for Quantitative Elastohydrodynamics


Book Description

Computational elastohydrodynamics, a part of tribology, has existed happily enough for about fifty years without the use of accurate models for the rheology of the liquids used as lubricants. For low molecular weight liquids, such as low viscosity mineral oils, it has been possible to calculate, with precision, the film thickness in a concentrated contact provided that the pressure and temperature are relatively low, even when the pressure variation of viscosity is not accurately modelled in detail. Other successes have been more qualitative in nature, using effective properties which come from the fitting of parameters used in calculations to experimental measurements of the contact behaviour, friction or film thickness. High Pressure Rheology for Quantitative Elastohydrodynamics is intended to provide a sufficiently accurate framework for the rheology of liquids at elevated pressure that it may be possible for computational elastohydrodynamics to discover the relationships between the behaviour of a lubricated concentrated contact and the measurable properties of the liquid lubricant. The required high-pressure measurement techniques are revealed in detail and data are presented for chemically well-defined liquids that may be used as quantitative reference materials.* Presents the property relations required for a quantitative calculation of the tribological behaviour of lubricated concentrated contacts.* Details of high-pressure experimental techniques.* Complete description of the pressure and temperature dependence of viscosity for high pressures.* Some little-known limitations on EHL modelling.




Elasto-Hydrodynamic Lubrication


Book Description

Elasto-Hydrodynamic Lubrication deals with the mechanism of elasto-hydrodynamic lubrication, that is, the lubrication regime in operation over the small areas where machine components are in nominal point or line contact. The lubrication of rigid contacts is discussed, along with the effects of high pressure on the lubricant and bounding solids. The governing equations for the solution of elasto-hydrodynamic problems are presented. Comprised of 13 chapters, this volume begins with an overview of elasto-hydrodynamic lubrication and representation of contacts by cylinders, followed by a discussion on equations relevant to lubrication, including the Reynolds equation. The reader is then introduced to lubrication of rigid cylinders; the importance of film thickness in highly loaded rigid contacts; the elasticity of solids in contact; and the theory of elasto-hydrodynamic lubrication. Subsequent chapters focus on apparatus and measurements of film thickness and film shape; friction and viscosity; and lubrication of gears and roller bearings. This book will be of interest to tribologists.




Rheology and Elastohydrodynamic Lubrication


Book Description

This book gives a thorough overview on recent developments in lubricant rheology, elastohydrodynamic lubrication and the effects of surface roughness and particulate contamination in the lubricant on the overall behaviour of a heavily loaded lubricated contact. One of the aims of the book is to make clear to the reader that a Newtonian model for the lubricant behaviour does not have enough degrees of freedom to be able to describe the friction - traction behaviour of heavily loaded lubricated contacts or the oil film build-up and collapse under surface asperities for rough surfaces. The book contains quite a lot of experimental data of lubricants at high pressures, both solidification pressures, compressibilities and shear strength increase coefficients, which make it possible to estimate the friction and power loss in heavily loaded lubricated contacts for different pressures, temperatures, sliding speeds, and lubricant types. This is the first time that data of this type has been included in a textbook and it is hoped that the questions highlighted will serve to initiate and guide future research in this field.




Fundamentals of Fluid Film Lubrication


Book Description

Specifically focusing on fluid film, hydrodynamic, and elastohydrodynamic lubrication, this edition studies the most important principles of fluid film lubrication for the correct design of bearings, gears, and rolling operations, and for the prevention of friction and wear in engineering designs. It explains various theories, procedures, and equations for improved solutions to machining challenges. Providing more than 1120 display equations and an introductory section in each chapter, Fundamentals of Fluid Film Lubrication, Second Edition facilitates the analysis of any machine element that uses fluid film lubrication and strengthens understanding of critical design concepts.




NASA Technical Note


Book Description




Nonequilibrium Molecular Dynamics


Book Description

This coherent collection of theory, algorithms, and illustrative results presents the field of nonequilibrium molecular dynamics in detail.




Encyclopedia of Tribology


Book Description

TRIBOLOGY – the study of friction, wear and lubrication – impacts almost every aspect of our daily lives. The Springer Encyclopedia of Tribology is an authoritative and comprehensive reference covering all major aspects of the science and engineering of tribology that are relevant to researchers across all engineering industries and related scientific disciplines. This is the first major reference that brings together the science, engineering and technological aspects of tribology of this breadth and scope in a single work. Developed and written by leading experts in the field, the Springer Encyclopedia of Tribology covers the fundamentals as well as advanced applications across material types, different length and time scales, and encompassing various engineering applications and technologies. Exciting new areas such as nanotribology, tribochemistry and biotribology have also been included. As a six-volume set, the Springer Encyclopedia of Tribology comprises 1630 entries written by authoritative experts in each subject area, under the guidance of an international panel of key researchers from academia, national laboratories and industry. With alphabetically-arranged entries, concept diagrams and cross-linking features, this comprehensive work provides easy access to essential information for both researchers and practicing engineers in the fields of engineering (aerospace, automotive, biomedical, chemical, electrical, and mechanical) as well as materials science, physics, and chemistry.




Fundamentals of Engineering Tribology with Applications


Book Description

Tribology is related to friction, wear and lubrication of machine elements. Tribology not only deals with the design of fluid containment systems like seals and gasket but also with the lubrication of surfaces in relative motion. This book comprehensively discusses the theories and applications of hydrodynamic thrust bearing, gas (air) lubricated bearing and elasto-hydrodynamic lubrication. It elucidates the concepts related to friction, including coefficient of friction, friction instability and stick-slip motion. It clarifies the misconception that harder and cleaner surfaces produce better results in wear. Recent developments, including online condition monitoring (an integration of moisture sensor, wear debris and oil quality sensors) and multigrid technique, are discussed in detail. The book also offers design problems and their real-life applications for cams, followers, gears and bearings. MATLAB programs, frequently asked questions and multiple choice questions are interspersed throughout for easy understanding of the topics.




Springer Handbook of Mechanical Engineering


Book Description

This resource covers all areas of interest for the practicing engineer as well as for the student at various levels and educational institutions. It features the work of authors from all over the world who have contributed their expertise and support the globally working engineer in finding a solution for today‘s mechanical engineering problems. Each subject is discussed in detail and supported by numerous figures and tables.