Download or read book Investigation of Dynamic Friction in Lubricated Surfaces written by Hanuman Rachoor and published by . This book was released on 1995 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: The research reported in this dissertation is concerned with the development of friction models for lubricated contacts. A few analytical models have been developed to investigate the friction under dynamic velocity conditions. In this study, two different tribological situations such as conformal and non-conformal contacts have been chosen. Friction modeling covers boundary, mixed and full fluid film friction regions. A new theory based on the elastic properties of the surface materials, and fluid film properties of the lubricant at the contact has been developed to determine the dynamic friction in boundary, mixed and full hydrodynamic lubrication regions. In the full fluid film lubrication region, friction has been determined from the lubrication principles based on the tribological situation, i.e., hydrodynamic lubrication theory for a short journal bearing and elastohydrodynarnic lubrication theory for a line contact. A conformal contact formed by a short journal bearing operating in the region where hydrodynamic lubrication theory is valid has been considered to develop a model. The model is simulated for unidirectional as well as bi-directional sinusoidal velocity oscillations for various frequencies. Simulation resulted in a phase lag in the fiction and hysteresis in ftiction versus velocity (f vs. U) curves. The results obtained for unidirectional velocity oscillations indicate qualitative agreement with experimental work on lubricated line contact by Hess and Soom (1990). Results for bi-directional oscillations also show phase lag in friction and similar hysteresis in f vs U curves. In addition to the hysteresis, results for the bi-directional velocity oscillations show a discontinuity in friction at velocity reversals. These results have been verified experimentally. A special apparatus to measure the friction has been designed and built by using a sleeve bearing. Experiments have been conducted to measure friction under various velocity conditions, and the results have been used to determine the coefficients required to simulate the analytical model. The analytical model has been simulated for the above coefficients and the results have been compared with the friction measurements. The comparison shows similar hysteresis in f vs U curves for uni-directional and bi-directional velocity oscillations. However, the friction behavior of the apparatus during bi-directional oscillations differs in the magnitude of the discontinuity (step function) at velocity reversals. The above analytical friction model developed for the hydrodynamic short journal bearing has been extended to investigate the effect of resisting forces on the dynamic friction behavior at low speed. Resistance forces include sliding friction as well as the presliding friction Dahl effect. The Dahl effect is due to elastic deformation of the compliance in the system before the force reaches the breakaway magnitude when sliding initiates. In this study, stiffness of the asperities as well as elastic support have been considered. Simulation results of the model for uni-directional velocity oscillations are in qualitative agreement with earlier experimental work. Simulation of the model for bi-directional velocity oscillations shows that the discontinuity at velocity reversals has been replaced by a line with slope. This work indicates that the stiffness, of the elastic compliance can play a significant role in replacing the discontinuity. The above concepts of friction modeling has been extended for a non-conformal contact formed with a cylindrical surface sliding over a flat surface operating on elastohydrodynamic lubrication theory. In this model, elastohydrodynamic lubrication theory has been used to determine the friction in full fluid film region. Simulation results of this model for uni-directional as well as bi-directional sinusoidal velocity oscillations indicate a similar phase lag in the friction and hysteresis in f vs. U curves as observed in the earlier models. Results of the present investigation indicate that the instantaneous friction is not only a function of the instantaneous velocity, but it is also a function of previous velocity or velocity history. These models can be improved with the aid of more experimental work. Also, these models can be extended for stick-slip analysis and for friction compensation.
Download or read book A Preliminary Study on the Vapor Mist Phase Lubrication of a Spur Gearbox written by and published by . This book was released on 1999 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organophosphates have been the primary compounds used in vapor/mist phase lubrication studies involving ferrous bearing material. Experimental results have indicated that the initial formation of an iron phosphate film on a rubbing ferrous surface, followed by the growth (by cationic diffusion) of a lubricious pyrophosphate-type coating over the iron phosphate, is the reason organophosphates work well as vapor/mist phase lubricants. Recent work, however, has shown that this mechanism leads to the depletion of surface iron atoms and to eventual lubrication failure. A new organophosphate formulation was developed which circumvents surface iron depletion. This formulation was tested by generating an iron phosphate coating on an aluminum surface. The new formulation was then used to vapor/mist phase lubricate a spur gearbox in a preliminary study.
Download or read book Friction Wear and Lubrication in Vacuum written by Donald H. Buckley and published by . This book was released on 1971 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dynamics with Friction written by Ardshir Guran and published by World Scientific. This book was released on 1996 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt: The dynamics of dissipative mechanical and structural systems is being investigated at various institutions and laboratories worldwide with ever-increasing sophistication of modeling, analysis and experiments. This book offers a collection of contributions from these research centers that represent the state-of-the-art in the study of friction oscillators. It provides the reader with the fruits of a team effort by leaders in this fascinating field.The topics covered include friction modeling, self-excited friction oscillators, homogeneous frictional systems, unsteady lubricated friction, instantaneous contact geometry, impact damping, friction-induced instability and nonlinear dynamics of stick-slip systems, among other topics.This book gives a comprehensive picture of dynamics of dissipative mechanical and structural systems. It also gives an up-to-date account of the present state of the field. It will be of interest to engineers, rheologists, material scientists, applied mathematicians, physicists and historians of science and technology.
Download or read book Investigation of Friction of Lubricated Surfaces at Low Temperatures written by M. N. Buchin and published by . This book was released on 1951 with total page 57 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Superlubricity written by Ali Erdemir and published by Elsevier. This book was released on 2007-03-30 with total page 525 pages. Available in PDF, EPUB and Kindle. Book excerpt: Superlubricity is defined as a sliding regime in which friction or resistance to sliding vanishes. It has been shown that energy can be conserved by further reducing/removing friction in moving mechanical systems and this book includes contributions from world-renowned scientists who address some of the most fundamental research issues in overcoming friction. Superlubricity reviews the latest methods and materials in this area of research that are aimed at removing friction in nano-to-micro scale machines and large scale engineering components. Insight is also given into the atomic-scale origins of friction in general and superlubricity while other chapters focus on experimental and practical aspects or impacts of superlubricity that will be very useful for broader industrial community. * Reviews the latest fundamental research in superlubricity today* Presents 'state-of-the-art' methods, materials, and experimental techniques* Latest developments in tribomaterials, coatings, and lubricants providing superlubricity
Download or read book Sliding Friction written by Bo N.J. Persson and published by Springer Science & Business Media. This book was released on 2013-03-14 with total page 465 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sliding friction is one of the oldest problems in physics and certainly one of the most important from a practical point of view. The ability to produce durable low-friction surfaces and lubricant fluids has become an important factor in the miniaturization of moving components in many technological devices, e.g., magnetic storage, recording systems, miniature motors and many aerospace components. This book will be useful to physicists, chemists, materials scientists, and engineers who want to understand sliding friction. The book (or parts of it) could also form the basis for a modern undergraduate or graduate course on tribology.
Download or read book Friction Dynamics written by Xiandong Liu and published by Woodhead Publishing. This book was released on 2016-07-20 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt: Friction Dynamics: Principles and Applications introduces readers to the basic principles of friction dynamics, which are presented in a unified theoretical framework focusing on some of the most important engineering applications. The book's chapters introduce basic concepts and analytical methods of friction dynamics, followed by sections that explore the fundamental principles of frictions. Concluding chapters focus on engineering applications in brake dynamics, the friction dynamics of rods used in oil suck pump systems, and the friction impact dynamics of rotors. This book provides comprehensive topics and up-to-date results, also presenting a thorough account of important advancements in friction dynamics which offer insights into varied dynamic phenomena, helping readers effectively design and fabricate stable and durable friction systems and components for various engineering and scientific friction dynamical systems. Investigates the most critical engineering and scientific applications Provides the most comprehensive reference of its kind Offers a systematic treatment and a unified framework Explores cutting-edge methodologies to address non-stationary, non-linear dynamics and control
Download or read book Fundamentals of Friction written by I.L. Singer and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 638 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamentals of Friction, unlike many books on tribology, is devoted to one specific topic: friction. After introductory chapters on scientific and engineering perspectives, the next section contains the necessary background within the areas of contact mechanics, surfaces and adhesion. Then on to fracture, deformation and interface shear, from the macroscopic behavior of materials in frictional contact to microscopic models of uniform and granular interfaces. Lubrication by solids, liquids and gases is presented next, from classical flow properties to the reorganization of monolayers of molecules under normal and shear stresses. A section on new approaches at the nano- and atomic scales covers the physics and chemistry of interfaces, an array of visually exciting simulations, using molecular dynamics, of solids and liquids in sliding contact, and related AFM/STM studies. Following a section on machines and measurements, the final chapter discusses future issues in friction.
Download or read book Fundamental Studies of Friction Lubrication and Wear by Atomic Force Microscopy written by and published by . This book was released on 1993 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: To probe friction, lubrication, and wear on an atomic scale, a capacitance-based ultrahigh vacuum force microscope was developed. It measures both parallel and perpendicular forces between a tip and a surface. Friction between a diamond tip and chemical-vapor-deposited (CVD) diamond films at loads below one micronewton showed a sublinear dependence of friction on load, with the effective friction coefficient varying between 0.2 and 0.8 depending on load and location. Stick-slip behavior resulting from both surface heterogeneity and static/dynamic friction was observed. A CVD process was developed for growing single crystal diamond tips with radii as small as 30 nm. The normal force between these tips and diamond (100) and (111) surfaces agrees with calculated dispersion forces. The frictional force variation on the (100) surface are tentatively associated with a reconstructed geometry convoluted over an asymmetric tip shape, while the (111) surface exhibits features which cannot be simply associated with the surface structure. Friction is approximately 3 nanonewtons independent of loads up to 100 nanonewtons. A field emission technique was developed for continuously observing the motion of individual adsorbed atoms and molecules. The hopping of individual Cs atoms between sites on a tungsten tip was observed with 2 ps and 5 Angstrom resolution.
Download or read book Fundamentals of Tribology written by Rahnejat Homer and published by World Scientific. This book was released on 1998-10-20 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamentals of Tribology deals with the fundamentals of lubrication, friction and wear, as well as mechanics of contacting surfaces and their topography. It begins by introducing the reader to the importance of tribology in everyday life and offers a brief history of the subject. It then describes the nature of rough surfaces and the mechanics of contacting elastic solids and their deformation under load and friction in their relative motion. The book goes on to discuss the importance of lubricant rheology with respect to viscosity and density. Then, the principles of hydrodynamic lubrication are covered with derivations of the governing Reynolds and energy equations. Applications of hydrodynamic lubrication in various forms of bearings -- journal bearings, thrust bearings and externally pressurised bearings -- are outlined. The important and still evolving subject of elastohydrodynamic lubrication is treated in some detail, both at its fundamentals and its applications in thin shell or overlay bearings, cam-followers and internal combustion engine pistons. The fundamentals of biotribology are also covered, particularly its applications to endo-articular mammalian joints such as hip and knee joints and their arthroplasty. In addition, there is a treatment of the rapidly emerging knowledge of tribological phenomena in lightly loaded vanishing conjunctions (nanotribology), in natural systems and very small devices, such as MEMS and high density data storage media. There is also a new chapter on the rapidly emerging subject of surface texturing to promote retention of microreservoirs of lubricant, acting as microbearings and improving lubrication of otherwise poorly lubricated conjunctions. This book targets the undergraduate and postgraduate body as well as engineering professionals in industry, where often a quick solution or understanding of certain tribological fundamentals is sought. The book can also form an initial basis for those interested in research into certain aspects of tribology.
Download or read book Research Needs and Opportunities in Friction written by and published by . This book was released on 1994 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Elements of Friction Theory and Nanotribology written by Enrico Gnecco and published by Cambridge University Press. This book was released on 2015-04-30 with total page 319 pages. Available in PDF, EPUB and Kindle. Book excerpt: A thorough guide to the mechanisms ruling friction processes, based on state-of-the-art models and experimental results, this multi-scale book for researchers and students combines the classical theories of contact mechanics and lubrication with nanotribology to explore friction in a range of forms.
Download or read book Experimental Methods in Tribology written by Gwidon Stachowiak and published by Elsevier. This book was released on 2004-05-18 with total page 373 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is an indespensible guide to both researchers in academia and industry who wish to perform tribological experiments more effectively. With an extensive range of illustrations which communicate the basic concepts in experimental methods tribology more effectively than text alone. An extensive citation list is also provided at the end of each chapter facilitating a more thorough navigation through a particular subject. * Contains extensive illustrations* Highlights limitations of current techniques
Download or read book The Friction and Lubrication of Solids written by Frank Philip Bowden and published by Oxford University Press. This book was released on 2001 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: This classic work, originally published in 1950, was a landmark in the development of the subject of tribology. When it was first published, one reviewer wrote that it 'marks the beginning of a new epoch in the study of friction and lubrication .... The most interesting and comprehensive work on a single branch of physics I have ever read.' For the 1986 reprint David Tabor wrote a new preface, reviewing developments in the subject in the 36 years since the book first appeared. He has also added an appreciation of the life and work of F.P. Bowden, who died in 1968.
Download or read book Fundamentals of Fluid Film Lubrication written by Bernard J. Hamrock and published by CRC Press. This book was released on 2004-03-15 with total page 794 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Tribology written by and published by University Science Press. This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
