Download or read book Friction at a Lubricated Line Contact Operating at Oscillating Sliding Velocities written by D. P. Hess and published by . This book was released on 1989 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although many contacts operate under unsteady loading and sliding conditions, friction behavior under such conditions is still not well understood. In this paper we report on a series of experiments that were run to examine friction-velocity characteristics of line contacts operating under unsteady sliding velocities in the mixed, elastohydrodynamic and hydrodynamic lubrication regimes. A periodic, time-varying velocity component was superimposed on a steady sliding speed in such a way that all three lubrication regimes could be covered in a cycle. It was found that as the frequency of oscillation was increased, a multi-valued friction coefficient appeared as a loop about the average (steady state) friction-velocity relation. It is shown that this behavior can be modeled by a characteristic time lag between a changing velocity and the corresponding steady state friction. The latter is described by a single equation that was matched to measured average friction data. In the mixed lubrication regime, which is where this lag most significantly affects friction behavior, the lag time increases with normal load and lubricant viscosity. It is shown that the time shift is not associated with a fixed characteristic distance. The observed delay arises due to entrainment and normal approach, which includes squeeze-films combined with rough surface contact deformations.
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 520 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 need to understand sliding friction. This second edition covers several new topics including friction on superconductors, simulations of the layering transition, nanoindentation, wear in combustion engines, rolling and sliding of carbon nanotubes, and the friction dynamics of granular materials.
Download or read book Tribology Issues and Opportunities in MEMS written by Bharat Bhushan and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 652 pages. Available in PDF, EPUB and Kindle. Book excerpt: Micro Electro Mechanical Systems (MEMS) is already about a billion dollars a year industry and is growing rapidly. So far major emphasis has been placed on the fabrication processes for various devices. There are serious issues related to tribology, mechanics, surfacechemistry and materials science in the operationand manufacturingof many MEMS devices and these issues are preventing an even faster commercialization. Very little is understood about tribology and mechanical properties on micro- to nanoscales of the materials used in the construction of MEMS devices. The MEMS community needs to be exposed to the state-of-the-artoftribology and vice versa. Fundamental understanding of friction/stiction, wear and the role of surface contamination and environmental debris in micro devices is required. There are significantadhesion, friction and wear issues in manufacturing and actual use, facing the MEMS industry. Very little is understood about the tribology of bulk silicon and polysilicon films used in the construction ofthese microdevices. These issues are based on surface phenomenaand cannotbe scaled down linearly and these become increasingly important with the small size of the devices. Continuum theory breaks down in the analyses, e. g. in fluid flow of micro-scale devices. Mechanical properties ofpolysilicon and other films are not well characterized. Roughness optimization can help in tribological improvements. Monolayers of lubricants and other materials need to be developed for ultra-low friction and near zero wear. Hard coatings and ion implantation techniques hold promise.
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 Control of Machines with Friction written by Brian Armstrong-Hélouvry and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is my ambition in writing this book to bring tribology to the study of control of machines with friction. Tribology, from the greek for study of rubbing, is the discipline that concerns itself with friction, wear and lubrication. Tribology spans a great range of disciplines, from surface physics to lubrication chemistry and engineering, and comprises investigators in diverse specialities. The English language tribology literature now grows at a rate of some 700 articles per year. But for all of this activity, in the three years that I have been concerned with the control of machines with friction, I have but once met a fellow controls engineer who was aware that the field existed, this including many who were concerned with friction. In this vein I must confess that, before undertaking these investigations, I too was unaware that an active discipline of friction existed. The experience stands out as a mark of the specialization of our time. Within tribology, experimental and theoretical understanding of friction in lubricated machines is well developed. The controls engineer's interest is in dynamics, which is not the central interest of the tribologist. The tribologist is more often concerned with wear, with respect to which there has been enormous progress - witness the many mechanisms which we buy today that are lubricated once only, and that at the factory. Though a secondary interest, frictional dynamics are note forgotten by tribology.
Download or read book Handbook of Friction Vibration Interactions written by Gang Sheng Chen and published by Elsevier. This book was released on 2014-07-10 with total page 409 pages. Available in PDF, EPUB and Kindle. Book excerpt: Friction-vibration interactions are common but important phenomena in science and engineering. Handbook of Friction-Vibration Interactions introduces the principles and provides the resources to understand and work with them. A unified theoretical framework includes some of the most important engineering applications. The first three chapters in the book introduce basic concepts and analytical methods of friction and vibration. The fourth chapter presents the general principles on friction-vibration interactions, and also touches on various engineering applications. In the fifth chapter the concepts and methods are extended to some of the most critical engineering applications in high-tech industry, presenting the friction-vibration interaction principle and applications in data storage systems. - Covers a key topic in science and engineering, with applications in daily life - Introduces the principles of friction-vibration interactions - Analyzes, presents experiments, and treats real systems ranging from nano to micro to macro scales
Download or read book Dynamics with Friction written by Ardshir Guran and published by World Scientific. This book was released on 2001 with total page 329 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 present part II of this volume on Dynamics with Friction is a continuation of the previous part I, and is designed to help synthesize our current knowledge regarding the role of friction in mechanical and structural systems as well as everyday life. The topics covered include interaction of vibration and friction at dry sliding contacts, friction-induced instability in disks, dynamics of lubricated flexible links in kinematic chains, modal interactions in periodic structures, dynamics of an experimentally excited beam, transient waves in viscoelastic materials, dynamic stability of plates with damping, friction modeling and dynamic computation, damping through use of passive and semi-active dry friction forces.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 Transient Effects in Friction written by Andreas Goedecke and published by Springer Science & Business Media. This book was released on 2014-07-08 with total page 211 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transient friction effects determine the behavior of a wide class of mechatronic systems. Classic examples are squealing brakes, stiction in robotic arms, or stick-slip in linear drives. To properly design and understand mechatronic systems of this type, good quantitative models of transient friction effects are of primary interest. The theory developed in this book approaches this problem bottom-up, by deriving the behavior of macroscopic friction surfaces from the microscopic surface physics. The model is based on two assumptions: First, rough surfaces are inherently fractal, exhibiting roughness on a wide range of scales. Second, transient friction effects are caused by creep enlargement of the real area of contact between two bodies. This work demonstrates the results of extensive Finite Element analyses of the creep behavior of surface asperities, and proposes a generalized multi-scale area iteration for calculating the time-dependent real contact between two bodies. The toolset is then demonstrated both for the reproduction of a variety of experimental results on transient friction as well as for system simulations of two example systems.
Download or read book Dynamics With Friction Modeling Analysis And Experiments Part Ii written by Ardeshir Guran and published by World Scientific. This book was released on 2001-06-01 with total page 329 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 present part II of this volume on Dynamics with Friction is a continuation of the previous part I, and is designed to help synthesize our current knowledge regarding the role of friction in mechanical and structural systems as well as everyday life. The topics covered include interaction of vibration and friction at dry sliding contacts, friction-induced instability in disks, dynamics of lubricated flexible links in kinematic chains, modal interactions in periodic structures, dynamics of an experimentally excited beam, transient waves in viscoelastic materials, dynamic stability of plates with damping, friction modeling and dynamic computation, damping through use of passive and semi-active dry friction forces.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 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 Seismic Behavior of Steel Storage Pallet Racking Systems written by Carlo Andrea Castiglioni and published by Springer. This book was released on 2016-02-04 with total page 502 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the main outcomes of the first European research project on the seismic behavior of adjustable steel storage pallet racking systems. In particular, it describes a comprehensive and unique set of full-scale tests designed to assess such behavior. The tests performed include cyclic tests of full-scale rack components, namely beam-to-upright connections and column base connections; static and dynamic tests to assess the friction factor between pallets and rack beams; full-scale pushover and pseudodynamic tests of storage racks in down-aisle and cross-aisle directions; and full-scale dynamic tests on two-bay, three-level rack models. The implications of the findings of this extensive testing regime on the seismic behavior of racking systems are discussed in detail, highlighting e.g. the confirmation that under severe dynamic conditions “sliding” is the main factor influencing rack response. This work was conceived during the development of the SEISRACKS project. Its outcomes will contribute significantly to increasing our knowledge of the structural behavior of racks under earthquake conditions and should inform future rack design.
Download or read book Dynamics and Control of Robotic Manipulators with Contact and Friction written by Shiping Liu and published by John Wiley & Sons. This book was released on 2019-02-11 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive guide to the friction, contact and impact on robot control and force feedback mechanism Dynamics and Control of Robotic Manipulators with Contact and Friction offers an authoritative guide to the basic principles of robot dynamics and control with a focus on contact and friction. The authors discuss problems in interaction between human and real or virtual robot where dynamics with friction and contact are relevant. The book fills a void in the literature with a need for a text that considers the contact and friction generated in robot joints during their movements. Designed as a practical resource, the text provides the information needed for task planning in view of contact, impact and friction for the designer of a robot control system for high accuracy and long durability. The authors include a review of the most up-to-date advancements in robot dynamics and control. It contains a comprehensive resource to the effective design and fabrication of robot systems and components for engineering and scientific purposes. This important guide: Offers a comprehensive reference with systematic treatment and a unified framework Includes simulation and experiments used in dynamics and control of robot considering contact, impact and friction Discusses the most current tribology methodology used to treat the multiple–scale effects Contains valuable descriptions of experiments and software used Presents illustrative accounts on the methods employed to handle friction in the closed loop, including the principles, implementation, application scope, merits and demerits Offers a cohesive treatment that covers tribology and multi-scales, multi-physics and nonlinear stochastic dynamics control Written for graduate students of robotics, mechatronics, mechanical engineering, tracking control and practicing professionals and industrial researchers, Dynamics and Control of Robotic Manipulators with Contact and Friction offers a review to effective design and fabrication of stable and durable robot system and components.
Download or read book Force and Position Control of Mechatronic Systems written by Tong Heng Lee and published by Springer Nature. This book was released on 2020-12-11 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: Force and Position Control of Mechatronic Systems provides an overview of the general concepts and technologies in the area of force and position control. Novel ideas and innovations related to this area are presented and reported in detail, and examples of applications in medical technology are given. The book begins by introducing force sensing, and modelling of contacting objects. In then moves steadily through a variety of topics, including: • disturbance observer-based force estimation; • force-based supervisory control; • stabilization systems; • controller design; and • control of tube insertion procedures. This book will be of interest to researchers, engineers and students interested in force control, particularly those with a focus on medical applications of these ideas. Advances in Industrial Control reports and encourages the transfer of technology in control engineering. The rapid development of control technology has an impact on all areas of the control discipline. The series offers an opportunity for researchers to present an extended exposition of new work in all aspects of industrial control.
Download or read book Contact Mechanics and Friction written by Valentin L. Popov and published by Springer Science & Business Media. This book was released on 2010-03-10 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt: The English edition of “Contact Mechanics and Friction” lying before you is, for st the most part, the text of the 1 German edition (Springer Publishing, 2009). The book was expanded by the addition of a chapter on frictional problems in ear- quake research. Additionally, Chapter 15 was supplemented by a section on elasto-hydrodynamics. The problem sections of several chapters were enriched by the addition of new examples. This book would not have been possible without the active support of J. Gray, who translated it from the German edition. I would like to thank Prof. G. G. - charyan and Prof. S. Sobolev for discussions and critical comments on the chapter over earthquake dynamics. Dr. R. Heise made significant contributions to the - velopment and correction of new problems. I would like to convey my affecti- ate thanks to Dr. J. Starcevic for her complete support during the composition of this book. I want to thank Ms. Ch. Koll for her patience in creating figures and Dr. R. Heise, M. Popov, M. Heß, S. Kürscher, and B. Grzemba for their help in pro- reading. Berlin, November 2009 V.L. Popov Preface to the German Edition
Download or read book ASME Technical Papers written by and published by . This book was released on 1996 with total page 664 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Friction Dynamics in Low Speed Lubricated Sliding of Rubber written by Dirk Alan Wassink and published by . This book was released on 1996 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Mechanical Engineering) in the University of Michigan, 1996.
Download or read book Stribeck Curves and Stick slip Phenomena in the Friction of Fibers written by Ching-Fang Tu and published by . This book was released on 1997 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt:
