2015 届毕业文献翻译
题 目 固体力学中摩擦学综述 专业班级 学 号
学生姓名
指导老师
指导老师职称 副教授
学院名称 机电工程学院
完成日期：2015年6月11日
1
翻译原文：
Review of solid mechanics in tribology
John A. Tichy*, Donna M. Meyer
The study of solid mechanics is essential to the field of tribology, (friction, lubrication and wear). Tribology is of immense economic importance. The potential savings, were tribological principles better understood and applied to friction and wear reduction) may be several percent of the gross national product. Solutions to tribology problems often enable current technologies in a broad spectrum of applications from friction contact in the turbine shrouds of aircraft engines, to bearing contact in motor vehicle gear assemblies, to the sliding contact of magnetic storage disk drives. Conversely, tribology issues, e.g., the coefficient of friction, may impact solid mechanics problems and tangential tractions are essentially free parameters in many cases.
Active issues of research in tribology where solid mechanics is applied include: friction and wear in dynamic loading of bearings to extend bearing life; models for contact and thermal stresses of sliding surface asperities; design criteria for magnetic recording heads, and behavior of human artificial joints to extend service life. Countless other applications exist, requiring the development of essential theories of conforming and non?conforming surface behavior. Information such as the frictional response of surfaces in relative motion, and modes of stress and deformation emerges from the fusion of solid mechanics and tribology.
Tribology is the science and technology of interacting surfaces in relative motion. The word itself was first used in England the 1960's and comes from the Greek work 'tribos' meaning 'to rub'. The term was coined as a conscious attempt to combine the historically independent fields of friction, lubrication and wear in an interdisciplinary manner, as well as to attach a scientific sounding name to studies which were, for the most part, at that time, very applied. The attempt seems to have succeeded and the term tribology has found wide acceptance in both science and engineering. The study of fluid film bearings, rolling element bearings, seals, gears, cams, viscous dampers,
1
human joints, and magnetic storage devices are some of the applications in which tribology is currently used.
Tribology is of immense economic importance, which certainly motivates its study. An improvement in the engineering practice of tribology through better understanding of a contact mechanics problem may involve savings in the billions of dollars. The Jost Report Jost (1966)，in which the term tribology was first used, attributed about ￡515M/y (about 1% of the British gross national product) of potential savings were tribological principles better understood and applied. Such a huge economic impact was much derided at the time as self-serving exaggeration; however, the economics may have been greatly understated. The Jost Report primarily focused on energy loss due to friction but overlooked the much large pervasive costs of wear on maintenance, loss due to breakdowns, depreciation of machinery, etc. Such potential savings through tribology are huge, but clearly very difficult to rigorously quantify. Recent textbooks discuss the economic impact of tribology in their introductions, Rabinowicz (1995), and Hutchings (1992).
The history of the subject dates back to the studies of friction by Thermistius in 350 BC who found that the friction for sliding is greater than that for rolling. This finding led to the understanding in modern terms that the static friction coefficient is greater than the kinetic coefficient of friction. First noted in the 1500，s by da Vinci, re-discovered by Amontons in 1699, verified by Euler in 1750 and Coulomb in 1781: each found that friction is proportional to load and independent of the area of sliding surfaces. Thus the coefficient of friction is independent of load, and in the case of dry (unlubricated) sliding, independent of velocity. Dowson (1997) presents an entertaining history of the field.
Little fundamental understanding into solid mechanics aspects of tribology was gleaned until this century when measurements could be taken of surface roughness, and inferences made as to the real area of contact between surfaces. Even the smoothest surfaces are rough on the atomic scale and contact only occurs at the tips of asperity peaks, Bowden and Tabor (1967). At first the deformation is elastic in the manner of the Hertz problem between spherical surfaces, see the discussion below.
2
For metal surfaces, eventually the elastic limit is exceeded and plastic deformation occurs. With fully plastic asperity deformation, the real area of contact Ar is the (global) normal force P divided by the yield hardness H, Ar 二 P/H, and the friction force Q for dry sliding is the real area of contact times the shear strength Y. The asperity junctions are assumed to be joined by adhesion and then ruptured during sliding. Thus the friction coefficient is shear strength divided by hardness, ^ 二 Q/P 二 Y/H.
With similarly simplistic reasoning, a dimensionless wear coefficient K can be defined, Archard (1953), which is wear volume divided by real contact area times sliding distance, K 二 Vol/ArS 二 Vol H/PS. If the plastically deformed zone below the asperity is the same order as the real contact area, then K represents a ratio of worn volume to the plastically deformed zone. For adhesive wear, K loosely represents the probability that an asperity adhesive junction leads to a wear particle. Adhesive wear occurs when asperities are in contact accompanied by high local pressures and sometimes the resulting weld can be stronger than the bulk asperity; the cohesive strength of the softer material being less than the interfacial strength. For abrasive wear, where the asperity material is harder than the material surface through which it is ploughing, a simple ploughing idealization leads to K 二 tan S/n where S is the cutting angle, Rabinowicz (1995). For adhesive wear K is order 10_4 to 10\and for abrasive wear K is order 10_1.
In recent times, tribology is often a so-called pacing technology being crucial to a wide range of applications including high temperature engines made of ceramics, machine tools, metal cutting and forming processes, and biotechnology to name a few. Whether counter surfaces are conforming or nonconforming, made of like or unlike materials, lightly or highly loaded, under steady or dynamic loads, the study of solid mechanics is integral in solving tribological problems.
Many of the present day tribology problems, just as during its early beginnings, require knowledge of a combination of several areas of science. Researchers in the field come from a wide variety of backgrounds: surface science, chemistry of lubricants, machine design and behavior, material science, rheology, fluid mechanics
3
and the like. Relatively few of the past and presently well-known people in tribology come from the solid mechanics field. Of the three areas of friction, wear and lubrication, only the latter has been broadly tractable to a theoretical foundation until very recently. In 1886，Osborne Reynolds developed his theory of hydrodynamic lubrication and the equation that bears his name. Reynolds' equation is a solution to the governing equations of Newtonian fluid mechanics (Navier— Stokes) for a thin confined film in which a three-dimensional nonlinear equation can be integrated to a two-dimensional linear partial differential equation. Solutions to Reynolds' equation form the basis of design and analysis of fluid film bearings. Probably due to the relatively straightforward nature of Reynolds' equation, many researchers have approached tribology from a fluid mechanics perspective.
The field of solid mechanics as applied to contacting surfaces began in the same era as lubrication theory with the publication of Heinrich Hertz's classic paper 'On the Contact of Elastic Solids' (Hertz, 1882). As pointed out by K.L. Johnson in the preface to his text Contact Mechanics (Johnson, 1987), Hertz' theory was confined to the case of frictionless surfaces and perfectly elastic solids. Removal of the former restriction has led to more realistic consideration of the sliding and rolling contacts of machine elements. Much early work in this direction is due to R.D. Mindlin (1949). Development of theories of plasticity and viscoelasticity has allowed application of solid mechanics to a wider range of materials and conditions. However, by contrast with lubrication, no single governing equation or set of equations could be said to adequately define the solid mechanics of friction and wear problems. Most applications of solid mechanics to tribology are concerned with
non-conformal surfaces, which touch first at a point or along a line. Even under finite load, the region affected by the contact is much smaller than the dimensions of the bodies themselves. The contact zone can generally be regarded as a region of stress concentration within the larger body. Strictly speaking, by most conventions, these types of problems comprise the field of contact mechanics. Most of this paper concerns contact mechanics in the sense just described, but we will use the term to mean 'solid mechanics aspects of tribology.
4