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Friction Characteristics (friction + characteristic)
Selected AbstractsThe influence of contact geometry on friction and wear characteristicsLUBRICATION SCIENCE, Issue 4 2000R. Michalczewski Abstract This paper describes some results of evaluating the influence of contact geometry on tribological characteristics. Friction characteristics obtained for a distributed contact (pin-on-disc and block-on-ring), a linear concentrated contact (pin and vee-block and block-on-ring) and a point concentrated contact (ball-on-disc and three cylinder-cone) are presented. The wear scars were analysed using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results show different values of friction and wear coefficients for the different types of contact geometry. The paper also assesses the effect of non-test characteristics, e. g., vibration. [source] Torsional Vibration Damping Through Frictional Torsion Damper with Structural Friction and Slide Taken into ConsiderationPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2005Zbigniew Skup Ph. DSC The paper is concerned with a non-linear discrete stationary mechanical system containing a frictional torsion damper. Proper effect of vibration damping in a two-degree-of freedom system can be reached by the right selection of geometrical parameters for given loads, as pre-determined by a mathematical model. Structural friction was considered, as well as small relative sliding of damper's discs cooperating with a plunger. The system vibrates under harmonic excitation. The problem was considered on the assumption of uniform unit pressure distribution between the contacting surfaces of friction discs and the plunger. When the discs are sliding, the friction coefficient varies, depending on relative angular velocity. Friction characteristics were assumed on the basis of the author's own research and experimental testing by other authors. Properties of the material were assumed to be in accordance with classical theory of elasticity. The author analysed the influence of parameters of the dynamic system upon amplitude and frequency characteristics as well as on phase and frequency characteristics. The equation of motion was solved by means of the slowly-varying-parameters method and, in order to compare the results, by means of numerical simulation. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Comparison of performance of heat regenerators: Relation between heat transfer efficiency and pressure dropINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2001Franēoise Duprat Abstract Heat regenerators transfer heat from one gas to another, with an intermediate storage in solids. The heat transfer surface for gas flow application should provide at the same time high surface area and low friction factor. Three geometries of heat transfer surface, monolith, stack of woven screens and bed of spheres, have been compared. Their performance was evaluated from the pressure drop of the heat regenerator working at a given heat transfer efficiency. The comparison was performed using numerical simulation and published measurements of heat transfer and flow friction characteristics. By adjusting the length and the period of the exchanger, it is possible to obtain the same heat transfer efficiency with the three geometries. Beds of spheres give very short and compact heat regenerators, working at high pressure drop. At the opposite, monoliths form long regenerators working at low pressure drop. Stacks of woven screens cover a wide range of performance: low porosity woven screens give high heat transfer efficiency and high pressure drop, while high porosity woven screens offer performance similar to that of the monoliths. Copyright © 2001 John Wiley & Sons, Ltd. [source] Speed- and topography-dependent boundary friction characteristics of steelLUBRICATION SCIENCE, Issue 8 2010Saiko Aoki Abstract A novel tribometer that undergoes significant changes at ultra-slow (>5.0,µm,s,1) to moderate (<20,cm,s,1) sliding speeds was developed in order to study the friction-speed characteristics of steel lubricated with oil. Three different surface topographies were applied to the specimens, and the friction characteristics with an additive-free base oil (MO91) and a stearic acid-formulated oil (StA/MO91) were studied to understand the effects of surface textures on the lubrication performance of an adsorbed molecular layer formed by StA. Friction reduction behaviour of the adsorbed layer observed in the transverse direction was attributed to microscopic hydrodynamic action that maintained the load-carrying performance of the adsorbed layer. Copyright © 2010 John Wiley & Sons, Ltd. [source] Impact of lubricant formulation on the friction properties of carbon fiber clutch platesLUBRICATION SCIENCE, Issue 1 2006R. C. Oldfield Since their introduction over ten years ago, carbon fiber based friction materials have been employed by transmission builders in a wide variety of applications, including torque converter clutches, synchronizers, limited slip devices and shifting clutches. This new generation of materials gives improved durability relative to cellulose; carbon fiber materials offer inherently greater wear resistance and improved resistance to thermal degradation. However, carbon fiber based materials also bring inherently different friction characteristics than their cellulose based counterparts. As a result, a different approach to lubricant formulation is required to provide optimized friction control in applications where they are used. It is well known that in order to achieve and maintain the required friction in a clutch, the correct combination of surface properties and additive chemistry is required. In this paper the impact of different additive chemistries on the friction of carbon fiber clutch plates has been investigated. It will be shown that with the appropriate choice of additive system, carbon fiber based friction plates can offer a number of performance improvements over more conventional materials. Copyright © 2006 John Wiley & Sons, Ltd. [source] Assessing friction characteristics of liquid lubricantsLUBRICATION SCIENCE, Issue 4 2006D.J. Hargreaves A reduction in friction in tribological contacts will lead to reduced energy requirements. It is therefore important to be able to measure the frictional characteristics of various liquid lubricants. Current laboratory tests measure friction, but the test rigs invariably induce wear between the mating contacts. A new test rig, the wire-on-capstan rig, is presented which measures friction without inducing wear between the wire and the rotating capstan. All seven lubricants tested (three without additives and four proprietary hydraulic oils) exhibit a reducing coefficient of friction with increasing temperature. Temperatures ranged from 25°C to 100°C. The mineral-based oil showed the lowest friction coefficient and the three synthetic ester based oils produced the highest friction coefficient over the complete temperature range. Future testing will extend the range of operating conditions and product types. Copyright © 2006 John Wiley & Sons, Ltd. [source] Wet clutch transmission fluid for AWD differentials: base fluid influence on friction characteristicsLUBRICATION SCIENCE, Issue 1 2006Rikard Mäki Abstract During the past few years several electronically controllable automotive transmission systems, where wet clutches are used as intelligent differentials, have emerged in the market. In this type of application the anti-shudder properties of the lubricants are of vital importance. This paper investigates the influence of base fluids on the anti-shudder properties of transmission fluids for wet clutches in all-wheel-drive systems. The investigated all-wheel-drive system featuring a wet multi-plate clutch with a sintered brass-based friction material is described. The test equipment used to determine the frictional characteristics of the transmission fluid is described. The parameters studied include base fluid type and base fluid viscosity. It is shown that the choice of base fluid has no impact on torque capacity, but that the base fluid influences the temperature dependence of the dynamic friction and the anti-shudder properties. It is also shown that the major effect on the friction characteristics is caused by additive effects rather than base fluid effects. Copyright © 2006 John Wiley & Sons, Ltd. [source] Friction and wear effects on a micro/nano-scaleLUBRICATION SCIENCE, Issue 1 2001E. Santner Abstract In this paper are described tribological effects which can be found in micro-tribological systems, and in those macro-systems which can be analysed by micro-methods, e.g., by atomic force microscopy (AFM) or related methods. Micro-tribology systems have friction contacts with loads in the micro/nano-newton range and/or dimensions in the micro/nanometre range. Experiments on the micro/nano-scale should be easier to explain by theoretical modelling due to their simpler system structure. An example is discussed of adhesion and friction measurements between AFM tips and clean, flat, solid surfaces in ultra-high vacuum, which shows some of the special aspects of micro/nano-tribology. Surprising friction characteristics on surfaces with an artificial micro-structure can be explained by skilled and careful topographical analysis of the friction path with an AFM. In micro-sensor contacts, ,single wear events' can be detected using AFM analysis of the contact region. For ceramic compounds, different friction levels for the components of the material can be found. The problems, difficulties, and dangers of misinterpretation are also discussed. [source] | ||||||||||