摘要:

Generally, the selection of design variables in bearing design is done by a trial and error method using many design charts. However, it is not so easy to successfully select optimum design variables by such a method, and a considerable amount of working time and cost is needed to complete the optimum design of bearings. In this paper, an optimum design procedure for high-speed, short journal bearings operated in both laminar and turbulent flow regimes is developed based on mathematical programming. Under the short bearing assumption, simplified closed-form design formulas are obtained for the eccentricity ratio, maximum film pressure, fluid film temperature rise, supply lubricant quantity and whirl onset velocity. The radial clearance, slenderness ratio and average viscosity of lubricant, which minimize the weighted sum of fluid film temperature rise and supply lubricant quantity for various combinations of journal rotational speed and applied load, are determined by successive quadratic programming, which is a mathematical programming method. From the optimized results, the characteristics of optimized design variables in both the laminar and turbulent flow regimes were clarified.Presented at the 50th Annual Meeting in Chicago, Illinois May 14–19, 1995

ISSN:1040-2004    

DOI:10.1080/10402009708983657

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The kinetics of the absorption of lubricating oils and moisture from air into porous polyimide, as well as the exchange of oil between porous polyimide retainers and oil baths or operating bearings, have been measured. Oil absorption into porous polyimide is much faster than into cotton-phenotic. Water is absorbed by oil-impregnated polyimide, but little or no oil is lost during the process. Oil is absorbed by air-equilibrated polyimide at a slower rate than by dry polyimide. Porous polyimide is much easier to impregnate with oil than cotton-phenolic, and is also much more tolerant, of storage in air once impregnated. Oil within a porous polyimide ball bearing retainer exchanges slowly with oil in a bath in which the retainer is placed. The exchange is due to diffusion of the oils, and the diffusion coefficient is determined to be 3 × 10−9cm2/s for the oils used in these experiments. Oil is exchanged quickly between polyimide retainers and well-lubricated operating bearings. The exchange is faster than a diffusion process, and is probably driven by bearing action. In these experiments, the authors could detect no net gain or loss of oil from the retainer or the bearing parts. Only about one-half of the oil originally supplied to the parts is available to the retainer; the rest remains elsewhere in the bearing.

ISSN:1040-2004    

DOI:10.1080/10402009708983658

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Increasing areal densities on the order of I Gbit/in2in magnetic disk drives demands the use of supersmooth disk substrates which can, however, lead to a severe sticlion problem. A practical solution involves the creation of bumps in a dedicated landing zone near the disk inner diameter using a focused laser beam. The tribological performance of the laser-textured disk depends on the size and number of bumps on its surface. A large number of asperities (bumps) can result in high sticlion force. On the other hand, to prevent plastic deformation, the number of asperities must be greater than a certain number. A statistical contact model has been developed to generate design curves for estimating the critical number of asperities as a function of asperity radius which can prevent both plastic deformation and severe sticlion.Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in San Francisco, California, October 13–17, 1996

ISSN:1040-2004    

DOI:10.1080/10402009708983659

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A complete evaluation of the tribological characteristics of a given material/mechanical system is a time-consuming operation since the friction and wear process is extremely systems-sensitive. As a result, experimental designs, i.e., Latin Square and Taguchi, have been implemented in an attempt to not only reduce the total number of experimental combinations needed to fully characterize a material/mechanical system, but also to acquire life data for a system without having to perform an actual life test. Unfortunately, these experimental designs still require a great deal of experimental testing and the output does not always produce meaningful information. In order to further reduce the amount of experimental testing required, this study employs a computer neural network model to investigate different material/mechanical systems. The work focuses on the modeling of the wear behavior, while showing the feasibility of using neural networks to predict life data. The model is capable of defining which input variables will influence the tribological behavior of the particular material/mechanical system being studied based on the specifications of the overall system.Presented at the 51st Annual Meeting in Cincinnati, Ohio May 19–23, 1996

ISSN:1040-2004    

DOI:10.1080/10402009708983660

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Pin-on-disk tribology experiments were conducted on a perfluoro-polyalkylelher (PFPE) liquid lubricant with and without a new PFPE lubricant antiwear additive material: a silane. It was found that the silane provided moderate improvement in the antiwear performance of the PFPE lubricant when applied to the metallic surface as a surface coating or when added to the PFPE as a dispersion (emulsion). Slightly belter results were obtained by using the combination of a surface coating and an emulsion of the silane. The silane emulsions or coalings did not affect the friction properties of the lubricant. Micro-Fourier transformation infrared (μFFIR) spectroscopy analysis was performed to study silane transfer films and the degradation of the PFPE. The silane was found to mitigate degradation of the PFPE which may have been the major reason for the improved antiwear performance, observed.Presented at the 50th Annual Meeting in Chicago, Illinois May 14–19, 1995

ISSN:1040-2004    

DOI:10.1080/10402009708983661

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Dynamic light scattering was used to measure the translational diffusion coefficient of neutral diisobutyl zinc dithiophosphate in hexane. The experimental data were then analyzed using the method of cumulant, expansion (1) and CONTIN (2), (3). Translational diffusion coefficients were obtained and compared with the predictions of stick (4), (5) diffusion theory. The stick calculations approximated the shape of the molecules as ellipsoids (6), (7) and cylinders (4). Assumed, diameters of 10 angstroms in the ellipsoidal case and 7.5 angstroms in the cylindrical case were used in these calculations.

ISSN:1040-2004    

DOI:10.1080/10402009708983662

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Effects of oil-soluble copper salts on oil oxidation and corrosion have been extensively studied in the literature. However, little attention has been paid to the deposits produced from the copper-containing additives by tribochemical reactions on the rubbing surface.

ISSN:1040-2004    

DOI:10.1080/10402009708983663

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The subject of this paper is an analysis of progressive, wear and other surface alteration processes which take place on deep drawing dies. The deep drawing process was simulated using strip test evaluation equipment. A theory on the influence of different surface alterations on the die surface topography was then, developed. The wear progress was quantified using conventional surface roughness parameters as well as a set of recently developed parameters based on the bearing curve and extended to thee dimensions. It was concluded from conventional surface roughness measurements that maximum wear takes place at angles of 20° and 70° from the vertical direction on the die. Furthermore, it was observed from three-dimensional measurements that the progressive wear is initialed by ploughing after only a few drawings and this mechanism continues until the die is worn out. In the investigations described in this work, the wear progress was interpreted using the. three-dimensional parameters Spkand Svkin terms of an initial ploughing stage followed by a second stage during which ploughing and abrasive wear occur simultaneously.Presented at the 50th Annual Meeting in Chicago, Illinois May 14–19, 1995

ISSN:1040-2004    

DOI:10.1080/10402009708983664

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A theoretical study of the elastohydrodynamic lubrication (EHL) of line contacts with couple stress fluids as lubricants is presented. The paper mainly deals with the theoretical values of the central film thickness within the elastic contacts of rolling and sliding surfaces in terms of equivalent radius of a cylinder and a plane. The central film thickness is numerically calculated based on Grubin's theory of inlet builtup pressure and considering the effect of a couple stress parameter in complex fluids. In particular cases, film thickness and pressure distribution are also numerically calculated and graphically presented by considering the cavitation boundary condition. A comparative study of the couple stress behavior with the Newtonian behavior of lubricants has been made. As per experimental studies, the central film thickness in EHL contacts depends on a variety of lubricants under identical operational conditions. The present theoretical consideration with couple stress fluid indicates that the presence of a couple stress parameter increases the central film thickness in EHL contacts lubricated with complex fluids, e.g., polymeric and synthetic lubricants.

ISSN:1040-2004    

DOI:10.1080/10402009708983665

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

An analysis is developed for the simulation of stick-slip friction between lubricated surfaces at low sliding velocity. The simulation shows the time-dependent motion and unsteady friction force. The simulation is based on a fundamental dynamic friction model which considers the hydrodynamic forces as well as the friction due to direct contact between the surface asperities. In addition, the Dahl effect which demonstrates presliding displacement is considered. The analysis considers a system of a motor driving a journal with inertia through a flexible shaft. The journal is supported by hydrodynamic journal bearing where slick-slip friction can be generated in the mixed friction region. This problem is equivalent to a closed-loop proportional control of the angular rotation of a rigid shaft. The stick-slip is simulated and the physical phenomena are elucidated.Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in San Francisco, California, October 13–17, 1996

ISSN:1040-2004    

DOI:10.1080/10402009708983666

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor