摘要:

Water has been found to exhibit significant effects on the tribological behavior of alumina. A film-like substance was found on the surfaces of water lubricated alumina wear surfaces, suggesting the possibility of tribochemical reaction between water and alumina in the contact junction.

ISSN:1040-2004    

DOI:10.1080/10402008908981900

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

General Elastohydrodynamic Lubrication Code (GEHLC) is a FORTRAN code for calculating the lubrication performance of line and point contacts used in machine elements such as gears, rolling bearings, cam and follower systems, and traction drives, etc. It adopts the most recent results published by Chittenden and Dowson et al. (1), to evaluate isothermal film thickness of point contacts, and uses the thermal reduction factor (2) to account for the inlet heating effects on the film thickness. By using Bair and Winer's analysis (3), a viscoelastic fluid model has been employed in this program to calculate shear stress in the film with bisection technique and In predict the coefficient of friction. Using this program one can also obtain flash temperature distribution on the two solid surfaces from a simplified heat conduction analysis based on work by Bolt (4), Jaeger (5), and Archard (6), et al. Typical results are presented for elliptical contacts used in rolling bearings.Presented at the 42nd Annual Meeting in Anaheim, California May 11–14, 1987

ISSN:1040-2004    

DOI:10.1080/10402008908981901

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The friction and wear behavior of a polymer/metal oscillatory sliding system is largely dictated by the film of polymer which may form on the metallic counterface. This research utilizes scanning electron microscopy as the principal tool for examination of post-test frictional surfaces in an effort to identify the processes of film formation in an ultra-high molecular weight polyethylene pin/440C stainless steel counterface oscillatory pair. Strong adhesive junction formation at contacts leads to fibril drawing upon continued motion. Eventual fibril rupture deposits polyethylene residues upon the counterface and these residues are cumulatively smeared by the pin into a film. An increase in temperature from 15 to 30 degrees C aids the smearing process, forming a smoother film which reduces wear rate by limiting polymer/metal interaction. Comparative tests with polytetrafluoroethylene support earlier conclusions that film peeling due to weaker adhesion results in higher wear rates for PTFE than UHMWPE.

ISSN:1040-2004    

DOI:10.1080/10402008908981902

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

An investigation was conducted to examine the deformation and fracture behavior of single-crystal and sintered polycrystalline SiC surfaces exposed to cavitation. Cavitation erosion experiments were conducted in distilled water at 25°C using a magnetostrictive oscillator in close proximity (1 mm) to the surface of SiC. The horn frequency was 20 kHz, and the double amplitude of the vibrating disk was 50 μm. The results of the investigation indicate that the SiC {0001} surface could be deformed, in a plastic manner during cavitation. Dislocation etch pits ware formed when the surface was chemically etched. The number of defects, including dislocations in the SiC {0001} surface, increased with increasing exposure time to cavitation. The presence of intrinsic defects such as voids in the surficial layers of the sintered polycrystalline SiC determined the zones at which fractured grains and fracture pits (pores) were generated during cavitation. Single-crystal SiC had superior erosion resistance to that of sintered polycrystalline SiC.Presented at the 43rd Annual Meeting in Cleveland, Ohio May 9–12, 1988

ISSN:1040-2004    

DOI:10.1080/10402008908981903

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

In the boundary lubricated sliding of metals, lubricant molecules desorb from metal surfaces as the interfacial temperature exceeds the transition temperature. As a consequence, numerous metallic contacts will be established, leading to adhesion and wear particle formation. The wear particles so formed plow the sliding surfaces, resulting in high friction and severe wear. In this paper, it is shown that friction can be reduced at elevated temperatures even with additive-free lubricants by using undulated surfaces. Flat and undulated OFHC copper surfaces were tested with various lubricants at different temperatures. Experimental results and theoretical analysis show that undulated surfaces minimize the plowing component of friction due to wear debris, thereby keeping the friction coefficient at a low value after the transition.Presented at the 43rd Annual Meeting in Cleveland, Ohio May 9–12, 1988

ISSN:1040-2004    

DOI:10.1080/10402008908981904

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A finite element method is used for solving Reynolds equation of hydrodynamic journal bearings. Once a matrix expression for calculating bearing film reaction force, i.e., components fx, fy, is obtained, a matrix expression for calculating all the dynamic coefficients can be obtained immediately only by differentiating fx,fyexpression with respect to the perturbations of displacements x,y and to the velocity u,v respectively. With this “Matrix Method”, we also get a result that both cross damping coefficients, Dxyand Dyx, are equal to each other. This method makes the program very simple and for calculating all these eight dynamic coefficients it is possible to solve Reynolds equation once only.xs

ISSN:1040-2004    

DOI:10.1080/10402008908981905

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A FORTRAN, MS-DOS operating system algorithm was constructed and implemented to predict ester-based lubricant behavior in a turbine engine. Input data consists of selected lubricant flow rates, bulk lubricant and bearing temperatures, and laboratory generated data. Execution of the program uses lubricant property data as a function of time at several temperatures to produce mathematical functions describing total acid number, viscosity change and evaporation as a function of temperature at selected times. Static coker data are employed to estimate coking at the hot end bearing cover. The program output data are predicted values of critical lubricant properties as a function of engine hours, reflecting lubricant additions to the system because of evaporative and seal losses and also degradation predicted to occur during cool-down cycles. Computer-generated data are compared with actual engine data; the benefits and limitations of the program are identified.Presented at the 43rd Annual Meeting in Cleveland, Ohio May 9–12, 1988

ISSN:1040-2004    

DOI:10.1080/10402008908981906

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Wear debris from ZDDP lubricated tests run under mild wear conditions have been investigated by X-ray Absorption Fine Structure Spectroscopy (EXAFS). Special attention has been paid to the state of iron in the amorphous wear fragments. Results indicate the presence of Fe3+species as a modifier of the phosphate network formed during tribo-reaction. As the anti-wear regime of ZDDP is characterized by a decrease of the abrasive wear, it is suggested that the anti-wear action of ZDDP is reliable to the diffusion of iron oxides in the phosphate, this latter being gently delaminated.Presented at the 43rd Annual Meeting in Cleveland, Ohio May 9–12, 1988

ISSN:1040-2004    

DOI:10.1080/10402008908981907

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The need for increased efficiency in transmissions has focussed attention upon the traction characteristics of lubrication in elastohydrodynamic contacts. Until now most studies in this field have employed a disc machine to obtain mean values of traction coefficient across an entire elastohydrodynamic contact. This obscures details of the way the lubricant responds to the varying pressure and temperature across the contact.

ISSN:1040-2004    

DOI:10.1080/10402008908981908

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor