摘要:

The wear mechanisms of a 3% mol yttria stabilized tetragonal zirconia ceramics (TZP)/52100 steel reciprocating sliding couple under water lubrication were investigated in this paper. The wide ranges of normal loads and sliding speeds were chosen in order to study the relationship between the tribological performance of this sliding couple and the testing conditions. Different wear regions were identified as a function of normal load and speed. The wear surfaces were carefully examined by scanning electron microscopy (SEM). The mild wear and severe wear of TZP ceramics are respectively related to plastic deformation and surface fracture. The mild and severe wear of a 52100 steel ball are respectively related to slight polishing and abrasive wear. At very high normal load and low sliding speed, TZP ceramics experience negative wear due to steel transfer caused by the strong adherence between TZP ceramics and the 52100 steel ball. The wear mechanisms of TZP ceramics and 52100 steel under different sliding conditions are illustrated by their respective wear transition diagrams.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:10.1080/10402009708983701

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The aggregation of a calcium sulfonate in organic solvents was studied by the Fourier Transform Infrared (FTIR) spectroscopy and dynamic light scattering techniques. The symmetric stretching band of the S = O bond was found to be sensitive to the concentration of the additive and to the polarity of the solvent. A critical micelle concentration (CMC) may exist in the concentration range of 0.04–0.11 millimole/liter. As the solvent polarity increased, the width in half height of the symmetric stretching band of S = O increased, and the interaction between the solvent and the polar head of calcium sulfonate increased accordingly. This interaction weakened the interaction between the polar heads themselves, and thereby the size of the micelle decreased as found by dynamic light scattering. When the polarity of a solvent is strong enough, e.g., in heptanoic acid or water, the micelles formed may revert back to normal micelles. The FTIR spectra and aggregation size of calcium sulfonate in hexadecane showed that higher temperatures decreased the width in half height of the asymmetric stretching bands and concurrently decreased the size of the aggregation.Presented at the 50th Annual Meeting in Chicago, Illinois May 14–19, 1995

ISSN:1040-2004    

DOI:10.1080/10402009708983702

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This paper describes a research program in which the goal is to alter the thermal expansion coefficient of a composite solid lubricant coating PS300, by compositional tailoring. PS300 is a plasma-sprayed coating consisting of chrome oxide, silver and barium fluoride/calcium fluoride eutectic in NiCr binder. By adjusting the composition, the thermal expansion coefficient can be altered, and hence chosen, to more closely match a selected substrate preventing coating spallation at extreme temperatures. Thermal expansion coefficients (CTEs) for a variety of compositions were measured from 25° to 800°C using a commercial dilatometer. The CTEs ranged from 7.0 to 13 × 10−6/°C depending on the binder content. Subsequent tribological testing of a modified composition indicated that friction and wear properties were generally comparable, and for some operating conditions superior, to the original composition.Presented at the 52nd Annual Meeting in Kansas City, Missouri May 18–22, 1997

ISSN:1040-2004    

DOI:10.1080/10402009708983703

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The development of hot hinge joints requires suitable substrates and solid lubricant coatings. Promising coatings were selected based on an assessment of lubrication mechanisms. As a substrate, C/-SiC material is applied. Lack of literature data and test equipment make it necessary to investigate the selected materials experimentally with test rigs that have, in part, been specially developed for these purposes. The test program covers tests for material preselection, lubrication material characterization and feasibility tests on a hinge joint prototype. Regarding the operation conditions, the development of such hot hinge joints seems to be possible from the tribological point of view.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:10.1080/10402009708983704

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A mixed lubrication model for axisymmetric seals, intended as a practical design tool, has been developed. The model considers such physical mechanisms as surface roughness effects on the film lubrication, elastic-plastic face contact, face deformation caused by pressure and contact forces, thermal deformation due to viscous and frictional heating phase change, and temperature and viscosity variations in the film. A numerical scheme that utilizes the influence coefficient method to calculate the face deformations has been developed. This scheme considerably reduces computation time while still maintaining the accuracy of the results. Numerical results obtained through parametric studies show good agreement with available test data.Presented at the 52nd Annual Meeting in Kansas City, Missouri May 18–22, 1997

ISSN:1040-2004    

DOI:10.1080/10402009708983705

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This paper begins, with a discussion on the limitations of the bearing lubrication parameter, i.e., the Lambda ratio, as well as the variables which influence surface fatigue of rolling bearings, based on close examination of results of bearing tests and peeling tests. Since most rolling bearings in service operate in the “low Lambda” regime, the maximum stress in the microcontact of asperities can be much higher than that in the macrocontacts of rolling members. A localized residual stress field is generated as a result of plastic deformation in microcontact. This residual stress contains a tensile component, which is believed to be more detrimental than compressive stress. A new unified bearing surface (micropitting) failure theory is proposed based on the tensile (residual and applied) stress in the material. This theory can be used to quantify the effect of asperity contact maximum pressure, residual compressive stress, tensile hoop stress and hardness on pitting fatigue life.Presented at the 52nd Annual Meeting in Kansas City, Missouri May 18–22, 1997

ISSN:1040-2004    

DOI:10.1080/10402009708983706

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Under the influence of extreme contact pressure and high factional heating, the real contact areas of diamond films may undergo phase transformation and gradual wear during long-duration dry sliding contacts. The wear debris particles that accumulate at the contact interface can then dominate the long-term sliding friction and wear performance of these films. In this study, employing a combination of transmission electron microscopy, electron diffraction, Raman spectroscopy, and electron energy loss spectroscopy, the authors explored the structural chemistry of the diamond debris particles and the sliding contact interfaces of smooth diamond films (surface roughness: 20–40 nm, root mean square (RMS)) and described their friction and wear mechanisms in open air and dry nitrogen (N2). The results of tribological tests indicated that the friction coefficients of Si3N4balls against smooth diamond films were 0.04 in dry N2but 0.1–0.15 in air. Friction fluctuated substantially in dry N2, especially during long-duration tests. The wear rates of Si3N4balls were by factors of 5 to 6 lower in dry N2than in air, but a reverse situation was observed for diamond films; their wear rates were significantly higher in dry N2than in air. The results of the surface and structure analytical studies have suggested that the sp3-bonded crystalline diamond had transformed to a sp2-bonded amorphous state, but not to crystalline graphite.Presented at the 52nd Annual Meeting in Kansas City, Missouri May 18–22, 1997

ISSN:1040-2004    

DOI:10.1080/10402009708983707

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Large bore (150 mm) hybrid ceramic ball bearings and all-M50 steel bearings were tested with under-race lubrication to compare the heat generation and the temperature rise at speeds up to 2.25 million DN. Furthermore, oil shut-off tests were carried out with both bearings over 2.25 million DN.

ISSN:1040-2004    

DOI:10.1080/10402009708983708

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The wear mechanisms of Si-based ceramics are examined in terms of speed and load. The results are presented in wear maps which reveal different regimes of wear. This paper examines the effects of normal force and shear force on Si-based ceramic wear in the different wear regimes. In the mild wear regime, the wear processes are dominated by microabrasion and subsurface cracks. The severe wear regime is dominated by microfracture and tensile cracks on the surface. At still higher loads, surface cracks and gross fracture occur. The presence and the effects of third-body particles on the wear mechanisms are also discussed.Presented at the 50th Annual Meeting in Chicago, Illinois May 14–19, 1995

ISSN:1040-2004    

DOI:10.1080/10402009708983709

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The problem of vaporization in face seals operating on mixtures where the minority liquid is discontinuous and has the lower boiling point is analyzed. A model based on several simplifications is presented and used to solve a numerical example for water-in-oil mixtures. It is shown that even the smallest amount (in the order of 1 %) of water in the oil may considerably alter the seal performance and result in seal failure.Presented at the 52nd Annual Meeting in Kansas City, Missouri May 18–22, 1997

ISSN:1040-2004    

DOI:10.1080/10402009708983710

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor