摘要:

The presence of hard contaminants in lubricated rolling bearings is a major cause of premature failure, for example by fatigue or by abrasive wear of rolling elements, races or cages. However, the introduction of much harder ceramic (usually silicon nitride) balls or rollers running against steel races, in the hybrid bearing concept, is likely to change the interactions of hard particulate contaminants with the bearing components.

ISSN:1040-2004    

DOI:10.1080/10402009908982291

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Polymers as lubricating oil additives can play a significant role in tribological phenomena. The main effect of the polymer addition is an increase in the lubricant viscosity and film thickness at high operating temperatures.

ISSN:1040-2004    

DOI:10.1080/10402009908982292

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

New methodology is suggested to quantify the effect of temperature on oxidative degradation and compare test results obtained at different temperatures or evaluate changes in chemical mechanisms. Assumption of the pseudo-first-order kinetics to calculate activation energies in oxidative polymerization of uninhibited 100 percent oleic triglyceride under thin film oxidation provided only semiquantitative results from available oxypolymerization data at six temperatures from 100° to 175°C. As an alternative approach, Time and Temperature Superposition (TTS) was applied to analyze the data. Several TTS forms consistent with Arrhenius equation showed much greater accuracy in determining activation energies and induction periods. Different stages of oxidative degradation were identified after the data from different temperatures were combined into one kinetic map. Kinetic maps of alkali-refined high oleic sunflower oil, fully formulated synthetic oleate-based hydraulic fluid and additive-free super refined mineral oil showed their increasing resistance to oxypolymerization. Limitations of TTS were discussed.Presented at the 53rd Annual Meeting in Detroit, Michigan May 17–21, 1998

ISSN:1040-2004    

DOI:10.1080/10402009908982293

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Many grease lubricated roller bearings operate in the starved elastohydrodynamic (EHL) regime where there is a limited supply of lubricant to the contact (1). Under these conditions the film thickness drops to a fraction of the fully flooded value (2) and, thus, it is difficult to predict lubrication performance, or bearing life, from conventional EHL models. In this regime film thickness depends on the ability of the grease to replenish the track rather than the usual EHL considerations. The conventional view of grease lubrication is that base oil bleeds from the bulk reservoir close to the track, replenishing the inlet and forming a fluid EHL film (3). Resupply, under starved conditions, will thus depend on both operating conditions and grease parameters. The aim of this paper is to evaluate the influence of these parameters on starved lubrication in a rolling contact. Starved film thickness has been measured for a series of greases and the results have been compared to the fully flooded values. These show that the degree of starvation increases with increasing rolling speed, base oil viscosity and thickener content but decreases at higher temperatures. In many cases an increase in absolute film thickness is obtained when moving from high viscosity base oil to a low one, this result is the reverse of normally accepted EHL rules. Taking the fully flooded film thickness as a guide to lubrication performance is therefore not valid as grease film thickness in the starved regime is determined by local replenishment rather than bulk rheological properties.Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

ISSN:1040-2004    

DOI:10.1080/10402009908982294

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A model is developed to describe the effects of adapter crown wear on the misalignment of a railroad tapered-roller bearing. Wear of the crowned surface results in a flat on top of the adapter. This flat, in contact with the wear plate, is shown to have the capacity to transmit a moment between the bearing and the side-frame of the truck. The magnitude of the moment transmitted is dependent on the length of the flat. These analytical results are coupled with model results from a bearing manufacturer, which give the relationship between bearing misalignment, and thus transmitted moment, and reduction in fatigue life of the bearing. The analysis indicates that a slightly worn adapter has no appreciable effect on the rated fatigue life of the bearing, but once a threshold level in adapter crown wear is reached, the bearing fatigue life will begin to decrease. Large amounts of adapter crown wear will result in significant bearing misalignment and a corresponding reduction in the fatigue life of the bearing.Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

ISSN:1040-2004    

DOI:10.1080/10402009908982295

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

This paper presents the results of an experimental study conducted to determine friction coefficient of J-55 tubing with eight different compounds. Four of the compounds meet the specifications of API Modified, and four were lead-free. The specimens were machined and phosphatized with manganese phosphate. The surface roughness of the specimens was nominally 1.27 micron. Repeated tests were run at a rotational speed of 1.5 rpm and 5 rpm. In each test the bearing load was increased monotonically to a maximum of 625 kN. Friction coefficient data obtained during the tests are presented and discussed.Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Confernce in in Toronto, Ontario, Canada October 26–28, 1998

ISSN:1040-2004    

DOI:10.1080/10402009908982296

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

For tribological applications of ceramics, surface temperatures and thermal effects produced in frictional processes are important not only in influencing possible mechanisms of friction, wear, and lubricant film failure but also in initiating protective film formation, e.g., as in tribopolymerization. As part of a continuing combined experimental and theoretical study of surface temperatures generated by friction, the fundamental Greens function approach has been applied to a number of ceramics including those used in tribological applications such as bearings and advanced low heat-rejection ceramic engines. The ceramics examined consisted of (a) alumina, Al2O3, (b) single crystal sapphire, Al2O3, (c) partially stabilized zirconia, ZrO2, (d) tungsten carbide, WC, (e) silicon carbide, SiC, and (f) silicon nitride, Si3N4. In addition, three forms each of silicon carbide and silicon nitride were included in this study, i.e., sintered, hot-pressed, and reaction-bonded.

ISSN:1040-2004    

DOI:10.1080/10402009908982297

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Recent engine testing on separate neutral and basic zinc dithiophosphates (ZnDTPs) showed a difference in valve train wear performance, with the neutral ZnDTP giving statistically better wear inhibition in Sequence VE tests. Since the literature was lacking on the oxidation inhibition performance of the separate neutral and basic salts, we systematically examined the relative antioxidancy of several neutral and basic ZnDTP salts in various formulations. The results were dependent on the type of base oil and formulation used, and the presence of other additives.31P NMR Spectroscopy, coupled with Oxidator Bench Test studies, were used to reach these conclusions.Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

ISSN:1040-2004    

DOI:10.1080/10402009908982298

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The antiwear performance of tricresyl phosphate dissolved in 11 kinds of base oils of different polarities has been studied. A mineral oil (MO) and an alkylnaphthalene (AN) were used as non-or low-polarity base oils. Five polyol esters (POEs), i.e., three trimethylolpropane esters and two pentaerythritol esters, and four polyalkylene glycols (PAGs) were used as the high polarity base oils. A four-ball friction apparatus was used to determine the anti-wear performance, using commercially available bearing steel balls as test specimens. All the TCP-formulated base oils showed optimum concentration characteristics for minimizing wear. It is shown that the order of the optimum concentration for POEs and PAGs can be reasonably explained by the interaction between additive and base oils, by using their solubility parameters and molecular sizes. These oils' dielectric constants showed little correlation with optimum concentrations. The dielectric constant showed large effects on such non- or low-polarity oils as MO and AN. A good correlation of the optimum concentration for all the base oils was obtained when it was arranged as a function of (SPbase/SPTCP)14.2(MWbase/MWTCP)−2.78(ε)18.6.Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

ISSN:1040-2004    

DOI:10.1080/10402009908982299

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The tilting behavior of the centrally pivoted, externally pressurized tilting thrust pad is investigated. The pressure distribution in the oil film is obtained by solving the Reynolds' equation which takes into account the external pressurization induced by a constant-rate flow. The relation between the size of the hydrostatic recess and the tilt angle of the pad is described. Calculations show that a pad with pressure recesses may have a negative tilt angle, depending on the size of the recess. The pressure variation around the hydrostatic pressure recess causes the moment to force the pad to tilt backward. At high shaft rotational speeds, the pad tilts backward too much and eventually fails to support the load. The hydrostatic pressure recess that is utilized to avoid the metal contact may cause this. The result was confirmed by experiments.Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

ISSN:1040-2004    

DOI:10.1080/10402009908982300

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor