摘要:

The squeeze film forming ability of traction fluids is studied under impact load by a falling bearing steel ball against a stationary cylindrical surface or flat anvil made of mild steel, bearing steel, or aluminum. The effect of the pressure-viscosity coefficient and of the viscosity is investigated for plastic and elastic impact.

ISSN:1040-2004    

DOI:10.1080/10402009408983306

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

This paper presents the results of a disc machine gear simulation investigating the influence of lubricant traction characteristics and formulation on the load at which scuffing occurs. Scuffing theories in general link the onset of scuffing to the amount of heat generated in the contact and the authors hypothesized that reduced heat generation with low traction lubricants should lead to an increase in scuffing load. The study compared low traction PAO-based lubricants with mineral oils in basestock, antiwear and EP formulations and at both high (>6) and moderate (approximately 1.2) specific film thickness, λ. At λ > 6, the benefits of the synthetics over their mineral counterparts ranged from 25 percent to 220 percent and at λ ˜ 1.2, the benefits were a uniform 40 percent. It was particularly interesting to observe that the antiwear PAO-based oil gave a similar scuff load per unit contact width to an EP mineral gear oil. In addition, it was shown that scuffing load decreased with increasing traction coefficient to the power of approximately − 1.85, close to the −2.00 power predicted by the frictional power intensity concept. The agreement with flash temperature theory, with a predicted power of −1.33, was less close.Presented at the 47th Annual Meeting in Philadelphia, Pennsylvania May 4–7, 1992

ISSN:1040-2004    

DOI:10.1080/10402009408983307

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A solid lubricating surface film is modeled as a general linear viscoelastic material. The appropriate governing equations are solved for the displacement of such a thin film under repeated loadings. The predicted transient motion of the surface is monitored. The gradual diminution of the lubricant film thickness under repeated loadings is considered film wear. The failure of solid lubricating film occurs when the existing thickness is to the same order of magnitude as the substrate surface roughness.Presented as a Society of Tribologists and Lubrication Engineers paper at the STLE/ASME Tribology Conference in New Orleans, Louisiana, October 24–27, 1993

ISSN:1040-2004    

DOI:10.1080/10402009408983308

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A type of jewel bearing employing two sapphire cup surfaces (one fixed and the other movable) which were in contact with a free steel ball were analyzed. This arrangement reduced wear substantially as compared to conventional jewel bearings and had more degrees of freedom. The analysis of the ordinary jewel bearing was extended to the present case in order to determine the bearing steady-state motion reached asymptotically from an arbitrary starting state. Two different steady-state motions were investigated, i.e., when the ball was motionless (stationary), and when the ball attained pure rotation with reference to the frame. In the first case, there was no relative motion at the contact area with the fixed cup, and the relative motion at the contact area with the rotating cup consisted of rolling, sliding and spinning. In the second case, the relative motion at the contact area with the fixed cup consisted of rolling, sliding and spinning and the relative motion at the contact area with the rotating cup was pure rolling. The analysis was supported and validated by numerical simulation.Presented at the 47th Annual Meeting in Philadelphia, Pennsylvania May 4-7, 1992

ISSN:1040-2004    

DOI:10.1080/10402009408983309

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The improved performance of silicon nitride components over all-steel bearings in several applications has been demonstrated. However, the effects of grain size, intergranular phase composition, fracture toughness, and hardness on rolling wear and fatigue performance are not completely understood. Three commercial bearing materials were tested under standard conditions and their physical properties were obtained. Wear and fatigue properties were compared to physical properties and material composition. It was found that a high fracture toughness is not required for high fatigue life and wear resistance. Total wear and fatigue life of the assembly must be considered, in addition to performance of the ceramic material alone, for specific applications. Grain boundary composition did not appear to affect the wear mechanism of these hot-isostatically-pressed materials.Presented at the 48th Annual Meeting in Calgary, Alberta, Canada May 17–20, 1993

ISSN:1040-2004    

DOI:10.1080/10402009408983310

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Dissipative heating in turbulent flow can be expressed in terms of a dimensionless friction coefficient Cf, which is itself determined by wall roughness and local Reynolds number and is sensitive to viscosity changes. For a short-bearing flow with a sinusoidal film thickness perturbation, viscous heating is related to film thickness in a simple way. Perturbations in temperature and viscosity are included in the analysis, which predicts the partitioning of the heat-perturbation to the wavy and smooth surfaces. Convection is discussed and shown to be less influential than in laminar flow.Presented as a Society of Tribologists and Lubrication Engineers paper at the STLE/ASME Tribology Conference in New Orleans, Louisiana, October 24–27, 1993

ISSN:1040-2004    

DOI:10.1080/10402009408983311

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A study was performed to establish the transition temperature of two additives in cetane under severe conditions of pressure × velocity, which gave a surface temperature rise within the contact of up to 150°C. The interface temperature was measured using the slider as one leg of a thermocouple and the disk as the other; hence, an accurate interface temperature could be determined as the velocity and load varied. The test specimens were M50 tool steel, AISI 52100 steel and type 440C stainless steel balls against a fully hardened tool steel disc. The results complemented previous work which showed the identical trends but at slightly different absolute temperature levels.

ISSN:1040-2004    

DOI:10.1080/10402009408983312

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The flow field inside a whirling annular seal has been measured using a 3-D Laser Doppler Anemometer (LDA) system. The seal investigated has a clearance of 1.27 mm, a length of 37.3 mm and is mounted on a drive shaft with a 50 percent eccentricity ratio. This results in the rotor whirling at the same speed as the shaft rotation (whirl ratio = 1.0). The seal is operated at a Reynolds number of 12000 and a Taylor number of 6300 (3600 rpm). The 3-D LDA system is equipped with a rotary encoding system which is used to produce phase averaged measurements of the entire mean velocity vector field and Reynolds stress tensor field from 0.13 mm upstream to 0.13 mm downstream of the seal. The mean velocity field reveals a highly three-dimensional flow field with large radial velocities near the inlet of the seal as well as a recirculation zone on the rotor surface. The location of maximum mean axial velocity migrates from the pressure side of the rotor at the inlet to the stiction side at the exit. Turbulence production is a maximum near the seal inlet as indicated by the rapid increase of the turbulence kinetic energy (κ). However, turbulence production and dissipation attain equilibrium fairly quickly with K remaining relatively constant over the last half of the seal.

ISSN:1040-2004    

DOI:10.1080/10402009408983313

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The cam-tappet of an I. C. engine is a rubbing pair with high load and severe lubrication condition. In order to raise the anti-scuffing capacity of the cam-tappet, a laser microprecision treatment was adopted to make the topography with artificial regular asperities on the working surface of tappets. It was proved by experiment rising a full-scale engine rig that the tappets treated by laser microprecision had an obvious antiscuffing effect.

ISSN:1040-2004    

DOI:10.1080/10402009408983314

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor