摘要:

Results from particle squashing tests designed to simulate the process of rolled in lubricant debris in rolling element bearings, are presented and showed to compare well with an earlier published theory. Measurements of the harder anvils after squashing various hard particles confirm our earlier theoretical results, that even very soft debris materials can cause plastic deformation in the hard counterfaces.

ISSN:1040-2004    

DOI:10.1080/10402008908981890

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

It is customary in tribological research, and especially in practice, to employ smooth surfaces, for it is generally believed that smooth surfaces should have low sliding friction. However the wear particles produced during sliding get trapped at the interfaces, and plowing by the wear particles becomes the principal mechanism of friction. Through experimental and theoretical investigations, it is shown that the plowing friction component can be substantially reduced by means of surface undulations. Steel-titanium and titanium-titanium pairs were tested to investigate the role of surface undulations in boundary lubricated sliding. Compared with the experimental results of flat titanium surfaces, friction coefficient and wear rate were considerably reduced with the undulated titanium surfaces, especially when lubricants considered ineffective for titanium were used. In addition, the effects of pad width and cavity volume fraction of the undulated surface were also investigated. A plowing model proposed for boundary lubricated sliding is in good agreement with experimental results. It is suggested, furthermore, that the undulated surfaces provide an effective means of investigating many important effects of lubricants which are masked by the wear particles.

ISSN:1040-2004    

DOI:10.1080/10402008908981891

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This study determines the journal motion trajectories using nonlinear equations of motion including the deformation of the bearing shell. Trajectories and time displacement plots are drawn to investigate the effect of bearing deformation on the dynamic performance of the journal bearing system. The study reveals the important changes in the dynamic response of the journal bearing system if inherent bearing flexibility is accounted in the analysis. The study, interestingly finds the improved stability margin for the journal system when elastic nature of the bearing is considered.

ISSN:1040-2004    

DOI:10.1080/10402008908981892

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Temperature has been shown to be a key factor in the performance of rolling and sliding contacts. In normal bearing operation, contact areas on the bearing ball (or roller) and race are briefly heated due to ball or roller slip then cooled from convection to the surrounding medium. After numerous repetitive heating and cooling cycles, the bearing elements attain a steady state temperature that is dependent upon the heat input and the surrounding convective conditions.

ISSN:1040-2004    

DOI:10.1080/10402008908981893

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A study was performed wing a finite element model to compare the stresses, strains and deformations of repeated, two-dimensional, rolling-sliding contact for an elastic-kinematic-hardening-plastic (ELKP) representation of rail steel with those produced by elastic-perfectly plastic (EPP) material behavior. Kinematic-hardening produces fully reversed stress-strain hysteresis loops, and thus, no forward flow. Stresses, strain increments, and displacements are drastically reduced by the kinematic-hardening plasticity.Presented at the 43rd Annual Meeting in Cleveland, Ohio May 9–12, 1988

ISSN:1040-2004    

DOI:10.1080/10402008908981894

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A hydrostatic bearing flow restrictor was developed which accommodates large clearance changes. Essentially a miniature bearing land itself, the land-in-pocket or LIP restrictor has maintained a relatively constant pressure ratio over a four-fold clearance variation encountered in a high speed journal bearing. In addition, the LIP restrictor provides improved stiffness characteristics when compared with conventional fixed orifice and capillary restrictors. Also, the LIP restrictor-bearing system is tolerant of inlet viscosity variations. Dynamic data were obtained from a journal bearing equipped with conventional orifice and LIP restrictors on a high speed homopolar generator system tester which agree well with bearing model predictions.Presented at the 43rd Annual Meeting in Cleveland, Ohio May 9–12, 1988

ISSN:1040-2004    

DOI:10.1080/10402008908981895

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Demanding tribological properties are required of the materials used for the sliding seal between the sidewalls and the lower wall of the advanced hypersonic engine. Temperatures range from room temperature and below to operating temperatures of 1000°C in an environment of air, hydrogen and water vapor. A candidate sealing material for this application is an alumina-boria-silicate, ceramic, fabric rope sliding against the engine walls which may be made from copper or nickel based alloys. Using a pin-on-disk tribometer, the friction and wear properties of some of these potential materials and possible lubrication methods are evaluated. The ceramic fabric rope displayed unacceptably high friction coefficients (0.6 to 1.3) and, thus, requires lubrication. Sputtered thin films of gold, silver and calcium fluoride reduced the friction by a factor of two. Sprayed coatings of boron nitride did not effectively lubricate the fabric. Static heat treatment tests at 950°C indicate that the fabric may be chemically attacked by large quantities of silver, calcium fluoride and boron nitride. Sputtered films or powder impregnation of the fabric with gold may provide adequate lubrication up to 900—1000°C without showing any chemical attack.Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Baltimore, Maryland, October 16–19, 1988

ISSN:1040-2004    

DOI:10.1080/10402008908981896

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The unlubricated sliding wear of an alumina-silicon carbide whisker composite (20 volume percent whiskers) has been investigated in air at 20, 400, and 800°C. Mild wear was observed in room-temperature pin-on-disc tests at sliding velocities of 0.1 and 0.5 m/s for contact stresses up to 75 MPa. At a velocity of 0.5 m/s and a contact stress of 50 MPa. a transition to severe wear occurs after 6 to 8 km of sliding. Severe wear begins within the first kilometer of sliding at 400°C, while at 800°C mild wear results at stresses as great as 150 MPa. The severe wear debris produced at 400°C was examined by analytical electron microscopy (AEM) techniques and found to consist primarily of particles of Al2O3and SiC in the 10- to 50-nm-size range. The mild wear process at 800°C did not produce any significant debris, but did show evidence of surface chemical reaction. Auger analysis of the surface showed the wear track to be covered by a mixture of aluminum and silicon oxides and the exposed silicon carbide whisker surfaces to be oxidized.Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Baltimore, Maryland, October 16–19, 1988

ISSN:1040-2004    

DOI:10.1080/10402008908981897

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Hard nitride and carbide coatings of Ti, Zr, and Hf were deposited by physical vapor deposition processes on high-speed steel cutting tools to determine their effectiveness in improving the wear properties of the inserts and increasing cutting-tool performance. A collaborative research program involving industrial, university, and government laboratories was established to develop coating processes and tool wear models, to characterize the coating properties and the effect of process parameters on the coaling properties, and to evaluate the cutting performance of coated inserts. Two coating processes were selected for investigation: high-rate reactive sputtering and activated reactive evaporation. The lifetimes of coated inserts were extended 2 to 10 times, depending on the coating composition and process. Analysis of the wear modes that occurred during the cutting tests indicated that the coatings failed by fracture after plastic deformation of the underlying substrate occurred as a result of substrate softening at the high cutting speeds.Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Baltimore, Maryland, October 16–19, 1988

ISSN:1040-2004    

DOI:10.1080/10402008908981898

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A research program had been initiated to improve the analysis used for the design of spring-mounted, sector-pad thrust bearings by introducing a full thermohydrodynamic lubrication model. As part of this research program, the present study compared finite difference methods involving control volume and Taylor series formulations for the numerical analysis of thermohydrodynamic lubrication. A plane inclined surface bearing of infinite width was selected to illustrate the comparison. Detailed representations of both methods were presented along with five case studies and a total of nineteen thermohydrodynamic solutions. Based on our results, no significant differences in accuracy or computational effort were noted for the two solution methods. However, the control volume formulation did give slightly more accurate results for coarse calculation grids and handled situations involving backflow without difficulty. Thus, the present, authors gave a mild recommendation for selecting a control, volume formulation.Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in Baltimore, Maryland, October 16–19, 1988

ISSN:1040-2004    

DOI:10.1080/10402008908981899

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor