摘要:

Engine valve seat wear affects engine performance. A common goal for both valve and engine manufacturers is to improve both valve quality and life. By performing tests on a simulator which is verified to be capable of simulating an engine operating environment, the wear resistance of various valve materials is ranked, and the wear mechanisms are investigated.

ISSN:1040-2004    

DOI:10.1080/10402009708983647

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The rotor loss mechanisms associated with magnetic bearings have yet to be adequately characterized or quantified and thus pose a problem for the designer and user of magnetic bearings. Accurate calculations of losses associated with the operation of magnetic bearings is particularly important for high speed applications where the rotor losses are expected to be large and for aerospace applications where low power consumption of components is critical. Rotor losses in magnetic bearings are due to both windage effects and iron losses. The iron losses are the result of three different mechanisms including the generation of eddy currents and the occurrence of both alternating and rotational hysteresis effects in the magnetic material. While theoretical models for these losses exist for transformer and electric motor applications, they have not been adequately modified for magnetic bearings. This paper presents the results from a low speed experimental test rig and compares them to calculated values from a new modification of previous theory. Experimental data was taken over a range of 1.5 Hz (90 rpm) to 46.7 Hz (2800 rpm) for several bias currents, two different pole configurations, and for both a linear power amplifier and a switching power amplifier. With certain assumptions, agreement between measured and calculated power losses was within 10 percent for speed comparisons greater than 25 Hz and within 25 percent for the comparison at the 8.3 Hz speed. This body of work represents the foundation for upcoming extensive high speed tests on a larger scale.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:10.1080/10402009708983648

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In a previous paper, a simple model for failure and wear of unidirectional fiber-reinforced polymer composites was proposed. The model relates fiber stresses and sliding contact conditions to bulk wear rates for fiber orientation parallel to the sliding direction. In this work, the model has been extended to examine the case where the fibers are oriented transverse to the sliding direction, while still parallel to the plane of contact. When simulating the counterface contact with an ideal hemispherical asperity, the model overpredicts wear rates for the transverse fiber orientation. However, when the counter-face contact is simulated according to observed composite material transfer and corresponding surface topographical changes, indicating deviation from an ideal hemispherical asperity to a more general elongated or ellipsoidal form, the model correlation compares more favorably with existing friction and wear test data in the literature.Presented at the 50th Annual Meeting in Chicago, Illinois May 14–19, 1995

ISSN:1040-2004    

DOI:10.1080/10402009708983649

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In this paper an investigation is made to evaluate the experimental performance of misaligned cylindrical and three-lobe journal bearings. A three-bearing double-disc rotor system with a test bearing in the middle and driven by a variable speed DC motor through an electromagnetic coupling is used. Various parameters which have been studied are friction through coastdown analysis, unbalance response and film thickness. The system damping also has been evaluated. The film thickness decreases, friction increases and system damping increases as the bearing misalignment increases. While the first, third and fourth harmonics vibration response is found to be almost steady with a increasing degree of misalignment, the second harmonics vibration response tends to decrease slightly.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:10.1080/10402009708983650

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The efficient Newton-Raphson iterative solver is implemented for calculating the surface contact pressure under rough contact conditions. The improvement in computation efficiency is achieved by coupling the surface elastic deformation equation and the force equilibrium equation using the Newton-Raphson formulation and solving the two equations simultaneously. The developed model is first demonstrated in solving the classic Hertzian contact problem to verify the model accuracy. Results show the developed model converges extremely fast (in less than three iterations) and computation error in the contact width is within the discretization limit. For rough contact cases, the presented procedures also achieve the converged solutions rapidly; however, a relaxation factor is needed.Presented at the 51st Annual Meeting in Cincinnati, Ohio May 19–23, 1996

ISSN:1040-2004    

DOI:10.1080/10402009708983651

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A pseudospectral-finite difference solution of the thermal hydraulic flow through an infinitely wide convergent slider bearing configuration is presented. The model includes both thermal and inertial effects. The approach combines a collocation technique with orthogonal polynomial representations of velocities, temperatures and property variations through the thickness of the lubricant film with finite difference representations of derivatives in the streamwise direction. The technique is motivated by the need for general analyses of fluid film bearings which incorporate the before-mentioned effects. Results will be presented that separately demonstrate inertial and thermal effects in laminar flows.Presented at the 50th Annual Meeting in Chicago, Illinois May 14–19, 1995

ISSN:1040-2004    

DOI:10.1080/10402009708983652

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Numerical solutions are obtained for the thermoelastohydrodynamic lubrication of a tilting pad based on the three-dimensional flow of lubricant. For elastic deformation, the pad is idealized as a uniform plate with free boundaries so that a displacement coefficient matrix can be established by the conventional finite difference method. For pressure distribution, a fast Newton-Raphson's approach is used in solving the generalized Reynolds equation, film thickness equation, inlet pressure buildup equation, and the force balance and moment balance equations of the pad, simultaneously. For temperature distribution, the finite difference method is carried out with the help of a sweeping scheme.

ISSN:1040-2004    

DOI:10.1080/10402009708983653

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Increasing quantities of aluminum matrix composites (AMCs) are being used to replace conventional materials in many weight-critical fields for energy savings. More efforts are employed to improve the antiscuffing and antiwear properties of AMCs. In this paper, silicon carbide (SiC) whisker-reinforced Al-Fe-Ce (AFC) aluminum matrix composites were fabricated by a powder metallurgy method. A 440C stainless steel ball was run against the composite in a small amplitude reciprocal sliding tester at applied loads of 40 to 200 N and an average speed of 0.045 ms−1at ambient conditions. The lubricant was a liquid paraffin (LP) base oil without and with 3 wt% tricresyl phosphate (TCP), sulphurized olefin (SO) or chlorinated paraffin (CP). The composites exhibited obvious antiwear properties. The Auger electron spectroscopy and X-ray pholoelectron spectroscopy analysis showed that the iron of the composite reacted with TCP, SO and CP additives and produced antiwear films on the worn surfaces. Scanning electron microscope and optical microscopy were used to analyze the worn morphologies. The main wear mechanisms observed were ploughing and tribochemical wear when additives were used. Adhesive wear (at low loads) and severe ploughing (at high loads) were found when additives were not used.Presented at the 51st Annual Meeting in Cincinnati, Ohio May 19–23, 1996

ISSN:1040-2004    

DOI:10.1080/10402009708983654

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The traction behavior of several perfluoropolyalkylether (PFPAE) fluids is investigated. Experimental traction data obtained with a conventional rolling-disk apparatus are correlated to a Newtonian pressure-viscosity-temperature relation. Appropriate rheological constants are estimated, as a function of inlet temperature and rolling speed, from regression analysis of experimental data.Presented at the 50th Annual Meeting in Chicago, Illinois May 14–19, 1995

ISSN:1040-2004    

DOI:10.1080/10402009708983655

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A series of trialkyl carbamates of the general formula HC(Ph NHCOOCnH2n+1)3with n = 16, 18, 20 and 22 were synthesized from alkanols and tris(p-isocyanatophenyl)methane. The star-shaped compounds effectively depress the pour point of wax-containing paraffin oil. A quantity of 0.1 wt.% of the C18 derivative, by far the most effective depressant, reduces the pour point of paraffin oil containing 11.5 wt.% wax (mp 56–61° C) from 33° C to - 4°C. The extent of the depression varies with the concentration and composition of the wax. The depressants are ineffective when pure alkane waxes are added to the paraffin oil.

ISSN:1040-2004    

DOI:10.1080/10402009708983656

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor