摘要:

Various tests have been developed to measure the mechanical bonding or adhesion of thin coatings deposited on substrates. In the pull test, pins that have been bonded to the coating under test are pulled with increasing force normal to the coating until the coating is pulled from the substrate. For many systems, large scatter in the data is often observed due to uncontrolled defects in the interface and the brittle nature of the pull test.

ISSN:1040-2004    

DOI:10.1080/10402009408983296

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Wear of ceramics occurs in two major modes, i.e., tribochemical wear and microscopic fracture wear. The present paper discusses the possibility of a fracture-mechanics approach to the latter, which is responsible for detrimental surface damage. A longitudinal contact-point model is employed, and stress intensity at wear cracks is evaluated by three-dimensional finite element analysis. It is revealed that, when a contact point passes over an L-shaped crack which is composed of a vertical and an interconnected horizontal rectangular component or a horizontal rectangular subsurface crack, amplitudes of the Mode II stress-intensity factor having a considerable magnitude are predicted. A brief review of literature on fatigue of ceramics suggests that wear cracks could grow under reasonable loading conditions, and that growth should occur more readily when the absence of the toughening mechanisms with small cracks is taken into account.Presented at the 48th Annual Meeting in Calgary, Alberta, Canada May 17–20, 1993

ISSN:1040-2004    

DOI:10.1080/10402009408983297

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A recently formulated hypothesis relates the viscosity of polydimethylsiloxane (PDMS) additives to neutral, profoamant, or antifoamant performance in esters. At ten parts-per-million of PDMS addition, very low viscosity PDMS additives are hypothesized as neutral or ineffectual, due to solubility in the ester. Intermediate viscosity PDMS additives are profoamant due to increased surface activity attributed to more limited solubility of the partially miscible PDMS in esters, and Lewis acid-base interaction of the siloxaneester couple. High viscosity dispersed particulate polydimethylsiloxanes are antifoamant, inducing bubble collapse by a Griffith flaw mechanism. The foaming tendencies of an ester are related here to varying concentrations of PDMS of intermediate viscosities, i.e., 500, 1000, and 5000 mm2s−1(cSt), which are similarly neutral, profoamant, and antifoamant as concentration is increased. The hypothesis proposed is supported by the observations reported and provides a basis for a more complete understanding of observed foaming behavior.Presented at the 48th Annual Meeting in Calgary, Alberta, Canada May 17–20, 1993

ISSN:1040-2004    

DOI:10.1080/10402009408983298

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Tlie resistance to cavitation erosion of aluminum alloy, and cast and sinte-red lead-bronze, materials which are most frequently used for engine bearings, has been evaluated. The tests were carried out in motor oil at a temperature of 80°C, using a magnetostrictive vibratory tester (20 kHz). The results showed that the cavitation erosion resistance was the greatest in cast lead-bronze. On the contrary, sintered lead-bronze, though of the same chemical composition, had the greatest erosion rate. Additionally, the investigation of the overlay plated bearings showed the overlay was nonresistive to this type of wear.

ISSN:1040-2004    

DOI:10.1080/10402009408983299

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

This paper deals with microgeometrically-determined cavitation in oscillating slider bearings. After explaining the difference in the origin of cavitation in journal and linear bearings, the theoretical idea of a computer simulation program on the basis of a combined microhydrodynamic/solid-solid-contact approach is introduced. With the help of this program, slider surface geometry, inertia effects, lubricant properties, normal load, and lubricant film temperatures were found as parameters of microcavitation.

ISSN:1040-2004    

DOI:10.1080/10402009408983300

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A transient analysis for a dent passing through the conjunction of a point EHL contact was developed and solved numerically by using the multigrid method. Results show that the presence of sliding produces a noticeable pressure ridge and thus, a surface indentation at either leading side of the dent if the dent moves slower than the opposite surface, or at the trailing side if the dent moves faster than the opposite surface. The pressure ridge and surface indentation extend their lengths forward or backward from the dent in the sliding direction at a rate approximately half the sliding speed. The pressure fluctuation associated with the dent increases with increasing slide-to-roll ratio and dent depth, and decreases with increasing dent width in both x- and y-directions. The agreement between numerical simulation and experimental results obtained by Wedeven and Cusano (I) is remarkably close.Presented at the 48th Annual Meeting in Calgary, Alberta, Canada May 17–20, 1993

ISSN:1040-2004    

DOI:10.1080/10402009408983301

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

This paper describes the finite-element solution of the nonlinear and coupled hydrodynamic and thermal equations for pressure and temperature profiles in an oil seal including misalignment. Fluid properties are evaluated at the center of each element. For centered seals, results obtained are in good agreement with previous finite-difference analysis with approximate temperature distribution. For eccentric or axially tapered seals, use of the true temperature profile gives significantly different results. This analysis shows that the circumferential temperature variation should be considered in oil seal analysis and that reducing clearance taper produces a stabilizing effect.Presented at the 48th Annual Meeting in Calgary, Alberta, Canada May 17–20, 1993

ISSN:1040-2004    

DOI:10.1080/10402009408983302

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Variable axial land geometry dampers can significantly alter the unbalance response, and in particular, the likelihood of undesirable jump behavior, of circular orbit-type squeeze film dampers. Assuming end feed, the pressure distribution, the fluid film forces, and the stiffness and damping coefficients are obtained for such variable axial land geometry dampers, as well as the jump-up propensity for vertical squeeze film damped rigid rotors. It is shown that variable land geometry dampers can reduce the variation of stiffness and damping coefficients, thereby reducing the degree of damper force non-linearity, and presumably reducing the likelihood of undesirable bistable operation. However, it is also found that regardless of unbalance and regardless of the depth, width or shape of the profile, parallel land dampers are least likely to experience jump-up to undesirable operation modes. These conflicting conclusions may be accounted for by the reduction in damping. They will need to be qualified for practical dampers which normally have oil hole feed rather than end feed.Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference in San Diego, California, October 19–21, 1992

ISSN:1040-2004    

DOI:10.1080/10402009408983303

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The friction loss of gears and its quantitative estimation are important problems because of their relevance to energy conservation and load-carrying capacity. Recent research results do not provide satisfactory estimates of friction loss of spur gears. Therefore, the authors carried out experiments to study the influences of lubricating oil viscosity and additives, as well as base oil type and load and rotational speed on friction loss of spur gears. Base oil types used were paraffin mineral, poly-α-olefin, and polyglycol with several oil viscosities. An EP and a mild EP additive were studied in these oils. Finally, the temperature rise of teeth of gears as a function of friction power loss was investigated, and an empirical formula for calculating the temperature rise of the spur gear teeth was derived.Presented at the 48th Annual Meeting in Calgary, Alberta, Canada May 17–20, 1993

ISSN:1040-2004    

DOI:10.1080/10402009408983304

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A test program to determine the relative slitting durability of an alumina-silica candidate ceramic fiber for high temperature sliding seal applications is described. Pin-on-disk tests were used to evaluate the potential seal material by sliding a tow or bundle of the candidate ceramic fiber against a superalloy test disk. Friction was measured during the tests and fiber wear, indicated h the extent of fibers broken in the tow or bundle, was measured at the end of each test. Test variables studied included ambient temperature from 25° to 900°C, loads from 1.3 to 21.2 N, and sliding velocities from 0.025 to 0.25 m/sec. In addition, the effects of fiber diameter and elastic modulus on friction and wear were measured. Thin gold films deposited on the superalloy disk surface were evaluated in an effort to reduce friction and wear of the fibers.

ISSN:1040-2004    

DOI:10.1080/10402009408983305

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor