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  • 1980-1984  (7)
  • 1
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    Thermal and thermomechanical effects in dry sliding (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Developments in the study of interrelated thermal and mechanical phenomena in sliding systems are reviewed. The topics reviewed include mechanisms of frictional heating and the distribution of heat during sliding friction, the experimental measurement and analysis of surface and near-surface temperatures resulting from frictional heating, thermal deformation around sliding contacts and the changes in contact geometry caused by thermal deformation and thermoelastic instability, and the thermomechanical stress distribution around the frictionally heated and thermally deformed contact spots. The influence of the thermal and thermomechanical contact phenomena on friction and wear, surface melting, softening, chemical deterioration, and thermocracking are discussed. The phenomena have important implications in the design and application of sliding or sliding-rolling mechanical components such as dynamic seals, brakes, clutches, plastic bearings, solid or boundary-lubricated bearings, and gears.
    Keywords: MECHANICAL ENGINEERING
    Type: Wear (ISSN 0043-1648); 100; 453-476
    Format: text
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  • 2
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    Thermomechanical phenomena in high speed rubbing (1980)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: An analytical approach is presented for the modeling of the thermomechanical interactions which occur in high speed sliding situations. These sliding contact problems which are characterized by active and interrelated thermal and mechanical phenomena could be called 'rub energetics' problems. Analytical models were developed to simulate two different rub situations: high energy braking of disk brakes and high speed rubs of gas path seals in turbine engines. The models proved to be particularly useful in predicting the severe temperatures and deformations near hot contact patches on the rubbing surfaces. The size of the hot patches is generally determined by normal load and the properties of the contacting materials. Temperatures at the contact patches can approach the melting point of the materials, especially at high sliding velocities. These high temperatures can lead to large amounts of near-surface deformation and high wear rates. Decreased contact temperatures can result from using materials with increased thermal conductivity and increased heat capacity or choosing mechanical properties (decreased stiffness, yield stress or coefficient of thermal expansion) which give larger hot spot size.
    Keywords: MECHANICAL ENGINEERING
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  • 3
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    Analytical and experimental investigation of rubbing interaction in labyrinth seals for a liquid hydrogen fuel pump (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Cracking of the titanium knife edges on the labyrinth seals of the liquid hydrogen fuel pump in the Space Shuttle main engine is considered. Finite element analysis of the thermal response of the knife edge in sliding contact with the wear ring surface shows that interfacial temperatures can be quite high and they are significantly influenced by the thermal conductivity of the surfaces in rubbing contact. Thermal shock experiments on a test specimen similar to the knife edge geometry demonstrate that cracking of the titanium alloy is possible in a situation involving repeated thermal cycles over a wide temperature range, as might be realized during a rub in the liquid hydrogen fuel pump. High-speed rub interaction tests were conducted using a representative knife edge and seal geometry over a broad range of interaction rates and alternate materials were experimentally evaluated. Plasma-sprayed aluminum-graphite was found to be significantly better than presently used aluminum alloy seals from the standpoint of rub performance. Ion nitriding the titanium alloy knife-edges also improved rub performance compared to the untreated baseline.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-174657 , NAS 1.26:174657 , CREARE-TN-371
    Format: application/pdf
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  • 4
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    Determination of near-surface plastic deformation in sliding contacts (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: It is pointed out that substantial plastic deformation occurs on and near the contact surfaces, when two solid bodies slide against each other without lubrication. It has been found that this deformation plays an important role in the tribological behavior of the sliding contact. The present investigation has the objective to develop an analytical model to predict the near-surface plastic deformation resulting from a single pass of one metallic surface over another. A finite element viscoplasticity program was written relating velocities to forces in a two-dimensional domain. The program was employed in the study of plastic deformation during a single pass of a hardened tool steel slider over a copper rub specimen. It was found that essentially the only material set in motion by the slider was directly under the contact zone. The agreement between values obtained in the analysis and experimental data is reasonably good.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME, Transactions, Journal of Applied Mechanics (ISSN 0021-8936); 51; 687-689
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  • 5
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    Single-pass rub testing of abradable seal materials (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A pendulum-type test device has been built for use in studying rubs between a turbine or compressor blade tip or labyrinth seal knife edge and specimens of abradable gas path seal materials. The device allows measurement of the rub energy dissipated in a single wear event, along with friction and normal forces and wear. Subsequent rubs over the same surface can also be monitored, with microscopic observation of the rub surface being possible after any of the passes. The device was used in tests of several potential abradable materials, ranging from porous to fully dense. It was shown that the rub energy dissipated in initial and subsequent passes is a fundamental parameter in the evaluation of material abradability. Rub energy was found to be influenced by such factors as: density and tensile (or yield) strength of the abradable material, prior densification or work hardening of the rub surface, and the sharpness of the leading edge of the blade tip.
    Keywords: METALLIC MATERIALS
    Type: ASLE PREPRINT 81-AM-1D-1 , Annual Meeting; May 11, 1981 - May 14, 1981; Pittsburgh, PA
    Format: text
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  • 6
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    Single pass rub phenomena - Analysis and experiment (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An experimental and analytical investigation is presented of contact phenomena for the case of a fully-dense copper gas path seal segment which is rubbed by a single steel blade tip at room temperature. The experiments were executed on a pendulum-type test device, with forces, rub energy, surface temperature and residual deformation being determined for each single-path rub test. The thermal and mechanical factors influencing single-pass rub surface temperatures were modeled analytically. It is found that large plastic strains occurred on or near the contact surface of the copper rub specimens. A study of the influence of various material properties on surface temperature showed that increased thermal conductivity of the stationary component played a role in lowering contact temperatures. Increased thermal conductivity of the moving blade tip component and increased thermal diffusivity of the stationary material also had a beneficial effect.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME PAPER 81-LUB-55 , Joint Lubrication Conference; Oct 05, 1981 - Oct 07, 1981; New Orleans, LA
    Format: text
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  • 7
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    Surface temperatures in sliding systems - A finite element analysis (1980)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Finite element equations are developed for studying surface temperatures resulting from frictional heating in sliding systems. The equations include the effect of velocity of moving components, an effect which is found to be quite significant, even at low sliding velocities. A program was written using the equations and it was applied to the study of surface temperatures in two different sliding systems: dry or boundary lubricated sleeve bearings and a labyrinth gas path seal configuration. Very good agreement was achieved between analytical predictions using the program and experimental temperature measurements. The program was used to study the influence of various material parameters on surface temperatures in the two sliding systems.
    Keywords: ENGINEERING (GENERAL)
    Type: ASME PAPER 80-C2/LUB-28 , Century 2 International Lubrication Conference; Aug 18, 1980 - Aug 21, 1980; San Francisco, CA; US
    Format: text
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