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  • 1
    Publikationsdatum: 2019-06-28
    Beschreibung: A new Reynolds equation was developed that takes into account the nonlinear viscous behavior of the fluid. The new Reynolds equation considers the nonlinear viscous fluid model of Eyring, the equilibrium equation, the constant mass flow, and the kinematic boundary condition. The new Reynolds equation and the elasticity equation are solved simultaneously by using a system approach and a Newton-Raphson technique. Comparisons are made with results obtained from the classical Reynolds equation. The effects of sliding speed and introducing a bump or a groove within the conjunction are studied. Results are shown for both moderate and heavy loads.
    Schlagwort(e): MECHANICAL ENGINEERING
    Materialart: NASA-TM-87097 , E-2658 , NAS 1.15:87097
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2019-06-28
    Beschreibung: Based on analytical calculations assuming isothermal elastohydrodynamic (EHD) lubrication conditions, and on curve-fitting of a thermal correction factor, a new formula is proposed to calculate the sliding traction force developed in a concentrated contact, assuming a nonlinear, viscoelastic lubricant and undirectional sliding. When sliding occurs in the rolling and transverse directions (bidimensional sliding), a simplified numerical method is outlined by which the components of the local shear stress are quickly calculated. The latter method is applied to the calculation of the shear stress and temperature distribution in the ball-raceway contacts of an angular-contact ball bearing. Because of the viscoelastic behavior of the lubricant, a nonzero lateral traction force is obtained.
    Schlagwort(e): MECHANICAL ENGINEERING
    Materialart: ASME PAPER 84-TRIB-26
    Format: text
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  • 3
    Publikationsdatum: 2019-07-13
    Beschreibung: The film thicknesses and pressures in elastohydrodynamically lubricated contacts have been calculated for a line contact by using an improved version of Okamura's approach. The new approach allows for lubricant compressibility, the use of Roelands' viscosity, a general mesh (nonconstant step), and accurate calculations of the elastic deformation. The new approach is described, and the effects on film thickness, pressure, and pressure spike of each of the improvements are discussed. Successful runs have been obtained at high pressure (to 4.8 GPa) with low CPU times.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA-TM-87032 , E-2581 , NAS 1.15:87032 , Joint Lubrication Conf.,; Oct 08, 1985 - Oct 10, 1985; Atlanta, GA; United States
    Format: application/pdf
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  • 4
    Publikationsdatum: 2019-07-12
    Beschreibung: The film thicknesses and pressures in elastohydrodynamically lubricated contacts have been calculated for a line contact by using an improved version of Okamura's approach. The new approach allows for lubricant compressibility, the use of Roelands' viscosity, a general mesh (nonconstant step), and accurate calculations of the elastic deformation. The new approach is described, and the effects on film thickness, pressure, and pressure spike of each of the improvements are discussed. Successful runs have been obtained at high pressure (to 4.8 GPa) with low CPU times.
    Schlagwort(e): MECHANICAL ENGINEERING
    Materialart: ASME PAPER 85-TRIB-42 , ASME, Transactions, Journal of Tribology (ISSN 0742-4787); 108; 411-419;
    Format: text
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  • 5
    facet.materialart.
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    In:  Other Sources
    Publikationsdatum: 2019-07-12
    Beschreibung: New Reynolds equation developed for elastohydrodynamic-lubrication analysis. Method developed to study macro- and micro-EHL, without restriction on load applied to contact. Macro-EHL refers to lubricantfilm thickness developed in inlet zone of EHL conjunction. Powerful tool used to study scuffing. Using new approach, researchers have analyzed stress concentrations near both bump and groove in bearing surface.
    Schlagwort(e): MECHANICS
    Materialart: LEW-14364 , NASA Tech Briefs (ISSN 0145-319X); 10; 4; P. 91
    Format: text
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  • 6
    Publikationsdatum: 2021-02-08
    Materialart: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
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  • 7
    Publikationsdatum: 2022-01-31
    Beschreibung: To provide an observational basis for the Intergovernmental Panel on Climate Change projections of a slowing Atlantic meridional overturning circulation (MOC) in the 21st century, the Overturning in the Subpolar North Atlantic Program (OSNAP) observing system was launched in the summer of 2014. The first 21-month record reveals a highly variable overturning circulation responsible for the majority of the heat and freshwater transport across the OSNAP line. In a departure from the prevailing view that changes in deep water formation in the Labrador Sea dominate MOC variability, these results suggest that the conversion of warm, salty, shallow Atlantic waters into colder, fresher, deep waters that move southward in the Irminger and Iceland basins is largely responsible for overturning and its variability in the subpolar basin.
    Materialart: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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  • 8
    Publikationsdatum: 2023-02-08
    Beschreibung: The Atlantic Meridional Overturning Circulation (AMOC) is a key mechanism of heat, freshwater, and carbon redistribution in the climate system. The precept that the AMOC has changed abruptly in the past, notably during and at the end of the last ice age, and that it is “very likely” to weaken in the coming century due to anthropogenic climate change is a key motivation for sustained observations of the AMOC. This paper reviews the methodology and technology used to observe the AMOC and assesses these ideas and systems for accuracy, shortcomings, potential improvements, and sustainability. We review hydrographic techniques and look at how these traditional techniques can meet modern requirements. Transport mooring arrays (TMAs) provide the “gold standard” for sustained AMOC observing, utilizing dynamic height, current meter, and other instrumentation and techniques to produce continuous observations of the AMOC. We consider the principle of these systems and how they can be sustained and improved into the future. Techniques utilizing indirect measurements, such as satellite altimetry, coupled with in situ measurements, such as the Argo float array, are also discussed. Existing technologies that perhaps have not been fully exploited for estimating AMOC are reviewed and considered for this purpose. Technology is constantly evolving, and we look to the future of technology and how it can be deployed for sustained and expanded AMOC measurements. Finally, all of these methodologies and technologies are considered with a view to a sustained and sustainable future for AMOC observation.
    Materialart: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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  • 9
    Publikationsdatum: 2024-02-07
    Beschreibung: Changes in the Atlantic Meridional Overturning Circulation, which have the potential to drive societally-important climate impacts, have traditionally been linked to the strength of deep water formation in the subpolar North Atlantic. Yet there is neither clear observational evidence nor agreement among models about how changes in deep water formation influence overturning. Here, we use data from a trans-basin mooring array (OSNAP—Overturning in the Subpolar North Atlantic Program) to show that winter convection during 2014–2018 in the interior basin had minimal impact on density changes in the deep western boundary currents in the subpolar basins. Contrary to previous modeling studies, we find no discernable relationship between western boundary changes and subpolar overturning variability over the observational time scales. Our results require a reconsideration of the notion of deep western boundary changes representing overturning characteristics, with implications for constraining the source of overturning variability within and downstream of the subpolar region.
    Materialart: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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