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  • Other Sources  (6)
  • 1
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    Adaptive finite element analysis based on p-convergence (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The results of numerical experiments are presented in which a posteriori estimators of error in strain energy were examined on the basis of a typical problem in linear elastic fracture mechanics. Two estimators were found to give close upper and lower bounds for the strain energy error. The potential significance of this is that the same estimators may provide a suitable basis for adaptive redistribution of the degrees of freedom in finite element models.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Langley Res. Center Res. in Computerized Structural Analysis and Syn.,; p 43-50
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  • 2
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    The effect of limiting aerodynamic and structural coupling in models of mistuned bladed disk vibration (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A model has been developed for studying the effect of mistuning on bladed disk vibration which has the unique feature that the extent of aerodynamic and structural interaction which it simulates can be readily varied from full coupling of all blades on the disk to coupling of each blade with only its nearest neighbors. Simulations utilizing the resulting algorithm show that limited coupling models may be used to predict the statistical distribution of blade amplitudes that characterizes the mistuning effect, which in turn determines stage durability. This approach is used to study the effect of changing various system parameters on amplitude scatter. Gas density, the number of blades on the disk, disk stiffness, and the engine order of the excitation are considered. The results are used to draw some conclusions about how to improve laboratory tests and component design.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Format: text
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  • 3
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    A simplified model for two phase face seal design (1990)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A simplified quasi-isothermal low-leakage laminar model for analyzing the stiffness and the stability characteristics of two-phase face seals with real fluids is developed. Sample calculations with this model for low-leakage operations are compared with calculations for high-leakage operations, performed using the adiabatic turbulent model of Beatty and Hughes (1987). It was found that the seal characteristics predicted using the two extreme models tend to overlap with each other, indicating that the simplified laminar model may be a useful tool for seal design. The effect of coning was investigated using the simplified model. The results show that, for the same balance, a coned seal has a higher leakage rate than a parallel face seal.
    Keywords: MECHANICAL ENGINEERING
    Type: STLE Tribology Transactions (ISSN 0569-8197); 33; 315-324
    Format: text
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  • 4
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    Centrifugal inertia effects in two-phase face seal films (1987)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A simplified, semianalytical model has been developed to analyze the effect of centrifugal inertia in two-phase face seals. The model is based on the assumption of isothermal flow through the seal, but at an elevated temperature, and takes into account heat transfer and boiling. Using this model, seal performance curves are obtained with water as the working fluid. It is shown that the centrifugal inertia of the fluid reduces the load-carrying capacity dramatically at high speeds and that operational instability exists under certain conditions. While an all-liquid seal may be starved at speeds higher than a 'critical' value, leakage always occurs under boiling conditions.
    Keywords: MECHANICAL ENGINEERING
    Type: ASLE Transactions (ISSN 0569-8197); 30; 177-186
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  • 5
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    Adaptive Finite Element Technology in Integrated Design and Analysis (1981)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An assessment of the potential impact of adaptive finite element technology on the analysis part of the aircraft structural synthesis process is presented. The main conclusion is that adaptive application of the p-version of the finite element method based on indirect error estimation procedures results in substantial cost reduction and increased reliability of the computed data. Adaptivity based on direct a posteriori error estimation has the potential for additional savings.
    Keywords: NUMERICAL ANALYSIS
    Type: NASA-CR-164560 , WU/CCM-81/1
    Format: application/pdf
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  • 6
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    Stress corrosion in titanium alloys and other metallic materials (1971)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Multiple physical and chemical techniques including mass spectroscopy, atomic absorption spectroscopy, gas chromatography, electron microscopy, optical microscopy, electronic spectroscopy for chemical analysis (ESCA), infrared spectroscopy, nuclear magnetic resonance (NMR), X-ray analysis, conductivity, and isotopic labeling were used in investigating the atomic interactions between organic environments and titanium and titanium oxide surfaces. Key anhydrous environments studied included alcohols, which contain hydrogen; carbon tetrachloride, which does not contain hydrogen; and mixtures of alcohols and halocarbons. Effects of dissolved salts in alcohols were also studied. This program emphasized experiments designed to delineate the conditions necessary rather than sufficient for initiation processes and for propagation processes in Ti SCC.
    Keywords: MATERIALS, METALLIC
    Type: NASA-CR-139562
    Format: application/pdf
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