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  • 1
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    Some aspects of algorithm performance and modeling in transient thermal analysis of structures (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The status of an effort to increase the efficiency of calculating transient temperature fields in complex aerospace vehicle structures is described. The advantages and disadvantages of explicit and implicit algorithms are discussed. A promising set of implicit algorithms with variable time steps, known as the GEAR package is described. Four test problems, used for evaluating and comparing various algorithms, were selected and finite element models of the configurations are described. These problems include a space shuttle frame component, an insulated cylinder, a metallic panel for a thermal protection system, and a model of the space shuttle orbiter wing. Results generally indicate a preference for implicit oer explicit algorithms for solution of transient structural heat transfer problems when the governing equations are stiff.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Computational Aspects of Heat Transfer in Struct.; p 91-98
    Format: application/pdf
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  • 2
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    The SPAR thermal analyzer: Present and future (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The SPAR thermal analyzer, a system of finite-element processors for performing steady-state and transient thermal analyses, is described. The processors communicate with each other through the SPAR random access data base. As each processor is executed, all pertinent source data is extracted from the data base and results are stored in the data base. Steady state temperature distributions are determined by a direct solution method for linear problems and a modified Newton-Raphson method for nonlinear problems. An explicit and several implicit methods are available for the solution of transient heat transfer problems. Finite element plotting capability is available for model checkout and verification.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Computational Aspects of Heat Transfer in Struct.; p 35-50
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  • 3
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    Evaluation of the SPAR thermal analyzer on the CYBER-203 computer (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The use of the CYBER 203 vector computer for thermal analysis is investigated. Strengths of the CYBER 203 include the ability to perform, in vector mode using a 64 bit word, 50 million floating point operations per second (MFLOPS) for addition and subtraction, 25 MFLOPS for multiplication and 12.5 MFLOPS for division. The speed of scalar operation is comparable to that of a CDC 7600 and is some 2 to 3 times faster than Langley's CYBER 175s. The CYBER 203 has 1,048,576 64-bit words of real memory with an 80 nanosecond (nsec) access time. Memory is bit addressable and provides single error correction, double error detection (SECDED) capability. The virtual memory capability handles data in either 512 or 65,536 word pages. The machine has 256 registers with a 40 nsec access time. The weaknesses of the CYBER 203 include the amount of vector operation overhead and some data storage limitations. In vector operations there is a considerable amount of time before a single result is produced so that vector calculation speed is slower than scalar operation for short vectors.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Computational Aspects of Heat Transfer in Struct.; p 405-424
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  • 4
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    Chemical vapor deposition coatings for oxidation protection of titanium alloys (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Results of an experimental investigation of the oxidation protection afforded to Ti-14Al-21Nb and Ti-14Al-23Nb-2V titanium aluminides and Ti-17Mo-3Al-3Nb titanium alloy by aluminum-boron-silicon and boron-silicon coatings are presented. These coatings are applied by a combination of physical vapor deposition (PVD) and chemical vapor deposition (CVD) processes. The former is for the application of aluminum, and the latter is for codeposition of boron and silicon. Coating thickness is in the range of 2 to 7 microns, and coating weights are 0.6 to 2.0 mg/sq cm. Oxidation testing was performed in air at temperatures to 1255 K in both static and hypersonic flow environments. The degree of oxidation protection provided by the coatings is determined from weight change measurements made during the testing and post test compositional analyses. Temperature-dependent total normal emittance data are also presented for four coating/substrate combinations. Both types of coatings provided excellent oxidation protection for the exposure conditions of this investigation. Total normal emittances were greater than 0.80 in all cases.
    Keywords: CHEMISTRY AND MATERIALS (GENERAL)
    Type: In: Damage and oxidation protection in high temperature composites. Vol. 1; Proceedings of the Symposium, 112th ASME Winter Annual Meeting, Atlanta, GA, Dec. 1-6, 1991 (A93-53937 23-24); p. 1-8.
    Format: text
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  • 5
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    The effectiveness of multi-layer insulation as meteoroid and orbital debris shielding (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: This paper presents the results of a study of the penetration resistance of Type I Multi-Layer Insulation (MLI) to meteoroid and orbital debris particles. Hypervelocity impact tests on MLI were performed and the collected data was compared to data and empirical equations developed for aluminum. The study results indicate that MLI can be an effective shield from meteoroids and orbital debris for short duration missions and for non-critical elements. However, long missions which require high levels of protection cannot rely on MLI without a thorough investigation of the overall system reliability.
    Keywords: CHEMISTRY AND MATERIALS (GENERAL)
    Type: AIAA PAPER 92-1460
    Format: text
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  • 6
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    Studies of implicit and explicit solution techniques in transient thermal analysis of structures (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Studies aimed at an increase in the efficiency of calculating transient temperature fields in complex aerospace vehicle structures are reported. The advantages and disadvantages of explicit and implicit algorithms are discussed and a promising set of implicit algorithms with variable time steps, known as GEARIB, is described. Test problems, used for evaluating and comparing various algorithms, are discussed and finite element models of the configurations are described. These problems include a coarse model of the Space Shuttle wing, an insulated frame tst article, a metallic panel for a thermal protection system, and detailed models of sections of the Space Shuttle wing. Results generally indicate a preference for implicit over explicit algorithms for transient structural heat transfer problems when the governing equations are stiff (typical of many practical problems such as insulated metal structures). The effects on algorithm performance of different models of an insulated cylinder are demonstrated. The stiffness of the problem is highly sensitive to modeling details and careful modeling can reduce the stiffness of the equations to the extent that explicit methods may become the best choice. Preliminary applications of a mixed implicit-explicit algorithm and operator splitting techniques for speeding up the solution of the algebraic equations are also described.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TP-2038 , L-15245 , NAS 1.60:2038
    Format: application/pdf
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  • 7
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    Non-catalytic coatings for hypersonic vehicle applications (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: CVD coatings of boron-oxygen-silicon and aluminum-boron-oxygen and silicon compositions were applied to alpha 2 and gamma titanium-aluminide alloys, and tested under simulated earth reentry conditions to evaluate oxidation protection, recombination effifiency and total emittance under cyclic exposures between temperatures of 300 and 1255 K. The degree of oxidation protection afforded to the alloys was evaluated from the amount of specimen weight gain after a 100 hour exposure to air at atmospheric pressure and at a temperature of 1255 K. Data are presented for two types of coatings, a monolithic and a multilayer, which have recombination efficiencies from 0.005 to 0.020 after ten one-half hour long simulated reentry cycles. Total normal emittance was 0.80 or greater and weight gain was less than 10 g/sq m both coating types. Compositional and morphological changes resulting from the exposures are discussed in relation to time-dependent variations in recombination efficiency.
    Keywords: CHEMISTRY AND MATERIALS (GENERAL)
    Type: AIAA PAPER 90-1742
    Format: text
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  • 8
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    Some aspects of algorithm performance and modeling in transient analysis of structures (1981)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The status of an effort to increase the efficiency of calculating transient temperature fields in complex aerospace vehicle structures is described. The advantages and disadvantages of explicit algorithms with variable time steps, known as the GEAR package, is described. Four test problems, used for evaluating and comparing various algorithms, were selected and finite-element models of the configurations are described. These problems include a space shuttle frame component, an insulated cylinder, a metallic panel for a thermal protection system, and a model of the wing of the space shuttle orbiter. Results generally indicate a preference for implicit over explicit algorithms for solution of transient structural heat transfer problems when the governing equations are stiff (typical of many practical problems such as insulated metal structures).
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-83190 , ASME Winter Ann. Meeting; Nov 15, 1981 - Nov 20, 1981; Washington, DC; United States
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