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  • 1
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    Kinetic Study of Methyl Acetate Oxidation in a Pt/Al2O3 Fixed-Bed Reactor (1994)
    In:  CASI
    Details
    Publication Date: 2004-10-30
    Description: To support technology development for future long-term missions, a metabolic simulator will be used in a closed chamber to test the functions of a Controlled Ecological Life Support System (CELSS). Methyl acetate (MA) was selected as the fuel because its metabolic respiratory quotient is near that of humans. A kinetic study of the catalytic oxidation of MA over Pt/Al203 was then conducted to support the design and operation of the simulator. Kinetic data were obtained as a conversion percentage of MA versus retention time. The reaction was studied at one atmosphere and temperatures from 220 to 340 deg. C. The inlet MA concentration was varied from 100 to 2000 ppm with retention times from 0.01 to 10 sec. A first-order rate law and a Langmuir-Hinshelwood rate equation were tested by nonlinear regression of the kinetic data to estimate rate constants in the rate law. Regression results of the L-H equation explain the kinetic data better than the results of the first-order rate law. A Taguchi experimental design was used to study the effects of temperature, retention time, and concentrations of MA, CO2, and O2 on the conversion of MA. Results indicate that temperature has greatest effect, followed by retention time, and finally MA concentration. It was further determined that the effects of CO2 and O2 concentrations, and the cross effects, are negligible.
    Keywords: Man/System Technology and Life Support
    Type: Dual-Use Space Technology Transfer Conference and Exhibition; Volume 1; 226-235; NASA-CP-3263-Vol-1
    Format: text
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  • 2
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    Creep-fatigue interaction of titanium alloy Ti-6Al-2Cb-1Ta-0.8Mo at room temperature (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The present investigation is concerned with the mutual influence of creep and fatigue in the case of Ti-6211, which represents a new weldable, stress-corrosion resistant alloy. Attention is given to the effect of creep on fatigue, the effect of fatigue on creep, and microstructural studies. It is found that prior creep in the amounts investigated, from 0.2 percent to 2.7 percent, is beneficial to low-cycle fatigue life. Hold time at peak strain is found to be beneficial to low-cycle fatigue life. Hold time at constant stress has no effect on low-cycle fatigue when specimens are cycled only once between hold times; but increasing fatigue loading for 50 or more cycles between hold times can prolong the fatigue life. There is an acceleration of creep by cyclic loading when comparison of cyclic and static creep is based on mean stress.
    Keywords: METALLIC MATERIALS
    Format: text
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  • 3
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    Low Temperature Creep of a Titanium Alloy Ti-6Al-2Cb-1Ta-0.8Mo (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This paper presents a methodology for the analysis of low temperature creep of titanium alloys in order to establish design limitations due to the effect of creep. The creep data on a titanium Ti-6Al-2Cb-1Ta-0.8Mo are used in the analysis. A creep equation is formulated to determine the allowable stresses so that creep at ambient temperatures can be kept within an acceptable limit during the service life of engineering structures or instruments. Microcreep which is important to design of precision instruments is included in the discussion also.
    Keywords: Composite Materials
    Type: NASA-TM-104641 , NAS 1.15:104641 , Rept-97B00021
    Format: application/pdf
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  • 4
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    A matrix for evaluating Schwarz's form. (1966)
    In:  Other Sources
    Details
    Publication Date: 2019-05-30
    Description: Transformation matrix converting phase variable form into Schwartz form for application to Liapunov function and Hurwitz criterion
    Keywords: MATHEMATICS
    Type: IEEE TRANSACTIONS ON AUTOMATIC CONTROL
    Format: text
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  • 5
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    Fixed points in a transformation group. (1965)
    In:  Other Sources
    Details
    Publication Date: 2019-05-30
    Description: Proof of theorem, let /X, T, pi/ be transformation group, where X is Peano continuum with end point fixed under T
    Keywords: MATHEMATICS
    Format: text
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  • 6
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    Assessment of probability of detection of delaminations in fiber-reinforced composites (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Delamination is one of the critical defects in composite materials and structures. An ultrasonic C-scan imaging technique which maps out the acoustic impedance mismatched areas with respect to the sample coordinates, is particularly well suited for detecting and characterizing delaminations in composites. To properly interpret the results, it is necessary to correlate the indications with the detection limits and probability of detection (POD) of the ultrasonic C-scan imaging technique. The baseline information on the assessment of POD of delaminations in composite materials and structures is very beneficial to the evaluation of spacecraft materials. In this study, we review the principle of POD, describe the laboratory set-up and procedure, and present the experimental results as well as assessment of POD of delaminations in fiber reinforced composite panels using ultrasonic C-scan techniques.
    Keywords: ACOUSTICS
    Type: NASA-TM-104553 , NAS 1.15:104553 , REPT-92B00022
    Format: application/pdf
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  • 7
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    Experiments on the flow field physics of confluent boundary layers for high-lift systems (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The use of sub-scale wind tunnel test data to predict the behavior of commercial transport high lift systems at in-flight Reynolds number is limited by the so-called 'inverse Reynolds number effect'. This involves an actual deterioration in the performance of a high lift device with increasing Reynolds number. A lack of understanding of the relevant flow field physics associated with numerous complicated viscous flow interactions that characterize flow over high-lift devices prohibits computational fluid dynamics from addressing Reynolds number effects. Clearly there is a need for research that has as its objective the clarification of the fundamental flow field physics associated with viscous effects in high lift systems. In this investigation, a detailed experimental investigation is being performed to study the interaction between the slat wake and the boundary layer on the primary airfoil which is known as a confluent boundary layer. This little-studied aspect of the multi-element airfoil problem deserves special attention due to its importance in the lift augmentation process. The goal of this research is is to provide an improved understanding of the flow physics associated with high lift generation. This process report will discuss the status of the research being conducted at the Hessert Center for Aerospace Research at the University of Notre Dame. The research is sponsored by NASA Ames Research Center under NASA grant NAG2-905. The report will include a discussion of the models that have been built or that are under construction, a description of the planned experiments, a description of a flow visualization apparatus that has been developed for generating colored smoke for confluent boundary layer studies and some preliminary measurements made using our new 3-component fiber optic LDV system.
    Keywords: AERODYNAMICS
    Type: NASA-CR-197318 , NAS 1.26:197318
    Format: application/pdf
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  • 8
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    A remark on complete controllability. (1965)
    In:  Other Sources
    Details
    Publication Date: 2019-05-30
    Description: Complete controllability of particular plant
    Keywords: ELECTRONICS
    Format: text
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  • 9
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    An asymptotic solution of conical shells of constant thickness Progress report no. 6 (1965)
    In:  CASI
    Details
    Publication Date: 2019-05-29
    Description: Asymptotic solution of thin walled conical shell of revolution under lateral stress
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-71023
    Format: application/pdf
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  • 10
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    Fracture toughness of SiC/Al metal matrix composite (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: An experimental study was conducted to evaluate fracture toughness of SiC/Al metal matrix composite (MMC). The material was a 12.7 mm thick extrusion of 6061-T6 aluminum alloy with 40 v/o SiC particulates. Specimen configuration and test procedure conformed to ASTM E399 Standard for compact specimens. It was found that special procedures were necessary to obtain fatigue cracks of controlled lengths in the preparation of precracked specimens for the MMC material. Fatigue loading with both minimum and maximum loads in compression was used to start the precrack. The initial precracking would stop by self-arrest. Afterwards, the precrack could be safely extended to the desired length by additional cyclic tensile loading. Test results met practically all the E399 criteria for the calculation of plane strain fracture toughness of the material. A valid K sub IC value of the SiC/Al composite was established as K sub IC = 8.9 MPa square root of m. The threshold stress intensity under which crack would cease to grow in the material was estimated as delta K sub th = 2MPa square root of m for R = 0.09 using the fatigue precracking data. Fractographic examinations show that failure occurred by the micromechanism involved with plastic deformation although the specimens broke by brittle fracture. The effect of precracking by cyclic loading in compression on fracture toughness is included in the discussion.
    Keywords: COMPOSITE MATERIALS
    Type: International SAMPE Technical Conference; Sept. 25-28, 1989; Atlantic City, NJ; United States
    Format: text
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