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  • 1
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    Mode I fracture behavior of nonlinear materials (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: A finite element analysis is presented for the Mode I fracture behavior of cracked plates (stationary crack) made of different nonlinear materials (elastoplastic or elastic locking). The assumed stress-strain behavior of the nonlinear materials was piecewise linear. For each given 'stationary' crack size, the corresponding critical remote tensile stress was calculated based on the maximum crack-tip stress failure criterion. It was found that in the log-log plots of the critical remote stress versus critical crack length, the fracture data of the piecewise linear materials obey a 'stepwise-linear-inverse-square-root' fracture law. It is also shown how the fracture data of the piecewise linear materials can be fitted by proper piecewise graphical shifting of the classical 'inverse-square-root' fracture curve for the linearly elastic materials.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal of Fracture; 16; June 198
    Format: text
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  • 2
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    Reentry heat transfer analysis of the space shuttle orbiter (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A structural performance and resizing finite element thermal analysis computer program was used in the reentry heat transfer analysis of the space shuttle. Two typical wing cross sections and a midfuselage cross section were selected for the analysis. The surface heat inputs to the thermal models were obtained from aerodynamic heating analyses, which assumed a purely turbulent boundary layer, a purely laminar boundary layer, separated flow, and transition from laminar to turbulent flow. The effect of internal radiation was found to be quite significant. With the effect of the internal radiation considered, the wing lower skin temperature became about 39 C (70 F) lower. The results were compared with fight data for space transportation system, trajectory 1. The calculated and measured temperatures compared well for the wing if laminar flow was assumed for the lower surface and bay one upper surface and if separated flow was assumed for the upper surfaces of bays other than bay one. For the fuselage, good agreement between the calculated and measured data was obtained if laminar flow was assumed for the bottom surface. The structural temperatures were found to reach their peak values shortly before touchdown. In addition, the finite element solutions were compared with those obtained from the conventional finite difference solutions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Langley Research Center Computational Aspects of Heat Transfer in Struct.; p 295-325
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  • 3
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    Reentry heating analysis of space shuttle with comparison of flight data (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Surface heating rates and surface temperatures for a space shuttle reentry profile were calculated for two wing cross sections and one fuselage cross section. Heating rates and temperatures at 12 locations on the wing and 6 locations on the fuselage are presented. The heating on the lower wing was most severe, with peak temperatures reaching values of 1240 C for turbulent flow and 900 C for laminar flow. For the fuselage, the most severe heating occured on the lower glove surface where peak temperatures of 910 C and 700 C were calculated for turbulent flow and laminar flow, respectively. Aluminum structural temperatures were calculated using a finite difference thermal analyzer computer program, and the predicted temperatures are compared to measured flight data. Skin temperatures measured on the lower surface of the wing and bay 1 of the upper surface of the wing agreed best with temperatures calculated assuming laminar flow. The measured temperatures at bays two and four on the upper surface of the wing were in quite good agreement with the temperatures calculated assuming separated flow. The measured temperatures on the lower forward spar cap of bay four were in good agreement with values predicted assuming laminar flow.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Langley Research Center Computational Aspects of Heat Transfer in Struct.; p 271-294
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  • 4
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    Metal Sandwith Panel With Biaxially Corrugated Core (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Biaxially-corrugated sandwich core, formed by concurrent diffusion bonding and superplastic deformation, makes a proposed sandwich panel unusually strong and stiff. New panel should be useful where light-weight panel that resists bending is needed. Panel would have internal core consisting of multitude of hollow, truncated pyramids. Four layers of panel would be diffusion-binded at all contacting areas.
    Keywords: FABRICATION TECHNOLOGY
    Type: FRC-11026 , NASA Tech Briefs (ISSN 0145-319X); 6; 1; P. 106
    Format: text
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  • 5
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    Elastic constants for superplastically formed/diffusion-bonded corrugated sandwich core (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Formulas and associated graphs for evaluating the effective elastic constants for a superplastically formed/diffusion bonded (SPF/DB) corrugated sandwich core, are presented. A comparison of structural stiffnesses of the sandwich core and a honeycomb core under conditions of equal sandwich core density was made. The stiffness in the thickness direction of the optimum SPF/DB corrugated core (that is, triangular truss core) is lower than that of the honeycomb core, and that the former has higher transverse shear stiffness than the latter.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TP-1562 , H-1094
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  • 6
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    Comparison of structural behavior of superplastically formed/diffusion-bonded sandwich structures and honeycomb core sandwich structures (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A superplasticity formed/diffusion-bonded (SPF/DB) orthogonally corrugated core sandwich structure is discussed and its structural behavior is compared to that of a conventional honeycomb core sandwich structure. The stiffness and buckling characteristics of the two types of sandwich structures are compared under conditions of equal structural density. It is shown that under certain conditions, the SPF/DB orthogonally corrugated core sandwich structure is slightly more efficient than the optimum honeycomb core (square-cell core) sandwich structure. However, under different conditions, this effect can be reversed.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-81348
    Format: application/pdf
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  • 7
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    Radiation from an open-ended waveguide with beam equalizer - A spectral domain analysis (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A septum and an impedance matching post are used as a beam equalizer in an open-ended waveguide feed for reflectors used in satellite communications systems. The performance of this design over a frequency band is evaluated using a spectral domain approach. The computed radiation patterns in the E- and H-planes, as well as the results for the impedance match are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-30; Jan. 198
    Format: text
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  • 8
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    Compression panel studies for supersonic cruise vehicles (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Results of analytical and experimental studies are summarized for titanium, boron fiber reinforced aluminum matrix composite, Borsic fiber reinforced aluminum matrix composite, and titanium sheathed Borsic fiber reinforced aluminum matrix composite stiffened panels. The results indicate that stiffened panels with continuous joints (i.e., brazed, diffusion bonded or adhesive bonded joints) are more structurally efficient than geometrically similar panels with discrete joints (i.e., spotwelded or bolted joints). In addition, results for various types of fiber reinforced aluminum matrix stiffened panels indicate that titanium sheathed Borsic fiber reinforced aluminum matrix composite panels are the most structurally efficient. Analytical results are also presented for graphite fiber reinforced polyimide matrix composite stiffened panels and superplastically formed and diffusion bonded titanium sandwich panels.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TP-1617 , L-13525 , NAS 1.60:1617
    Format: application/pdf
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  • 9
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    Superplastically formed diffusion bonded metallic structure (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A metallic sandwich structure particularly suited for use in aerospace industries comprising a base plate, a cover plate, and an orthogonally corrugated core is described. A pair of core plates formed of a superplastic alloy are interposed between the base plate and the cover plate and bonded. Each of the core plates is characterized by a plurality of protrusions comprising square-based, truncated pyramids uniformly aligned along orthogonally related axes perpendicularly bisecting the legs of the bases of the pyramids and alternately inverted along orthogonally related planes diagonally bisecting the pyramids, whereby an orthogonally corrugated core is provided.
    Keywords: COMPOSITE MATERIALS
    Format: application/pdf
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  • 10
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    Pre-flight transient dynamic analysis of B-52 carrying Space Shuttle solid rocket booster drop-test vehicle (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: This paper concerns the transient dynamic analysis of the B-52 aircraft carrying the Space Shuttle solid-rocket booster drop-test vehicle (SRB/DTV). The NASA structural analysis (NASTRAN) finite-element computer program was used in the analysis. The B-52 operating conditions considered for analysis were (1) landing and (2) braking on aborted takeoff runs. The transient loads for the B-52 pylon front and rear hooks were calculated. The results can be used to establish the safe maneuver envelopes for the B-52 carrying the SRB/DTV in landings and brakings.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 83-2698
    Format: text
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