Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Thin Section”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1947

Calculations of the Supersonic Wave Drag of Nonlifting Wings with Arbitrary Sweepback and Aspect Ratio: Wings Swept Behind the Mach Lines

On the basis of a recently developed theory for finite sweptback wings at supersonic speeds, calculations of the supersonic wave drag at zero lift were made for a series of wings having thin symmetrical biconvex sections with untapered plan forms and various angles of sweepback and aspect ratios. The results are presented in a unified form so that a single chart permits the direct determination of the wave drag for this family of airfoils for an extensive range of aspect ratio and sweepback angle for stream Mach numbers up to a value corresponding to that at which the Mach line coincides with the wing leading edge. The calculations showed that in general the wave-drag coefficient decreased with increasing sweepback. At Mach numbers for which the Mach lines are appreciably ahead of the wing leading edge, the 'wave-drag coefficient decreased to an important extent with increases in aspect ratio or slenderness ratio. At Mach numbers for which the Mach lines approach the wing leading edge (Mach numbers approaching a value equal to the secant of the angle of sweepback), the wave-drag coefficient decreased with reductions in aspect ratio or slenderness ratio. In order to check the results obtained by the theory, a comparison was made with the results of tests at the Langley Memorial Aeronautical Laboratory of sweptback wing attached to a freely falling body. The variation of the drag with Mach number and aspect ratio as given by the theory appeared to be in reasonable

Harmon, Sidney M↗
NASA NTRS2010

Curation of Antarctic Meteorites at NASA Johnson Space Center

The U.S. Antarctic meteorite program began in the 1970 s and has provided more than 18,000 samples in over three decades. The program is based on a three agency agreement between NASA, the National Science Foundation, and the Smithsonian Institution. The collection, stored at the Johnson Space Center and the Smithsonian, is one of the largest collections of meteorites in the world and features samples from the moon and Mars, asteroids, and material from the early solar system. A brief consideration of the collection shows that it contains 92.2% ordinary chondrites, 3.2% carbonaceous chondrites, 3.7% achondrites (1.7% HED), as well as many puzzling ungrouped meteorites. JSC has sent splits of nearly 20,000 meteorite samples to more than 500 scientists around the world since 1977. After the meteorites are collected in Antarctica, they are shipped frozen to JSC in Houston, usually arriving in April following the field season. The Astromaterials Curation Office at JSC is responsible for: - receiving the frozen meteorites. - staging: repackaging and changing the samples field identification numbers with official names. - submitting the names to the Nomenclature Committee of the Meteoritical Society for approval as new meteorites. - initial processing: weighing, measuring, describing and photographing the sample and providing a chip for classification to the Smithsonian Institution staff. - the issuing of two newsletters per year, announcing hundreds of new meteorites. - the handling of requests from the scientific community and the allocation of those requests that are approved. - providing supplies and tools for the field team such as teflon bags and tape, aluminum foil, clean tweezers and tongs. - maintaining the meteorite database with more than 76,000 sample splits. - making petrographic thin and thick sections for the JSC library and scientific investigators. - providing storage and handling of the meteorites in a class 10,000 clean room. Samples that have not been requested for three years are sent to the Smithsonian for permanent storage. There have been several seasons in recent years with two field teams, increasing the number of acquired samples (>1000 in a few seasons). We have recently increased our storage space and additional staff to better serve the scientific community.

McBride, K. M.↗
NASA NTRSDate not supplied

Requesting Antarctic Meteorite Samples for Research

The U.S. Antarctic meteorite program began in the 1970’s and has provided more than 24,000 samples. The program is based on a three agency agreement between NASA, the National Science Foundation, and the Smithsonian Institution. The collection, stored at the Johnson Space Center and the Smithsonian, is one of the largest collections of meteorites in the world and features samples from the moon, Mars, asteroids, and material from the early solar system. A brief overview of the collection shows it contains 92.2% ordinary chondrites (7205 H, 9126 L, 3890 LL, 146 enstatite, 30 R chondrites, 3.2% (973) carbonaceous chondrites, 3.7% (560) achondrites (1.7% HED), 118 irons, 27 pallasites, 41 mesosiderites, as well as many puzzling, ungrouped meteorites. JSC has sent splits of over 20,000 meteorite samples to more than 500 scientists around the world since 1977. After the meteorites are collected in Antarctica, they are shipped frozen to JSC in Houston, TX, arriving in April following the field season. The Astromaterials Curation Office at JSC is responsible for: - providing supplies and tools for the field team. - receiving the frozen meteorites. - staging: repackaging and changing the samples’ field identification numbers with official names. - submitting the names to the Nomenclature Committee of the Meteoritical Society for approval as new meteorites. - providing storage and handling of the meteorites in a class 10,000 clean room. - initial processing: weighing, measuring, describing, and photographing the sample and providing a chip for classification to the Smithsonian Institution staff. - the issuing of two newsletters per year, announcing hundreds of new meteorites. - the handling of requests from the scientific community and the allocation of those requests that are approved. - making petrographic thin and thick sections for the JSC library and scientific investigators. - maintaining the meteorite database with more than 76,000 sample splits.

C.E. Satterwhite↗
NASA NTRS1987

Nature and origin of mineral coatings on volcanic rocks of the Black Mountain, Stonewall Mountain and Kane Springs wash volcanic centers, southern Nevada

Mineral coatings, including desert varnish on volcanic rocks of the semi-arid Basin and Range province are composted of amorphous, translucent films of Fe, Mn, Si, and Al rich compounds. Coatings are chiefly thin films that impregnate intergranularly to depths of about 0.1 to 0.3 mm, rarely deeper. Sixteen coating sections and subsurface interiors were probed by SEM; 20 samples were scanned by infrated spectrometry; 10 samples were scanned for visible-near IR spectra; inductin coupling plasma analyses were collected on 34 samples; 2 desert varnish surgaces were investigated by optical density slice imagery; a few XRD analyses were conducted in addition to the 50 reported in the last period; thin section observation continued; and imagery processing focused on classification techniques. In late May, approximately 10 field days were spent at the Stonewall and Black Mountain study sited conducting more detailed mapping and observation base on imagery results and collecting spectra with the Collins Field Spectrometer. Approximately 100 spectral analyses were collected and are currently being processed.

Taranik, James V.↗
NASA NTRS1977

NASCAP user's manual

The NASCAP (NASA Charging Analyzer Program) code simulates the charging process for a complex object in either tenuous plasma or ground test environment. Detailed specifications needed to run the code are presented. The object definition section, OBJDEF, allows the test object to be easily defined in the cubic mesh. The test object is composed of conducting sections which may be wholly or partially covered with thin dielectric coatings. The potential section, POTENT, obtains the electrostatic potential in the space surrounding the object. It uses the conjugate gradient method to solve the finite element formulation of Poisson's equation. The CHARGE section of NASCAP treats charge redistribution among the surface cells of the object as well as charging through radiation bombardment. NASCAP has facilities for extensive graphical output, including several types of object display plots, potential contour plots, space charge density contour plots, current density plots, and particle trajectory plots.

Mandell, M. J.↗
NASA NTRS1939

Local instability of centrally loaded columns of channel section and Z-section

Charts are presented for the coefficients in formulas for the critical compressive stress at which cross-sectional distortion begins in a thin-wall member with either a channel section or a Z-section with identical flanges. The energy method of Timoshenko was used in the theoretical calculations required for the construction of the charts. The deflection equations were carefully selected to give good accuracy. The calculation of the critical compressive stress at stresses beyond the elastic range is briefly discussed. In order to demonstrate the use of the formulas and the charts in engineering calculations, two illustrative problems are included.

ELASTICITY↗
NASA NTRS1949

Some New Problems on Shells and Thin Structures

Cylindrical shells of arbitrary section, reinforced by longitudinal and transverse members (stringers and ribs) are considered by us, for a sufficiently close spacing of the ribs, as in our previously published papers (references 1 end 2), as thin-walled orthotropic spatial systems at the cross-sections of which only axial (normal and shearing) forces can arise. The longitudinal bending and twisting moments, due to their weak effect on the stress state of the shell, are taken equal to zero. Along the longitudinal sections of the shell there may arise transverse forces in addition to the normal ~d shearing forces. Under the so-called static assumptions there is taken for the computation model of the shell a thin-walled spatial system consisting along its length (along a generator) of an infinite number of elementary strips capable of bending. Each of these strips is likened to a curved rod operating in each of its sections not only in tension (compression)but also in transverse bending and shear. The interaction between two adjoining transverse strips in the shell expresses itself in the transmission from one strip to the other of only the normal and shearing stresses. The static structure of the computation model here described is shown in figure 1, where the connections through which the normal and shearing stresses transmitted from one transverse strip to smother are indicated schematically by the rods located in the middle surface of the shell. In addition to the static hypothesis we introduce also geometric hypotheses. According to the latter the elongational deformations of the shell along lines parallel to the generator of its middle surface and the shear deformations in the middle surface, as ma+gitudes having . little effect on the state of the fundamental internal forces of the shell, are taken equal to zero. The deformations of the shell in our computational model are such that in the first place the lines of this surface perpendicular to the generator are inextensible at each point end in the second place the angles between the lines of principal curvature (the coordinate lines) which are straight before the deformation remain straight after the deformation.

Vlasov, V. S.↗
NASA NTRS2002

Long-Term Creep of a Thin-Walled Inconel 718 Stirling Power-Convertor Heater Head Assessed

The Department of Energy and NASA have identified Stirling power convertors as candidate power supply systems for long-duration, deep-space science missions. A key element for qualifying the flight hardware is a long-term durability assessment for critical hot section components of the power convertor. One such critical component is the power convertor heater head. The heater head is a high-temperature pressure vessel that transfers heat to the working gas medium of the convertor, which is typically helium. An efficient heater head design is the result of balancing the divergent requirements of thin walls for increased heat transfer versus thick walls to lower the wall stresses and thus improve creep resistance and durability. In the current design, the heater head is fabricated from the Ni-base superalloy Inconel 718 (IN 718, Inco Alloys International, Inc., Huntington, WV). Although IN 718 is a mature alloy system (patented in 1962), there is little long-term (>50,000-hr) creep data available for thin-specimen geometries. Since thin-section properties tend to be inferior to thicker samples, it is necessary to generate creep data using specimens with the same geometry as the actual flight hardware. Therefore, one facet of the overall durability assessment program involves generating relatively short-term creep data using thin specimens at the design temperature of 649 C (1200 F).

Bowman, Randy R.↗
DOE OSTI2021

Extremely Lightweight Optical Structures for Rapid Deployment

The structures that surround and support optical components play a key role in the performance of the overall optical system. For aerospace applications, creating an opto-mechanical structure that is athermal, lightweight, robust, and can be quickly developed from concept through to hardware is challenging. This project demonstrates a design and fabrication method for optical structures using origami-style folded, photo-etched sheetmetal pieces that are micro-welded to each other or to 3d printed metal components. Thin flexures, critical for athermal mounting of optics, can be thinner with sheetmetal than from standard machining, which leads to more compact designs and the ability to mount smaller optics. Building a structure by starting with the thinnest features, then folding that thin material to make the ''thicker'' sections is the opposite of standard machining (cutting thin features from thicker blocks). A design method is shown with mass savings of >90%, and stiffness to weight ratio improvements of 5x to 10x compared to standard methods for space systems hardware. Designs and processes for small, flexured, actively aligned systems are demonstrated as are methods for producing lightweight, structural, Miura-core sandwich panels in both flat and curved configurations. Concepts for deployable panels and component hinges are explored, as is a lens subcell with tunable piston movement with temperature change and an ultralight sunshade.

42 ENGINEERING↗
NASA NTRS1989

Extension-torsion coupling behavior of advanced composite tilt-rotor blades

An analytic model was developed to study the extension-bend-twist coupling behavior of an advanced composite helicopter or tilt-rotor blade. The outer surface of the blade is defined by rotating an arbitrary cross section about an initial twist axis. The cross section can be nonhomogeneous and composed of generally anisotropic materials. The model is developed based upon a three dimensional elasticity approach that is recast as a coupled two-dimensional boundary value problem defined in a curvilinear coordinate system. Displacement solutions are written in terms of known functions that represent extension, bending, and twisting and unknown functions for local cross section deformations. The unknown local deformation functions are determined by applying the principle of minimum potential energy to the discretized two-dimensional cross section. This is an application of the Ritz method, where the trial function family is the displacement field associated with a finite element (8-node isoparametric quadrilaterals) representation of the section. A computer program was written where the cross section is discretized into 8-node quadrilateral subregions. Initially the program was verified using previously published results (both three-dimensional elasticity and technical beam theory) for pretwisted isotropic bars with an elliptical cross section. In addition, solid and thin-wall multi-cell NACA-0012 airfoil sections were analyzed to illustrate the pronounced effects that pretwist, initial twist axis location, and spar location has on coupled behavior. Currently, a series of advanced composite airfoils are being modeled in order to assess how the use of laminated composite materials interacts with pretwist to alter the coupling behavior of the blade. These studies will investigate the use of different ply angle orientations and the use of symmetric versus unsymmetric laminates.

Kosmatka, J. B.↗
NASA NTRS1939

Local instability of columns with I-, Z-, channel, and rectangular-tube sections

Charts are presented for the coefficients in the formulas for the critical compressive stress at which cross-sectional distortion begins in thin-wall columns of I-, Z-, channel, and rectangular-tube sections. The energy method of Timoshenko was used in the theoretical calculations required for the construction of the charts. The deflection equations were carefully selected to give good accuracy. The calculation of the critical compressive stress at stresses above the elastic range is briefly discussed in order to demonstrate the use of the formulas and the charts in engineering calculations. Two illustrative problems are included.

STRESSED SKIN LMAL↗
NASA NTRS1996

Cyclically controlled welding purge chamber

An arrangement for butt-welding cylindrical sections of large, thin-wall tanks includes a rotatable mandrel with side-by-side sets of radial position adjusters. Each set of adjusters bears on one of the tank sections adjacent the seam, to prevent the sections from sagging out-of-round. The mandrel rotates relative to the welder, so that a continuous seam is formed. A purge chamber is fixed in position behind the seam at the weld head, and is flushed with inert gas. The purge chamber includes a two-sided structure which is contiguous with the cylindrical sections and a circumferential vane to form an open-ended tube-like structure, through which the radial position adjusters pass as the mandrel and cylindrical workpiece sections rotate. The tube-like structure is formed into a chamber by a plurality of movable gates which are controlled to maintain a seal while allowing adjusters to progress through the purge chamber.

Gallagher, Robert L.↗
NASA NTRS1983

W-shaped occultation signatures - Inference of entwined particle orbits in charged planetary ringlets

A model for the ringlets of Saturn is proposed where concentration of material near the inner and outer radial edges of the ringlets is a natural consequence of particles in entwined elliptical orbits, with the same particles alternately defining both edges. The existence of a collisionless state where particles fly along entwined paths in a compressed helical formation on and within a toroidal surface whose meridional cross section is a very thin ellipse is explained. The cancellation of strong oblateness perturbations by an extremely weak force normal to the orbit planes and directed primarily outward from the major axis of the meridional cross section of the torus is shown, and the possibility that electric repulsion of like-charged particles could provide the expansion force preventing cross-sectional collapse is examined. The model features a large stability domain within which orbital inclinations and arguments of periapse oscillate but do not progress. Features of the model that can be tested experimentally are mentioned.

Eshleman, V. R.↗
NASA NTRS1996

Structural Concepts Study of Non-circular Fuselage Configurations

A preliminary study of structural concepts for noncircular fuselage configurations is presented. For an unconventional flying-wing type aircraft, in which the fuselage is inside the wing, multiple fuselage bays with non-circular sections need to be considered. In a conventional circular fuselage section, internal pressure is carried efficiently by a thin skin via hoop tension. If the section is non-circular, internal pressure loads also induce large bending stresses. The structure must also withstand additional bending and compression loads from aerodynamic and gravitational forces. Flat and vaulted shell structural configurations for such an unconventional, non-circular pressurized fuselage of a large flying-wing were studied. A deep honeycomb sandwich-shell and a ribbed double-wall shell construction were considered. Combinations of these structural concepts were analyzed using both analytical and simple finite element models of isolated sections for a comparative conceptual study. Weight, stress, and deflection results were compared to identify a suitable configuration for detailed analyses. The flat sandwich-shell concept was found preferable to the vaulted shell concept due to its superior buckling stiffness. Vaulted double-skin ribbed shell configurations were found to be superior due to their weight savings, load diffusion, and fail-safe features. The vaulted double-skin ribbed shell structure concept was also analyzed for an integrated wing-fuselage finite element model. Additional problem areas such as wing-fuselage junction and pressure-bearing spar were identified.

Mukhopadhyay, Vivel↗
NASA NTRS1957

Torsional stiffness of thin-walled shells having reinforcing cores and rectangular, triangular, or diamond cross section

A theoretical investigation has been made of the Saint-Venant torsion of certain composite bars. These bars are composed of two materials -- one material in the form of a thin-walled cylindrical shell and the other material in the form of a core which fills the interior of the shell and is bonded to it. An approximate boundary-value problem is formulated on assumptions similar to those of the theory of torsion of hollow thin-walled shells (Bredt theory). This boundary-value problem is solved exactly for a rectangular cross section and approximately for slender triangular and diamond cross sections. Results for the torsional stiffness constants are presented graphically.

Mccomb, Harvey G , Jr↗