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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.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Elastic torsional buckling of thin-walled composite cylinders

The elastic torsional buckling strength has been determined experimentally for thin-walled cylinders fabricated with glass/epoxy, boron/epoxy, and graphite/epoxy composite materials and composite-reinforced aluminum and titanium. Cylinders have been tested with several unidirectional-ply orientations and several cross-ply layups. Specimens were designed with diameter-to-thickness ratios of approximately 150 and 300 and in two lengths of 10 in. and 20 in. The results of these tests were compared with the buckling strengths predicted by the torsional buckling analysis of Chao.

Marlowe, D. E.↗
NASA NTRS1993

Impact damage tolerance of thin wall composite struts

An experimental investigation was made to study the impact damage tolerance of thin wall composite struts made of both brittle epoxy and toughened epoxy based composite materials. Damage parameters such as barely visible surface damage and internal damage represented by the ultrasonic C-scan, and residual compressive strengths were evaluated against impact energy for two impactor sizes. From both a damage resistance (internal damage vs. impact energy) and a damage tolerance (residual compressive strength vs. internal damage) point of view, the toughened IM7/977-2 struts exhibited better performance than the brittle epoxy based T50/934 struts. This is attributed to the toughening mechanism in 977-2 which impedes delamination initiation from impact, and delamination growth and subsequent buckling under a compression loading. At barely visible damage thresholds, regardless of the impactor sizes, a maximum strength reduction of 45-55 percent was observed for the T50/934 struts, and approximately 10 percent for IM7/977-2 struts. This is of great interest for developing a damage tolerance design approach and risk assessment methodology in which the design allowable would be defined by the residual strength at the threshold of barely visible damage.

Chen, G.-S.↗
NASA NTRS1951

Buckling of thin-walled cylinder under axial compression and internal pressure

An investigation was made of a thin-walled cylinder under axial compression and various internal pressures to study the effect of the internal pressure on the compressive buckling stress of the cylinder. A theoretical analysis based on a large-deflection theory was also made. The theoretically predicted increase of compressive buckling stress due to internal pressure agrees fairly well with the experimental results. (author)

Lo, Hsu↗
NASA NTRS1969

Repair of weld defects in thin-walled stainless steel tubes

Hand-operated tool repairs weld defects in large-diameter, thin-walled stainless steel tubes. Tool consists of a three-roll external planisher and an internal backup mandrel, both hydraulically pressurized by hand pumps, and an external restraining mandrel, which keeps the tube from turning during the planishing operations.

Fiorelli, F.↗
NASA NTRS1947

Critical stress of thin-walled cylinders in axial compression

Empirical design curves are presented for the critical stress of thin-walled cylinders loaded in axial compression. These curves are plotted in terms of nondimensional parameters of small-deflection theory and are compared with theoretical curves derived for the buckling of cylinders with simply supported and clamped edges. An empirical equation is given for the buckling of cylinders having a length-radius ratio greater than about 0.75. The test data obtained from various sources follow the general trend of the theoretical curve for cylinders with clamped edges, agreeing closely with the theory in the case of short cylinders, but falling considerably below the theoretical results for long cylinders. The discrepancy in the case of long cylinders increases with increasing values of the ratio of radius to wall thickness. Plotting curves for different values of this ratio reduces the scatter in the test data and a certain degree of correlation with theory is achieved. Advantage is taken of this correlation to obtain estimated design curves for cylinders with simply supported edges, for which little experimental information is available. (author)

Batdorf, S B↗
NASA NTRS1947

Critical stress of thin-walled cylinders in axial compression

Empirical design curves are presented for the critical stress of thin-wall cylinders loaded in axial compression. These curves are plotted in terms of the nondimensional parameters of small-deflection theory and are compared with theoretical curves derived for the buckling of cylinders with simply supported and clamped edges. An empirical equation is given for the buckling of cylinders having a length-radius ratio greater than about 0.75.

Batdorf, S B↗
NASA NTRS1938

The Twisting of Thin-walled, Stiffened Circular Cylinders

On the basis of the present investigation of the twisting of thin-walled, stiffened cylinders the following conclusions can be reached: 1) there is as yet no generally applicable formula for the buckling moment of the skin; 2) the mathematical treatment of the condition of the shell after buckling of the skin is based on the tension-field theory, wherein the strain condition is considered homogenous.

Schapitz, E↗
DOE OSTI2025

Microstructural evaluation of thin-wall sections of 316L stainless steel produced by laser powder-bed fusion processing

The synthesis of thin wall sections that are only 0.4 mm thick is achieved with LPBF AM. Sample preparation is optimized using metallographic polishing to produce samples with only 0.3 um rms roughness for scanning electron microanalysis with EBSD and EDS. A fully austenitic 316L phase is found without evidence of secondary phases. Unlike some AM products that can readily evidence composition segregation due to solute rejection as attributable to temperature gradients within the solidification

Jankowski, Alan F. [Sandia National Laboratories (↗
NASA NTRS1984

Interactive buckling of thin-walled structural components under static and dynamic loads

Recent advances in the study of interactive buckling of thin walled structural components achieved with the aid of finite strip technique used in conjunction with the theory of mode interaction are summarized. The interaction of the primary local mode with Euler buckling (in columns) and flexural torsional buckling (in columns and beams) is of primary interest. The interaction of two companion local modes with the overall mode is also considered briefly for the columns with doubly symmetric cross sections. The effect of dynamic loads in the form of suddenly applied and compression is also investigated.

Sridharan, S.↗
NASA NTRS1992

Bending response of thin-walled laminated composite cylinders

Closed-form linear response solutions are presented for the bending response of thin-walled laminated composite cylinders. Displacements and intralaminar stresses are computed using the Donnell theory, and interlaminar stresses are computed using 3D equilibrium equations of elasticity. Laminates with stacking sequencies and an aluminum cylinder are used to illustrate the displacement response, intralaminar, and interlaminar stresses for two length-to-radius ratios of 1 and 5. Data obtained indicate that if only fiber breakage causes ultimate failure, material failure will occur on the compression side of the cylinders, at the ends, due to fiber compression. The interlaminar normal stress is an order of magnitude smaller than the interlaminar shear stresses and it is not likely to initiate failure.

Fuchs, H. P.↗
NASA NTRS1995

Stresses In And Near A Bend In A Thin-Walled Duct

Report describes computational study of distributions of stresses in and near 90 degrees bend in thin-walled duct subject to various applied loads. Purpose of study to help satisfy need for more accurate knowledge of local concentrations of stresses caused by loads: such knowledge makes possible to design light-weight ducts to survive reasonably foreseeable operating conditions with some degree of reliability. Also guides selection of locations for mounting strain gauges to measure local stresses for comparison with computed values, contributing to refinement of theoretical concepts and computational techniques.

Min, J. B.↗