37 research outputs found
Torsional stiffness of thin-walled shells having reinforcing cores and rectangular, triangular, or diamond cross section
A theoretical investigation is presented of the torsional stiffness of thin-walled aerodynamic surfaces filled with cores which stabilize the skins. Rectangular, slender triangular, and slender diamond cross sections are considered. Results for the torsional stiffness constants are shown graphically
Stress distributions caused by three types of loading on a circular semimonocoque cylinder with flexible rings
Equations are derived for the stress distributions caused by three types of loading on infinitely long circular, semimonocoque cylinders with flexible rings. The results are given as formula for the stringer loads and shear flows in the shell due to each type of loading. For each loading case these formulas can be used to construct tables of influence coefficients giving stringer loads and shear flows in the neighborhood of the load due to a unit magnitude of the load. (author
Stress analysis of circular semimonocoque cylinders with cutouts
A method is presented for analyzing the stresses about cutouts in circular semimonocoque cylinders with flexible rings. The method involves the use of so-called perturbation stress distributions which are superposed on the stress distribution that would exist in the structure with no cutout in such a way as to give the effects of a cutout. The method can be used for any loading case for which the structure without the cutout can be analyzed and is sufficiently versatile to account for stringer and shear reinforcement about the cutout
Stress analysis of circular semimonocoque cylinders with cutouts by a perturbation load technique
A method is presented for analyzing the stresses about a cutout in a circular cylinder of semimonocoque construction. The method involves the use of so-called perturbation solutions which are superposed on the stress distribution that would exist in the structure with no cutout in such a way as to give the effects of a cutout. The method can be used for any loading case for which the structure without the cutout can be analyzed and is sufficiently versatile to account for stringer and shear reinforcement about the cutout. (author
Structures and materials technology for hypersonic aerospacecraft
Major considerations in structural design of a transatmospheric aerospacecraft are discussed. The general direction of progress in structures and materials technology is indicated, and technical areas in structures and materials where further research and development is necessary are indicated. Various structural concepts under study and materials which appear to be most applicable are discussed. Structural design criteria are discussed with particular attention to the factor-of-safety approach and the probabilistic approach. Structural certification requirements for the aerospacecraft are discussed. The kinds of analyses and tests which would be required to certify the structural integrity, safety, and durability of the aerospacecraft are discussed, and the type of test facility needed to perform structural certification tests is identified
Structural Considerations of Inflatable Reentry Vehicles
The state of the design art for inflated structures applicable to reentry vehicles is discussed. Included are material properties, calculations of buckling and collapse loads, and calculations of deflections and vibration frequencies. A new theory for the analysis of inflated plates is presented and compared with experiment
A variational theorem for creep with applications to plates and columns
A variational theorem is presented for a body undergoing creep. Solutions to problems of the creep behavior of plates, columns, beams, and shells can be obtained by means of the direct methods of the calculus of variations in conjunction with the stated theorem. The application of the theorem is illustrated for plates and columns by the solution of two sample problems
Discovery of very high energy gamma-ray emission coincident with molecular clouds in the W28 (G6.4-0.1) field
We observed the W28 field (for ~40 h) at Very High Energy (VHE) gamma-ray
energies (E>0.1 TeV) with the H.E.S.S. Cherenkov telescopes. A reanalysis of
EGRET E>100 MeV data was also undertaken. Results from the NANTEN 4m telescope
Galactic plane survey and other CO observations have been used to study
molecular clouds. We have discovered VHE gamma-ray emission (HESSJ1801-233)
coincident with the northeastern boundary of W28, and a complex of sources
(HESSJ1800-240A, B and C) ~0.5 deg south of W28, in the Galactic disc. The VHE
differential photon spectra are well fit by pure power laws with indices
Gamma~2.3 to 2.7. The NANTEN ^{12}CO(J=1-0) data reveal molecular clouds
positionally associating with the VHE emission, spanning a ~15 km s^{-1} range
in local standard of rest velocity. The VHE/molecular cloud association could
indicate a hadronic origin for HESSJ1801-233 and HESSJ1800-240, and several
cloud components in projection may contribute to the VHE emission. The clouds
have components covering a broad velocity range encompassing the distance
estimates for W28 (~2 kpc), and extending up to ~4 kpc. Assuming a hadronic
origin, and distances of 2 and 4 kpc for cloud components, the required cosmic
ray density enhancement factors (with respect to the solar value) are in the
range ~10 to ~30. If situated at 2 kpc distance, such cosmic ray densities may
be supplied by a SNR like W28. Additionally and/or alternatively, particle
acceleration may come from several catalogued SNRs and SNR candidates, the
energetic ultra compact HII region W28A2, and the HII regions M8 and M20 along
with their associated open clusters. Further sub-mm observations would be
recommended to probe in detail the dynamics of the molecular clouds at
velocites >10 km s^{-1}, and their possible connection to W28.Comment: 10 pages, 4 figures. Accepted for publication in Astronomy &
Astrophysics. (Abstract shortened