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  • STRUCTURAL MECHANICS  (15)
  • ATOMIC AND MOLECULAR PHYSICS  (6)
  • AIRCRAFT DESIGN, TESTING AND PERFORMANCE  (3)
  • 1
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    An evaluation of the pressure proof test concept for 2024-T3 aluminium alloy sheet (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The concept of pressure proof testing of fuselage structures with fatigue cracks to insure structural integrity was evaluated from a fracture mechanics viewpoint. A generic analytical and experimental investigation was conducted on uniaxially loaded flat panels with crack configurations and stress levels typical of longitudinal lap splice joints in commercial transport aircraft fuselages. The results revealed that the remaining fatigue life after a proof cycle was longer than that without the proof cycle because of crack growth retardation due to increased crack closure. However, based on a crack length that is slightly less than the critical value at the maximum proof stress, the minimum assured life or proof test interval must be no more than 550 pressure cycles for a 1.33 proof factor and 1530 pressure cycles for a 1.5 proof factor to prevent in-flight failures.
    Keywords: STRUCTURAL MECHANICS
    Type: In: Structural integrity of aging airplanes (A93-45772 19-01); p. 115-129.
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Impact damage and residual tension strength of a thick graphite/epoxy rocket motor case (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Impacters of various masses were dropped from various heights onto thick graphite/epoxy filament-wound cylinders. The cylinders represented filament-wound cases made for the booster motors of the Space Shuttle. Tups of various shapes were affixed to the impacters. Some of the cylinders were filled with inert propellant, and some were empty. The cylinders were impacted numerous times around the circumference and then cut into tension coupons, each containing an impact site. The size of the damage and the residual tension strength were measured. For hemispherical tups, strength was reduced as much as 30 percent by nonvisible damage. The damage consisted of matrix cracking and broken fibers. Analytical methods were used to predict the damage and residual tension strength. A factor of safety to account for nonvisible damage was determined. For corner and rod shaped tups, any damage that resulted in strength loss was readily visible.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 29; 3, Ma
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Some factors that affect the inspection of aircraft for fatigue damage (1971)
    In:  CASI
    Details
    Publication Date: 2005-11-27
    Description: Fatigue crack length relationship with aircraft inspection intervals and structural reinforcement, high strength materials, and aircraft usage effects
    Keywords: STRUCTURAL MECHANICS
    Type: NASA AIRCRAFT SAFETY AND OPERATING PROBL., VOL. 1 1971; P 391-401
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Many-body-theory study of lithium photoionization (1975)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: A detailed theoretical calculation is carried out for the photoionization of lithium at low energies within the framework of Brueckner-Goldstone perturbational approach. In this calculation extensive use is made of the recently developed multiple-basis-set technique. Through this technique all second-order perturbation terms, plus a number of important classes of terms to infinite order, have been taken into account. Analysis of the results enables one to resolve the discrepancies between two previous works on this subject. The detailed calculation also serves as a test on the convergence of the many-body perturbation-expansion approach.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: Physical Review A - General Physics; vol. 11
    Format: text
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  • 5
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    An assessment of buffer strips for improving damage tolerance of composite laminates (1980)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Graphite/epoxy panels with buffer strips were tested in tension to measure their residual strength with crack-like damage. Panels were made with (45/0/-45/90)2S and (45/0/-45/0)2S layups. The buffer strips were parallel to the loading direction. They were made by replacing narrow strips of the 0 deg graphite plies with strips of either 0 deg S-Glass/epoxy or Kevlar-90/epoxy on either a one-for-one or a two-for-one basis. In a third case, 0 deg graphite/epoxy was used as the buffer material and thin, perforated Mylar strips were placed between the 0 deg plies and the cross-plies to weaken the interfaces and thus to isolate the 0 deg plies. Some panels were made with buffer strips of different width and spacings. The buffer strips arrested the cracks and increased the residual strengths significantly over those of plain laminates without buffer strips. A shear-lag type stress analysis correctly predicted the effects of layup, buffer material, buffer strip width and spacing, and the number of plies of buffer material
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Composite Materials Supplement; 14; 1, 19; 1980
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  • 6
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    Rotational and vibrational transitions for Li + H2 collisions (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Close coupling calculations for integral and differential cross sections have been carried out for Li + H2 collisions with an ab initio Hartree-Fock potential energy surface. Rotational, vibrational, and vib-rotational excitation cross sections are reported at 0.4336 eV, 0.7 eV, and 0.8673 eV in the center of mass system. For pure rotational excitations, which dominate the inelastic scattering, coupling with vibrational states is not very important. For vibrational transitions, the influence of large multiquantum rotational transitions is far less than that found for Li(+) + H2 collisions.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: Chemical Physics Letters; 48; June 1
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  • 7
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    Two- and three-photon ionization of hydrogen and lithium (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: We present the detailed result of a calculation on two- and three-photon ionization of hydrogen and lithium based on a recently proposed calculational method. Our calculation has demonstrated that this method is capable of retaining the numerical advantages enjoyed by most of the existing calculational methods and, at the same time, circumventing their limitations. In particular, we have concentrated our discussion on the relative contribution from the resonant and nonresonant intermediate states.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: Physical Review A - General Physics; vol. 16
    Format: text
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  • 8
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    Demonstrating damage tolerance of composite airframes (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Commercial transport aircraft operating in the United States are certified by the Federal Aviation Authority to be damage tolerant. On 28 April 1988, Aloha Airlines Flight 243, a Boeing 727-200 airplane, suffered an explosive decompression of the fuselage but landed safely. This event provides very strong justification for the damage tolerant design criteria. The likely cause of the explosive decompression was the linkup of numerous small fatigue cracks that initiated at adjacent fastener holes in the lap splice joint at the side of the body. Actually, the design should have limited the damage size to less than two frame spacings (about 40 inches), but this type of 'multi-site damage' was not originally taken into account. This cracking pattern developed only in the high-time airplanes (many flights). After discovery in the fleet, a stringent inspection program using eddy current techniques was inaugurated to discover these cracks before they linked up. Because of concerns about safety and the maintenance burden, the lap-splice joints of these high-time airplanes are being modified to remove cracks and prevent new cracking; newer designs account for 'multi-site damage'.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Computational Methods for Failure Analysis and Life Prediction; p 323-345
    Format: application/pdf
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  • 9
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    Impact force as a scaling parameter (1994)
    In:  Other Sources
    Details
    Publication Date: 2013-08-29
    Description: The Federal Aviation Administration (FAR PART 25) requires that a structure carry ultimate load with nonvisible impact damage and carry 70 percent of limit flight loads with discrete damage. The Air Force has similar criteria (MIL-STD-1530A). Both civilian and military structures are designed by a building block approach. First, critical areas of the structure are determined, and potential failure modes are identified. Then, a series of representative specimens are tested that will fail in those modes. The series begins with tests of simple coupons, progresses through larger and more complex subcomponents, and ends with a test on a full-scale component, hence the term 'building block.' In order to minimize testing, analytical models are needed to scale impact damage and residual strength from the simple coupons to the full-scale component. Using experiments and analysis, the present paper illustrates that impact damage can be better understood and scaled using impact force than just kinetic energy. The plate parameters considered are size and thickness, boundary conditions, and material, and the impact parameters are mass, shape, and velocity.
    Keywords: STRUCTURAL MECHANICS
    Type: Workshop on Scaling Effects in Composite Materials and Structures; p 305-338
    Format: text
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  • 10
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    An assessment of buffer strips for improving damage tolerance (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Graphite/epoxy panels with buffer strips were tested in tension to measure their residual strength with crack-like damage. Panels were made with 45/0/-45/90(2S) and 45/0/450(2S) layups. The buffer strips were parallel to the loading directions. They were made by replacing narrow strips of the 0 deg graphite plies with strips of either 0 deg S-Glass/epoxy or Kevlar-49/epoxy on either a one for one or a two for one basis. In a third case, O deg graphite/epoxy was used as the buffer material and thin, perforated Mylar strips were placed between the 0 deg piles and the cross-plies to weaken the interfaces and thus to isolate the 0 deg plies. Some panels were made with buffer strips of different widths and spacings. The buffer strips arrested the cracks and increased the residual strengths significantly over those plain laminates without buffer strips. A shear-lag type stress analysis correctly predicted the effects of layups, buffer material, buffer strip width and spacing, and the number of plies of buffer material.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Supersonic Cruise Res., 1979, Pt. 2; p 657-673
    Format: text
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