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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of engineering mathematics 37 (2000), S. 93-109 
    ISSN: 1573-2703
    Keywords: perfectly elastic ; incompressible ; Varga strain-energy ; spherical eversion ; exact solution.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract For perfectly elastic rubber-like materials, which are capable of undergoing extremely large deformations, the number of exact solutions remains limited, especially in the context of fully three-dimensional deformations. Here a simple exact solution describing the finite elastic eversion of a sector of a thick-walled incompressible spherical shell is determined for the modified Varga elastic material. This new solution, which describes a portion of a spherical shell being turned inside out, is deduced from a known simplified system and it is shown, by solving the full equilibrium equations, that no further solutions of this type can be deduced for this particular material. Further, a general family of response functions is considered, which involves an arbitrary index n, and which incorporates standard materials such as the neo-Hookean and Varga strain-energy functions. It is established that other than n=1 (namely the Varga material) only the special case n=2 admits nontrivial solutions to the eversion problem, but the resulting second-order highly nonlinear ordinary differential equation appears not to admit any simple analytical solutions. Finally, the new solution is examined as a potential solution of the 'snap-buckling' problem of a spherical cap. Unfortunately, the solution appears not to be applicable to this problem and instead it is presented in the specific context of the eversion of a thick-walled spherical cap, with no applied forces acting on one of the surfaces of the deformed configuration.
    Type of Medium: Electronic Resource
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  • 2
    facet.materialart.
    Unknown
    In:  Other Sources
    Publication Date: 2019-07-13
    Description: The problem of making very large glass mirrors for astronomical telescopes is examined, and the advantages of honeycomb mirrors made of borosilicate glass are discussed. Thermal gradients in the glass that degrade the figure of thick borosilicate mirrors during use can be largely eliminated in a honeycomb structure by internal ventilation (in air) or careful control of the radiation environment (in space). It is expected that ground-based telescopes with honeycomb mirrors will give better images than those with solid mirrors. Materials, techniques, and the experience that has been gained making trial mirrors and test castings as part of a program to develop 8-10-m-diameter lightweight mirrors are discussed.
    Keywords: OPTICS
    Type: International Conference on Advanced Technology Optical Telescopes; Mar 11, 1982 - Mar 13, 1982; Tucson, AZ
    Format: text
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  • 3
    Publication Date: 2019-07-13
    Description: Single silica fibers of the type developed for communications are useful in the design of astronomical spectrographs. They can be used to couple light from many objects over a wide field to a single spectrograph, or to eliminate wavelength errors from image motion and gravitational flexure. For many applications it will be advantageous to use small lenses to make the most efficient coupling into and out of a fiber. If the telescope pupil is imaged on the fiber core, an efficient coupling can be made that preserves image size over a certain range. This method is demonstrated by a laboratory test using sapphire spheres as coupling lenses.
    Keywords: OPTICS
    Type: Instrumentation in astronomy V; Sep 07, 1983 - Sep 09, 1983; London
    Format: text
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  • 4
    Publication Date: 2019-07-13
    Description: The making of large astronomical mirrors with borosilicate glass honeycomb structure is discussed. Particular attention is given to a single casting technique for making borosilicate honeycomb mirror blanks up to 7 meters in diameter. Current work on the development of this technique involves the casting of blanks 60 cm in diameter which have the full thickness (33 cm), cell size (15 cm), and faceplate thickness (2.5 cm) needed for a 1.8-m mirror.
    Keywords: OPTICS
    Type: Instrumentation for astronomy with large optical telescopes; Sep 08, 1981 - Sep 10, 1981; Zelenchukskaya; USSR
    Format: text
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