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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of engineering mathematics 30 (1996), S. 557-572 
    ISSN: 1573-2703
    Keywords: Torsion ; Nonhomogeneity ; Elastic layer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract Two circular discs of different radii on the opposite faces of an infinite, non-homogeneous elastic layer, whose rigidity is assumed to vary with two cylindrical coordinates r, z by a power law (% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbnL2yY9% 2CVzgDGmvyUnhitvMCPzgarmWu51MyVXgaruWqVvNCPvMCG4uz3bqe% fqvATv2CG4uz3bIuV1wyUbqee0evGueE0jxyaibaieYlf9irVeeu0d% Xdh9vqqj-hEeeu0xXdbba9frFf0-OqFfea0dXdd9vqaq-JfrVkFHe9% pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr0-vqpWqaaeaabiGaciaaca% qabeaadaabauaaaOqaaiabeY7aTjabg2da9iabeY7aTnaaBaaaleaa% cqaHXoqycaGGSaaabeaakiabek7aInaaCaaaleqabaGaeqiXdq3aaW% baaWqabeaacqaHXoqyaaWccaWG6bWaaWbaaWqabeaacqaHYoGyaaaa% aaaa!4CAB!\[\mu = \mu _{\alpha ,} \beta ^{\tau ^\alpha z^\beta } \]), are forced to rotate through two different angles of rotation. The rest of each surface is kept stress free. Using the Hankel integral transform, this problem is shown to lead to two pairs of dual integral equations, the solution of which is governed by two simultaneous Fredholm integral equations of the second kind. The latter may be solved either numerically or by iteration (in the case of sufficiently large values of the layer's thickness compared to the maximum of the radii of the circles and for β=0). The solutions for some particular cases previously investigated are recovered by assigning specific numerical values to physical and geometrical parameters. Expressions for some quantities of physical importance, such as the torques applied on the two surfaces and the stress intensity factors, are obtained for the two surfaces and some numerical values are displayed graphically.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of engineering mathematics 30 (1996), S. 547-555 
    ISSN: 1573-2703
    Keywords: Torsion ; Nonhomogeneity ; Elastic cylinder ; Circular cut
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract We consider the torsional deformation of a non-homogeneous infinite elastic cylinder slackened by an external circular cut. The shear modulus of the material of the cylinder is assumed to vary with the radial coordinate by a power law. It is assumed that the lateral surface of the cylinder as well as the surface of the cut are free of stress. The main object of this study is to establish the effect of the non-homogeneity on the stress intensity factor at the tip of the cut. The problem leads to a pair of dual series relations, the solution of which is governed by a Fredholm integral equation of the second kind with a symmetric kernel. This equation is solved numerically by reducing it to an algebraic system. It is concluded that for any degree of non-homogeneity and for D, the relative depth of the cut, greater than 0.6, the cylinder may be replaced by a half-space. However, as the non-homogeneity increases, D decreases.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 9 (1971), S. 1591-1601 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of polyurethanes (PU) prepolymers with NCO/OH ratios of 2.1:1 and 1.9:1 were prepared by reacting hydrogenated methylene di-p-phenyl diisocyanate (HMDI) with triol mixtures of TP740 (molecular weight 740) and TP1540 (molecular weight 1540). Stress-strain (S/S) and swelling equilibrium measurements were performed using thin-film samples prepared by moisture-curing the prepolymer at room temperature. The swollen PU networks gave an S/S curve which is fully described by rubber elasticity theory. The Mooney-Rivlin constant C1 (swollen) was found to increase directly while the molecular weight between crosslinks Mc decreases as the number of branches per cubic centimeter is increased. The solvent - polymer interaction parameter χ determined in benzene was 0.077 + 0.97vr, where vr is the volume fraction of rubber in the swollen network. The crosslink density v′, and Mc were calculated from the relations v′ = pNB and Mc = 0.667 B-1, where B denotes moles of branches per gram, and were found to be in good agreement with v′ and Mc established from S/S and swelling-equilibrium measurements. In calculating v′ and Mc, the water-PU crosslinking reaction at room temperature was assumed to occur mainly through the formation of a urea linkage.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 12 (1974), S. 655-664 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The 100-MHz proton NMR spectra of commercial and laboratory-prepared poly(vinyl chloride) (PVC) have been measured in various solvents at high temperature (80-150°C). Tacticity in PVC was determined by the analysis of the β-proton spectrum. The spectrum was calculated assuming that the PVC chain consists of tetrad sequences of monomer units and that their distribution in the chain is described by a simple Bernoulli-sequence statistics with a Pm (the probability of isotactic placement) of 0.45 for commercial PVC polymerized at 50°C. Tacticity calibration curves based on measurements made for the polymer in pentachloroethane and β-dichlorobenzene were established, and they provide a simple method for the measurement of tacticity in PVC directly from the observed spectra. Excluding samples prepared in butyraldehyde solution, the formation of syndiotactic structures in PVC (prepared by free-radical polymerization) was found to be favored by lowering the polymerization temperature. This preference is due to an increase in the activation enthalpy of 510 cal/mole which is required for forming an isotactic placement in the chain during the propagation step.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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