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  • 1
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 14 (1992), S. 279-286 
    ISSN: 0392-6737
    Keywords: Anelasticity, internal friction, and mechanical resonances
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The internal friction (loss tangent) of solids is normally measured, as a function of temperature, with a torsion pendulum operating in free decay. Curves of the internal friction and the oscillation frequency, against temperature, are obtained at various moments of inertia, to extract the parameters characteristic of the relaxation process (relaxation time and strength). In all these experiments only the temperature is considered as an independent variable and the moment of inertia of the pendulum is mainly used to shift the internal friction peaks in the temperature scale. It is pointed out in the paper that the moment of inertia is also an independent variable which can be used to determine, with high accuracy, if the measured peak is of the Debye type or not. A new torsion pendulum, with continuously variable moment of inertia is presented, which allows measurements of the partial derivative of the internal friction and the oscillation frequency with respect to the moment of inertia, at constant temperature. Finally, some measurements of the Snoek relaxation in Nb-O alloys are presented, to show the applicability of the concepts developed in the paper.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 14 (1992), S. 287-332 
    ISSN: 0392-6737
    Keywords: Anelasticity, internal friction, and mechanical resonances
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary An analysis of the internal friction produced by grain boundary relaxation in metals and alloys and ceramics is presented. The different interpretations given in the literature to relaxation phenomena occurring at temperatures above about half the melting point which include the influence of grain boundaries and their interaction with solutes and precipitates are discussed in detail. A complete set of the experimental data disposable in this field since 1972 up today is rewiewed. Finally, some recent experiments are discussed and new ones are suggested. They might solve the actual controversy about the real origin of the relaxation phenomena observed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 21 (1986), S. 3539-3547 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The high-temperature internal friction spectrum of polycrystalline Zircaloy-4 is investigated in detail, for a wide range of frequencies. Two internal friction maxima are observed. The lower-temperature peak is interpreted in terms of a relaxation mechanism produced by the sliding of particle-free grain boundaries. The higher-temperature peak is attributed to the sliding of boundaries blocked by small precipitates. Values for the activation enthalpy and the preexponential factor for diffusion along grain boundaries are given, and the viscosity coefficient associated with grain-boundary sliding is determined as a function of temperature.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 21 (1986), S. 3539-3547 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The high-temperature internal friction spectrum of polycrystalline Zircaloy-4 is investigated in detail, for a wide range of frequencies. Two internal friction maxima are observed. The lower-temperature peak is interpreted in terms of a relaxation mechanism produced by the sliding of particle-free grain boundaries. The higher-temperature peak is attributed to the sliding of boundaries blocked by small precipitates. Values for the activation enthalpy and the preexponential factor for diffusion along grain boundaries are given, and the viscosity coefficient associated with grain-boundary sliding is determined as a function of temperature.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 495-497 (Sept. 2005), p. 719-724 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Some ancient metallic art craft, utensils, silverware and weapons are externally undistinguishable from modern ones. Not only the general aspect and shape but also some uses have not changed through the ages. Moreover, when just some small pieces can be recovered from archaeological sites, the samples can not easily be ascribed to any known use and consequently identified. It is clear that mechanical processing has changed along history but frequently only a "microscopic" inspection can distinguish among different techniques. Some bronze samples have been collected from the Quarto d’Altino (Veneto) archaeological area in Italy (paleovenetian culture) and some model samples have been prepared by a modern artisan. The sample textures have been measured by X-ray Diffraction techniques. (111), (200) and (220) pole figures were used to calculate Orientation Distribution Functions and further recalculate pole figures and inverse pole figures. The results were compared with modern forging technology results. Textures are able to discern between hammering ancient techniques for sheet production and modern industrial rolling procedures. However, as it is demonstrated in the present work, forgery becomes difficult to detect if the goldsmith, properly warned, proceeds to erase the texture history with some hammering post-processing. The results of this contribution can offer to the archaeologists the opportunity to take into consideration the texture techniques in order to discuss the origin (culture) of the pieces and the characteristic mechanical process developed by the ancient artisan. Texture can also help the experts when discussing the originality of a certain piece keeping however in mind the cautions indicated in this publication
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 31 (1996), S. 4047-4053 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Domain growth of bulk partially melted Nd1+xBa2−xCu3O7−δ in air was found to be severely limited by liquid-phase segregation and losses. The use of a reduced oxygen pressure greatly improved the stoichiometry control, leading to the formation of well-developed domains and enhanced superconducting properties. Direct nucleation of Nd1+xBa2−xCu3O7−δ from the liquid phase by dissolution of Nd2BaCuO5 and a spiral growth mechanism in three perpendicular directions of the platelets stacked in the domains, are suggested.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 29 (1994), S. 3497-3504 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Large domains with platelets almost parallel to each other were obtained in bulk YBa2Cu3O7−δ by a single-step partial melting procedure. The mechanisms of nucleation and growth of platelets are discussed. The nucleation of peritectic material from the liquid phase is favoured by heterogeneities in the melt. Experimental evidence of spiral growth of the nuclei in the [0 0 1] direction is given. Furthermore, structures of growth, which could also be an indication of spiral growth in the [0 1 0]/[1 0 0] directions, are shown. The final morphology of the domains can be explained on the basis of the periodic bond chain (PBC) theory if the growth rates of flat (F) faces of the platelets are dominated by kinetic coefficients which differ between them. The morphology of the as-grown (0 0 1) surface is explained in the framework of the PBC theory with the shape of the steps of macrospirals governed by the transition from roughness to smoothness of the liquid-solid interface. An account of large step heights is given by the model of giant screw dislocations caused by an impurity-induced lattice-constant gradient. Even higher step heights are correlated to the presence of obstacles and lack of liquid phase.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 20 (1985), S. 3649-3660 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Hysteresis effects present on the high temperature internal friction of annealed polycrystalline zirconium are investigated in detail. It is shown that two internal friction maxima are present when the measurements are performed on heating. If a high enough temperature is reached, only one internal friction maxima is observed on cooling. Furthermore, when the temperature is not decreased below a certain value (critical temperature) only the lower temperature peak is present during a subsequent heating cycle. The critical temperature is strongly dependent on the grain size. Finally, both the hysteresis effects and the internal friction maxima are explained by relaxation mechanisms associated with grain boundary sliding and segregation of impurities to the grain boundaries.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 13 (1994), S. 1108-1110 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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