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  • 1
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Mechanics of composite materials 5 (1969), S. 531-534 
    ISSN: 1573-8922
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The tensile strengths of uniaxially oriented polystyrene films with molecular orientation determined by IR spectroscopy are compared. Two different orientation methods involving different time and temperature regimes are employed. It is found that the tensile strength is a unique function of the degree of orientation of the molecular segments of the polystyrene carbon chain irrespective of the means used to orient the specimens and increases linearly with increase in the degree of molecular orientation of the polymer. The experimental dependence is in satisfactory agreement with the results of a theoretical analysis.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 26 (1984), S. 295-307 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Résumé Un examen du temps de rupture pour des échantillons de traction uniaxes d'environ 50 matériaux, mesuré dans certains cas sur 10 décades de temps, a suggéré une relation universelle entre la durée de la résistance, la traction et la température, de la forme: τ = τo exp [(Uo - γσ)/kT] La constante τo est essentiellement la réciproque de la fréquence naturelle d'oscillation des atomes dans le solide, Uo est l'énergie de liaison des atomes et γ est proportionnel à la désorientation de la structure moléculaire. En admettant la nature cinétique de la destruction de la liaison, par le mécanisme de fluctuation thermique, la vérification expérimentale directe du phénomène à été obtenue, pour des polymères, par la technique de la résonance paramagnétique des électrons.
    Abstract: Zusammenfassung Eine Betrachtung der Bruchzeit von einachsigen Spannungsprüflingen aus ungefähr 50 verschiedenen Materialien gemessen in manchen Fällen über zehn Zeitdekaden, lässt einen allgemeinen Zusammenhang zwischen der Zeit bis zum Bruch (lifetime), der Zugspannung und der Temperatur, der Form τ = τo exp [(Uo - γσ)/kT] vermuten. Die Konstante τo ist im wesentlichen die reziproke natürliche Schwingungsfrequenz der Atome im Festkörper, Uo ist die bindungsenergie zwischen den Atomen, und γ ist proportional des Disorientierung der molekularen Struktur. Unter der Annahme, dass die Bindungszerstörung kinetischer Natur ist und durch Thermofluktuation erfolgt, wurde eine direkte experimentelle Bestätigung der Zusammenhänge bei Polymeren durch Beobachtung der paramaguetischen Elcktronenresonanz erhalten.
    Notes: Abstract An examination of the time to failure for uniaxial tensile specimens of some 50 materials, measured in some cases over test decades of time, has suggested a universal rate relation between lifetime, stress, and temperature of the form τ = τo exp [(Uo - γσ)/kT]. The constant τo is essentially the reciprocal of the natural oscillation frequency of atoms in the solid, Uo is the binding energy on the atomic scale, and γ is proportional to the disorientation of the molecular structure. Assuming the kinetic nature of bond destruction through the thermofluctuation mechanism, direct experimental verification of the phenomenon for polymers has been obtained using electron paramagnetic resonance.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 11 (1975), S. 629-639 
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Résumé On étudie la formation de fissures submicroscopiques dans les polymères sous contraintes par la dispersion de rayon X à faible angle d'incidence, et on analyse les principales conditions de formation de la fissure sous des charges différentes. On montre les relations entre la concentration de fissures submicroscopiques et la déformation d'un polymère sous contrainte. On établit les principaux paramètres qui régissent la formation de la fissure, et qui déterminent la résistance d'un polymère, à savoir la dimension des fissures submicroscopiques normales à l'axe de sollicitation, qui dépend de l'hétérogénénté structurale du matériau, et la concentration de fissures submicroscopiques avant la rupture. Par une analyse corrélative de ces paramètres, on peut formuler les principales assertions sur le micromecanisme de la rupture des polymères. Une comparaison des paramètres volumiques et de surface intervenant dans la formation de fissures dans un polymère sous tension permet de démontrer le rôle déterminant que joue la surface dans le processus de la rupture.
    Notes: Abstract Formation of incipient submicroscopic cracks in polymers under load have been studied by small-angle X-ray scattering. The main regularities of crack formation under different loading conditions have been analyzed. The connection between the submicrocrack concentration and the deformation of a stressed polymer has been shown. The main parameters of crack formation defining the strength properties of a polymer, i.e., the size of initial submicrocracks transverse to the axis of loading, which is determined by the structural heterogeneity of a material, and the concentration of submicrocracks before rupture, have been established. The analysis of the quantitative correlation between these parameters allows one to formulate the main statements regarding the micromechanics of polymer fracture. From comparing the volume and surface parameters of crack formation of a stressed polymer, the dominating role of the surface in the process of fracture has been demonstrated.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Mechanics of composite materials 10 (1974), S. 687-694 
    ISSN: 1573-8922
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Small-angle x-ray scattering has been used to investigate the formation of embryonic submicroscopic cracks in polymers under a load. The main characteristics of crack formation in various loading regimes are analyzed. It is shown that there is a relation between the submicrocrack concentration and the deformation of the loaded polymer. The principal parameters of crack formation determining the strength properties of the polymer are found to be the transverse dimension of the initial submicrocracks relative to the loading axis, which is determined by the structural heterogeneity of the material, and the submicrocrack concentration in the prefracture state. The principles of the micromechanics of polymer fracture are formulated on the basis of the results of an analysis of the quantitative relationship between these parameters. The dominant role of the surface in the fracture process is demonstrated by comparing the parameters of crack formation in the interior and at the surface of the loaded polymer.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Strength of materials 3 (1971), S. 162-167 
    ISSN: 1573-9325
    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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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 10 (1972), S. 1509-1520 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Submicrocracks, free radicals, and endgroups of scissioned molecules formed in polyethylene, polypropylene, and polycaprolactam under uniaxial tension have been investigated. Measurements were carried out by small-angle x-ray scattering, electron paramagnetic resonance, and infrared spectroscopy. The concentration of submicrocracks is almost the same as that of free radicals but is smaller than the concentration of scissioned macromolecules by approximately three orders of magnitude. The number of scissions per crack proved to be close to the number of macromolecules passing through the cross section of a submicrocrack calculated on the assumption of close packing. It is concluded that submicrocracks in stressed polymers are formed as a result of chain reactions of macromolecular decomposition initiated by the active end primary free radicals.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Strength of materials 3 (1971), S. 157-161 
    ISSN: 1573-9325
    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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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 12 (1974), S. 385-398 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Macromolecular chain scission under mechanical stress has been studied by infrared spectroscopy. The dependence of accumulation of chemical bond scissions on temperature T and uniaxial tensile stress σ has been investigated. The rate constant K for bond dissociation under mechanical stress has been found to obey the modified Arrhenius equation: K = K0 exp{ - (EA - ασ)/RA}. The quantitative connection between the rate constant for bond dissociation and mechanical lifetime τ has been established. Analysis of the experimental data indicates that the strength and mechanical lifetime of polymers is determined by the kinetics of mechanochemical scission of the main chains of polymer molecules.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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