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  • 1980-1984  (5)
  • 1975-1979  (10)
Material
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 16 (1981), S. 1881-1886 
    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 Slow crack growth at elevated temperatures is studied in one experimental and two commercial LAS glass ceramics. All show intergranular crack growth with the crack also passing along the interfaces of precipitates even when these are needle-shaped. The commercial materials differ from the experimental in that the shape of the cracks in them indicates an environmental effect absent in the experimental material. In one of the commercial materials, lifetimes as a function of initial stress-intensity factors are determined. Lifetimes are found to increase as the testing temperature is reduced and as the material is heat treated.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 14 (1979), S. 443-449 
    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 Two types of fracture toughness specimens, double cantilever beam and single-edge notch, were constructed from nickel wires in an epoxy resin matrix. The critical stress intensity factor to cause propagation of an unbridged matrix crack arrested at a wire was found to be greater than that for plain resin. Subsequent crack propagation could be described by taking account of the stress intensity factor due to known forces in the crack-bridging wires which subtracted from that due to the applied forces. The debonding and pull-out behaviour observed previously in single-wire specimens was confirmed in the multi-wire fracture toughness specimens.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 17 (1982), S. 2671-2676 
    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 Microstructure and grain growth were studied in two glass ceramics of the Li2O-Al2O3-SiO2 system, one an experimental material of basic composition Li2O-Al2O3-4SiO2 and the second a commercial material of approximately 0.7Li2O-Al2O3-6SiO2 composition with small amounts of other oxides. There was evidence from transmission electron microscopy that the commercial material contained residual glass at grain-boundary triple points and glass layers at some but not all grain boundaries. No definite evidence was found for residual glass in the experimental material. The composition of secondphase regions in the commercial material was studied by STEM microanalysis. Al-rich regions of irregular morphology were found but there was no evidence that residual glass was SiO2-rich, as has been previously suggested for this type of glass-ceramic. Grain growth showed a fairly similar time dependence in the two materials with growth more rapid in the commercial material at a given temperature. It is suggested that grain growth is controlled by precipitate particles rather than by residual glass phase.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 16 (1981), S. 1874-1880 
    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 microstructures and creep properties of one experimental and two commercial LAS glass ceramics have been studied. The commercial materials creep at lower temperatures and exhibit more prominently non-linear creep (creep rate decreasing with time). Heat treatment causes grain growth and a redistribution of precipitate and leads to a reduction in creep rates in all materials.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 18 (1983), S. 1615-1624 
    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 β → γ transformation in dicalcium silicate has been studied by a combination of optical microscopy and transmission electron microscopy (TEM). The γ-phase forms as long needles or laths whose long axis is parallel to [001] γ. These tend to occur in bundles. TEM shows that regions of γ in partially transformed specimens are not internally twinned but contain a high density of dislocations and of low angle grain boundaries running parallel to the long axis of the particles. γ particles can be induced to form by the stress near a microhardness indentation. The nature of the β → γ transformation and the effect of the very large dilatation (14%) which accompanies the transformation are discussed. The α′ ⇄ β transformation has been studied on a TEM hot stage. It is confirmed that (100) β twins are formed on cooling through the α′ → β transformation temperature. Local stresses set up at the intersection of twin lamellae with domain boundaries are relaxed by slip on (100).
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 13 (1978), S. 611-619 
    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 A glass of composition Li2O-Al2 O3-4SiO2 with TiO2 as nucleating agent was heat-treated to produce either β-quartz or β-spodumene crystal phases and the tensiie creep properties of the two structures were investigated. Both exhibited substantial creep ductility and the strain rate ε in both could be expressed by an equation of the form: $$\dot \in = A\sigma ^n \exp ( - \Delta H/RT),$$ where σ is the tensile stress and T the temperature. Within experimental error the stress exponent n and activation energy ΔH were the same for β-quartz and β-spodumene (n=1.4 and ΔH=695 kJ mol−1) but the constant A was approximately 103 times larger for β-quartz than for β-spodumene. This more rapid creep in β-quartz is attributed to its much finer grain size. The mechanism of deformation is believed to be grain-boundary sliding accommodated by grain-boundary diffusion. This belief is supported by observations of the microstructure of the β-spodumene after tensile strains as large as 30%. Creep tests terminated in brittle fracture when an intergranular crack growing slowly from a surface defect reached a critical size. It is interesting to note that this phenomenon of subcritical crack growth occurred in the absence of any detectable intergranular glass phase.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 13 (1978), S. 639-646 
    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 deformation behaviour of single crystal texture HDPE has been examined in tension as a function of the orientation of the tensile axis with respect to the chain direction. Over most of the orientation range examined, it was found that slip processes parallel to the chain direction were the dominant modes of deformation. Fibrillar slip becomes relatively more important than chain slip as the strain increases and as θ0, the initial value of the angle between the tensile axis and the chain direction, decreases. Lamellar slip was only observed over a limited range of orientations due to the high initiation stress required for the process. At low θ0 values, lamellar separation accounted for a substantial part of the applied strain. Stress-induced martensitic transformation, which was observed in samples with θ0〉26°, cannot account for an important fraction of the strain although the resolved shear stress required for the activation of the martensitic transformations is of the same order of magnitude as that required for chain slip.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 14 (1979), S. 431-442 
    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 An experimental investigation into the debonding and pull-out of nickel wires from epoxy resin and cement paste matrices has been carried out. Above a critical embedded length both the debonding and pull-out stresses attain limiting values. A theory based on the model of a yielded zone travelling up the wire behind a debonding front was shown to describe the observed dependence of the limiting debonding stress on the yield stress, diameter and surface roughness of the wire. Pull-out behaviour subsequent to debonding was explained using this model in terms of an unyielded plug at the end of the wire. Orientation of the wire to the loading direction was found to raise the limiting debonding and pull-out stresses due to enhanced friction at the wire exit point.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 16 (1981), S. 1063-1070 
    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 Thin sections of Portland cement clinker have been prepared by ion-beam thinning and examined in the electron microscope. The three most abundant phases, alite, belite and tricalcium aluminate have been identified. Features of interest include unexplained reflections in the diffraction patterns from alite and internally twinned or faulted martensite plates in belite. Hydrate gel coatings are obtained on the silicate phases but not on the aluminate phase, by immersing the thinned clinker in water. Dislocations in the aluminate phase do not appear to affect its reaction with water. On alite, easily observable hydrate coatings are obtained after immersion times as short as 5 min.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 10 (1975), S. 170-172 
    ISSN: 1573-4803
    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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