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  • 1970-1974  (11)
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Material
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Year
  • 1
    Electronic Resource
    Electronic Resource
    The mechanical properties of nickel oxide and their relationship to the morphology of thick oxide scales formed on nickel (1972)
    Springer
    Oxidation of metals 4 (1972), S. 151-170 
    Details
    ISSN: 1573-4889
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation of metals that form P-type semiconducting oxide scales, such as NiO on nickel and CoO on cobalt, takes place by outward cation diffusion and inward vacancy diffusion. The large number of cation vacancies precipitate in the scale near the oxide-metal interface and may coalesce to form macroscopic pores, resulting in a transition from a dense, columnar scale to a duplex scale which contains an inner, fine-grained, equiaxed, porous layer. Increasing temperature and/or purity eliminate the transition, which has been found to depend upon oxide plasticity. The mechanical properties of bulk nickel oxides having a range of porosities have been studied in compression. Three regimes were observed: (1) brittle at low temperatures, (2) ductile at elevated temperatures, and (3) a transition region at intermediate temperatures. Fracture strength in the brittle region was strongly dependent on porosity due to the effect of pores on the elastic modulus and the size of fracture-initiating flaws. The plastic flow stress in the ductile region depended primarily on grain size and impurity content except for very porous materials in which porosity substantially reduced the plastic flow stress. The development of the duplex structure in scales during oxidation has been shown to depend upon inhibition of slip on the {110} 〈110〉 system in the highly textured grains rather than by diffusion-controlled processes such as creep. The duplex structure forms when the rate of deformation of the scale is less than the rate of void formation. Grain size, porosity, and impurities play an important role; all of these effects are discussed in detail.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00613090
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Slow crack growth in brittle materials under dynamic loading conditions (1974)
    Springer
    International journal of fracture 10 (1974), S. 251-259 
    Details
    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 La rupture des matériaux due à une propagation lente d'une fissure sous des charges dynamiques est analysée en termes de relations entre la vitesse de propagation et l'intensité des contraintes. On montre que le type d'analyse envisagé peut complètement décrire les caractéristiques d'une rupture sous charges caracterisées par une vitesse constante de déformation, ou par une vitesse constante de tension. On utilise l'analyse pour prédire les variations de la résistance et la propagation subcritique de la fissure en fonction de la vitesse de déformation ou de mise sous tension. L'application de l'analyse à divers systèmes céramiques fournit des données qui satisfont entièrement les données expérimentales disponibles.
    Abstract: Zusammenfassung Der Bruch von Material durch langsame Rißausdehnung, unter dynamischer Beanspruchung wird in Hinsicht der Beziehung zwischen der Rißausdehnungsgeschwindigkeit und der Spannungsintensität untersucht. Man zeigt daß diese Form von Untersuchung die Bruchbegebenheiten vollständig beschreiben kann sowohl für eine Belastung, sowohl unter konstantem Verformungsgrad, als unter konstantem Spannungsgrad. Die Untersuchung wird zur Voraussagung der Änderungen der Festigkeit und des subkritischen Rißwachstums mit dem Verformungs- und dem Spannungsgard. Die Anwendung der Untersuchung auf verschiedene Keramiksysteme ergibt Ergebnisse die vorzüglich mit bestehenden Versuchsergebnissen übereinstimmen.
    Notes: Abstract The failure of materials due to slow crack growth, under dynamic loading conditions, is analyzed in terms of crack velocity, stress intensity relationships. It is shown that this type of analysis can fully describe the failure characteristics for both constant strain-rate and constant stress-rate loading. The analysis is used to predict the variations of strength and subcritical crack growth with strain-rate and stress-rate. Application of the analysis to several ceramic systems give data which are entirely consistent with available experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00113930
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Proof testing of ceramic materials—an analytical basis for failure prediction (1974)
    Springer
    International journal of fracture 10 (1974), S. 379-392 
    Details
    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 présente une analyse permettant de prédire avec précision la durée de vie d'un composant céramique après épreuve de réception. L'analyse a trait aux ruptures dont la propagation des fissures est contrôlée, mais est utilisable en tant que prédiction conservative, dans le cas où l'amorçage de la fissure est la phase prédominante. Les prédictions analytiques se voient confirmées par des séries de mesures de durée de vie à rupture.
    Abstract: Zusammenfassung Man berichtet von einer Analyse die die genaue Voraussagung der Lebensdauer eines Keramikbestandteiles, nach den Abnahmeversuchen, ermöglicht. Die Analyse wird auf den durch Rißausdehnung kontrolierten Bruch angewandt, kann aber auch als eine konservative Voraussagung benützt werden im Fall wo die Rißeinleitung ausschlaggebend ist. Die analytische Voraussagung wurde durch eine Reihe von “Zeit bis zum Bruch” Messungen bestätigt.
    Notes: Abstract An analysis is presented which permits the accurate prediction of component lifetimes after proof testing. The analysis applies to crack propagation controlled fracture but can be used as a conservative prediction when crack initiation is predominant. The analytical predictions are confirmed in a series of time-to-failure measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00035499
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    The strength and oxidation of reaction-sintered silicon nitride (1970)
    Springer
    Journal of materials science 5 (1970), S. 314-325 
    Details
    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 structure of reaction-sintered silicon nitride is studied using scanning electron and optical microscopy at various stages during nitriding, for a range of nitriding and compacting conditions. The strength is then evaluated and interpreted in terms of the microstructure. It is found that fracture always occurs in a brittle manner by the extension of the largest pores. The effects of prolonged annealing in air above 1000† C on both the structure and strength are investigated. At 1400† C, cristobalite is formed. If the temperature is then maintained above 250† C, the strength is enhanced, but below this temperature the oxide layer cracks and reduces the strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00552282
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Microstructural studies on silicon nitride (1971)
    Springer
    Journal of materials science 6 (1971), S. 1292-1302 
    Details
    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 specimens of reaction sintered and hot pressed silicon nitride have been prepared by ion beam thinning and examined in the Harwell million volt microscope. It has been found that reaction sintered material consists of large grains, which are mostlyβ-Si3N4, in a fine grained matrix ofα-Si3N4. Fibres are frequently observed within the pores, the type of fibre depending on the size of the pore. The hot pressed material consists largely of two types of grain, small angular grains ofβ-Si3N4 and larger irregular grains. There is also some non-crystalline material between the angular grains and there are numerous small unidentified inclusions. The grains ofβ-Si3N4 generally contain dislocations and examination of these shows that most have a 〈0001〉 Burgers vector. The remaining dislocations appear to be more complex, frequently occurring as multiple images, and have not been unambiguously identified. An analysis of dislocations inβ-Si3N4 shows that 〈0001〉 dislocations are the most stable and are also likely to be most mobile with {10¯10} as the primary slip plane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00552043
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    The temperature-dependence of the strength of polycrystalline MgO (1970)
    Springer
    Journal of materials science 5 (1970), S. 187-197 
    Details
    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 temperature-dependence of the strength of a range of polycrystalline magnesias has been studied. Fracture occurs either by the extension of inherent flaws or is initiated by plastic flow. It has been possible to give a quantitative account of the effects of temperature, grain-size, porosity and surface condition on the strength of polycrystalline magnesia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00550995
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    The strength and oxidation of reaction-sintered silicon nitride (1970)
    Springer
    Journal of materials science 5 (1970), S. 314-325 
    Details
    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 structure of reaction-sintered silicon nitride is studied using scanning electron and optical microscopy at various stages during nitriding, for a range of nitriding and compacting conditions. The strength is then evaluated and interpreted in terms of the microstructure. It is found that fracture always occurs in a brittle manner by the extension of the largest pores. The effects of prolonged annealing in air above 1000† C on both the structure and strength are investigated. At 1400† C, cristobalite is formed. If the temperature is then maintained above 250† C, the strength is enhanced, but below this temperature the oxide layer cracks and reduces the strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02397783
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    A method for evaluating the time-dependent failure characteristics of brittle materials — and its application to polycrystalline alumina (1972)
    Springer
    Journal of materials science 7 (1972), S. 1137-1146 
    Details
    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 simple method for evaluating stress intensity factor, crack velocity (K, V) diagrams is described. The method is evaluated for the glass/water system and is shown to generate data that are entirely consistent with data obtained on the same system using other techniques. The method is applied to the alumina/water system and the K, V diagrams are used to predict times to failure (Ψ) and effects of strain-rate on strength (σ f). The calculated Ψ and σ f, are in excellent agreement with available data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00550196
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Crack propagation and failure prediction in silicon nitride at elevated temperatures (1974)
    Springer
    Journal of materials science 9 (1974), S. 270-278 
    Details
    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 technique for studying high temperature crack propagation in ceramic materials is developed. The technique is used to obtain relationships between the crack propagation rate and the stress intensity factor for hot-pressed silicon nitride up to 1400° C. The data are then used to develop proof test diagrams which give values for the safe working stress levels for this material after proof testing (or any other flaw detection procedure).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00550951
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    The role of inclusions in the fracture of ceramic materials (1974)
    Springer
    Journal of materials science 9 (1974), S. 1145-1152 
    Details
    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 stress concentrations that occur at inclusions due to thermal expansion and elastic modulus mismatch are discussed and the stress intensity factors at interface cracks that result from these stresses are calculated. It is shown that conservative failure prediction based on an equivalence between inclusion size and crack size is usually acceptable if the shear modulusμ or thermal expansion coefficientα for the inclusion is larger than the matrix values. If, however,μ andα are smaller for the inclusion than the matrix, extensive cracking can develop at the inclusions which may lead to premature failure. For this case the only effective methods for failure prediction are techniques which give directly the maximum stress intensity factor, i.e., proof testing and/or acoustic emission.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00552831
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    Paper (German National Licenses)
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