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  • 1
    Electronic Resource
    Electronic Resource
    Brittle Fracture and Toughening Mechanisms in Ceramics (1984)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Materials Research 14 (1984), S. 373-403 
    Details
    ISSN: 0084-6600
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.ms.14.080184.002105
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  • 2
    Electronic Resource
    Electronic Resource
    Stresses in ion-exchange layers of soda-lime-silicate glass (2005)
    PO Box 1354, 9600 Garsington Road, Oxford OX4 2XG, UK. : Blackwell Science Ltd
    Fatigue & fracture of engineering materials & structures 28 (2005), S. 0 
    Details
    ISSN: 1460-2695
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper presents a new method to determine both the magnitude and the sign of the surface stresses that develop as a consequence of sodium/hydrogen ion exchange in soda-lime-silicate glass immersed in water. At 90 °C, very thin layers that develop at the surfaces of polished glass specimens are found to have extremely high compressive stresses, −2.4 GPa. The negative sign of the stress is consistent with earlier findings that the ion-exchange process involves hydronium ions (H3O+) and not bare protons (H+).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-2695.2005.00888.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of sliding friction forces on the strength of brittle materials (1984)
    Springer
    Journal of materials science 19 (1984), S. 2561-2569 
    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 model is developed for the strength degradation of brittle surfaces in sliding contact with spherical indenters. The loss of strength is associated with the propagation of partial cone cracks in the wake of the indenter. Detailed fracture mechanics calculations are circumvented by working in the limit of ideal point-load contacts, with the key proposition that the crack dimensions remain insensitive to rotations of the cone axis relative to the specimen free surface. In this way the simple Roesler solution for classical, well-developed cone cracks may be retained as a convenient “reference state” for a more general theoretical description, whereby the superposition of a tangential friction force onto the normal loading is accommodated via a straightforward coordinate transformation operation. The major predictions of the model are tested by measuring the strengths of glass surfaces after contact with a sliding steel sphere. In particular, the degraded strengths are not strongly influenced by the coefficient of friction, contrary to expectations from some earlier indentation analyses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00550810
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  • 4
    Electronic Resource
    Electronic Resource
    Creep and fracture of a vitreous-bonded aluminium oxide (1986)
    Springer
    Journal of materials science 21 (1986), S. 810-824 
    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 Creep and creep-rupture behaviour of a commercial grade of glass-bonded, 96% aluminum oxide was characterized as a function of temperature and applied stress. The creep data were fitted to the classical empirical relation usually used to describe this phenomenon. The apparent activation enthalpy, ΔH = 926 kJ mol−1, and the stress exponent,n = 4.8, lie at the high end of the range reported for two-phase materials, primarily as a result of structural modifications that occur during creep. A stress-modified Monkman-Grant relationship was fitted to the creep-rupture data to give a stress exponent of −4.2. None of the available theories of creep rupture provided a satisfactory description of the present set of data. Analytical electron microscopy was used to characterize the composition and structure of this material. In the as-received material the intergranular phase was a glass of nearly uniform composition. During high-temperature exposure, devitrification of the glass resulted in the formation of various crystalline phases within the intergranular region of the material. Devitrification depended on both the proximity to the surface, where it was most pronounced, and on the state of stress. In this regard, flexural creep samples exhibited extensive crystallization within the tensile region of the flexural specimens, but little crystallization within the compressive cross-section. From the composition of the retained glass, estimates of the viscosity of the glass at the grain boundaries were made and used, in combination with microstructural information, to compare the creep behaviour with available theories of creep. The results of this paper are consistent with percolation and solution precipitation mechanisms of creep deformation. By contrast, cavitation did not seem to play a major role in the creep deformation process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01117359
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  • 5
    Electronic Resource
    Electronic Resource
    Tensile creep of whisker-reinforced silicon nitride (1991)
    Springer
    Journal of materials science 26 (1991), S. 3931-3939 
    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 This paper presents a study of the creep and creep rupture behaviour of hot-pressed silicon nitride reinforced with 30 vol% SiC whiskers. The material was tested in both tension and compression at temperatures ranging from 1100 to 1250°C for periods as long as 1000 h. A comparison was made between the creep behaviour of whisker-reinforced and whisker-free silicon nitride. Principal findings were: (i) transient creep due to devitrification of the intergranular phase dominates high-temperature creep behaviour; (ii) at high temperatures and stresses, cavitation at the whisker-silicon nitride interface enhances the creep rate and reduces the lifetime of the silicon nitride composite; (iii) resistance to creep deformation is greater in compression than in tension; (iv) the time to rupture is a power function of the creep rate, so that the temperature and stress dependence of the failure time is determined solely by the temperature and stress dependence of the creep rate; (v) as a consequence of differences in grain morphology and glass composition between whisker-free and whisker-reinforced material, little effect of whisker additions on the creep rate was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01184994
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  • 6
    Electronic Resource
    Electronic Resource
    Transient creep behaviour of hot isostatically pressed silicon nitride (1993)
    Springer
    Journal of materials science 28 (1993), S. 445-453 
    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 Transient creep is shown to dominate the high-temperature behaviour of a grade of hot isostatically pressed silicon nitride containing only 4 wt% Y2O3 as a sintering aid. Contributing factors to transient creep are discussed and it is concluded that the most likely cause of longterm transient creep in the present study is intergranular sliding and interlocking of silicon nitride grains. In early stages of creep, devitrification of the intergranular phase, and intergranular flow of that phase may also contribute to the transient creep process. The occurrence of transient creep precluded the determination of an activation energy on the as-received material. However, after creep in the temperature range 1330–1430°C for times exceeding approximately 1100 h, an apparent activation energy of ≈ 1260 kJ mol−1 was measured. It is suggested that the apparent activation energy for creep is determined by the mobility and concentration of diffusing species in the intergranular glassy phase. The time-to-rupture was found to be a power function of the minimum strain rate, independent of applied stress or temperature. Hence, creep-rupture behaviour followed a Monkman-Grant relation. A strain rate exponent of − 1.12 was determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00357822
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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Proof testing of ceramics (1980)
    Springer
    Journal of materials science 15 (1980), S. 2275-2281 
    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 effectiveness of proof testing as a method of improving component reliability was studied by comparing strength distributions of soda-lime-silica glass before and after proof testing. The effects of unloading rate from the proof stress, hold time at the proof stress, and proof test environment were examined. The results indicate that the proof test must be conducted with rapid unloading rates and good environmental control to be effective. The theoretical implications of these results are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00552317
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  • 9
    Electronic Resource
    Electronic Resource
    Proof testing of ceramics (1980)
    Springer
    Journal of materials science 15 (1980), S. 2282-2295 
    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 Theoretical estimates are made of strength distributions after proof testing. Assuming that the crack velocity can be expressed as a power function of the stress intensity factor,v=AK I n , an analysis of the amount of strength loss during a load cycle is presented for single-region crack propagation. For multi-region crack propagation, a numerical analysis is used to describe strength loss. In both analyses, the effects of environment and loading rate are studied. For single region crack propagation, the strength after proof testing can be represented by two Weibull curves: one with a slope ofm at high cumulative failure probability levels; the other with a slope ofn–2 at low failure probability levels. Truncation of the strength distribution always occurs as the result of proof testing; the truncation strength depends on the rate of unloading. Multi-region crack propagation results in a more complicated strength distribution after proof testing. Bimodal strength distributions occur as a consequence of region II type crack growth (i.e.n=0). Theoretical results confirm experimental findings that proof tests must be conducted at rapid unloading rates and with good environmental control to be effective.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00552318
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  • 10
    Electronic Resource
    Electronic Resource
    Proof-testing of hot-pressed silicon nitride (1978)
    Springer
    Journal of materials science 13 (1978), S. 1781-1793 
    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 Proof-testing was investigated as a method for insuring the reliability of hot-pressed silicon nitride in high temperature structural applications. The objective of the study was to determine if the strength distribution of a population of test specimens could be truncated by proof-testing. To achieve this objective the strength of silicon nitride was measured at 25° C and 1200° C, both with and without proof-testing. At 25° C, however, the strength distribution was effectively truncated by proof-test ing. At 1200° C, however, the effectiveness of proof-testing as a means of truncating the strength distribution was determined by the resistance of the silicon nitride to oxidation. Although oxidation removes machining flaws that limit the strength of silicon nitride, long-term exposure to high temperature oxidizing conditions resulted in the formation of surface pits that severely degraded the strength. Provided the effects of high temperature exposure are taken into account, proof-testing is shown to be useful for truncating the strength distribution of hot-pressed silicon nitride at elevated temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00548742
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