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  • 1
    Electronic Resource
    Electronic Resource
    A novel resonant beam technique to determine the elastic moduli in dependence on orientation and temperature up to 2000 °C (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 3052-3058 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new equipment was developed to determine the elastic moduli from the resonance frequencies of the flexural vibrations of a beam up to temperatures of 2000 °C. The elastic moduli are calculated by minimizing the difference of the experimental versus the theoretical resonance frequencies. The theoretical frequencies are obtained by numerically solving Timoshenko's equation, which takes into account the influence of the shear deformation and the rotatory inertia. From the fundamental frequency and the higher modes of vibration, one Young's modulus and two shear moduli (e.g., E11, G12, and G13) are obtained, the latter two coincide for an elastically isotropic material. With the additional effort of cutting out specimens in specific directions, the complete elastic tensor of anisotropic materials can be measured at high temperatures. The limits and the precision of the method are discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149867
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  • 2
    Electronic Resource
    Electronic Resource
    Fatigue behaviour of metallic fibre-reinforced materials: a study of steel fibre-reinforced silver (1982)
    Springer
    Journal of materials science 17 (1982), S. 277-289 
    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 Fatigue damage and crack propagation modes in composites with unidirectionally aligned fibres may be affected by several variables such as fibre and matrix strength, fibre—matrix interfacial bonding and possible fluctuations in the strength of the reinforcing fibres. The influence of the different parameters on the behaviour of metallic fibre-reinforced materials was investigated up to 108 cycles in a model compound of steel-fibre-reinforced silver. The fatigue tests were carried out at a frequency of 20 kHz using an ultrasonic equipment. Two fundamentally different failure mechanisms and several transitional modes have been observed: (a) failure by nucleation and propagation, usually of one matrix fatigue crack, with simultaneous failure of the reinforcing fibres, (b) failure by gradual accumulation of matrix and interface fatigue damage and fibre-inhibited propagation of the final fatigue crack. The occurrence of both mechanisms depends mainly on the development of the local stress conditions when a matrix fatigue crack is approaching a fibre. This is discussed in terms of a simple model. Additionally, the effect of the failure mechanism on fatigue life and on the design of an appropriate failure criterion is considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00809063
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  • 3
    Electronic Resource
    Electronic Resource
    R-curve evaluation with ceramic materials at elevated temperatures by an energy approach using direct observation and compliance calculation of the crack length (1985)
    Springer
    Journal of materials science 20 (1985), S. 2586-2596 
    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 An experimental procedure is presented which allows the direct visual observation and measurement of crack extension in ceramic materials at high temperatures. The directly measured crack lengths, gained from displacement-controlled three-point bend tests, are compared to those calculated from the compliance. An energy approach is presented to calculateR-values from the load-displacement curves. TheseR-values for a pure alumina and an alumina containing a glassy phase, for which the load-displacement curves show non-linearity at high temperatures, are compared toK-values andJ-values. The stress intensity approach, based on traction-free surfaces, gives unrealistic data for the nonlinear behaving material owing to adhesive effects behind the actual crack front. TheJ-values, calculated by two methods developed for investigations with moving cracks, are identical to those from the energy approach.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00556090
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  • 4
    Electronic Resource
    Electronic Resource
    Crack resistance curves of alumina and zirconia at room temperature (1986)
    Springer
    Journal of materials science 21 (1986), S. 411-418 
    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 Ceramic three-point bend specimens were pre-cracked in a displacement-controlled test in air at room temperature to form sharp cracks of different lengths. Critical stress intensity factors (K IC were then measured as a function of sharp crack length in a fast-fracture, load-controlled test. Crack resistance curves (K IC against crack length) were determined for three commercially pure aluminas of different grain size, a debased alumina containing a glassy phase, and a partially stabilized zirconia (PSZ) material. The crack resistance curves proved to be flat for the finer-grained and the debased alumina. A steeply rising crack resistance curve was, however, observed for a pure coarse-grained alumina material which is explained by friction effects of the cracked microstructure behind the measured crack front. The effect is influenced by the test procedure itself. Though crack branching takes place the crack resistance curve of PSZ is completely flat, which is attributed to fast fracture testing where only the most dangerous flaw is activated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01145502
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  • 5
    Electronic Resource
    Electronic Resource
    Crack resistance curves of alumina at high temperatures (1987)
    Springer
    Journal of materials science 22 (1987), S. 1352-1358 
    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 Ceramic three-point bend specimens were pre-cracked in a displacement-controlled test in air at room temperature to form sharp cracks of different lengths. Critical stress intensity factors (K lc) were then measured as a function of sharp crack length in a fast-fracture, load-controlled test at 900, 1000 and 1100° C. By means of these fast fracture tests, crack resistance curves (K lc against crack length) were determined for two commercially pure aluminas of different grain size and for a debased alumina containing a glassy phase. The crack resistance curve for the pure, fine grained alumina proved to be flat at 900° C, as was found for room temperature. A steeply rising crack resistance was, however, observed for the pure coarse-grained alumina at 1100° C and for the debased alumina at 1000 and 1100° C. This rise in KR curves is explained by friction effects of the cracked microstructure behind the crack front for the coarse grained alumina and by adhesive forces caused by the second phase behind the crack front for the debased alumina. These facts are proved by comparison to experiments on notched specimen and by annealing experiments. From the annealing experiments the size of the adhesive zone is estimated for the debased material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01233133
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  • 6
    Electronic Resource
    Electronic Resource
    Lifetime predictions for a ceramic cutting tool material at high temperatures (1987)
    Springer
    Journal of materials science 22 (1987), S. 2051-2057 
    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 Dynamic loading experiments are performed at different loading rates and temperatures in three-point bending with a commercial cutting tool material. Strength data from time-dependent failure analysis are combined with Weibull statistics to make lifetime predictions for static loading (STP diagrams). Stress corrosion is concluded to be active from ambient temperatures up to 1100° C. Additionally at high temperatures an energy dissipation process caused by plastic and viscous second phase is activated. Both these mechanisms are interacting. With the application of Weibull statistics, strength data are shown to be strongly influenced by the area of loaded surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01132938
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  • 7
    Electronic Resource
    Electronic Resource
    Statistical properties of Weibull estimators (1991)
    Springer
    Journal of materials science 26 (1991), S. 6741-6752 
    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 Weibull parameters were estimated for data produced by Monte Carlo simulations using three different approaches: linear regression, moments method, and maximum likelihood method. The last of these was shown to be the most appropriate approach for the whole range of sample sizes of 4 to 100 for estimating the Weibull parameters of a brittle material. In each simulation 10000 estimators were produced. Using these values histograms of the estimators were created, which showed the asymmetry of the Weibull modulus distribution. The integrals of these density functions were directly used to determine confidence intervals for the estimated Weibull moduli. Furthermore it was reaffirmed that a minimum of 30 samples are required for a good characterization of the strength of a brittle material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02402669
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  • 8
    Electronic Resource
    Electronic Resource
    Viscoelastic effects in testing of an Al2O3 ceramic containing a glassy phase (1993)
    Springer
    Journal of materials science 28 (1993), S. 4341-4346 
    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 An alumina with 3 wt% glassy phase was tested at different loading rates at two temperatures (900 and 1000 °C). It was found that an increase in fracture toughness was accompanied by a decrease of the bending strength at the same loading rates. A model is given, which describes the experimental results by linear viscoelasticity of the second phase. Whereas the bulk properties are mainly due to the alumina grains and, therefore, remain nearly unchanged, the crack growth and the fracture behaviour in the intergranular regions is dominated by the viscosity of the glassy phase. This leads to a non-unique value ofK Ic, which is dependent on the temperature and the loading rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01154940
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of heat treatments on the microstructure of a yttria/alumina-doped hot-pressed Si3N4 ceramic (1993)
    Springer
    Journal of materials science 28 (1993), S. 2089-2096 
    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 effects of post-sintering heat treatments on the microstructure in an Y2O3-Al2O3-doped hot-pressed silicon nitride ceramic in an argon atmosphere were studied. The degree of crystallization of the secondary crystalline phase depended more on the time than the temperature of the heat treatments. Analytical transmission electron microscopy studies revealed a spencite-(Y, N)-apatite solid solution as the secondary crystalline phase, while the aluminium content in the residual glass was high.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367567
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  • 10
    Electronic Resource
    Electronic Resource
    Statistical properties of Weibull estimators (1991)
    Springer
    Journal of materials science 26 (1991), S. 6741-6752 
    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 Weibull parameters were estimated for data produced by Monte Carlo simulations using three different approaches: linear regression, moments method, and maximum likelihood method. The last of these was shown to be the most appropriate approach for the whole range of sample sizes of 4 to 100 for estimating the Weibull parameters of a brittle material. In each simulation 10000 estimators were produced. Using these values histograms of the estimators were created, which showed the asymmetry of the Weibull modulus distribution. The integrals of these density functions were directly used to determine confidence intervals for the estimated Weibull moduli. Furthermore it was reaffirmed that a minimum of 30 samples are required for a good characterization of the strength of a brittle material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00553701
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