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  • 1
    Electronic Resource
    Electronic Resource
    Stress-induced crack path in Aji granite under tensile stress (1992)
    Springer
    Pure and applied geophysics 138 (1992), S. 641-656 
    Details
    ISSN: 1420-9136
    Keywords: Stress-induced crack ; granite ; tensile strength ; fractal ; double-torsion test ; stress corrosion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The double-torsion test using Aji granite was carried out to investigate the interaction between stress-induced crack path and mineral grains. Crack velocities were controlled at range 10−7 m/s to 10−1 m/s. After the stressed specimens were dyed, we checked the crack path by thin section analysis, using an optical microscope. The stress-induced crack path was divided into two types, transgranular and intergranular cracks, and each path was subdivided with respect to mineral grains. In spite of the extensive range of crack velocities, the ratios between the transgranular and intergranular crack lengths did not change. The crack paths were all jagged, and often showed detour around the grain boundary when faced with obstacles like hard grains or preexisting cracks. That is to say, quartz grain played an important role as an obstacle. Feldspar grain could change the crack path because of its cleavage plane. Biolite grain had a serious effect on the path even if its constitution ratio is very small. Fractal dimensions of the crack paths were calculated by three methods, as indicators of surface roughness. The fractal dimensions were shown in a slight trend with the change of crack velocity. This trend can be explained from the point of limited cracking rate in stress corrosion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876342
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  • 2
    Electronic Resource
    Electronic Resource
    Relation of fracture resistance to fabric for granitic rocks (1992)
    Springer
    Pure and applied geophysics 138 (1992), S. 657-677 
    Details
    ISSN: 1420-9136
    Keywords: Granite ; subcritical crack growth ; stress corrosion ; double-torsion ; anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Double-torsion specimens of two granitic rocks were prepared in several directions with reference to microcracks fabric. Even for the same rock and at the same stress levels, the observed crack velocities in two granitic rocks were dependent on both the propagation direction and the opening direction. The maximum difference by several orders of magnitude was found for both rocks. The highest crack velocity was observed when the subcritical crack was parallel to most of the preexisting cracks. The maximum critical stress intensity factor was about twice as high as the minimum one in different directions. An analysis for a thin plate having anisotropic elasticity under torsional load showed that the observed difference in the crack velocity and the critical stress intensity factor was not an error due to conventional equations derived on the assumption of isotropic elasticity but the true material's property. As the preferred orientation of microcracks has been pointed out for many granitic rocks, we can conclude that the anisotropic nature of the fracture resistance of the two granitic rocks used in this study was not exceptional. A region of a transport-limited velocity was not found for rocks, even at the velocity of 10−2 m/s, that is almost equal to the theoretical limit of the stress corrosion cracking.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876343
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  • 3
    Electronic Resource
    Electronic Resource
    A revision of the double-torsion technique for brittle materials (1988)
    Springer
    Journal of materials science 23 (1988), S. 2505-2511 
    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 Serious doubts about the constant-K characteristics of double-torsion specimens have been expressed in recent years. However, compliance calibration shows that the energy release rate and hence the stress intensity factor are independent of the crack length in this technique. Relatively large scattering in the results obtained by the load-relaxation method makes the data unreliable. The load-relaxation experiments should be carried out in combination with other methods. A theoretical calculation of the load-deformation curve under a constant displacement rate gives a rough estimation of the stress corrosion index. The subcritical crack growth data can be given, in principle, by only one experimental run of the constant displacement rate method of double-torsion testing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01111909
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  • 4
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    A revision of the double-torsion technique for brittle materials (1988)
    Springer
    Details
    Publication Date: 1988-07-01
    Print ISSN: 0022-2461
    Electronic ISSN: 1573-4803
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 5
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    Stress-induced crack path in Aji granite under tensile stress (1992)
    Springer
    Details
    Publication Date: 1992-01-01
    Print ISSN: 0033-4553
    Electronic ISSN: 1420-9136
    Topics: Geosciences , Physics
    Published by Springer
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  • 6
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    Relation of fracture resistance to fabric for granitic rocks (1992)
    Springer
    Details
    Publication Date: 1992-01-01
    Print ISSN: 0033-4553
    Electronic ISSN: 1420-9136
    Topics: Geosciences , Physics
    Published by Springer
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  • 7
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    Crucial effect of system compliance on the maximum stress estimation in the hydrofracturing method: Theoretical considerations and field-test verification (2006)
    Springer
    Details
    Publication Date: 2006-08-01
    Description: Why do the currently available data sets from field hydrofracturing tests indicate that the measured re-opening pressure lies close to the shut-in pressure far more often than can reasonably be expected? In order to explain such a strange phenomenon, it is necessary to take into consideration two additional factors, those of (1) a residual aperture of fracture and (2) hydraulic compliance of the test equipment, both of which are ignored in the conventional theory of hydraulic fracturing. The residual aperture causes pressure penetration into the fracture prior to opening, and its effect is to reduce the re-opening pressure by a factor of two from the value expected when the conventional theory is used. The conventional theory implies that the fracture always begins to open at a borehole pressure less than the shut-in pressure. However, due to the effect of large hydraulic compliance, the reopening pressure measured in the conventional manner becomes larger than the true reopening pressure and approaches the shut-in pressure. Contrary to this, the reopening pressure measured using the test equipment with sufficiently small compliance represents a good estimate of the true reopening pressure. This pressure is related to the maximum horizontal stress S H, and its measured value allows us to estimate the value of S H.
    Print ISSN: 1343-8832
    Electronic ISSN: 1880-5981
    Topics: Geosciences , Physics
    Published by Springer
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