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  • 1
    Electronic Resource
    Electronic Resource
    A probabilistic model of brittle crack formation (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 4124-4129 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Probability of a brittle crack formation in an elastic solid with fluctuating strength is considered. A set Ω of all possible crack trajectories reflecting the fluctuation of the strength field is introduced. The probability P(X) that crack penetration depth exceeds X is expressed as a functional integral over Ω of a conditional probability of the same event taking place along a particular path. Various techniques are considered to evaluate the integral. Under rather nonrestrictive assumptions we reduce the integral to solving a diffusion-type equation. A new characteristic of fracture process, "crack diffusion coefficient,'' is introduced. An illustrative example is then considered where the integration is reduced to solving an ordinary differential equation. The effect of the crack diffusion coefficient and of the magnitude of strength fluctuations (ratio of minimal and mean values of the strength field) on probability density of crack penetration depth is presented. Practical implications of the proposed model are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339128
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  • 2
    Electronic Resource
    Electronic Resource
    Strain-energy effects on dynamic fragmentation (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 1379-1380 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Grady's model of the dynamic fragmentation process, in which the average fragment size is determined by balancing the local kinetic energy and the surface energy, is modified to include the stored elastic (strain) energy. The revised model predicts that the strain energy should dominate for brittle materials, with low fracture toughness and high fracture-initiation stress. This conclusion is not borne out, however, by limited experimental data on brittle steels, even when the kinetic-energy density is small compared with the strain-energy density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336532
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  • 3
    Electronic Resource
    Electronic Resource
    A fracture mechanics model of fragmentation (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 1224-1226 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A model of the fragmentation process is developed, based on the theory of linear elastic fracture mechanics, which predicts the average fragment size as a function of strain rate and material properties. This approach permits a unification of previous results, yielding Griffith's solution in the low-strain-rate limit and Grady's solution at high strain rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337373
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  • 4
    Electronic Resource
    Electronic Resource
    Thermodynamics of the quasiequilibrial growth of crazes (1981)
    Springer
    Journal of materials science 16 (1981), S. 35-44 
    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 By comparing the morphology and physical properties (averaged over the scale of 1 to 10μm) of a crazed and uncrazed polymer, it can be concluded that crazing is a new phase development in the initially homogeneous material. The present study is based on recent work on the general thermodynamic explanation of the development of a damaged layer of material. The treatment generalizes the model of a crack-cut in mechanics. The complete system of equations for the quasiequilibrial craze growth follows from the conditions of local and global phase equilibrium, mechanical equilibrium and a kinematic condition. Constitutive equations of craze growth-equations are proposed that are between the geometric characteristics of a craze and generalized forces. It is shown that these forces, conjugated with the geometric characteristics of a craze, can be expressed through the known path independent integrals (J, L, M,). The criterion of craze growth is developed from the condition of global phase equilibrium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00552056
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of residual stress on crack propagation in MDPE pipes (1987)
    Springer
    Journal of materials science 22 (1987), S. 3873-3879 
    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 Crack propagation behaviour in single edge notched specimens prepared from medium-density polyethylene (MDPE) pipe is examined under creep condition. The crack grown from an exterior notch (inbound) initiated faster than that grown from an interior notch (outbound). Subsequently, the outbound crack propagated monotonically to ultimate failure. The inbound crack showed anomalous behaviour involving two arrest stages prior to ultimate failure. The pipe is found to possess substantial residual stresses. The energy release rate for each case was calculated taking into account the respective residual stream distribution. The fact that the rates of crack propagation are not a unique function of the energy release rate indicates that the fracture is also influenced by morphological gradients imposed by processing conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01133334
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  • 6
    Electronic Resource
    Electronic Resource
    On the constancy of the specific enthalpy of fracture (1988)
    Springer
    Journal of materials science 23 (1988), S. 2321-2324 
    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 specific enthalpy of fracture due to ductile crack propagation in commercial polycarbonate sheet is calculated as γ* =A 1c/R 1c, whereA 1c is the critical energy release rate associated with the onset of unstable crack propagation andR 1c is the corresponding amount of damage (yielded material) formed per unit crack extension.A 1c andR 1c are determined from fatigue crack propagation experiments conducted at different maximum loads, load ratios and frequencies. The value of γ* obtained from all experiments is found to be 9.8±1.4 cal g−1 (1cal = 4.184 J) which indicates that γ* is a material constant. This finding substantiates predictions of the crack layer theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01111883
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  • 7
    Electronic Resource
    Electronic Resource
    Observations of the micro-mechanisms of fatigue-crack initiation in polycarbonate (1994)
    Springer
    Journal of materials science 29 (1994), S. 5903-5910 
    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 mechanisms of crack initiation in tensile fatigue of single-edge notched specimens of polycarbonate of varying thickness have been elucidated. At low stresses and long times microcracking and localized yielding occurred to form regular diamond-shaped cells on a scale of 2–4 Μm. On increasing the stress level with thin specimens (〈1 mm), the microshear bands coalesced to form macroscopic damage zones of yielded material around the notch, followed by crack tearing from the notch surface. With increasing specimen thickness, restriction of shear banding ensued and a stable, semi-elliptical cavitation, or pop-in, formed about 10–100 Μm ahead of the notch, dependent on specimen geometry. As a result, the ligament formed between the notch and pop-in consists of yielded material. Brittle behaviour resulted with further increases in specimen thickness on loading, i.e. when the ligament could not be stabilized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366874
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  • 8
    Electronic Resource
    Electronic Resource
    On the accuracy of the calculated stress field around a crazeThis work performed at Sandia National Laboratories and supported by the U. S. Department of Energy under Contract #de-aac04-76dp00789. (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 426-431 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Several recent calculations of the stress field around crazes in glassy polymers have been based on experimentally obtained craze opening displacements. Although various techniques for performing these calculations have been presented (i.e., Fourier transform, boundary integral, and finite element methods), all are based on the solution of the same ill-conditioned boundary value problem. Specific boundary conditions required to calculate the stresses around a craze lead to a large change in the stress field with small changes in the craze profile which are within the reported experimental tolerance.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760290612
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  • 9
    Electronic Resource
    Electronic Resource
    Pulsations of damage during a fast running crack (1987)
    Springer
    International journal of fracture 33 (1987), S. R67 
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00044420
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  • 10
    Electronic Resource
    Electronic Resource
    Probabilistic fracture mechanics of 2D carbon-carbon composites (1992)
    Springer
    International journal of fracture 55 (1992), S. 179-191 
    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
    Notes: Abstract The fracture toughness of two types of carbon fabric reinforced carbon composite (KKARB®, Types A and C) is evaluated, the mechanisms of crack propagation resistance are identified and both are related to microstructural differences. The two composites have the same constituents, i.e. fibers, yarns, fabric weaving and matrix precursor. However, different processing cycles result in apparent differences in microstructure (e.g. different number and length distribution of microcracks, crimp angle) and toughness. The crack diffusion model (CDM) is invoked to parameterize the fluctuating strength field of the composite in terms of an average fracture energy 〈γ〉, a minimum fracture energy 179-1 and a shape parameter α. The values of 179-1 are in direct correlation with the average size of microcracks in each composite, and α is found to correlate with the scatter in fracture toughness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017276
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