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  • 1990-1994  (23)
  • 1
    Electronic Resource
    Electronic Resource
    Interaction of an edge dislocation with an interfacial crack (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2215-2226 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stress and displacement fields of an edge dislocation near a semi-infinite or a finite interfacial crack are formulated by using the complex potential theory of Muskhelishvili's elasticity treatment of plane strain problems. The image forces exerted on the dislocation have an oscillatory character (with respect to the dislocation position) if the dislocation is originated elsewhere and moves to the vicinity of a finite interfacial crack. There is no such oscillation of image forces if the edge dislocation is emitted from the finite interfacial crack or if the crack is semi-infinite. The stress intensity factors produced by the edge dislocation also have an oscillatory character for both semi-infinite and finite interfacial cracks. They also depend on whether the dislocation is emitted from the crack or comes from elsewhere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351614
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  • 2
    Electronic Resource
    Electronic Resource
    Mode-III cracks in piezoelectric materials (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5865-5870 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stress and electric fields around a mode-III crack containing a dielectric medium are formulated. Mechanical equilibrium requires that the crack surfaces be traction free. Previous solutions have used the electrical boundary condition that the electric displacement component perpendicular to the crack surfaces should be zero. However, cracks that are filled with a dielectric medium, such as vacuum or air, require that the electric displacement be continuous across the crack faces. Using the boundary condition appropriate for an insulating crack, the stress, strain, and electric-field strength are found to exhibit r−1/2 singularities while the electric displacement does not. The singularity in the electric-field strength arises from piezoelectricity. The driving force for crack growth is only related to the effective level of applied stress. Under constant displacement, the applied field may increase or decrease the effective applied stress depending on its direction. As a result the electric field may promote or retard the crack propagation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350483
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  • 3
    Electronic Resource
    Electronic Resource
    An edge dislocation near a macrocrack with a microcrack (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6079-6087 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The elastic interaction between an edge dislocation and a macrocrack with a microcrack has been investigated by means of the Muskhelishvili potential method. The stress and displacement fields were obtained. From the stress field, we derived the stress intensity factor at each crack tip and the image force on the dislocation. The effects of the distance between two cracks on the crack shielding and of the image force on the edge dislocation were examined. The effects of the microcrack length on the shielding of the macrocrack and of the image force of the dislocation were also considered. The dislocations in the microcrack play an important role in fracture. Two conditions, an edge dislocation emitting from the microcrack and originating from elsewhere, are discussed. We compare the mechanical behavior between edge and screw dislocations near the macrocrack with the microcrack. Newton's third law is satisfied for this system. Two special cases are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355192
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  • 4
    Electronic Resource
    Electronic Resource
    Interaction of a screw dislocation with an interface crack (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 744-751 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interaction between a screw dislocation and an interface cylindrical hole is found to depend on the source and location of the screw dislocation. When a screw dislocation is inside one of the media it has one image in the other medium. If the real dislocation is emitted from the hole which is originally stress free, it has only two images inside the hole. However, if the real dislocation is emitted from elsewhere and moves to the vicinity of the hole, there is a third image at the center of the hole to keep the total Burgers vector of the images in the hole zero. These considerations were used to study the interaction of a screw dislocation with an interface crack (or elliptical hole) by means of conformal mapping. The effect of the screw dislocation on the stress intensity factor at the crack tip is continuous when the screw dislocation moves from one medium across the interface to the other medium. The image force can be divided into two parts. One part is due to the interface and the other is due to the interface crack. The composite solid behaves like a homogeneous solid with an effective shear modulus when the dislocation is in the interface. The interaction between two or more screw dislocations in the presence of an interface crack is studied also. The latter result can be used to study the emission of an array of screw dislocations from an interface crack.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349630
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  • 5
    Electronic Resource
    Electronic Resource
    An array of dislocations in a strained epitaxial layer. I. Elastic energy (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 2358-2362 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The total energy of an array of dislocations in a strained epitaxial layer is composed of the self energy of the dislocations, the strain energy which arises from the lattice mismatch between the layer and its substrate and the interaction energy between the dislocations and the mismatch strains. The sum of the self energy and the interaction energy represents the formation energy of the dislocations. In this study, the self energy is formulated using complex potentials. Two limiting conditions are used to check the solution. The first is that the self energy of the array reduces to that for an isolated single dislocation as the dislocation spacing in the array approaches infinity. Secondly, as the layer thickness approaches infinity, the self energy reduces to that for a dislocation wall. A negative formation energy promotes dislocation generation while a positive formation energy implies a suppression of dislocation generation. A critical thickness required for the generation of an isolated dislocation is found by locating the layer thickness which corresponds to a zero value of the formation energy. The critical dislocation density at a given thickness is also determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356255
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  • 6
    Electronic Resource
    Electronic Resource
    An array of dislocations in a strained epitaxial layer. II. Work hardening (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 2363-2366 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The sequential generation of dislocations in a strained epitaxial layer is considered. It is found that an additional work component results from dislocation-dislocation interactions after some dislocations are generated and located in the interface between the epitaxial layer and the substrate. The interaction energies induced by a single dislocation and a dislocation array are derived. It is found that, in general, when the distance between a fresh dislocation and the nearest pre-existing dislocation is comparable to the layer thickness, the additional work component achieves the level of the self energy of an isolated dislocation. The additional work increases sharply with decreasing distance between the fresh and pre-existing dislocations. If the spacing between the dislocations exceeds approximately 20 times the layer thickness, the additional work becomes insignificant. These results are consistent with experimental observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356256
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  • 7
    Electronic Resource
    Electronic Resource
    A lattice realization for 2-D separable-denominator digital filters (1993)
    Springer
    Circuits, systems and signal processing 12 (1993), S. 465-488 
    Details
    ISSN: 1531-5878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract New properties useful in connection with 1-D and 2-D lattice realizations are developed. These properties enable one to represent given, complicated 2-D separable-denominator digital filters in terms of simpler, more elemental building blocks which consist of two 1-D lattice realizations having dynamics in different directions and connected in a cascade form. The matrix-relationship between a 2-D discrete Schwarz form and a controller-observer canonical form is also derived. A notable property of the proposed 2-D lattice realization is that the impulse response energy of a 2-D separable-denominator digital filter can be readily obtained from the reflection coefficients and input/output tapped coefficients of the realization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01223322
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  • 8
    Electronic Resource
    Electronic Resource
    J-integral measurement for piezoelectric materials (1993)
    Springer
    International journal of fracture 68 (1993), S. R33 
    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/BF00032468
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  • 9
    Electronic Resource
    Electronic Resource
    Elastic analysis of an edge dislocation and two collinear cracks of different length (1994)
    Springer
    International journal of fracture 68 (1994), S. 333-350 
    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 elastic interaction between an edge dislocation and two collinear internal cracks of different length has been investigated. The effect of the distance between two collinear cracks on the crack shielding and image force on the edge dislocation were examined. The effect of the length of the right-hand-side crack on the shielding of the left-hand-side crack and the image force of the dislocation were also considered. The dislocations in the crack play an important role in fracture. Three conditions consisting of an edge dislocation emitting from the right-hand-side crack, originating elsewhere, and emitting from the left-hand-side crack are discussed. We compared the mechanical behavior between edge and screw dislocations near two collinear cracks. Newton's third law is satisfied in this system. Three special cases are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00033960
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of sample width on the energy release rate and electric boundary conditions along crack surfaces in piezoelectric materials (1994)
    Springer
    International journal of fracture 66 (1994), S. R33 
    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/BF00020086
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