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  • 1
    Electronic Resource
    Electronic Resource
    Emission of an Edge Dislocation from a Thin-Film-Covered Crack (1997)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 145-149 (Oct. 1997), p. 161-166 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/44/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.145-149.161.pdf
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  • 2
    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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  • 3
    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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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Interaction of an edge dislocation with a wedge crack (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4873-4880 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The elastic interaction of an edge dislocation with a wedge crack is investigated using Muskhelishvili's complex potential treatment of elasticity. The stress intensity factors induced by the dislocation, the strain energy, and the image force acting on the dislocation are formulated, calculated, and plotted. Especially, the influence of wedge angle on the shielding effects and on image forces is investigated. The results show that the radial component of the image force is inversely proportional to the distance from the crack tip to the dislocation and the tangential image force increases with increasing wedge angle as the dislocation position is kept unchanged. When the slip plane passes the crack tip, whether the edge dislocation shields or antishields the crack tip depends on its Burgers vector. In this case, the slip plane of the edge dislocation of Burgers vector b1+ib2=beiθmax inclined at an angle θmax with respect to the positive real axis corresponding to the maximum mode I crack shielding increases slightly to a maximum and then decreases with increasing wedge angle. Regardless of wedge angle, the maximum mode II shielding (or anti-shielding) occurs when the dislocation is located at the positive real axis. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359775
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  • 6
    Electronic Resource
    Electronic Resource
    Anisotropic elasticity study of the critical thickness of an epilayer on a substrate with different elastic constants (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4948-4957 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The critical thickness of an epilayer on a substrate with different elastic constants is investigated by following Stroh's treatment of anisotropic elasticity [Philos. Mag. 3, 625 (1958)]. A closed formula is derived to calculate the critical thickness and an exact solution may involve numerical evaluation of the equation. The results indicate that the self-energy of the dislocation is controlled by the soft phase between the epilayer and the substrate, while the interaction energy depends only on the elastic constants of the thin film. It is easier for a dislocation to be formed if the substrate is softer than the film, and consequently the critical thickness is smaller. On the other hand, a soft epilayer can have a large thickness without any mismatch dislocation. Explicit equations are given here for the {100}, {110}, and {111} epitaxial planes. The system of a GexSi1−x epilayer on a Si substrate was taken as an example to demonstrate the influence of the difference in elastic constants on the critical thickness. Even though the difference between the elastic constants of the epilayer and the substrate is not very large, ignoring this difference can cause a relative error over 20% in calculation of the critical thickness. For this system, a simplified equation yields sufficiently accurate results. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359785
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  • 7
    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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  • 8
    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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  • 9
    Electronic Resource
    Electronic Resource
    Criteria for formation of interface dislocations in a finite thickness epilayer deposited on a substrate (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 7579-7586 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The critical epilayer thickness for the formation of misfit dislocations at the interface between an epilayer and a substrate with a finite thickness is derived in the present study. The analysis is based on the energy approach, in which the self-energy of dislocation, the interaction energy between the dislocation and free surfaces, and the lattice mismatch energy of substrate and epilayer are calculated. To satisfy the free surface condition, the methodology of superposition principle and Fourier transformation are used in analyzing the stress field due to the interface dislocation. The critical epilayer thickness is compared with those reported in the literature. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370558
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of absorption and desorption on the chemical stress field (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 2002-2008 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The present work studies the effects of absorption and desorption on the chemical stress field in a membrane during permeation or both-side charging of a diffusing species. The permeation and both-side charging processes are analyzed with the consideration of the absorption and desorption processes, wherein the flux continuity boundary conditions are adopted. The results show that the chemical stresses are compressive near the surfaces and tensile in the center of the membrane. The maximum magnitude of stress occurs at the entry surface for the permeation process and at both surfaces for the both-side charging process. For the permeation process, the compressive stress at the entry surface increases with time to a maximum and then decreases with time gradually to zero. A similar phenomenon is found at both surfaces in the both-side charging process. In both processes, the stress magnitude depends upon the ratio of the drift velocity through surface to the drift velocity through bulk. When this ratio approaches infinity, the flux continuity boundary conditions reduce to the concentration boundary condition and the highest chemical stress field will be produced. Therefore, reducing the drift velocity through surface would be an efficient means to reduce the strength of the chemical stress. In general, designed surface alloying can introduce diffusing species traps at the surfaces of a membrane, which may efficiently decrease the drift velocity through surface. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1433177
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