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A solution for a dilatation line which occupies an arbitrary position in an elastic wedge with free surfaces and an arbitrary apex angle is found for the first time. The analytical expressions are given in the Mellin space for the stress fields of the dilatation line. It is shown that the free surfaces of the wedge strongly affect upon the stress fields. The axial and hydrostatic stress components are not equal to zero outside the dilatation line. They are strongly inhomogeneous and can change their signs, while their magnitude is comparable with that of the other non-vanishing stress components. They also demonstrate strong non-monotonic and alternating dependence on the wedge apex angle. For the wedge apex angles of 180° and 360°, the non-vanishing stress components of the dilatation line are represented in an explicit form. The results obtained can be used for solving similar problems for long elastic dilatation inclusions of arbitrary cross section embedded to wedge-shaped elastic bodies. The paper is devoted to the memory of our friend and colleague Igor Sevostianov who gave a great contribution to micromechanics of composite and porous materials. [ABSTRACT FROM AUTHOR]

The elastic behavior of an arbitrary oriented wedge disclination dipole located inside a nanowire, which in turn is embedded in an infinite matrix, is studied within the surface/interface theory of elasticity. The corresponding boundary value problem is provided using complex potential functions. The potential functions are defined through modeling the wedge disclination in terms of an equivalent distribution of edge dislocations. The interface effects on the stress field and strain energy of the disclination dipole and image forces acting on it, the influence of relative shear moduli of the nanowire and the matrix, as well as the different characteristics of the interface are studied thoroughly. It is shown that the positive interface modulus leads to increased strain energy and extra repulsive forces on the disclination dipole. The noticeable effect of the negative interface modulus is the non-classical oscillations in the stress field of the disclination dipole and an extra attractive image force on it.

To exploit unique properties of thin films of group III-nitride semiconductors, the production of native substrates is to be developed. The best choice would be AlN; however, presently available templates on sapphire or SiC substrates are defective. The quality of AlN could be improved by eliminating the substrate during the layer growth. In this paper, we demonstrate freestanding AlN layers fabricated by an SiC substrate evaporation method. Such layers were used to investigate dislocation structures near the former AlN-SiC interface. Specimens were characterized by synchrotron radiation imaging, triple-axis diffractometry and transmission electron microscopy (TEM). We found that the evaporation process under non-optimal conditions affected the dislocation structure. When the growth had been optimized, AlN layers showed a uniform distribution of dislocations. The dislocations tended to constitute low-angle subgrain boundaries, which produced out-of-plane and in-plane tilt angles of about 2-3 arc-min. Similar broadening was observed in both symmetric and asymmetric rocking curves, which proved the presence of edge, screw as well as mixed dislocation content. TEM revealed arrays of edge threading dislocations, but their predominance over the other threading dislocations was not supported by present study. To explain the experimental observations, a theoretical model of the dislocation structure formation is proposed. [ABSTRACT FROM AUTHOR]