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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    The @Journal of Steroid Biochemistry and Molecular Biology 48 (1994), S. 129-137 
    ISSN: 0960-0760
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Terra nova 15 (2003), S. 0 
    ISSN: 1365-3121
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: We present a new survey of several Palaeozoic sections in both the Taurus range and the Border Folds that documents typical glacial features including a glacial pavement and striated dropstones (Halevikdere Formation) and demonstrates the former presence of an ice sheet in southern and south-eastern Turkey. Evidence for the late Ashgill (Hirnantian) age of this episode is provided by macro- and microfossils found within the glacial formation. The extension of ice-related deposits into the northernmost part of the Arabian Platform (Mardin region) implies a much wider distribution of the Ordovician ice sheet than was previously believed, and strongly suggests that southern Turkey lay close to Egypt during the Lower Palaeozoic.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper deals with recovery of potential gradient (∇u) in the resolution of the two-dimensional Laplace equation by boundary element method. The emphasis is placed on ∇u-recovery near and on the boundary, where error behaviour and convergence rate are studied in detail. Conventional hypersingular (HS) and strongly singular (SS) boundary integral representations (BIRs) of ∇u are compared with two recovery procedures recently introduced by Mantič, Graciani and París, Comput. Methods Appl. Mech. Engrg (1999) 178, pp. 267–289: DSC – a local smoothing procedure, and SSC - applying SS BIR with the integral density obtained previously from DSC. The theoretical analysis of error of ∇u recovered by ∇u-BIRs presented is supported by numerical examples. The numerical study of convergence carried out using an h-refinement of (quasi)uniform meshes of linear boundary elements shows a slow convergence rate, O(h) or less, of HS and SS BIRs in comparison with superconvergence rate O(h 2) of DSC (only on the boundary) and SSC near the boundary and at element centres and junctions between elements. A slow convergence rate is obtained by all approximations at boundary corners, SSC clearly providing the most accurate results. Superconvergent results of HS and SS BIRs are only obtained in a particular case of evaluation of tangential derivative of potential on a straight part of the boundary.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Computational mechanics 22 (1998), S. 77-87 
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The theory of the direct and indirect formulations of the Somigliana displacement and stress identities for anisotropic materials subjected to generalized plane strain deformations is revised and rounded off. By making use of the powerful Stroh formalism of anisotropic elasticity, explicit and compact formulae of all integral kernels appearing in these identities are derived and relations between these kernels are analysed. Somigliana stress identity is derived directly from the Betti theorem of reciprocity of work using the singularity source of a dislocation dipole (i.e. a kind of eigenstrain nucleus or concentrated initial strain). Explicit formula of the hypersingular integral kernel in the Somigliana stress identity reveals that this kernel is fully symmetrical with respect to index permutation when only in-plane components are considered. Finally, some comments on the applications of the results presented in the stress analysis of anisotropic materials by collocation BEM and Symmetric Galerkin BEM are presented.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 82 (1990), S. 11-29 
    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 calculation of the energy release rate of a debonding interface crack between fiber and matrix in plane strain requires a knowledge of the stress state and displacements at the neighbourhood of the crack tip. Analytical solutions which involve interpenetrations of the free boundaries of the fiber and matrix have classically been used to predict the variation of the energy release rate with the debonding angle. In this paper a numerical study of this problem as a contact problem, using Boundary Elements, is carried out. The singular stress components are modelled by means of singular discontinuous elements, a particular contact algorithm, which is very appropriate for cases like that under consideration where the fiber is much stiffer than the matrix, having been proposed. The numerical procedure shows the appearance of a contact zone with physical meaning starting at a certain value of the debonding angle, which implies the presence of a pure mode II of fracture. The values of G found by BEM are compared with those predicted by the use of an analytical solution showing clear discrepancies when the contact zone starts to develop, BEM always predicting smaller values of the energy release rate, in accordance with the absence of mode I in the presence of a contact zone.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    International journal of fracture 83 (1997), S. 67-90 
    ISSN: 1573-2673
    Keywords: linear elasticity ; orthotropic materials ; stress singularities ; notches ; cracks ; Stroh relations ; composite materials.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new technique for analysis of two-dimensional linear elastostatic solutions with stress singularities at orthotropic corners is developed. An explicit and general representation of the associated eigenequation given as ‘zero determinant condition’ of a matrix with half dimension in comparison with the current approach is derived by application of Stroh relations of anisotropic elasticity. The technique is directly applicable to anisotropic corners. Analytical formulae for stress singularity exponents, roots of the associated eigenequations, at orthotropic half-plane and semiinfinite crack problems for all combinations of basic homogeneous boundary conditions, including slip with friction, are derived. it is noteworthy that the singularity exponents are invariant with respect to the relative orientation of boundary edges and orthotropic material for nine of these combinations. Numerical analysis of singularity exponents for some configurations typical in the modelization of material tests of fiber-matrix composite materials is presented.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of elasticity 43 (1996), S. 137-145 
    ISSN: 1573-2681
    Keywords: 73B40 ; 73C05 ; anisotropic elasticity ; Stroh formalism ; Betti theorem of reciprocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This paper establishes that the Stroh orthogonality relations for an anisotropic body are a direct consequence of the fact that the system of equations of equilibrium is self-adjoint and positive definite. It is demonstrated that, assuming a complex representation of displacements and boundary tractions, the Betti theorem of reciprocity implies the ‘orthogonality’, and positive definiteness of strain energy implies the full rank of the normalization matrix, in the Stroh orthogonality relations. The presented proof is applicable to both the Lekhnitskii and Eshelby theories of an anisotropic body.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-2681
    Keywords: Anistropic materials ; Stroh formalism ; stress representation ; straight dislocation ; straight dislocation dipole ; straight wedge disclination ; boundary integral equations ; Somigliana stress identity.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Symmetrical stress representation in the Stroh formalism for anisotropic elastic bodies is introduced and the range of its applicability is analysed. By making use of this stress representation new formulae for influence functions giving stresses in an infinite anisotropic medium subjected to a straight dislocation and a straight dislocation dipole are derived. The advantage of the new formulae is that they explicitly show the symmetrical structure of these influence functions not referred to previously. Relations of these influence functions to influence functions giving stresses and Airy stress function due to a straight wedge disclination, whose explicit expressions are also introduced, are derived. Application of these results in computation of stresses by the hypersingular and regularized Somigliana stress identities is discussed.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 23 (1986), S. 173-191 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Plates governed by Kirchhoff's equation have been analysed by the boundary integral equation method using the fundamental solution of the biharmonic equation. In the case of supported plates, the boundary conditions permit the uncoupling of the field equation into two harmonic equations that originate, due to the nature of the fundamental solution, easier integration kernels and a simpler system of equations. The calculation of bending and twisting moments and transverse shear force can be formed, combining derivatives of the integral equation which defines the expression of the deflection on any point of the plate. The uncoupling of the biharmonic equation into two Poisson's equations involves the discretization of the domain of the studied problems. Nevertheless, the unknown quantity of the problem does not appear in the domain integrations for which a refined discretization is unnecessary. In the paper, however, a numerical alternative is considered to express the domain integral by means of boundary integrals. In this way, we need only discretize the boundary of the plate, making it necessary to solve a supplementary system of equations in order to calculate the coefficients of the approximation carried out.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 39 (1996), S. 4021-4038 
    ISSN: 0029-5981
    Keywords: boundary element method ; rigid-body motions ; support conditions ; elasticity ; Fredholm theory ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A theoretical and numerical study of the removal of rigid body motions in the solution of the boundary form of Somigliana identity and of the corresponding discretized linear system of the direct BEM is presented. This study is based on the Fredholm theory of linear operators and mechanical aspects of the problem. Various methods suitable for implementation in BEM codes are analyzed and relations between apparently different methods are shown. The relation between global equilibrium conditions and solvability of the discretized linear system of the direct BEM is discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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