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  • Elasticity  (2)
  • fracture mechanics  (2)
  • *Morphogenesis  (1)
  • Animals  (1)
  • 2000-2004  (4)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    International journal of fracture 102 (2000), S. 371-392 
    ISSN: 1573-2673
    Schlagwort(e): Elasticity ; body force method ; singular integral equations ; numerical analysis ; three-dimensional analysis ; stress concentration factor ; ellipsoidal inclusion.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract In this paper the interaction among a row of N ellipsoidal inclusions of revolution is considered. Inclusions in a body under both (A) asymmetric uniaxial tension in the x-direction and (B) axisymmetric uniaxial tension in the z-direction are treated in terms of singular integral equations resulting from the body force method. These problems are formulated as a system of singular integral equations with Cauchy-type or logarithmic-type singularities, where unknowns are densities of body forces distributed in the r,θ,z directions. In order to satisfy the boundary conditions along the ellipsoidal boundaries, the unknown functions are approximated by a linear combination of fundamental density functions and polynomials. The present method is found to yield rapidly converging numerical results for interface stresses. When the elastic ratio E 1⇒E I/E M〉1, the primary feature of the interaction is a large compressive or tensile stress σn on the interface θ=0. When E 1⇒E I/E M〈1, a large tensile stress σθ or σt on the interface θ=1/2π is of interest. If the spacing b/d and the elastic ratio E I/E M are fixed, the interaction effects are dominant when the shape ratio a/b is large. For any fixed shape and spacing of inclusions, the maximum stress is shown to be linear with the reciprocal of the squared number of inclusions.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    International journal of fracture 105 (2000), S. 367-389 
    ISSN: 1573-2673
    Schlagwort(e): Stress intensity factor ; tribology ; contact problem ; friction coefficient ; fracture mechanics ; rolling contact fatigue ; surface crack ; body force method.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract In rolling/sliding contact fatigue, it is known that the crack propagates at a characteristic angle θ=15–30 deg to the surface. To analyze the mechanism, however, the body force method has been widely used assuming 3D crack models for θ=45–90. In this study, therefore, the unknown body force densities are newly approximated by using fundamental density functions and polynomials. Then, a semi-elliptical crack model is analyzed for θ=15–90 under compressive residual stresses and Hertzian contact loads. The stress intensity factors K II, K III are calculated with varying the crack shape b/a, inclination crack angle θ, and crack face friction coefficient μ. The calculations show that the present method is useful for the analysis for θ=15–30 deg with high accuracy. It is seen that the K II-values when b/a→0 are larger than the ones when b/a=1 by 0–24% for both under compressive residual stress and Hertzian contact load. Regarding the maximum K II values under Hertzian contact load, the results of θ=15 deg are smaller than the ones of θ=45 deg by 23–34%. Regarding the amplitude of (K II max−K II min), the results of θ=15 deg are smaller than the ones of θ=45 deg by 4–24%. With increasing the value of friction coefficient μ for crack faces the value of K II decreases significantly. When the crack is short and the inclination angle θ is small, the value of friction coefficient f for Hertzian contact load largely affect the K II value.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    International journal of fracture 103 (2000), S. 19-39 
    ISSN: 1573-2673
    Schlagwort(e): Elasticity ; composite material ; fracture mechanics ; fiber ; generalized stress intensity factor ; end effect ; interaction ; rectangular inclusions.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract To evaluate the mechanical strength of fiber reinforced composites it is necessary to consider singular stresses at the end of fibers because they cause crack initiation, propagation, and final failure. The singular stress is expressed by generalized stress intensity factors defined at the corner of fibers. As a 2D model an interaction between rectangular inclusions under longitudinal tension is treated in this paper. The body force method is used to formulate the problem as a system of singular integral equations with Cauchy-type or logarithmic-type singularities, where the unknown functions are the densities of body forces distributed in infinite plates having the same elastic constants as those of the matrix and inclusions. In order to analyze the problem accurately, the unknown functions are expressed as piecewize smooth functions using two types of fundamental densities and power series, where the fundamental densities are chosen to represent the symmetric stress singularity of 1/r 1−λ 1 and the skew-symmetric stress singularity of 1/r 1−λ 2. Then, generalized stress intensity factors at the end of inclusions are systematically calculated for various locations, spacings and elastic modulus of two rectangular inclusions in a plate subjected to longitudinal tension.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Publikationsdatum: 2001-07-07
    Beschreibung: In the visual system, the establishment of the anteroposterior and dorsoventral axes in the retina and tectum during development is important for topographic retinotectal projection. We identified chick Ventroptin, an antagonist of bone morphogenetic protein 4 (BMP-4), which is mainly expressed in the ventral retina, not only with a ventral high-dorsal low gradient but also with a nasal high-temporal low gradient at later stages. Misexpression of Ventroptin altered expression patterns of several topographic genes in the retina and projection of the retinal axons to the tectum along both axes. Thus, the topographic retinotectal projection appears to be specified by the double-gradient molecule Ventroptin along the two axes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sakuta, H -- Suzuki, R -- Takahashi, H -- Kato, A -- Shintani, T -- Iemura Si -- Yamamoto, T S -- Ueno, N -- Noda, M -- New York, N.Y. -- Science. 2001 Jul 6;293(5527):111-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Molecular Neurobiology, National Institute for Basic Biology, The Graduate University for Advanced Studies, 38 Nishigonaka, Myodaiji-cho, Okazaki 444-8585, Japan.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11441185" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Alternative Splicing ; Amino Acid Sequence ; Animals ; Bone Morphogenetic Protein 4 ; Bone Morphogenetic Proteins/*antagonists & inhibitors/genetics/metabolism ; Chick Embryo ; Cloning, Molecular ; Electroporation ; Embryo, Nonmammalian/cytology/metabolism ; Eye Proteins/chemistry/genetics/*metabolism ; *Gene Expression Regulation, Developmental ; Gene Library ; Humans ; In Situ Hybridization ; Mice ; Microinjections ; Molecular Sequence Data ; *Morphogenesis ; Nerve Tissue Proteins ; Precipitin Tests ; Protein Binding ; Protein Isoforms/chemistry/genetics/metabolism ; RNA, Messenger/analysis/genetics ; Retina/*embryology/*metabolism ; Sequence Alignment ; Surface Plasmon Resonance ; Xenopus Proteins ; Xenopus laevis/embryology/metabolism
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Standort Signatur Erwartet Verfügbarkeit
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