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  • 1
    Electronic Resource
    Electronic Resource
    On the symbolic manipulation and code generation for elasto-plastic material matrices (1986)
    Springer
    Engineering with computers 1 (1986), S. 205-215 
    Details
    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A computerized procedure for symbolic manipulations and FORTRAN code generation of elasto-plastic material matrix for finite element applications is presented. Special emphasis is placed on expression simplifications during intermediate derivations, optimal code generation, and interface with the main program. A systematic procedure is outlined to avoid redundant algebraic manipulations. Symbolic expressions of the derived material stiffness matrix are automatically converted to RATFOR code which is then translated into FORTRAN statements through a preprocessor. To minimize the interface problem with the main program, a template file is prepared so that the translated FORTRAN statements can be merged into the file to form a subroutine (or a submodule). Three constitutive models; namely, von Mises plasticity, the Drucker-Prager model, and a concrete plasticity model, are used as illustrative examples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01200137
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Stress intensity factors in a fully interacting, multicracked, isotropic plate (1993)
    Springer
    Computational mechanics 12 (1993), S. 297-314 
    Details
    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 An essential part of describing the damage state and predicting the damage growth in a multicracked plate is the accurate calculation of stress intensity factors (SIF's). Analytical derivations of these SIF's for a multicraked plate can be complex and tedious. Recent advances, however, in intelligent application of symbolic computation can overcome these difficulties and provide the means to rigorously and efficiently analyze this class of problems. Here, the symbolic algorithm required to implement the methodology for the rigorous solution of the system of singular integral equations for SIF's is presented. The special problem-oriented symbolic functions to derive the fundamental kernels are described, and the associated automatically generated FORTRAN subroutines are given. As a result, a symbolic/FORTRAN package named SYMFRAC, capable of providing accurate SIF's at each crack tip, has been developed and validated. Simple illustrative examples using SYMFRAC show the potential of the present approach for predicting the macrocrack propagation path due to existing microcracks in the vicinity of a macrocrack tip, when the influence of the microcracks' location, orientation, size, and interaction are accounted for.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00372174
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Symbolic derivation of potential based constitutive equations (1990)
    Springer
    Computational mechanics 6 (1990), S. 237-246 
    Details
    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 Structural alloys used in high temperature applications exhibit complex thermomechanical behavior that is inherently time dependent and hereditary, as the current behavior depends not only on current conditions but on the thermomechanical history. Derivation of mathematical expressions (constitutive equations) which describe this high temperature material behavior can be quite time consuming, involved, and error-prone, thus intelligent application of symbolic systems to facilitate this tedious processes can be of significant benefit. Here a computerized package, running under MACSYMA, capable of efficiently deriving potential based constitutive models, in analytical form (involving tensors, partial differentiation, invariants, and the like) is presented. Special purpose utility algorithms are designed and implemented to perform partial differentiation (chain rule), tensor manipulation, case distinction and simplification. Four constitutive theories reported in the literature are utilized to verify implementation accuracy. It is expected that this symbolic package can and will provide a significant incentive to the development of new constitutive theories.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350240
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    On symbolic manipulation and code generation of a hybrid three-dimensional solid element (1991)
    Springer
    Engineering with computers 7 (1991), S. 47-59 
    Details
    ISSN: 1435-5663
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract A symbolic procedure is utilized to derive the analytical expressions of the component matrices resulting to the closed-form integration of a stiffness matrix of a hybrid finite element. In order to alleviate the expression growth problem, we employ special techniques, including the use of symmetry conditions, pattern search, and introduction of intermediate variables, so that the final form of the derived stiffness matrix is suitable for coding implementation. Application of the symbolic procedure is made on a hybrid three-dimensional 8-node solid element. The same procedure is equally applicable to other types of hybrid elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01208345
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Expression of insulin-like growth factors I and II in conceptuses from normal and diabetic mice (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 37 (1994), S. 382-390 
    Details
    ISSN: 1040-452X
    Keywords: Insulin-like growth factors ; Diabetes ; Embryos ; Mouse ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Insulin-like growth factors (IGF-I and IGF-II) play an important regulatory role in fetal growth and development. Alterations in expression of these growth factors may result in developmental abnormalities, macrosomia, and intrauterine growth retardation, which occur with a higher incidence in diabetic pregnancies. In situ hybridization histochemistry was employed to investigate the distribution and abundance of IGF-I and IGF-II in peri-implantation and postimplantation conceptuses from normal and streptozotocin-treated diabetic mice. Animals were sacrificed on gestational days 5, 6, 7, 8, and 9. The entire uterine horn was prepared for hybridization with antisense and sense α-35S-dATP labeled oligonucleotide probes for IGF-I, IGF-II, and mouse β-actin. IGF-I transcript was apparent only in myometrium at 6 days of gestation in normal and diabetic mice. IGF-II transcripts were restricted to trophoectoderm cells within the implantation chamber on day 5. Following implantation, IGF-II transcripts were found in trophoectodermal derivatives, primitive endoderm, mesoderm, heart, walls of the foregut, and mesenchyme in normal and diabetic postimplantation conceptuses. There were no apparent differences between normal and diabetic samples in the distribution and abundance of the IGF-II transcript from gestational days 7, 8, and 9. The embryos from the diabetic mother at day 6 were growth retarded and had a significant decrease in the expression of IGF-II. These results suggest that maternal hyperglycemia may retard development of the early implanting conceptus in a narrow window around day 6 through a mechanism involving decreased IGF-II expression. Fetuses from diabetic pregnancies that escape this critical period appear to develop and express IGF-II in an equivalent manner to those of the control group. © 1994 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080370404
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Explicit robust schemes for implementation of a class of principal value-based constitutive models: Symbolic and numeric implementation (1994)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 37 (1994), S. 1931-1944 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The issue of developing effective and robust schemes to implement a class of the Ogden-type hyperelastic constitutive models is addressed. To this end, special purpose functions (running under MACSYMA) are developed for the symbolic derivation, evaluation, and automatic FORTRAN code generation of explicit expressions for the corresponding stress function and material tangent stiffness tensors. These explicit forms are valid over the entire deformation range, since the singularities resulting from repeated principal-stretch values have been theorectically removed. The required computational algorithms are outlined, and the resulting FORTRAN computer code is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620371110
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    Paper (German National Licenses)
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