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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of optimization theory and applications 14 (1974), S. 585-597 
    ISSN: 1573-2878
    Keywords: Invariant imbedding ; boundary-value problems ; Riccati equations ; difference equations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The determination of the configuration of equilibrium in a number of problems in mechanics and structures such as torsion, deflection of elastic membranes,etc., involve the solution of variational problems defined over irregular regions. This problem, in turn, may be reduced to the solution of elliptic differential equations subject to boundary conditions. In this paper, we study a method for the solution of such a problem when the region is of irregular shape. The method consists in solving the problem over a larger, imbedding, rectangular domain subject to appropriate constraints such as to satisfy the conditions of the original problem at the boundary. In this paper, we introduce the constraints by considering appropriate factors on the Green's function of the auxiliary problem. A conveniently discretized version of the problem is then treated by invariant imbedding, yielding some earlier results plus some new ones, namely, a direct one-sweep procedure that minimizes storage requirements. In addition, the present solution appears to be very convenient when the solution is required at a limited number of points. The derivations are specialized to Laplace's equation, but the method can be applied readily to general systems of second-order elliptic equations with no essential modifications. Finally, the existence of the necessary matrices in the imbedding equations is established.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of optimization theory and applications 15 (1975), S. 13-26 
    ISSN: 1573-2878
    Keywords: Structural optimization ; dynamic programming ; minimum weight design ; minimum of maximum deviation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The optimal design of elastic trusses is discussed from a dynamic programming point of view. Emphasis is placed on minimum volume design of statically determinate trusses with displacement and stress constraints in the discrete case, i.e., when the cross-sectional areas of the bars are available from a discrete set of values. This, a design constraint usually very difficult to handle with standard nonlinear programming algorithms, is naturally incorporated in the present formulation. In addition, the functional equation approach is shown to furnish a direct solution to the problem of determining a design, among all possible ones satisfying certain volume and displacement constraints, for which the maximum stress is a minimum. A successive approximation approach is briefly indicated as an extension of the method to solve statically indeterminate trusses. Finally, several numerical examples are presented and the main features of the methods are briefly exposed.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of optimization theory and applications 23 (1977), S. 27-40 
    ISSN: 1573-2878
    Keywords: One-sweep method ; invariant imbedding ; fluid-structure interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A one-sweep method for the numerical solution of finite-element equations is presented. This procedure is especially efficient in computing time and storage when the solution is required at only a few nodes of the finite-element mesh. Furthermore, the method is particularly useful in dealing with problems on infinite or semi-infinite domains. Artificial boundaries must be introduced in such cases, and the one-sweep method affords an extremely efficient algorithm by which the dependence of the solution on the location of these boundaries can be assessed. An application of the method to the vibration of a half-submerged circular cylinder in a heavy fluid is presented.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of optimization theory and applications 10 (1972), S. 109-128 
    ISSN: 1573-2878
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The minimum-weight design of elastic rotating disks under various design criteria has been studied using ideas of dynamic programming and invariant imbedding. It is shown that the criterion of minimum potential energy furnishes a remarkably simple solution in terms of a linear partial differential equation subject to initial conditions. The treatment of more general design constraints leads to the development of a number of stable, two-sweep iterative procedures. A series of numerical examples incorporating various design constraints is presented to show the accuracy and feasibility of the method. The sensitivity of the radial stresses to small changes in the thickness of the disk is noticed. On the other hand, the high stability of the volume with respect to the design criteria is stressed.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of optimization theory and applications 23 (1977), S. 15-26 
    ISSN: 1573-2878
    Keywords: Dynamic programming ; structural optimization ; invariant imbedding ; boundary-value systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The two-point boundary-value system is treated as a chain composed of a number of 2N-dimensional blocks. This system is optimized using invariant imbedding relations in coupled dynamic programming. Two numerical examples from the field of structural mechanics are used to demonstrate the procedure. This method of optimal design may be applied to systems in many other fields. The size of the problem can be greatly reduced by using invariant imbedding, rather than standard dynamic programming.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of engineering mathematics 6 (1972), S. 117-123 
    ISSN: 1573-2703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Summary In [1] we reduced the solution of a classical boundary-value problem, namely the biharmonic equation in a rectangular domain, to a Cauchy formulation. The theory was developed in the context of elementary thin plate theory. It was shown that a rectangular plate with three edges clamped and the fourth edge free can be completely described by a system of integro-differential equations subject to initial values. In this paper we prove the converse, i.e., that any solution of the Cauchy system is a solution of the biharmonic equation, completing the equivalence.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Acta mechanica 13 (1972), S. 179-190 
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Diese Arbeit behandelt ein Identifizierungsproblem im Rahmen der Theorie thermorheologisch-einfacher Stoffe. Ein Optimierungsalgorithmus zur Bestimmung von Schätzfunktionen zweier das Material kennzeichnende Funktionen wird angegeben, wobei die Art und die Zahl der experimentell ermittelten Spannungs-Verzerrungsgeschichten keinen Einschränkungen, außer der, in der Praxis im allgemeinen zutreffenden Beschränkung auf isotherme Versuche, unterliegen. Zwei Methoden, deren Anwendbarkeit durch die Art der verfügbaren Daten, der Anwendbarkeit des Verschiebungspostulates und durch andere Überlegungen festgelegt ist, werden angegeben. Nach beiden Methoden erhält man eine der beiden Materialfunktionen als Lösung einer gewöhnlichen Differentialgleichung, also in einer Form, die zu einer nachfolgenden Spannungsrechnung mit Hilfe einer elektronischen Ziffernrechenanlage paßt. Abschließend wird ein numerisches Beispiel zur Illustration der Durchführbarkeit und der Genauigkeit der Methoden angegeben.
    Notes: Summary In this paper, an identification problem in the theory of thermorheologically simple materials is discussed. An optimization procedure for estimation of the shift function and characteristic master curve is developed using ideas of differential approximation and quasilinearization. The nature and number of experimental stress and strain history pairs used for identification purposes is not restricted, but the procedure is limited to isothermal tests, a condition generally met in practice. Two methods, depending on the nature of available data, applicability of the shift postulate, and other considerations are presented. In both instances the characteristic master curve is finally given as the solution of a suitable differential equation subject to initial conditions, a convenient functional parameterization if a digital computer is to be used in subsequent stress analysis. Finally, a numerical example is presented to illustrate the feasibility and accuracy of the method.
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  • 8
    Publication Date: 1974-12-01
    Print ISSN: 0022-3239
    Electronic ISSN: 1573-2878
    Topics: Mathematics
    Published by Springer
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  • 9
    Publication Date: 1972-09-01
    Print ISSN: 0001-5970
    Electronic ISSN: 1619-6937
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Published by Springer
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  • 10
    Publication Date: 1972-08-01
    Print ISSN: 0022-3239
    Electronic ISSN: 1573-2878
    Topics: Mathematics
    Published by Springer
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