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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Structural and multidisciplinary optimization 6 (1993), S. 233-237 
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The two-point exponential approximation method was introduced by Fadelet al. (1990) and tested on structural optimization problems with stress and displacement constraints. It was subsequently tested on problems with frequency constraints (Sareenet al. 1991). The results reported in earlier papers showed reductions in the number of iterations needed to reach an optimum, and a smoother convergence towards that optimum. The method, which consists in correcting Taylor series approximations using previous design history, is used in the present paper to automatically determine move-limits. Move-limits are the allowable changes in design variables during the optimization of the approximate problem. The exponents, computed in the two-point exponential approximation by matching slopes between two design iterations, are used as a measure of non-linearity of the objective function and constraints with respect to each of the design variables. The relationships between the move-limits and the exponents are established and individual move-limits are computed and applied to each design variable. The method is applied to two classical structural optimization examples. It provides the engineer with more flexibility when choosing the move-limits and typically converges in less iterations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Structural and multidisciplinary optimization 11 (1996), S. 50-55 
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Structural optimization has progressed significantly in the past twenty years and is now commonly used in the design of mechanical and aeronautical components. A multitude of optimization programs exist and many have been incorporated in finite element programs and are an integral part of that design tool. Problems consisting of a single discipline such as structural, vibrational, etc., have been dealt with successfully by researchers. Multidisciplinary problems such as the design of an aircraft which involves structural, aerodynamic, control and other disciplines were solved using sequentially generated optimized solutions. These sequentially generated optimized solutions need not necessarily lead to a global optimum solution for a coupled problem, as the interdisciplinary effects play a major role in reaching a globally optimized design. This work is aimed at formulating an efficient procedure for coupling multiple disciplines, sensing the effect of one discipline over the other using approximations and move limit strategies. It involves using the information generated from the Two Point Exponential Approximation (TPEA) (which is a first-order approximation modified to include a parameter equivalent to the curvature of functions with respect to the design variables) in the coordination procedure for optimization of multidisciplinary problems. An algorithm, the Best Design Selection Strategy (BDSS), for coupling the multiple disciplines is proposed. The main feature of this algorithm is that the coupling is done such that parallel analysis without any interdependency of one process over the other is still possible. BDSS uses the rule of “survival of the fittest”. The BDSS algorithm is tested on three problems: a beam, a three-bar truss with lumped mass and a ten-bar truss with lumped mass, considering stress and displacement constraints as one discipline (static) and frequency constraints as a second discipline (dynamic).
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Structural and multidisciplinary optimization 2 (1990), S. 117-124 
    ISSN: 1615-1488
    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 examines various first order approximation methods commonly used in structural optimization. It considers several attempts at improving the approximation by using previous analytical results and introduces an adaptation of a first order approximation method using an exponent adjusted to better fit the constraints and reduce the overall number of iterations needed to attain the optimum.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2009-06-24
    Print ISSN: 1059-9495
    Electronic ISSN: 1544-1024
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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  • 5
    Publication Date: 2011-08-19
    Description: This paper examines various first order approximation methods commonly used in structural optimization. It considers several attempts at improving the approximation by using previous analytical results and introduces an adaptation of a first order approximation method using an exponent adjusted to better fit the constraints and reduce the overall number of iterations needed to attain the optimum.
    Keywords: STRUCTURAL MECHANICS
    Type: Structural Optimization (ISSN 0934-4373); 2; 117-124
    Format: text
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  • 6
    Publication Date: 2019-06-28
    Description: The point exponential approximation method was introduced by Fadel et al. (Fadel, 1990), and tested on structural optimization problems with stress and displacement constraints. The reports in earlier papers were promising, and the method, which consists of correcting Taylor series approximations using previous design history, is tested in this paper on optimization problems with frequency constraints. The aim of the research is to verify the robustness and speed of convergence of the two point exponential approximation method when highly non-linear constraints are used.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-187800 , NAS 1.26:187800
    Format: application/pdf
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