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  • 1
    Electronic Resource
    Electronic Resource
    Computational methods for optimum design of large complex systems (1986)
    Springer
    Computational mechanics 1 (1986), S. 221-242 
    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 Computational procedures for optimal design of large complex systems are described. Requirements of a good algorithm are discussed. A general design optimization model applicable to several classes of problems is defined. Several optimization algorithms are outlined and differences between them are highlighted. Modern algorithms generate and use approximate Hessian of the Lagrange function to calculate the search direction. They are quite reliable and become extremely efficient when a potential constraint strategy is incorporated into them. Based on recent experience with them, they are recommended for general engineering design applications. Several other computational aspects are also discussed, such as robust implementation of algorithms, use of knowledge base in providing consulting and diagnostic support to the designer, interactive use of optimization, and role of a database and database management system in design optimization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00272625
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  • 2
    Electronic Resource
    Electronic Resource
    Design sensitivity analysis of nonlinear structures using endochronic constitutive model (1992)
    Springer
    Computational mechanics 10 (1992), S. 39-57 
    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 A continuum form of design sensitivity analysis is developed for the history dependent nonlinear structural problems. In particular, a rearranged, form of the non-yield-surface endochronic constitutive theory is used which has a unifying feature of describing the plastic, viscoplastic and viscoelastic behavior in one simple form. Both the total Lagrangian and the updated Lagrangian formulations are developed. The principle of virtual work in the rate form is used to initiate the development. Shape, nonshape and material design sensitivity problems are treated simultaneously using the reference domain concept. Conservative and nonconservative systems as well as static and dynamic problems are treated. An analytical comparison of the total Lagrangian and the updated Lagrangian approaches is made, and conclusions are given. The finite element discretization, computer implementation and numerical evaluations are given in Part 2 of the paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370018
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  • 3
    Electronic Resource
    Electronic Resource
    Design sensitivity analysis of nonlinear structures using endochronic constitutive model (1992)
    Springer
    Computational mechanics 10 (1992), S. 59-72 
    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 The continuum formulation for design sensitivity analysis incorporating the unified endochronic constitutive model described in Part 1 is discretized and implemented using the standard isoparametric finite element procedure. Only the total Lagrangian approach is investigated since it has been concluded to be surperior to the updated Lagrangian approach. Solution of the sensitivity equation and its convergence criterion are reported. Several cases of a ten-member truss under static and dynamic loads are investigated for sensitivity verification for both nonshape and shape design problems. It is concluded that the incremental solution procedure for design sensitivity analysis of history dependent nonlinear problems can give quite accurate sensitivities. However, the equation of motion, constitutive equations and the sensitivity equations must be integrated very accurately. Thus small increments are generally needed and the computational effort for such problems can be substantial.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370019
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  • 4
    Electronic Resource
    Electronic Resource
    Differential dynamic programming technique for constrained optimal control (1991)
    Springer
    Computational mechanics 9 (1991), S. 27-40 
    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 In this paper, two computational procedures based on the differential dynamic programming (DDP) are presented for linear or nonlinear constrained optimal control problems (OCP). The first procedure solves a quadratic programming problem at every time step and thus constructs the differential control law, and the other one uses the multiplier method to sum up all the point-wise constraints and then uses the unconstrained DDP approach to construct the differential control law. In the first approach, the constraints need to be explicitly dependent on the control variables when continuous-time model is used, whereas in the second approach, there is no such limitation. Therefore the second approach is more general than the first one. Detailed algorithms are given for numerical implementation. Numerical evaluation of the techniques is presented in Part 2 of the paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369913
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  • 5
    Electronic Resource
    Electronic Resource
    Design sensitivity analysis of non-linear buckling load (1988)
    Springer
    Computational mechanics 3 (1988), S. 129-140 
    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 This paper describes three procedures for calculating design derivatives of the non-linear critical load. Constraints on the critical load arise naturally in optimal design of structures having non-linear behavior. The incremental procedures used for non-linear analysis can fail before reaching the final load level due to buckling or collapse of the structure. Therefore, load carrying capability of the structure must be improved before optimal design process can proceed further. This requires design derivatives of the critical load factor. A very simple and effective procedure among the three derived, is selected. It uses most of the information already calculated during analysis and sensitivity analysis of other constraints. Design sensitivity analysis is verified using two known examples. Several other structures are optimized to show effectiveness of the procedure. The sensitivity analysis can be combined with another constraints to optimize structures with more general requirements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317060
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  • 6
    Electronic Resource
    Electronic Resource
    An optimization approach for material-constant determination for the endochronic constitutive model (1991)
    Springer
    Computational mechanics 8 (1991), S. 25-41 
    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 optimization approach for material-constant determination is developed and demonstrated for the endochronic constitutive model in this study. This model is rearranged so that it describes the plastic, viscoplastic and viscoelastic behavior in one simple form. Material constants for 304 stainless steel, alpha-titanium and viscoelastic elastomer Wingfoot@ are determined using this approach. Reduction of the general constitutive model and detailed formulation of the optimization problem for each specific case are given. Accurate optimization results giving good description of the material behavior are obtained. Superiority of the optimization approach over the trial-and-error method is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370546
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  • 7
    Electronic Resource
    Electronic Resource
    Differential dynamic programming technique for constrained optimal control (1991)
    Springer
    Computational mechanics 9 (1991), S. 41-53 
    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 In Part 1, two approaches for constrained optimal control problems (OCP) using the differential dynamic programming (DDP) are presented. In the present paper, three illustrative examples are used to evaluate the approaches: (1) A linear quadratic problem (LQP) with an inequality constraint on the state variable, (2) a single degree of freedom nonlinear impact absorber with an inequality constraint on the state variable, and (3) a linear structural control problem with inequality constraints on the state and control variables. The solutions are compared with the results available in the literature. It is found that the DDP is far more efficient compared to the NLP approach. Also, the continuous-time DDP formulation is superior to the discrete-time formulation. The continuous-time DDP with the multiplier approach is recommended for applications since it is more general compared to the one based on quadratic programming.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369914
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  • 8
    Electronic Resource
    Electronic Resource
    An efficient implementation of adjoint sensitivity analysis for optimal control problems (1997)
    Springer
    Structural and multidisciplinary optimization 13 (1997), S. 223-229 
    Details
    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 In this paper an efficient implementation of design sensitivity analysis techniques is presented for nonlinear optimal control problems using the adjoint variable method. Techniques for functionals (integrals) and dynamic response (or pointwise) constraints are developed. Emphasis is placed on the proper choice of numerical techniques which exploit the structure of the problem to achieve efficiency. Numerical results for two optimal control examples show great improvement over previous implementations. Unlike previous results the computational effort required for DSA is shown to increase only linearly with the number of discretization points used and is a much smaller percentage of total CPU time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01197450
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  • 9
    Electronic Resource
    Electronic Resource
    Design sensitivity analysis of nonlinear dynamic response of structural and mechanical systems (1992)
    Springer
    Structural and multidisciplinary optimization 4 (1992), S. 37-46 
    Details
    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 describes a unified variational theory for design sensitivity analysis of nonlinear dynamic response of structural and mechanical systems for shape, nonshape, material and mechanical properties selection, as well as control problems. The concept of an adjoint system, the principle of virtual work and a Lagrangian-Eulerian formulation to describe the deformations and the design variations are used to develop a unified view point. A general formula for design sensitivity analysis is derived and interpreted for usual performance functionals. Analytical examples are utilized to demonstrate the use of the theory and give insights for application to more complex problems that must be treated numerically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01894079
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  • 10
    Electronic Resource
    Electronic Resource
    Robustness, generality and efficiency of optimization algorithms for practical applications (1990)
    Springer
    Structural and multidisciplinary optimization 2 (1990), S. 203-212 
    Details
    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 design of most engineering systems is a complex and time-consuming process. In addition, the need to optimize such systems where multidisciplinary analysis and design procedures are required can cost additional human and computational resources if proper software and numerical algorithms are not used. Several computational aspects of optimization algorithms and the associated software must be considered while making comparative studies and selecting a suitable algorithm for practical applications. Several parameters, such asaccuracy, generality, robustness, efficiency and ease of use, must be considered while deciding the superiority of an optimization approach. Approximate algorithms without sound mathematical basis can be sometimes more efficient for a specific problem, but fail to satisfy other requirements. They are, therefore, not suitable for general applications. An objective of the paper is to emphasize the critical importance of the above-mentioned parameters in large scalestructural optimization and other applications. Theoretical foundations of two promising approaches, thesequential quadratic programming (SQP) andoptimality criteria (OC), are presented and analysed. Recent numerical experiments and experiences with the SQP algorithm satisfying these requirements are described by solving a variety of structural design problems. An important conclusion of the paper is that the SQP method with a potential constraint strategy is a better choice as compared to the currently prevalent mathematical programming (MP) and OC approaches.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01748225
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