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  • 1
    Digitale Medien
    Digitale Medien
    Design sensitivity analysis of non-linear buckling load (1988)
    Springer
    Computational mechanics 3 (1988), S. 129-140 
    Details
    ISSN: 1432-0924
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00317060
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  • 2
    Digitale Medien
    Digitale Medien
    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
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00370546
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  • 3
    Digitale Medien
    Digitale Medien
    Differential dynamic programming technique for constrained optimal control (1991)
    Springer
    Computational mechanics 9 (1991), S. 41-53 
    Details
    ISSN: 1432-0924
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00369914
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  • 4
    Digitale Medien
    Digitale Medien
    Computational methods for optimum design of large complex systems (1986)
    Springer
    Computational mechanics 1 (1986), S. 221-242 
    Details
    ISSN: 1432-0924
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00272625
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  • 5
    Digitale Medien
    Digitale Medien
    Design sensitivity analysis of nonlinear structures using endochronic constitutive model (1992)
    Springer
    Computational mechanics 10 (1992), S. 39-57 
    Details
    ISSN: 1432-0924
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00370018
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  • 6
    Digitale Medien
    Digitale Medien
    Design sensitivity analysis of nonlinear structures using endochronic constitutive model (1992)
    Springer
    Computational mechanics 10 (1992), S. 59-72 
    Details
    ISSN: 1432-0924
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00370019
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  • 7
    Digitale Medien
    Digitale Medien
    Differential dynamic programming technique for constrained optimal control (1991)
    Springer
    Computational mechanics 9 (1991), S. 27-40 
    Details
    ISSN: 1432-0924
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00369913
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  • 8
    Digitale Medien
    Digitale Medien
    Object-oriented programming for engineering applications (1991)
    Springer
    Engineering with computers 7 (1991), S. 225-235 
    Details
    ISSN: 1435-5663
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Maschinenbau , Technik allgemein
    Notizen: Abstract The object-oriented programing (OOP) methodology is introduced as a means for improving the management of a complex engineering software. The drawbacks of existing engineering software development techniques are pinpointed. The basic concepts of the OOP methodology are interpreted in the context of engineering applications. The familiar concept of a matrix is used as an example to interpret the ideas presented. It is concluded that the OOP methodology facilitates the management of complex engineering software systems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01206364
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  • 9
    Digitale Medien
    Digitale Medien
    Data base design methodology for structural analysis and design optimization (1986)
    Springer
    Engineering with computers 1 (1986), S. 149-160 
    Details
    ISSN: 1435-5663
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Maschinenbau , Technik allgemein
    Notizen: Abstract A methodology to design data bases for finite element analysis and structural design optimization is described. The methodology considers three views of data organization-conceptual, internal, and external. Tabular and matrix forms of data are included. The relational data model is used in the data base design. Entity, relation, and attributes are considered to form a conceptual view of data. First, second, and third normal forms of data are suggested to design an internal model. Several aspects such as processing, iterative needs, multiple views of data, efficiency of storage and access time, and transitive data are considered in the methodology.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01200115
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  • 10
    Digitale Medien
    Digitale Medien
    Simultaneous analysis and design optimization of nonlinear response (1987)
    Springer
    Engineering with computers 2 (1987), S. 53-63 
    Details
    ISSN: 1435-5663
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Maschinenbau , Technik allgemein
    Notizen: Abstract The optimal structural design requiring nonlinear analysis and design sensitivity analysis can be an enormous computational task. It is extremely important to explore ways to reduce the computational effort so that more realistic and larger-scale structures can be optimized. The optimal design process is iterative requiring response analysis of the structure for each design improvement. A recent study has shown that up to 90 percent of the total computational effort is spent in computing the nonlinear response of the structure during the optimal design process. Thus, efficiency of the optimization process for nonlinear structures can be substantially improved if numerical effort for analyzing the structure can be reduced. This paper explores the idea of using design sensitivity coefficients (computed at each iteration to improve design) to predict displacement response of the structure at a changed design. The iterative procedure for nonlinear analysis of the structure is then started from the predicted response. This optimization procedure is called “mixed” and the original procedure where sensitivity information is not used is called the “conventional” approach. The numerical procedures for the two approaches are developed and implemented. They are compared on some truss type structures by including both geometric and material nonlinearities. Stress, strain, displacement, and buckling load constraints are imposed. The study shows the mixed method to be numerically stable and efficient.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01200177
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