In this study, an optimization code has been developed based on genetic algorithms associated with the finite element modeling for the shape optimization of plane stress problems. In genetic algorithms, constraints are mostly handled by using the concept of penalty functions, which penalize infeasible solutions by reducing their fitness values in proportion to the degrees of constraint violation. In this study, An Improved GA Penalty Scheme is used. The proposed method gives information about unfeasible individual fitness as near as possible to the feasible region in the evaluation function. The objective function in this study is the area of the structure. The area is minimized considering the Von-Misses stress criteria. In order to minimize the objective function, one-point crossover with roulette-wheel selection approach is used. Optimum dimensions of four problems available in the literature have been solved by the code developed . The algorithm is tested using several strategies such as / different initial population number, different probability of mutation and crossover. The results are compared with the ones in literature and conclusions are driven accordingly.

Thesis (Ph. D.)--Ohio State University, 2003. / Title from first page of PDF file. Document formatted into pages; contains xvi, 131 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Tamal K. Dey, Dept. of Computer and Information Science. Includes bibliographical references (p. 126-131).

As the use of carbon fiber reinforced polymers (CFRP) increases in aerospace struc- tures it is important to use this material in an efficient manner such that both the weight and cost of the structure are minimized while maintaining its performance. To com- bat undesirable vibrational characteristics of a structure an optimization program was developed which takes advantage of the orthotropic nature of composite materials to maximize eigenfrequency bandgaps. The results from the optimization process were then fabricated and subjected to modal testing. The experiments show that local fiber angle optimization is a valid method for modifying the natural frequencies of a structure with the theoretical results generally predicting the performance of the optimized composite plates.

As the use of carbon fiber reinforced polymers (CFRP) increases in aerospace struc- tures it is important to use this material in an efficient manner such that both the weight and cost of the structure are minimized while maintaining its performance. To com- bat undesirable vibrational characteristics of a structure an optimization program was developed which takes advantage of the orthotropic nature of composite materials to maximize eigenfrequency bandgaps. The results from the optimization process were then fabricated and subjected to modal testing. The experiments show that local fiber angle optimization is a valid method for modifying the natural frequencies of a structure with the theoretical results generally predicting the performance of the optimized composite plates.

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This dissertation presents a synthesis of methods for structural optimization of aircraft wing boxes. The optimization problem considered herein is the minimization of structural weight with respect to component sizes, subject to stress constraints. Different aspects of structural optimization methods representing the current state-of-the-art are discussed, including sequential quadratic programming, sensitivity analysis, parameterization of design variables, constraint handling, and multiple load treatment. Shortcomings of the current techniques are identified and a B-spline parameterization representing the structural sizes is proposed to address them. A new configurable B-spline parameterization method for structural optimization of wing boxes is developed that makes it possible to flexibly explore design spaces. An automatic scheme using different levels of B-spline parameterization configurations is also proposed, along with a constraint aggregation method in order to reduce the computational effort. Numerical results are compared to evaluate the effectiveness of the B-spline approach and the constraint aggregation method. To evaluate the new formulations and explore design spaces, the wing box of an airliner is optimized for the minimum weight subject to stress constraints under multiple load conditions. The new approaches are shown to significantly reduce the computational time required to perform structural optimization and to yield designs that are more realistic than existing methods.

This study describes the process of performing structural optimization using ANSYS. In the first part, the general concepts in optimization and optimization algorithms for different type of optimization problems are covered. Also finite element method is introduced briefly in this part. In the second part, important definitions in structural optimization are mentioned. Then the optimization methods available in ANSYS are explained with their theories. Necessary steps to perform optimization with ANSYS are described at the end of this part. In the next part, sample problems found from scientific papers are solved using ANSYS and the results are compared. At the end of the study, the results obtained from the example problems are discussed whether they came out as expected or not. Also conclusions are made about solving optimization problems and performing structural optimization with ANSYS.

Bibliography: leaves 208-221. / xi, 229 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Study initiated with the objective of using evolutionary techniques instead of the gradient-based methods to solve the optimisation problems embodied in both management and inverse models. / Thesis (Ph.D.)--University of Adelaide, Dept. of Civil and Environmental Engineering, 1998

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on September 29, 2008) Includes bibliographical references.

Thesis (Ph. D.)--Aerospace Engineering, Georgia Institute of Technology, 2007. / Bauchau, Olivier, Committee Member ; Hodges, Dewey, Committee Chair ; Singhose, William, Committee Member ; Costello, Mark, Committee Member ; Flannery, Raymond, Committee Member.