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Keywords: optimization, composite, stacking sequence, vibration, frequency, simplex algorithm, Nelder-Mead.

Summary

Laminated cylindrical shells are widely used in industries as structural elements, and their vibration characteristics are important in view of the current interest in designing with composite materials. Laminated composite construction offers many opportunities for engineers and designers to optimize structures for a particular or even multiple tasks.

In this paper, the governing equations based on three-dimensional elasticity have been derived. The composite cylindrical shell has a finite length and simply supported conditions at both ends. The governing equations which are in the form of partial differential equations, are changed into ordinary differential ones by using a Fourier expansion in the axial direction and then analytical exact solution to these equations has been employed to compute the fitness function for the natural frequency. Then a hybrid method combining two algorithms is proposed for the global optimization. It is necessary to well explore the whole domain. When a promising area is detected, the appropriate tools must be used to exploit this area and obtain the optimum as accurately and quickly as possible. Both tasks are hardly performed through only one method. Thus first we perform the exploration with a tabu-search and then exploit with a Nelder-Mead simplex search. Finally the results are presented for a muli-layered composite cylindrical shell and compared with similar ones obtained earlier by the authors based on genetic algorithm based optimization [1].

It is concluded that the genetic algorithm is less accurate and handles a population well distributed within the solution space at the beginning of the search. It localizes the promising zones more quickly than tabu search, but its convergence towards the solutions is slower.

References

1

M. Shakeri, M.H. Yas, M. Ghasemi Gol, "Optimal Stacking Sequence of Laminated Cylindrical Shells using Genetic Algorithm", Int. J. Mechanics of Advanced Materials and Structures, 12, 305-312, 2005. doi:10.1080/15376490590898501

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 86 PROCEEDINGS OF THE ELEVENTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING Edited by: B.H.V. Topping Paper 124 Stacking Sequence Optimization for a Laminated Cylindrical Shell using the Simplex Algorithm M.H. Yas¹, M. Shakeri² and R. Khaksar¹ ¹Department of Mechanical Engineering, Razi University, Kermanshah, Iran ²Department of Mechanical Engineering, Amirkabir University, Tehran, Iran doi:10.4203/ccp.86.124 purchase the full-text of this paper Full Bibliographic Reference for this paper M.H. Yas, M. Shakeri, R. Khaksar, "Stacking Sequence Optimization for a Laminated Cylindrical Shell using the Simplex Algorithm", in B.H.V. Topping, (Editor), "Proceedings of the Eleventh International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 124, 2007. doi:10.4203/ccp.86.124 Keywords: optimization, composite, stacking sequence, vibration, frequency, simplex algorithm, Nelder-Mead. Summary Laminated cylindrical shells are widely used in industries as structural elements, and their vibration characteristics are important in view of the current interest in designing with composite materials. Laminated composite construction offers many opportunities for engineers and designers to optimize structures for a particular or even multiple tasks. In this paper, the governing equations based on three-dimensional elasticity have been derived. The composite cylindrical shell has a finite length and simply supported conditions at both ends. The governing equations which are in the form of partial differential equations, are changed into ordinary differential ones by using a Fourier expansion in the axial direction and then analytical exact solution to these equations has been employed to compute the fitness function for the natural frequency. Then a hybrid method combining two algorithms is proposed for the global optimization. It is necessary to well explore the whole domain. When a promising area is detected, the appropriate tools must be used to exploit this area and obtain the optimum as accurately and quickly as possible. Both tasks are hardly performed through only one method. Thus first we perform the exploration with a tabu-search and then exploit with a Nelder-Mead simplex search. Finally the results are presented for a muli-layered composite cylindrical shell and compared with similar ones obtained earlier by the authors based on genetic algorithm based optimization [1]. It is concluded that the genetic algorithm is less accurate and handles a population well distributed within the solution space at the beginning of the search. It localizes the promising zones more quickly than tabu search, but its convergence towards the solutions is slower. References 1 M. Shakeri, M.H. Yas, M. Ghasemi Gol, "Optimal Stacking Sequence of Laminated Cylindrical Shells using Genetic Algorithm", Int. J. Mechanics of Advanced Materials and Structures, 12, 305-312, 2005. doi:10.1080/15376490590898501 purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £120 +P&P)
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