Evolutionary topology optimization of a folding missile wing for stiffness and frequency

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2023-1-25

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Ürün, Ata

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This thesis presents a study on the topology optimization of a folding wing structure for a cruise missile with the aim of minimizing the weight of the wing while maximizing its stiffness and/or maximizing the selected natural frequency values. The weight of the folding wing has a significant impact on the performance of the opening mechanism and the overall dynamic behavior of the missile. The Bidirectional Evolutionary Structural Optimization (BESO) method, a widely-used topology optimization technique, is employed in conjunction with the MSC NASTRAN finite element solver and MATLAB to optimize the wing topology. The proposed algorithm is first validated on benchmark cases and then applied to the folding wing structure to obtain the optimized designs. The wing structure studied in this work is composed of two parts and two design volumes. In order to minimize its weight, several optimization studies are performed with different objectives. The first objective is to maximize stiffness and the design space is optimized for this purpose under the aerodynamic load. The second objective is to maximize the first natural frequency which may be necessary if there are excitation sources (such as the missile's engine or the aircraft that carries it) at that frequency. Shifting the natural frequency of the structure away from the frequency of the excitation can be useful for many aerospace-related problems. At the same time, increasing the natural frequencies results in modes of lower amplitudes and this precaution can prevent structural damage and decrease the flutter risk. Lastly, a multi-objective study on wing structure by considering its stiffness and natural frequencies is shown. By using topology optimization, it is possible to tailor the structure to shift the natural frequencies in the desired direction and reduce its weight simultaneously. The algorithm used in this thesis obtains several novel wing structures which are suitable for manufacturing using conventional chip removal methods and have efficient material distribution around the design volume. These structures are compared with each other, and conclusions are drawn about their effectiveness. Results show that the topology optimization algorithm used in this thesis is able to generate highly efficient topologies with improved stiffness and natural frequency values. Furthermore, the impact of different parameters of the Bi-directional Evolutionary Structural Optimization (BESO) method on the resulting structures is demonstrated in this thesis. Overall, this thesis illustrates the capabilities of the used topology optimization method in aerospace engineering by providing examples of folding wing structures and contributes a novelty to the literature by operating in multi-design domains simultaneously due to multiple components of the folding wing, while most of the studies on topology optimization only focus on single design space.

Subject Keywords

Finite element method, Structural optimization, Topology optimization, Frequency optimization, Bi-directional evolutionary structural optimization (BESO), Folding-wing

URI

https://hdl.handle.net/11511/102093

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

A. Ürün, “Evolutionary topology optimization of a folding missile wing for stiffness and frequency,” M.S. - Master of Science, Middle East Technical University, 2023.