Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Topology Optimization of Non-Linear Elastic Microstructures(01. Izmir Institute of Technology, 2023) Özdemir, İzzet; Özdemir, İzzet; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyTopology optimization (TO) is used in a broad spectrum of engineering disciplines ranging from aerospace to civil engineering. A particular sub-field where topology optimization has been very instrumental is the design of microstructures that yield specific macroscopic properties, such as negative Poisson's ratio and negative magnetic permeability. In this thesis, based on a recently proposed method for nonlinear homogenization, a framework for topology optimization of nonlinear elastic microstructures is developed and implemented as a computer program using the Julia programming language. Following a plane strain formulation, a two-dimensional unit cell with periodic boundary conditions is used in combination with a neo-Hookean elastic material response. By exploiting the symmetry properties of the resulting orthotropic microstructure, it is shown that the computational domain can be reduced, and half of the original discretization is sufficient to carry out the optimization task. The obtained topologies from the developed computer program, the linear and nonlinear response comparison, and the computational gain achieved through domain reduction are presented along with the experiments on proof-of-concept type uni-axial tests.Master Thesis Stacking Sequences Optimization of the Anti-Buckled Laminated Composites Considering Various Failure Criteria(Izmir Institute of Technology, 2011) Söyleyici, Mehmet Umut; Artem, Hatice Seçil; Artem, Hatice Seçil; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn recent years, fiber-reinforced composite materials have been mostly used in engineering applications due to advantage of the ratio of strength to weight. Fiberreinforced laminated composites with an optimum stacking sequences have become critical issue especially for defence and automotive industry. In this study, stacking sequences optimization of laminated composites for maximum buckling load factor has been investigated using genetic algorithm (GA). Symmetrical and balanced laminated composite plates with 48 layers graphite/epoxy are considered for optimization process. The designs of composite plates have been investigated for various in-plane loadings and aspect ratios. Fiber orientation angles are chosen as design variables. The optimum designs obtained have been controlled by Tsai-Wu and maximum stress failure criteria. Furthermore, dispersed designs for specific cases have been converted to conventional designs and the advantages and disadvantages of various designs have been examined in terms of buckling resistance. Finally, buckling behaviors of 48- and 64-layered composite plates have been studied under overloaded conditions. In design process, the increase in the reliability of the optimization has been provided independently using a variety of genetic algorithm parameters. All the results have shown that the loading conditions and dimensions of composite plates are significant in stacking sequences optimization of laminated composite materials in terms of maximum critical buckling load factor. Furthermore, it has been seen that the fiber orientation angles determine which failure modes (buckling or static failure criteria) are critical.