Yazar "Usta, Fatih" seçeneğine göre listele

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    Öğe
    Crashworthiness Optimization of Nested and Concentric Circular Tubes Using Response Surface Methodology and Genetic Algorithm
    (Latin Amer J Solids Structures, 2018) Usta, Fatih; Eren, Zana; Kurtaran, Hasan; Turkmen, Halit S.; Kazanci, Zafer; Mecitoglu, Zahit
    In this study crashworthiness optimization of nested and concentric circular tubes under impact loading is performed by coupling Finite Element model, Response Surface Models and Genetic Algorithm. Specific Energy Absorption (SEA) and Crash Force Efficiency (CFE) are used in crashworthiness optimization since these criteria are important indicators for evaluating crashworthiness performance. Length and thickness of three concentric tubes as well as radius of one tube are adopted as design variables which are effective parameters on SEA and CFE. To reduce the computational cost of the optimization procedure, simple and computationally cheap Response Surface Models are created to replace finite element analyses in further calculations. The Non-dominated Sorting Genetic Algorithm -II (NSGAII) is applied to obtain the Pareto optimal solutions. Optimization results are presented for different selected designs that indicate relative importance of multi-objective functions. Results show that the total weight of the vehicles can be reduced by using nested tubes comparing to single tubes with identical masses. These designs can be adopted for use in practice.
  • [ X ]
    Öğe
    Design optimization of modified re-entrant auxetic metamaterials reinforced with asymmetric edge cells for crushing behavior using the Taguchi method
    (Springer Heidelberg, 2022) Usta, Fatih; Zhang, Zhennan; Kurtaran, Hasan; Scarpa, Fabrizio; Turkmen, Halit S.; Mecitoglu, Zahit
    This work describes the compressive failure behavior and optimization of modified hierarchical re-entrant auxetic metamaterials reinforced with asymmetrical edge cells. The mechanical behavior of these metamaterials is parametrized against the width, thickness and angles of the cells. A Taguchi design (L27 (3(boolean AND)13)) has been performed to determine the effect of the eight geometric factors on the maximum compressive strength (specific strength), mean crushing force (MCF), specific energy absorption (SEA) and Poisson's ratio of the metamaterials. An analysis of variance (ANOVA) has been also performed to find out the relative significance and contribution percentage of each parameter from a statistical standpoint. The results show that the cell wall angle between the lateral and inclined ribs of the re-entrant unit cells has the largest effect on the compressive strength and absorbed energy of the structure that exhibits a percent variation of 82.5%, 30.0%, 85.9% and 75.1% in specific strength, MCF, SEA and Poisson's ratio, respectively. Moreover, the size of slot width and thickness, especially in the inclined struts, have a considerable effect on the mechanical performance compared to the angle of asymmetrical cells. Lastly, two samples from the optimization design table showing the best and worst mechanical responses are manufactured by using 3D printing and are tested under compression loading. The effects of the design factors on the deformation mechanisms and mechanical responses have been discussed by comparing the experimental and FE simulation results. The results show that the deformation mechanism of the asymmetrical unit cells and inclined struts play a key role in the resistance of the structures under compressive loads.