Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Quasi-Static Crushing Behavior of Nomex Honeycomb Filled Thin-Walled Aluminum Tubes(Izmir Institute of Technology, 2008) Çakıroğlu, Cem; Güden, Mustafa; Güden, Mustafa; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe experimental and numerical studies presented in this thesis were focused on the experimental and numerical quasi-static crushing behavior of Nomexl1 honeycomb filled thin-walled aluminum tubes. Nomexl1 honeycombs having different cell sizes (3.2, 4.8 and 6.4 mm) and the same density (48 kg/m3) were used to fill thin walled aluminum tube, 25 mm in diameter and 0.29 mm in thickness. Compression tests were conducted at quasi-static the strain rates of 1.64 10-2, 6.56 10-3 and 3.28 10-3 s-1. The results showed that the honeycomb cell size had a strong effect on the crushing behavior. Decreasing cell size increased crushing loads and the specific absorbed energy values of empty tubes. The highest strengthening effect of filling was found in 3.2 mm cell size honeycomb filled tubes. Although no effects of 4.8 and 6.4 mm cellsize honeycomb filling on the deformation mode of tube was observed (mixed), 3.2 mm cell size honeycomb filling changed the deformation mode to mixed/concertina. The numerical model of empty tube, 6.4 mm cell size honeycomb and 6.4 mm cell size honeycomb filled tube were performed using LS-DYNATM and ANSYSTM finite element analysis programs. To acquire maximum computational efficiency, a mesh optimization was done. The effect of the honeycomb cell wall thickness was also investigated numerically and shown to have a strong effect on the crushing behavior of honeycomb. The experimental and numerical studies conducted showed that 3.2 mm cell size Nomex® honeycomb might become an alternative to aluminum foam filler in thin walled tubes as long as the tube crushing load was comparable with honeycomb crushing load.Master Thesis Crushing Behaviour of Aluminum Foam-Filled Composite Tubes(Izmir Institute of Technology, 2005) Yüksel, Sinan; Güden, Mustafa; Güden, Mustafa; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyAn experimental study has been conducted in order to determine the effect of Al-foam filling on the composite and hybrid (Al metal and composite) composite tubes.Tubes and fillers used in the experiments were prepared using the tube rolling and foaming from powder compacts methods, respectively. The composite was prepared using E-glass fiber fabric (2x2 twill fiber construction of 165 g/m2 areal density) and polyester matrix with a 45/45 fiber angle to the tube axis. The quasi-static crush tests were conducted axially on the empty, hybrid and foam filled tubes at 25 mm/min crosshead speed. The deformation sequences of the tubes were further recorded during the tests in order to identify the crushing modes of the tubes. Two failure mechanisms literally known as progressive crushing and catastrophic failure (compression shear) were observed during the crushing of empty composite tubes. The progressive crushing mode leaded to higher crushing loads hence Specific Absorbed Energies (SAE). The predominant progressive crushing mode of empty tubes of thinner wall section was attributed to the surface end defects introduced during sectioning of the tubes. In hybrid tubes, the deformation mode of Al tube was found to be a more complex form of the diamond mode of deformation, leading to higher SAE values than the sum of the SAEs of empty composite and empty metal tube. The increased load and SAE values ofhybrid tubes were attributed to the constraining effect of the composite to the metal tube folding. Results further showed that when the progressive crushing mode was taken into account hybrid tubes had lower SAE values than those of empty composite tubes. The foam filling of the composite tubes however showed two different results. It increased the foam filled tube crush loads over the sum of the crush loads of empty composite tube and foam. In the latter case it was not effective in increasing crush loads over the sum of the crush loads of empty composite tube and foam in the progressive crushing region. These two effects were discussed in terms of possible interactions between composite tube and foam.