Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Investigating the Filament Wound Hybrid Cylindrical Structures With Enhanced Thermal Properties by Numerical Analysis(01. Izmir Institute of Technology, 2023) Tanoğlu, Metin; Tanoğlu, Metin; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe filament winding method is a composite production technique found at the beginning of the 20th century. The technique has been used in different fields since the day it was introduced in literature. Today, with the developments in the continuous fiber structure used in this technique and the development of carbon technology, filament-wound composites are widely used in the automotive, aerospace, and defense industries. In this study, the finite element method was used to model filament-wound composite cylinders. It was wanted to observe the matrix effect of the composite structure numerically and criticize experimentally produced composites. Even though the current studies work on a hybridized composite structure with respect to the fiber, this study tried to find the hybridized matrix effect by numerical analysis. For this purpose, in this study, the finite element program ANSYS was used. In order to make realistic calculations with ANSYS, material data were observed from composite plates. Finite element models created with the obtained data were compared with the experimental results. The analysis results were observed with the help of the first-ply failure theory. In addition, since the pattern representations from the winding poles cannot be displayed in ANSYS, the pattern effect was ignored, and comparison were made with the assumption of a full layer at given angles. As a result of all this study, although there were differences between experimental and finite element methods' models in homogeneity and pattern, methods' comparisons gave consistent and close results.Master Thesis Experimental and Numerical Analysis of the Strain Rate Dependent Compressive Strength of a Cellular Concrete(Izmir Institute of Technology, 2019) Akyol, Burak; Taşdemirci, Alper; Güden, Mustafa; Güden, Mustafa; Taşdemirci, Alper; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyExperimental and numerical quasi-static and high strain rate tests, including compression, indentation and direct impact, were performed on a cellular concrete in order to investigate the effect of strain rate on the compressive strength. The results of compression tests indicated three distinct regions of the compressive strength dependence on strain rate. A relatively lower strain rate dependent compressive stress was found in the quasi-static strain rate-regime, 2x10-3-2x10-1 s-1, a relatively high strain rate dependent compressive stress in the dynamic strain rate-regime, 180-103 s-1 and a cut-off strength above 103 s-1. The dynamic increase factor (DIF=dynamic/static fracture strength) varied between 1 and 2.5 from quasi-static to dynamic strain rate-regime with a sharp increase after about 100 s-1. The indentation tests using 25 and 30 mm-diameter indenters in the quasi-static strain rate-regime (uniaxial state of strain) and resulted in moderate DIF values (1-1.13), very similar with those of the quasi-static compression tests (1-1.15). In the indentation tests, the DIF values significantly and also confirmed the numerically determined DIF values of concrete at 1000 s-1 (~1.30) without radial and axial inertia. The compression and direct impact tests in the Split Hopkinson Bar (SHPB) set-up were implemented numerically in LS-DYNA using an anisotropic strain rate insensitive material model, MAT_096 (MAT BRITTLE DAMAGE). The stress readings were performed at the specimen different locations of the SHPB and indicated that radial and axial inertia were dominant between 1 and 30 m s-1 (30-1000 s-1).Master Thesis Numerical Analysis of Finned Downhole Heat Exchangers: a Parametric Study(Izmir Institute of Technology, 2002) Alpay, Selda; İlken, Zafer; İlken, Zafer; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThis study investigates the performance of an U-type Downhole Heat Exchanger (DHE) with a new pipe arrangement, where circular fins are fitted around the legs of the DHE.In the present work the heat transfer performance of optimized DHE with circular fins is investigated and compared with that of optimized with bare type DHE. This study numerically models a well with a DHE to determine the heat flow that can be extracted by the DHE. A DHE program is written in BASIC language to investigate the heat transfer rate both for bare and finned type DHEs. In order to verify the accuracy of this program comparisons are made with an experimental work for bare type DHEs. Also a computational fluid dynamics program, FLUENT, is used to study fluid and heat flow processes in the well and DHE systems. The results of the FLUENT program are also used to compare the DHE program. The simulations carried out also enable us to determine the influence of the design parameters of the finned type DHEs. Some examples of optimized geometries are finally shown and discussed.