Makine Mühendisliği Bölümü Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/206

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Browsing Makine Mühendisliği Bölümü Koleksiyonu by Author "0000-0001-6395-4424"

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    Micro level two dimensional stress and thermal analysis anode/electrolyte interface of a solid oxide fuel cell
    (PERGAMON-ELSEVIER SCIENCE LTD, 2015) Celik, Selahattin); Ibrahimoglu, Beycan; Mat, Mahmut D.; Kaplan, Yuksel; Veziroglu, T. Nejat; 0000-0001-6395-4424; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Ibrahimoglu, Beycan
    The delamination and degradation of solid oxide fuel cells (SOFCs) electrode/electrolyte interface is estimated by calculating the stresses generated within the different layers of the cell. The stresses developed in a SOFC are usually assumed to be homogenous through a cross section in the mathematical models at macroscopic scales. However, during the operating of these composite materials the real stresses on the multiphase porous layers might be very different than those at macro-scale. Therefore micro-level modeling is needed for an accurate estimation of the real stresses and the performance of SOFC. This study combines the microstructural characterization of a porous solid oxide fuel cell anode/electrolyte with two dimensional mechanical and electrochemical analyses to investigate the stress and the overpotential. The microstructure is determined by using focused ion beam (FIB) tomography and the resulting microstructures are used to generate a solid mesh of two dimensional triangular elements. COMSOL Multiphysics package is employed to calculate the principal stress and Maxwell Stefan Diffusion. The stress field is calculated from room temperature to operating temperature while the overpotential is calculated at operating temperature.
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    Three dimensional stress analysis of solid oxide fuel cell anode micro structure
    (PERGAMON-ELSEVIER SCIENCE LTD, 2014) Celik, Selahattin; Ibrahimoglu, Beycan; Toros, Serkan; Mat, Mahmut D; 0000-0001-6395-4424; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Ibrahimoglu, Beycan
    One of the most common problems in solid oxide fuel cells (SOFCs) is the delamination and thus the degradation of electrode/electrolyte interface which occurs in the consequences of the stresses generated within the different layers of the cell. Nowadays, the modeling of this problem under certain conditions is one of the main issues for the researchers. The structural and thermo-physical properties of the cell materials (i.e. porosity, density, Young's modulus etc.) are usually assumed to be homogenous in the mathematical modeling of solid oxide fuel cells at macro-scale. However, during the real operation, the stresses created in the multiphase porous layers might be very different than those at macro-scale. Therefore, micro-level modeling is required for an accurate estimation of the real stresses and the performance of SOFCs. This study presents a microstructural characterization and a finite element analysis of the delamination and the degradation of porous solid oxide fuel cell anode and electrode/electrolyte interface under various operating temperatures, compressing forces and material compositions by using the synthetically generated microstructures. A multi physics computational package (COMSOL) is employed to calculate the Von Misses stresses in the anode microstructures. The maximum thermal stress in the electrode/electrolyte interface and three phase boundaries is found to exceed the yield strength at 900 C while 800 C is estimated as a critical temperature for the delamination and micro cracks due to thermal stress generated. The thermal stress decreases in the grain boundaries with increasing content of one of the phases (either Ni or YSZ) and the porosity of the electrode. A clamping load higher than 5 kg cm2 is also found to exceed the shear stress limit.