WoS İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394

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Language: search.filters.language.enSubject: search.filters.subject.FEA

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  • Article
    Citation - WoS: 9
    Citation - Scopus: 8
    Stress and Damage Distribution Analysis of Steel Reinforced Geopolymer Concrete Beams: Finite Element Method and Experimental Comparison Under Varying Design Parameters
    (Elsevier, 2025-06) Ozbayrak, Ahmet; Kucukgoncu, Hurmet; Aslanbay, Huseyin Hilmi; Aslanbay, Yuksel Gul
    Geopolymer concrete (GPC) is a sustainable and eco-friendly alternative to ordinary Portland cement-based concrete (OPC). However, its application in reinforced concrete structures remains limited due to insufficient research on structural performance. This study examines the effects of tensile reinforcement ratio, sodium silicate/sodium hydroxide ratio, and curing method on GPCreinforced concrete (GPC-RC) beams. Experimental and numerical bending tests were performed on GPC and OPC beams with similar tensile reinforcement and strength properties. Load- displacement and moment-curvature relationships were obtained and compared, while stress and stiffness behaviors were analyzed numerically. The results show that curing methods and reinforcement ratios significantly influence GPC beam behavior. In GPC samples, numerical and experimental displacement and load values differed by approximately 10 % at both yield and ultimate points. For OPC, these differences were 35 % and 14 % at the yield point and 17 % and 25 % at the ultimate point. GPC exhibited distinct stress and damage distribution characteristics compared to OPC. The finite element models were statistically validated, confirming their consistency with experimental results. These findings contribute to the understanding of GPC's structural behavior and provide guidance for its design and optimization in reinforced concrete applications.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Modified Induction Machine Equivalent Circuit Including Solid Shaft Eddy Currents
    (MDPI, 2023-12-15) Tekgun, Didem
    The shaft eddy currents cause a significant saturation in two-pole induction machines (IMs) as they generate an opposing field and repulse the main flux, thus tightening the flux path. This results in inaccurate performance estimations with the magnetizing inductance measured in no-load conditions when the machine is loaded. This article presents a modified IM equivalent circuit considering the rotor back iron saturation effects caused by the solid shaft eddy currents using experimental measurements and recursive parameter estimation techniques. The classical equivalent circuit (CEC) parameters are determined with the standard test techniques followed by the parameter estimation of the newly introduced modified equivalent circuit (MEC) parameters. The proposed modified equivalent circuit is benchmarked with CEC and finite element analysis (FEA) simulations with and without considering eddy effects. The proposed MEC model and the FEA that consider eddy effects performed better than the other models and yielded a negligibly small error over a wide range of loading conditions. Compared to the FEA, the proposed MEC estimates the IM performance much faster, which makes it more appealing for IM performance estimations.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 3
    Investigating the Role of Stator Slot Indents in Minimizing Flooded Motor Fluid Damping Loss
    (MDPI, 2023-12-14) Tekgun, Didem; Tekgun, Burak
    This research examines how fluid damping loss affects the operation of a two-pole, 5.5 HP (4 kW) induction machine (IM) within the context of different slot opening configurations developed for downhole water pump applications. Since these motors operate with their cavities filled with fluid, the variations in fluid viscosity and density, compared to air, result in the occurrence of damping losses. Furthermore, this loss can be attributed to the motor's stator and rotor surface geometry, as the liquid within the motor cavity moves unrestrictedly within the motor housing. This study involves the examination of the damping loss in a 24-slot IM under different stator slot indentations. The investigation utilizes computational fluid dynamics (CFD) finite element analysis (FEA) and is subsequently validated through experiments. The aim of this work is to emphasize the significance of fluid damping loss in submerged machines. Results reveal that the damping loss exceeds 8% of the motor output power when the stator surface has indentations, and it diminishes to 3.2% of the output power when a custom wedge structure is employed to eliminate these surface indentations.