Yazar "Gunay, M. Gokhan" seçeneğine göre listele

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    Free Vibration Analysis of Thin-Walled Beams Using Two-Phase Local-Nonlocal Constitutive Model
    (Asme, 2023) Gunay, M. Gokhan
    A mathematical model is developed based on the thin-walled beams theory for free vibration analysis of nano/micro scale beams having nonlocal properties and arbitrary cross sections. Constitutive relations are defined by using two-phase local-nonlocal constitutive formulation. Equations of motion are derived by use of Hamilton's principle. Both the local and nonlocal part of the model is solved by the displacement-based finite element method. Numerical results are obtained and examined for nonlocal box beams and collapsed carbon nanotubes. In general, it is observed that the natural frequency decreases by increasing the nonlocal parameter or the volume fraction of the nonlocal part.
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    A NOVEL DESIGN OF PERISTALTIC CARBON NANO PUMP AND AN ANALYSIS OF HELIUM FLOW
    (Inst Za Kovinske Materiale I In Tehnologie, 2021) Gunay, M. Gokhan; Kemerli, Ubade
    A novel nano-scale pump that can transport atoms or small molecules with a peristaltic motion is designed. It is proven by molecular-dynamics simulations that the introduced nano-pump design works properly. The designed nano-pump consists of one main carbon nanotube named the flow tube and two rotors where multi-walled carbon nanotubes are attached. The pumping of helium atoms by the designed peristaltic carbon nano-pump is investigated by molecular-dynamics simulations. For varying rotor speeds and blade counts, time-averaged velocity, temperature, and pressure results of pumped helium atoms are calculated, and relationships between them are modeled as polynomial surfaces. The results showed that rotor frequency increases the velocity of helium linearly and the temperature and pressure of helium non-linearly. Furthermore, the blade count of the proposed mechanism does not substantially affect the velocity as per the previous studies in the literature.
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    Review of functionalized nano porous membranes for desalination and water purification: MD simulations perspective
    (Academic Press Inc Elsevier Science, 2023) Gunay, M. Gokhan; Kemerli, Ubade; Karaman, Ceren; Karaman, Onur; Gungor, Afsin; Karimi-Maleh, Hassan
    Today, it is known that most of the water sources in the world are either drying out or contaminated. With the increasing population, the water demand is increasing drastically almost in every sector each year, which makes processes like water treatment and desalination one of the most critical environmental subjects of the future. Therefore, developing energy-efficient and faster methods are a must for the industry. Using functional groups on the membranes is known to be an effective way to develop shorter routes for water treatment. Accordingly, a review of nano-porous structures having functional groups used or designed for desalination and water treatment is presented in this study. A systematic scan has been conducted in the literature for the studies performed by molecular dynamics simulations. The selected studies have been classified according to membrane geometry, actuation mechanism, functionalized groups, and contaminant materials. Permeability, rejection rate, pressure, and temperature ranges are compiled for all of the studies examined. It has been observed that the pore size of a well-designed membrane should be small enough to reject contaminant molecules, atoms, or ions but wide enough to allow high water permeation. Adding functional groups to membranes is observed to affect the permeability and the rejection rate. In general, hydrophilic functional groups around the pores increase membrane permeability. In contrast, hydrophobic ones decrease the permeability. Besides affecting water permeation, the usage of charged functional groups mainly affects the rejection rate of ions and charged molecules.
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    Static analysis of thin-walled laminated composite closed-section beams with variable stiffness
    (Elsevier Sci Ltd, 2017) Gunay, M. Gokhan; Timarci, Taner
    Static behavior of thin-walled laminated composite closed cross-section beams having variable stiffness is investigated in this study. The analytical model used accounts for flexural-torsional coupling and warping effects as well as the variable stiffness along the contour of the cross-section of the beam. The variable stiffness is acquired by constructing the laminates with curvilinear fibres having certain specific paths. The orientation of fibres varies by depending on the fibre path along the contour of the cross-section in each layer. Equilibrium equations are derived by use of minimum potential energy principle. Although the formulation given can be applied to any shape of the closed cross-section with straight or curved edges, preliminary numerical results are presented only for box-beams. A displacement based finite element method is developed to solve the analytical model and to predict displacements and rotations under the effect of different types of loading conditions. Numerical results are obtained for different fibre paths and lay-up configurations and compared with the available solutions in the literature also with the results of a finite element analysis software using shell element. (C) 2017 Elsevier Ltd. All rights reserved.
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    Stresses in thin-walled composite laminated box-beams with curvilinear fibers: Antisymmetric and symmetric fiber paths
    (Elsevier Sci Ltd, 2019) Gunay, M. Gokhan; Timarci, Taner
    Stress analysis of thin-walled composite laminated box beams having variable stiffness is realized in this study based on an analytical model accounting for flexural-torsional coupling and warping effects. The variable stiffness of the beam is acquired by constructing laminates with curvilinear fibers having certain specific paths. The fiber paths of variable stiffness layers are classified in three groups as antisymmetric, symmetric and asymmetric. A displacement based finite element method is used to solve the analytical model and to calculate the distributions of axial and transverse shear stresses at different locations of the cantilever composite beam subjected to the transverse and the torsional loading at its free end. Numerical results obtained are compared with available results in the literature for specific cases. A detailed investigation is performed to understand the relation between the stress distributions along the cross section of the beam and the shape of curvilinear fibers for antisymmetric and symmetric cases.