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Öğe Axial dynamics of a nanorod embedded in an elastic medium using doublet mechanics(Elsevier Sci Ltd, 2017) Gül, Ufuk; Aydoğdu, Metin; Gaygusuzoğlu, GülerThis study investigates the axial vibration of carbon nanotubes (CNTs) embedded in an elastic medium using scale dependent doublet mechanics (DM) theory. Governing equations and all boundary conditions of CNTs are derived based on the variational principle. Free vibration frequencies are obtained and compared with the classical elasticity results for clamped-clamped (C-C) and clamped-free (C-F) boundary conditions. The effect of elastic medium stiffness, nanorod length and doublet separation distance on the axial vibration is examined. It is obtained that important differences exist between vibration frequencies predicted by classical elasticity theory and DM. DM theory can be used in the nano length scale design of structures. (C) 2016 Elsevier Ltd. All rights reserved.Öğe Malzeme özelliklerinin ve yalıtım sisteminin isi köprüsü davranışına etkisinin incelenmesi(2017) Gaygusuzoğlu, Güler; Bakış, AdemEnerji tüketiminin azaltılması ülkelerin gelişimi için çok önemlidir. Yapılarda enerji tüketimi bu nedenle büyük önem arz etmektedir. Binalarda ısı kaybını azaltmak için ısı köprülerini, ısı köprülerini oluşturan yalıtım sisteminin etkilerini ve kullanılan malzemenin davranışlarını çok iyi bilmek gerekmektedir. Bu çalışma, teras katlarda beton, duvar ve yalıtım malzemelerinin ısıl iletkenlik katsayılarının değişiminin ısı köprüsüne etkilerini incelenmektedir. Bunun için literatürden farklı olarak Türkiye'de betonarme binaların teras katları için en sık kullanılan 9 kesit üzerinde inceleme gerçekleştirilmiştir. "Yalıtım sistemi, beton ve/veya duvar malzemesinin değişiminin ısı köprüsüne etkisi ne olmaktadır?" sorusuna yanıt aranmıştır. Hesaplamalar TS 825'te belirtilen birinci derece gün bölgesi için sıvalı durum göz önünde bulundurularak yapılmış olup farklı yalıtım çeşitlerinde duvar-döşeme-kiriş birleşimlerinin Hesaplamalarda gerçeğe yakın değerler veren ve sonlu elemanlar metodunu kullanan, QuickField 5.6 programından yararlanılmıştır. Bu çalışmanın sonuçları ile ısı köprülerinde beton, duvar ve yalıtım malzemelerinin ısıl iletkenlik değerlerinin değişiminin iki boyutlu olarak nasıl değiştiği görülmektedir. En büyük ısı kaybı, betonun ısıl iletkenlik katsayısının artması sonucunda elde edilmektedir. Ayrıca elde edilen sonuçlarla teras katlarda kullanılan yalıtım çeşitlerinin hangisinin daha verimli olduğu sorularına da yanıt verilmektedir.Öğe Nonlinear Wave Modulation in Nanorods Using Nonlocal Elasticity Theory(Walter De Gruyter Gmbh, 2018) Gaygusuzoğlu, Güler; Aydoğdu, Metin; Gül, UfukIn this study, nonlinear wave modulation in nanorods is examined on the basis of nonlocal elasticity theory. Eringen's nonlocal elasticity theory is employed to derive nonlinear equations for the motion of nanorods. The analysis of the modulation of axial waves in nonlocal elastic media is performed, and the reductive perturbation method is used for the solution of the nonlinear equations. The propagation of weakly nonlinear and strongly dispersive waves is investigated, and the nonlinear Schrodinger (NLS) equation is acquired as an evolution equation. For the purpose of a numerical investigation of the nonlocal impacts on the NLS equation, it has been investigated whether envelope solitary wave solutions exist by utilizing the physical and geometric features of the carbon nanotubes. Amplitude dependent wave frequencies, phase and group velocities have been obtained and they have compared for the linear local, the linear nonlocal, the nonlinear local and the nonlinear nonlocal cases.Öğe Propagation of weakly nonlinear waves in nanorods using nonlocal elasticity theory(2019) Gaygusuzoğlu, GülerThe present research examines the propagation of weakly solitary waves in nanorods by employing nonlocal elasticity theory. Many systems in physics, engineering, and natural sciences are nonlinear and modeled with nonlinear equations. Wave propagation, as a branch of nonlinear science, is one of the most widely studied subjects in recent years. Nonlocal elasticity theory represents a technique with increasing popularity for the purpose of conducting the mechanical analysis of microelectromechanical and nanoelectromechanical systems. The nonlinear equation of motion of nanorods is derived by utilizing nonlocal elasticity theory. The reductive perturbation technique is employed for the purpose of examining the propagation of weakly nonlinear waves in the longwave approximation, and the Korteweg-de Vries equation is acquired as the governing equation. The steady-state solitary-wave solution is known to be admitted by the KdV equation. To observe the nonlocal effects on the KdV equation numerically, the existence of solitary wave solution has been investigated using the physical and geometric properties of carbon nanotubes.Öğe The effect of material properties and isolation system on thermal bridge behavior(Pamukkale Univ, 2017) Gaygusuzoğlu, Güler; Bakis, AdemReducing the energy consumption is very important for the development of the countries. For this reason, energy consumption at the buildings is very important. It is necessary to know behaviours of thermal bridges, affects at insulation system utilized and materials constituting the thermal bridges very well to cut down thermal loss in buildings, this study searches affects at change in the thermal conductivity coefficients of concrete, wall and insulation materials used in the terrace floors on the thermal bridges . For this reason, apart from literature, examination on 9 insulation sections most frequently used for the terrace floors at reinforced concrete buildings in Turkey were realized. What is the effect of changes at insulation system and/or the concrete and the wall materials on the thermal bridge?. Answers to this question was researched. Calculations were made for temperature and heat flux distributions at wall-floor-beam combinations at different insulation states considering plastered state for first degree day area, as mentioned in TS825 Standard. For the calculations, QuickField 5.6 program, which gives realistic values and utilizes finite elements method was used. With the results of this study, it was seen how the behavior of the variance of the concrete, wall and insulation heat conductivity values at the thermal bridges changes in a two-dimensional way. As a result of the calculations, the biggest heat loss was obtained when thermal conductivity coefficient of the concrete increased. Besides, answers are given to questions such as which is the most productive section used in terrace floors?Öğe Vibration and buckling analysis of nanotubes (nanofibers) embedded in an elastic medium using Doublet Mechanics(Springer, 2018) Gül, U.; Aydoğdu, Metin; Gaygusuzoğlu, GülerIn the present study, vibration and buckling of nanotubes (nanofibers) embedded in an elastic medium are studied. A length scale-dependent theory called Doublet Mechanics (DM) is used in the formulation. In this theory, discrete microstructure of solids is considered in the formulation and using a bottom-up approach macro level strains and stresses are obtained from microlevel strains and stresses. Taylor series expansion of the microlevel displacement is used in the definition of the micro strains. The number of terms in the Taylor series describes the microstructure of the considered solids. In this study, nanotube fibers are assumed as an Euler-Bernoulli beam embedded in an elastic medium. Simply supported and clamped boundary conditions are considered at the edges of the beams. Free vibration frequencies and critical buckling loads are obtained and compared with the classical elasticity results. It is shown that scale-dependent DM can be used at the nanolength scale.Öğe Weakly nonlinear wave propagation in nanorods embedded in an elastic medium using nonlocal elasticity theory(Springer Science and Business Media Deutschland GmbH, 2020) Gaygusuzoğlu, Güler; Akdal, S.In the present research, the nonlocal elasticity theory is utilized with the aim of examining nonlinear wave propagation in nanorods, which are embedded in an elastic medium. Constitutive equations on the basis of Eringen’s nonlocal elasticity theory are used in the formulations. Equations of motion are written in terms of material coordinates, and nonlinear equations of nanorods are obtained according to nonlocal elasticity theory. In the study, the rod material is treated as a single-walled carbon nanotube. With the solution of the field equation by the reductive perturbation method, the Korteweg–de Vries (KdV) equation is acquired as the evolution equation, which is governed by the nanorod in an elastic medium. The solitary wave solution of the KdV equation characterizing the motion of carbon nanorods in the elastic medium is given depending on the nonlocal parameter and the parameter of the stiffness of the elastic medium, and it is demonstrated how the nonlocal parameter and the stiffness parameter affect the wave profile. © 2020, The Brazilian Society of Mechanical Sciences and Engineering.Öğe Yerel olmayan elastisite teorisi kullanılarak elastik ortam içerisindeki nano çubuğun eksenel titreşiminin incelenmesi(2022) Gaygusuzoğlu, GülerBu çalışmada, yerel olmayan elastisite teorisi kullanılarak elastik ortamda bir nano çubuğun eksenel titreşimi ele alınmıştır. Probleme ait hareket denklemleri denge şartları vasıtasıyla elde edilmiş ve analitik olarak çözülmüştür. İki ucu ankastre ve bir ucu ankastre bir ucu serbest nano çubuğun serbest titreşim frekanslarını veren ifadeler yerel olmayan parametre ve elastik ortam parametrelerine bağlı olarak bulunmuştur. Ankastre-ankastre ve ankastre-serbest sınır koşulları için, titreşim frekansları ile elastik ortam parametresi ve yerel olmayan parametrenin ilişkileri incelenerek sonuçlar grafikler üzerinde gösterilmiştir. Sayısal sonuçlar için karbon nano çubuğa ait fiziksel ve malzeme özellikleri kullanılmıştır. Elde edilen sonuçlarla serbest titreşim frekanslarının boyuta önemli ölçüde bağlı olduğu ve boyut etkisinin yüksek modlarda daha etkili olduğu görülmüştür. Yerel teori ile elde edilen frekans değerleri, yerel olmayan elastisite teorisi kullanılarak elde edilenlerden çok farklıdır.
