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Öğe Düzlem-İçi Yüklenmiş Basit Destekli Simetrik Katmanlı Dikdörtgen Kompozit İnce Plakların Burkulma ve Titreşimi(Trakya Üniversitesi, 2004) Aydoğdu, Metin; Tımarcı, TanerBu çalışmada, tek eksenli düzlem-içi üniform yükler etkisindeki tüm kenarları basit destekli simetrik açı-lı-katmanlı kompozit plakların titreşim frekansları verilmiştir. Düzlem-içi yükler incelenen plakların kritik burkulma yüklerinin belirli oranları olarak seçilmiştir. Basit destekli açılı-katmanlı kompozit plakların burkul-ma ve titreşim problemlerine analitik bir çözüm bulmak mümkün olmadığından, problemin çözümünde yer de-ğiştirme bileşeninin trigonometrik olarak seçildiği Ritz yöntemi kullanılmıştır. Sonuçların doğruluğunu göster-mek amacıyla yakınsama çalışmaları verilmiştir. Elyaf yönlenme açısı, katman sayısı, kenar oranları ve farklı malzemelerin düzlem-içi yüklü kompozit plakların titreşimi üzerindeki etkileri araştırılmıştır.Öğe EKSTRÜZYON TİPİ DÖVME PROSESLERİNDE FARKLI KALIP GEOMETRİLERİNİN KUVVET ve MALZEME AKIŞINA ETKİSİ(Trakya Üniversitesi, 2009) Altınbalık, Tahir; Çan, YılmazEkstrüzyon tipi dövme proseslerinde malzeme akışı kapalı kalıpla dövme proseslerinin başlangıç aşamalarına benzer şekildedir ve özellikle yüksek dayanımlı parçaların imalatında tercih edilir. Kapalı kalıpla dövme yada ekstrüzyon tipi dövme gibi pekçok metal şekillendirme prosesinde şekillendirilen malzeme prosesin değişik aşamalarında akış yönünü değiştirebilmektedir. Özellikle ekstrüzyon tipi dövme proseslerinde malzeme akışı 3 farklı bölge içermektedir. Bu karmaşık akış takım gerilmeleri yada dövme kuvvetlerinin hesaplanmasını zorlaştırmaktadır. Bu amaçla kalıp şeklinin malzeme akışına etkilerinin incelenmesi yararlı olacaktır. Bu çalışmanın amacı ekstrüzyon tipi dövme proseslerinde aynı kesit alanına sahip farklı geometrilerde delik içeren kalıpların malzeme akışına ve kuvvet ihtiyacına olan etkilerinin belirlenmesidir. Bu amaçla imal edilen 3 farklı kalıpta ekstrüzyon tipi dövme deneyleri yapılarak sonuçlar çeşitli bakımlardan karşılaştırılmıştır. Deneyler 150 metrik ton kapasiteli bir hidrolik preste kurşun malzeme kullanılarak gerçekleştirilmiştirÖğe Edirne İlinde Optimum Duvar Yalıtım Kalınlığının Enerji Tasarrufuna Etkisi(Trakya Üniversitesi, 2009) Öztuna, Semiha; Dereli, EmreTürkiye’de tüketilen enerjinin önemli bir kısmı binalarda ısıtma enerjisi olarak kullanılmaktadır. Binalardaki ısıtma enerjisi ihtiyacını en aza indirgemek için yapılması gereken en önemli uygulamalardan biri ısı yalıtımıdır. Bu çalışmada ömür maliyet analizi yöntemi kullanılarak, Edirne ilinde, 6 farklı yakıt (yerli ve ithal kömür, doğalgaz, LPG, elektrik, fuel-oil) için; bina dış duvarına genleştirilmiş polistren (EPS) ve taş yünü yalıtım malzemesi ile sandviç duvar da EPS yalıtım malzemesinin uygulanması durumlarında yapılması gereken optimum yalıtım kalınlığı derece gün sayısı esas alınarak hesaplanmıştır. Bu hesaplamalarla 5 farklı duvar modelinde, 2 farklı yalıtım maddesi uygulamaları ve her bir yakıt için hesaplanan optimum yalıtım kalınlıklarının geri ödeme süreleri ile yıllık yakıt ve enerji tasarrufları belirlenmiştir. En iyi sonuç olarak; yerli kömürün yakıt , EPS yalıtım maddesinin uygulanmasında; optimum yalıtım kalınlığı 0,028-0.039m, geri ödeme süreleri 2,1- 4,2 yıl, enerji tasarrufu %24-%47 elde edilmiştirÖğe Buckling analysis of double nanofibers embeded in an elastic medium using doublet mechanics theory(ELSEVIER SCI LTD, 2018) Aydogdu, Metin; Gul, UfukThis study considers the buckling of double nanofibers embedded in an elastic matrix based on an EulerBernoulli beam model. A scale dependent doublet mechanics theory is used in modelling of the double nanobeam system. Critical buckling loads are obtained using doublet mechanics and results are compared with the classical elasticity theory. The variation of critical buckling loads with different beam length, doublet separation distance and stiffness of the springs are investigated. Some mode shapes of the double nanobeam system are presented.Öğe Nonlinear wave modulation in nanorods using nonlocal elasticity theory(Walter de Gruyter Gmbh, 2018) Gaygusuzoglu, Guler; Aydogdu, Metin; Gul, 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 Experimental study on the thermal conductivity of water-based CNT-SiO2 hybrid nanofluids(Pergamon-Elsevier Science Ltd., 2018) Dalkilic, Ahmet Selim; Yalcin, Gokberk; Kucukyildirim, Bedri Onur; Oztuna, Semiha; Eker, Aysegul Akdogan; Jumpholkul, Chaiwat; Nakkaew, Santiphap; Wongwises, SomchaiThis experimental study includes measurement of thermal conductivity of distilled water-based CNT-SiO2 hybrid nanofluids. Nanofluids were prepared by using two-step method, 3 different concentrations and 4 different mass range of CNT-SiO2. SiO2 has 2200 kg m(-)(3) density, 1.4 W m(-1) K (-1) thermal conductivity and 7 nm average particle size. CNT has 2620 kg m(-3) density, 25 W m (-1) K(-1 )thermal conductivity and 6-10 nm average particle size. Samples were placed in ultrasonic homogenizer maximum power capacity for 3 h. Throughout sonication process temperature of nanofluids have been kept under control in order not to chance volumetric fraction of nanofluids. All measurements of thermal conductivity were done by using thermal conductivity meter. Thermal conductivity meter was calibrated by di-water. Measurements of thermal conductivity was done range from 25 degrees C to 60 degrees C for every 5 degrees C. Validation of measurements had been performed by using di-water and shown in a thermal conductivity-temperature figure. Minimum and maximum thermal conductivity enhancements were revealed in detail. Alteration of the thermal conductivity with temperature according to various volumetric fractions were in literature rated and it is found that the thermal conductivity increases with temperature and vol. fraction clearly. Enhancement on the thermal conductivity to di-water were also depicted for various temperatures and vol. fraction in figures. Almost well-known correlations in the literature were given with their predictable rates. Moreover, comparisons with other studies were provided in this present study. A practical correlation was proposed for other researchers.Öğe Physical and mechanical properties of PP composites based on different types of lignocellulosic fillers(Journal Wuhan Univ Technology, 2018) Erdogan, Selcuk; Huner, UmitThe presents preparation and characterization of different types of lignocellulosic fillers (pine wood saw-dust/ walnut shell flour/black rice husk powder) reinforced polypropylene composites were presented. The effect of MAPP as coupling agent (4wt%) on the physical and mechanical properties was also investigated. Polypropylene composites were prepared at different rates of filler/matrix (wt%) by using extrusion (for melt blending) and hot compression molding process. Maximum values of tensile and flexural strength were obtained as 26.1 and 43.4 MPa, respectively, whereas the elongation at break value was 4.11% at 10% pine wood sawdust reinforced PP. Tensile and flexural modulus of composites reached the maximum values as 3855 and 3633 MPa with the composite of 30% walnut shell flour reinforced PP. Characterization of composites was carried out by using tensile test, flexural test, FT-IR, and SEM.Öğe Longitudinal magnetic field effect on torsional vibration of carbon nanotubes(Univ Tehran, 2018) Arda, Mustafa; Aydogdu, MetinTorsional dynamic analysis of carbon nanotubes under the effect of longitudinal magnetic field is carried out in the present study. Torque effect of an axial magnetic field on a carbon nanotube has been defined using Maxwell's relation. Nonlocal governing equation and boundary conditions for carbon nanotubes are obtained by using Hamilton's minimum energy principle. Eringen's nonlocal stress gradient elasticity theory is used in the formulation. Fourth order nonlocal equation of motion is solved by utilizing differential quadrature method. Clamped-clamped and clamped-free nonlocal boundary conditions are considered. Nonlocal and axial magnetic field effects on torsional vibration of carbon nanotubes are investigated. The magnetic field has significant effects on the dynamics of carbon nanotubes and may lead to torsional buckling. Critical torsional buckling load reduces with nonlocal effects. Nonlocality shows softening effect on carbon nanotube's lattice structure. Present results can be used in the design and analysis of nanoelectromechanical products like nano-motors.Öğe Finite strain nonlinear longitudinal vibration of nanorods(Techno-Press, 2018) Eren, Mehmet; Aydogdu, MetinThe nonlinear free vibration of a nanorod subjected to finite strain is investigated. The governing equation of motion in material configuration in terms of displacement is determined. By means of Galerkin method, the Fourier series solutions satisfying some typical boundary conditions are determined. The amplitude-ficquency relationship and interaction between the modes are studied. The effects of nonlocal elasticity are shown for different length of nanotubes and nonlocal parameter. The results show that nonlocal effects lead to additional internal modal interaction for nanorod vibrations.Öğe Dynamic response of a functionally graded tube embedded in an elastic medium due to SH-Waves(Elsevier, 2018) Kara, Hasan Faik; Aydogdu, MetinDynamic response of a cylindrical tube surrounded by an unbounded elastic medium due to plane harmonic SH-Waves is studied. A two-dimensional mathematical model is considered. Cylindrical coordinates are used for convenience. The surrounding medium is assumed to be homogeneous, isotropic and linear elastic. The tube is assumed to be made of linear elastic functionally graded materials (FGMs) such that shear modulus and shear wave velocity are assumed to change linearly from inner surface to outer surface. Material properties are constant along circumferential direction. It is assumed that the inner surface of the tube is traction-free and there is a welded contact between the tube and the surrounding medium. Governing equations are slightly different in the tube region and the unbounded region. Both of the governing equations are solved by applying Finite Fourier Transform in circumferential direction. The exact solution series are presented in terms of Fourier-Bessel series in the unbounded region and power series in the tube region. The presented numerical results show that when the incoming wave lengths decrease, shear stresses at the tube increase significantly. It was shown that for the shorter incoming wave lengths, tubes made of FGMs are subjected to smaller shear stresses compared to the tubes homogeneously made of outer surface material of the FG cases.
