Mühendislik Fakültesi
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Browsing Mühendislik Fakültesi by Department "Çankaya Üniversitesi, Mühendislik Fakültesi, Makine Mühendisliği Bölümü"
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Conference Object Analysis and simplified modelling of simulation of tests for mediumduty truck collision with twin antiram bollards(2020) Türkoğlu, Haşmet; 12941; Makine MühendisliğiArticle Assessment of the Use of AutoCAD in Mechanical Engineering Technical Drawing Education(2017) Akyürek, Turgut; Makine MühendisliğiAutoCAD is one of the widely used software tools in engineering education. In this study, a general assessment of AutoCAD for the usage in the mechanical engineering technical drawing education is made. AutoCAD is assessed in terms of the fulfilment of the requirements defined for the main two technical drawing courses. AutoCAD is assessed in terms of its capability in meeting the requirements of the technical drawing courses.Conference Object Chip-Based Immunomagnetic Separation of Human Chorionic Gonadotropin(2016) Çoğun, Ferah; Yıldırım, Ender; Çiftçi, Hakan; Çağlayan, M. Gökhan; Somay Selbes, Yeşim; Çoğun, Ferah; Yıldırım, Ender; Tamer, Uğur; Makine MühendisliğiConference Object Design, Production, Theoretical And Experimental Analysis Of Parabolic Trough Solar Collector With Sun Tracking Mechanism(2017) Özgirgin Yapıcı, Ekin; Ünver, Eymen; Çelik, Damla; Tercan, Furkan; Ünalan, Emre; Taşkan, Gökhan; 31329Conference Object Dört Kol Mekanizma Tabanlı Bir Tutucunun Kinematik Analizi ve Çalışma Uzayı(2019) Yavuz, Samet; 237938; Makine MühendisliğiBu çalışmada, temel olarak bir dört kol mekanizmasını taban kabul eden paralel bir tutucu mekanizması incelenmiştir. Dört kol mekanizma tabanlı tutucunun kinematik olarak denklemleri önerilmiş ve belirlenen boyutlarda mekanizmanın hangi hacimde cisimleri kavrayabileceği gösterilmiştir. Çalışmada öncelikle; dört kol mekanizma tabanlı tutucunun geometrisi incelenmiştir. Tutucunun kaç serbestlik derecesine sahip olduğu belirlenmiş ve uzuvları tanıtılmıştır. Bir sonraki başlık altında dört kol mekanizma tabanlı tutucunun kinematik çözümlemesi yapılmıştır. Kinematik çözümleme ile birlikte aktif eklemin hareketi ile mekanizma uzuvlarının nasıl ve hangi miktarda hareket ettikleri tespit edilmiş ve uç uzvun çalışma uzayı çıkartılmıştır. Tespit edilen çalışma uzayı ile birlikte hangi geometrilerde ve boyutlarda cisimlerin tutulup taşınabileceği gösterilmiştir.Conference Object Effect of alkali treatment parameters on surface structure and mechanical properties of porous Ti6A17NB scaffolds(2014) Yılmaz, Emre; Esen, Ziya; Yılmaz, Emre; Esen, Ziya; Bor, Şakir; 52373; Malzeme Bilimi ve Mühendisliği; Ortak Dersler BölümüIn the present study, highly porous Ti6Al7Nb alloy scaffolds having 70% pore contents with 200-250 µm average pore size were produced through the spacer holder technique as a result of evaporation of Mg powder from the Ti6Al7Nb-Mg powder mixtures. In order to make the manufactured Ti6Al7Nb foam surfaces more suitable for biomedical applications they were exposed to alkali and heat treatment. Porous samples were immersed in 5M NaOH (aq.) solutions at 60°C for 24 hours then subsequent heat treatment was carried out to obtain crystalline sodium titanate layer. Crystallization heat treatments were also conducted in muffle furnaces to investigate the effect of heat treatment environment on titanate formation. Then, the morphology, structure and chemical composition of the formed titanate layers were characterized by using scanning electron microscopy (SEM) and TF-XRD techniques. According to mechanical testing, produced Ti6Al7Nb alloy foams had elastic moduli and yield strength very close to that of bone which makes them suitable for biomedical application because of the lessened stress shielding problemArticle EXPERIMENTAL AND NUMERICAL ANALYSIS OF FLOW OVER A PICKUP TRUCK(2021) Onur, Nevzat; Mercan, Hatice; Onur, Nevzat; Makine MühendisliğiThe drag forces and the overall drag coefficient of a typical pickup truck are investigated experimentally and the 3D numerical analysis is performed. A detailed 1/4-scale model is constructed and experiments are performed at Reynolds numbers around 2 × 106in the Ankara Wind Tunnel (ART). The experimental study is divided into two stages: in the first stage the pressure distribution along the symmetry axis is measured and in the second stage the drag forces and overall drag coefficient are measured at five different wind speeds. The measured data are compared with the 3D numerical simulation performed in FLUENT. The turbulence standard, realizable, and RNG k-∈ models, the standard and SST k-ω models, and finally the RSM are compared for three near-wall treatments: standard wall function, nonequilibrium wall function, and enhanced wall function. The comparison revealed that for lower velocities the best turbulence model-wall treatment couple is the realizable k-∈ model with Reynolds stress model with standard wall function, whereas for higher velocities the standard k-∈ turbulence model is observed to be more compatible with experimental data. The highest pressure value is measured in front of the pickup truck and the lowest pressure value is evaluated at the rim where the windshield and the roof meet. © 2021 Begell House Inc.. All rights reserved.Article Gözenekli Düz Bir Yüzeye Çarpan Jetin Sayısal Olarak İncelenmesi(2017) Türkoğlu, Haşmet; Türkoğlu, Haşmet; 12941; Makine MühendisliğiBu çalışmada, gözenekli malzeme ile kaplanmış sabit sıcaklıkta tutulan düz levha üzerine çarpan jetin akış ve ısı transferine etkileri nümerik olarak incelenmiştir. Birbirine paralel olarak duran, iki yatay levhadan biri olan alt levha, gözenekli bir tabaka ile kaplanmış ve üst levhanın ortasında bulunan lüleden çıkan hava jeti alt levhaya çarptırılmıştır. Gözenekli tabakanın katı matrisi ile akışkan arasında yerel ısıl denge olduğu kabul edilerek, laminar ve kararlı rejim için çözümler yapılmıştır. Gözeneklilik, gözenekli tabakanın kalınlığı ve jet Reynolds sayısının farklı değerlerinde simülasyonlar yapılarak, bu parametrelerin yerel Nusselt sayısı’na (Nu) etkileri analiz edilmiştir. Sonuçlar, yatay (x) yönde; yerel Nu sayıları ve sıcak alt levhadan olan ısı akıları, gözenekli tabaka bulunmayan durum ile karşılaştırılarak yorumlanmıştır. Analizler için yazılım paketi olan ANSYS Fluent yazılımı kullanılmıştır. Sonuçlar, sıcak levha yüzeyinin gözenekli tabaka ile kaplandığı durumlarda, gözenekli malzemenin belirli gözeneklilik ve kalınlık değerleri aralığında olması halinde, ısı transferinin gözenekli tabaka kullanılmayan duruma göre daha etkin olduğunu göstermiştir.Article Hasar toleransında parametrik analiz-devir sayma tekniğinin etkisi(Çankaya Üniversitesi, 2013) Akyürek, Turgut; 48511; Makine MühendisliğiBu makalede hasar toleransında etken olan önemli parametrelerin hasar tolerans ömürleri üzerine etkileri çalışması kapsamında yük devirlerini sayma yönteminin yorulma çatlağı büyümesi tahminlerine etkileri analiz edilerek, sistemlerin hasar toleransına dayalı tasarımlarında en uygun, çözümü ararken göz önünde bulundurulması gerekli devir sayma teknikleri irdelenmektedir.Conference Object Investigation of a Francis Turbine Performance Using CFD and Site Efficiency Measurements(2020) Aylı, Ece; 265836Article Investigation Of Working Temperature Effect On Micro-Cogeneration Application Of Proton Exchange Membrane Fuel Cells(2018) Budak, Yağmur; Özgirgin Yapıcı, Ekin; Devrim, Yılser; 31329I n this study, micro-cogeneration application is used to increase the efficiency of Proton Exchange Membrane Fuel Cell (PEMFC) systems and effect of different operation temperatures on system performance is observed. For this reason, two different PEMFC systems were comparatively studied operating at 70o C and 160o C, respectively. Micro-cogeneration system design has done considering experimentally determined current density, power and temperature values. Since the amount of heat extracted from each PEMFC system is different related to the operating temperatures, different heat transfer fluids have been used for the cooling systems. These systems are designed for utilization of electricity and hot water for Atılım University Hydrogen Energy Laboratory. Heat loss calculation is made for the laboratory and thermal energy needed for heating the laboratory is calculated. Parallel to the design calculations, simple payback times for PEMFCs with micro-cogeneration applications were determined. LT-PEMFC and HT-PEMFC systems have 402 W and 456 W thermal powers respectively and 87.4 % and 92.8 % total cogeneration efficiencies were calculated for each system respectively. For each system maximum water temperatures and flow rates are calculated as a result of micro-cogeneration application. HT-PEMFC system has found to be capable of higher amount of heating. Even LT-PEMFC system has a lower thermal power and efficiency; it is determined to be more economical and has a lower pay pack time then HT-PEMFC system. For both systems, necessary number of stacks to be used for laboratory heating is calculated as four.Article Investigation of Working Temperature Effect on Micro-Cogeneration Application of Proton Exchange Membrane Fuel Cells(2018) Budak, Yağmur; Özgirgin Yapıcı, Ekin; Devrim, YılserIn this study, micro-cogeneration application is used to increase the efficiency of Proton Exchange Membrane Fuel Cell (PEMFC) systems and effect of different operation temperatures on system performance are observed. For his reason, two different PEMFC systems were comparatively studied operating at 70oC and 160oC respectively. Micro-cogeneration system design is done considering experimentally determined current density, power and temperature values. Since the amount of heat extracted from each PEMFC system is different related to the operating temperatures, different heat transfer fluids have been used for the cooling systems. These systems are designed for utilization of electricity and hot water for Atılım University Hydrogen Energy Laboratory. Heat loss calculation is made for the laboratory and thermal energy needed for heating the laboratory is calculated. Parallel to the design calculations, simple payback times for PEMFCs with micro-cogeneration applications were determined. LT-PEMFC and HT-PEMFC systems have 402 W and 456 W thermal powers respectively and 87.4 % and 92.8 % total cogeneration efficiencies are calculated for each system respectively. For each system maximum water temperatures and flow rates are calculated as a result of micro-cogeneration application. HT-PEMFC system is found to be capable of higher amount of heating. Even LT-PEMFC system has a lower thermal power and efficiency, it is determined to be more economical and has a lower pay pack time then HT-PEMFC system. For both systems, necessary number of stacks to be used for laboratory heating are calculated as four.Conference Object Kanat Profili-Silindir Konfigürasyonunun aerodinamik ve aeroakustik performansının sayısal analizi(2019) Türkoğlu, Haşmet; Aylı, Ece; Türkoğlu, Haşmet; 12941; Makine MühendisliğiFanlar, rüzgâr ve su türbinleri gibi birçok akım makinesinde ve uçak gövdesi bileşenlerinde akışın fiziğinin ve akustik performansının anlaşılmasında, kanat profili-silindir konfigürasyonlarının akış performansından yararlanılmaktadır. Silindirin arkasında meydana gelen kayma tabakası ayrılmaları ve Von Karman girdapları, kanat girişinde parçalanmakta ve birçok küçük yapılar meydana getirmektedir. Ortaya çıkan akış-katı yüzey etkileşimine bağlı olarak gürültü ve titreşim meydana gelmektedir. Akım makinelerinde geniş bant gürültüsünün en önemli sebebi, türbülanslı akış ve stator kanat giriş ucu etkileşimidir. Bundan dolayı akım makineleri gürültüsünün analizi için, kanat profili-silindir konfigürasyonu modellemesi yapılır. Bu çalışmada, kanat profili dairesel silindirin iz bölgesine yerleştirilerek sayısal simülasyonlar yapılmıştır. Simülasyonlar için Large Eddy Simulation (LES) metodu kullanılmıştır. Sayısal sonuçlar literatürdeki deneysel çalışmalar ile karşılaştırılarak sonuçlar doğrulandıktan sonra, farklı çaplardaki silindirler için simülasyonlar yapılarak, silindir çapının girdap oluşum bölgesi, akış birleşme noktası, akış ayrılma noktası, basınç dağılımı ve ses basınç seviyesi üzerindeki etkileri incelenmiştir. Elde edilen sonuçlar, Strouhal sayısındaki artış ile ses basınç seviyelerinin yükseldiğini göstermiştir.Article Kinematic Analysis Of A 5 Dof Overconstrained Manipulator For Rehabilitation Of Upper Extremite(2015) Selvi, Özgün; Al-dulaimi, Hasan; Makine MühendisliğiThis study deals with one of the applications of parallel manipulator as a rehabilitation robot. This device is an over –constrained parallel manipulator 5 degree of freedom with 3 legs. This manipulator consists of a moving platform which is connected to a fixed base via three legs. Each leg is made of RRR(RR) (revolute) joints where the first three joint in all legs are parallel and the recent two joint are intersecting .Inverse kinematics of this device is solved by dividing manipulator into two sub-manipulators with the help of three imaginary joints placed at the intersection of platform joints with a direction parallel to base joints.Article MEMS Malzeme karakterizasyonu için bütünleşik bir elektrostatik mikro bükülme test yapısı tasarımı ve gerçekleştirilmesi(Çankaya Üniversitesi, 2012) Yıldırım, Ender; Akın, Tayfun; Arıkan, M. A. Sahir; 31835; 104090; 163987; Makine MühendisliğiMikro elektromekanik sistemlerde kullanılan malzemelerin mekanik özelliklerinin, üretim yöntemleri nedeniyle, mikro boyuttaki test yapılarıyla tespit edilmesi gerekmektedir. Bu çalışmada, eyleyici, test numunesi ve ölçüm skalası tek bir yonga üzerinde bütünleşik olarak üretilmiş bir mikro bükülme test yapısı sunulmaktadır. Tüm bileşenlerin bütünleşik olarak üretilmiş olması, benzer sistemlerde gözlenen hizalama problemini ortadan kaldırmaktadır. Yapı, iki uçtan ankastre mesnetli bir test kirişinin orta noktasından tarak tipi bir elektrostatik eyleyici ile çekilmesi esasına dayanmaktadır. Bükülme miktarı, ölçüm skalası üzerinden, görüntü işleme yöntemleri kullanılarak tespit edilmektedir. Tasarlanan yapılar yalıtkan-üzeri-silisyum pullar kullanılarak üretilmiştir. Testler sonucunda, literatürde belirtilen sonuçlarla uyumlu olarak, silisyum elastik modülü 136 GPa olarak belirlenmiştirConference Object Microchip Based Determination of Bacteria by In Chip Sandwich Immunoassay International Multidisciplinary Symposium on Drug Research and Development(2015) Çoğun, Ferah; Yıldırım, Ender; Yıldırım, Ender; Boyacı, İsmail Hakkı; Çetin, Demet; Suludere, Zekiye; Tamer, Uğur; Ertaş, Nusret; Makine MühendisliğiArticle Molecular dynamic approach to predict thermo-mechanical properties of poly(butylene terephthalate)/CaCO3 nanocomposites(2021) Akar, Samet; Boğa, Cem; Akar, Samet; Pashmforoush, Farzad; 315516; Makine MühendisliğiThermo-mechanical properties of poly(butylene terephthalate) polymer reinforced with carbonate calcium nanoparticles have been investigated using molecular dynamics simulations. Detailed analyses have been conducted on the effects of nanofiller content, at concentration levels of 0–7 wt%, on the mechanical properties of PBT, i.e. Young's modulus, Poisson's ratio and shear modulus. Thermal properties, including thermal conductivity and glass transition temperature, have been determined using Perl scripts developed based on nonequilibrium molecular dynamics and a high temperature annealing procedure, respectively. Experiments have been performed to verify the accuracy of the results of MD simulations. The CaCO3/PBT nanocomposites were synthesized using melt blending and mold injection techniques. The uniaxial tensile test, thermal conductivity, differential scanning calorimetry and x-ray diffraction spectroscopy measurements were conducted to quantify the thermo-mechanical properties of such nanocomposites experimentally. The results showed significant improvements in the mechanical properties by addition of CaCO3 nanoparticles due to strong binding between rigid particles and PBT polymer and high nucleation effects of nanoparticles on the matrix. Thermal conductivity and glass transition temperature of nanocomposites represented a consistent increase with the ratio of CaCO3 nanoparticles up to 5 wt% with an enhancement of 38% and 36% with respect to that of pure PBT, respectively. © 2021 Elsevier LtdConference Object Numerical Analysis of Aerodynamic and Aeroacoustic Characteristics of Subsonic Rectangular Cavity with Different Aspect Ratios(2020) Koçak, Eyup; Türkoğlu, Haşmet; Türkoğlu, Haşmet; 283455; 265836; 12941; Makine MühendisliğiConference Object Numerical Analysis of Mixed Convection in a Channel with Open Cavity(2019) Deniz, A.; Aylı, Ece; 265836Article Numerical investigation on the performance of a small scale solar chimney power plant for different geometrical parameters(2020) Özgirgin Yapıcı, Ekin; Nsaif, Osama; Aylı, Ece; 265836; 31329In recent decades, demand for energy has been significantly increased, and considering environmental impacts and the degrading nature of fossil fuels, clean and emission-free renewable energy production has attracted a great deal of attention. One of the most promising renewable energy sources is solar energy due to low cost and low harmful emissions, and from the 1980s, one of the most beneficial applications of solar energy is the utilization of solar chimney power plants (SCPP). A SCPP is a simple and reliable system that consists of three main components; a solar collector, a chimney (tower) and a turbine to utilize electrical energy. Recently, by the advancement in computer technology, the use of CFD methodology for studying SCPP has become an extensive, robust and powerful technique. In light of the above, in this study, numerical simulations of a SCPP through three-dimensional axisymmetric modeling is performed. A numerical model is created using CFD software, and the results are verified with an experimental study from the literature. After ensuring good agreement with the experiments, chimney's and collector's geometric parameters effects and different configurations effects on SCPP performance, simultaneously and additively is investigated. The study introduces an insight to the performance enhancement methods and finding the best configuration of a SCPP model, which will be the basis of a detailed prototyping process. Based on the numerical results, the best configuration of the SCPP has been found as the diverging chimney which enhances the generated power. The results of the study showed that the chimney height and collector radius increase has a positive effect on the power output and efficiency of the system, but when construction and material costs are also considered, each has an optimal value. The maximum impact on the performance is found to be by the chimney tower radius and the collector height and inclination are found to have optimum values considering performance. According to the obtained results, the best performance for the SCPP was obtained with 3.5 m chimney height, 30 cm tower diameter, 400 cm of collector diameter with 6 cm height and zero inclination angle. By the correct selection of the dominant performance parameter which can be done by correctly interpreting the results of this study, "the best" design of a SCPP real scale prototype considering maximum power requirement can be done. (C) 2020 Elsevier Ltd. All rights reserved.
