Mechanical Engineering / Makina Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4129
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Research Project Otomobil endüstrisi için mukavemeti yüksek seramik katkılı kapalı hücre alüminyum köpük metallerin geliştirilmesi(2009) Güden, Mustafa; Taşdemirci, Alper; Yüksel, Sinan; Toksoy, Ahmet Kaan; Gültürk, Elif; Karsu, Nurettin DenizFarklı seramik ve metal toz katkılarının Al toz tabletlerinde köpükleşme ve mekanik davranışlara etkileri incelenmiştir. Katkı malzemesi olarak sıvı Al ile ıslatılan Ti6Al4V ve diyatomdan elde edilen silika parçacıkları ve Al tarafından yarı ıslatılan SiC parçacıkları, SiC nano toz ve SiC viskır kullanılmıştır. Ti6Al4V parçacıklarının sıvı Al içerisinde küçük boyutlu TiAl3 intermetalik fazı oluşturması ile artan sıvı tablet viskozitesi köpüğün kararlılığını artırmakta; fakat, köpükleşmeyi azalmaktadır. Köpük kararlılığı ve köpükleşme uzaması kullanılan Ti6Al4V toz boyutu ve yüzdesi ile değişmektedir. Sıvı Al tarafında ıslatılan bir diğer toz olan diyatom SiO2 katkısında ise düşük yüzdelerde köpükleşme maksimum uzamaya kadar artmaktadır. Artan katkı yüzdelerinde ise viskozite artışı ile tabletlerin köpükleşmesi azalmaktadır. SiC katkılı tabletlerde köpükleşme, kullanılan tozların toplam yüzey alanı ile değişmektedir. Optimum parçacık toplam yüzey alanında (~100000 mm2), SiC içeren tabletlerin uzamaları katkısız tabletlere göre daha yüksektir. Küçük boyutlu tozlarda artan yüzey alanı düşük parçacık yüzdelerinin, büyük parçacık boyutlarında ise daha yüksek parçacık yüzdelerinin kullanılmasının gerekliliği gösterilmiştir. Mikroskobik çalışmalar SiC parçacıklarının çoğunlukla hücre duvar yüzeylerinde asılı, Ti6Al4V ve SiO2 parçacıklarının ise tamamen hücre duvar içlerinde yer aldığını göstermiştir. Çalışılan parçacık boyu ve yüzdelerinde SiC katkısı plato gerilmesi ve enerji emme miktarlarını sırası ile %35 ve %20 artırmaktadır. Simülasyon sonuçları kritik köpük yoğunluğunun altında ticari olarak kullanılan boş 6063 T6 Al ve çelik tüplerin köpük dolu tüplerden maliyet ve ağırlık açısından daha avantajlı olduğunu göstermiştir.Article Citation - Scopus: 1Sizing of Autonomous Wind/Solar Hybrid Energy Conversion Systems for Urla, Turkey(ACTA Press, 2009) Özerdem, Barış; Ekren, OrhanIn this paper, an optimum sizing procedure of autonomous hybrid (wind + solar) energy system is presented which can be used to satisfy the requirements of given load distribution. The main purpose of this study is to find out an appropriate wind-photovoltaic hybrid energy system to satisfy electricity consumption of GSM (Global System for Mobile communication) base station at Izmir Institute of Technology Campus Area, Urla, Izmir, Turkey. To do this, monthly average daily solar radiation and wind speed data are collected. The monthly average wind speeds are measured at 10 m height during 3 years period on Izmir Institute of Technology Campus Area. The monthly average wind speed values are obtained between 5.7 and 7.7 m/s, on the other hand, the monthly average daily value of solar radiations on horizontal surfaces are ranged from 1.4 to 6.9kWh/m2 at Izmir Institute of Technology Campus Area. The hybrid system considered in the present analysis consists of one 5kW nominal power wind energy conversion systems (WECS), 21.82 m2 of photovoltaic (PV) panels (18 mono crystal PV panels each having 75 W power output) together with a battery storage system.Conference Object Problem of Cracked Infinite Hollow Cylinder With Two Rigid Inclusions(Civil-Comp Press, 2000) Artem, Hatice Seçil; Geçit, Mehmet RuşenThis paper is concerned with the fracture of an axisymmetric hollow cylindrical bar containing rigid inclusions. The cylinder is under the action of uniformly distributed axial tension applied at infinity. The hollow cylinder contains a ring-shaped crack at the symmetry plane whose surfaces are free of tractions and two ring-shaped rigid inclusions with negligible thickness symmetrically located on both sides of the crack. Geometry and the loading is symmetric about z-axis. Along the rigid inclusions displacements are constant and continuous whereas stresses have jumps. The inner and the outer surfaces of the cylinder are free of tractions It is assumed that the material of the cylinder is linearly elastic and isotropic. The mixed boundary conditions of the problem lead the analysis to a system of three singular integral equations for crack surface displacement derivative and normal and shear stress jumps on rigid inclusions. These integral equations are solved numerically and the stress intensity factors at the edges of the crack and at the edges of the inclusions are calculated. Results are presented in graphical form.Conference Object Kinematic and Dynamic Analysis of a New Type of Spatial 6-Dof Parallel Structure Manipulator(China Machine Press, 2004) Alizade, Rasim; Bayram, ÇağdaşThis paper addresses the dynamics and kinematics of a 6xUPS type parallel structure manipulator that consists of six branches and a platform. The problem of forward and inverse displacement analysis is considered on the base of solution of the forward displacement problem for each UPS branch as a serial manipulator. Basic dynamics equations have also been considered. The values of reduced moments and forces have been determined that provides the required input forces and moments. Thus, we deal with inverse dynamics problems. Dynamic model of this type of spatial manipulator is described by a system of six non-linear differential equations of second order with applying Lagrange-Euler methods.Conference Object Cash Flow Forecasting by Using Time Series Methods in Geothermal District Heating Systems: Balcova - Narlidere Case(National Technical University of Athens, 2006) Erdoğmuş, Abdullah Berkan; Özerdem, BarışCash flow forecasting is one of the difficult and important tasks in an economic evaluation of a geothermal investment. Geothermal district heating systems are characterized by a high capital cost. In addition, relatively low operation and maintenance costs occur throughout their life. The aim of this research is to estimate the potential cash flows for Balcova - Narlidere Geothermal District Heating System by using historical data accumulated over a period of time and several forecasting methods: moving average, exponential smoothing, adjusted exponential smoothing and curve fitting functions. Mean absolute percentage deviation (MAPD) which is the most common approach to select the appropriate method to a particular time series is used in the selection of the most suitable model. Alternative methods are compared with each other regarding to their MAPD values. It is found that the models represented by exponential curve fitting functions have smaller MAPD values and give better results in cash flow forecasting of investment investigated.Conference Object Underground Gasification in Western Black Sea Area and Thermodynamic Analysis(2006) Atagündüz, GürbüzAs known, western Black Sea carboniferous coal fields consist of two main fields: Zonguldak and Amasra. Previous research works have shown that Zonguldak area is not suitable for underground coal gasification. The joint studies done since 1994 by the Department of Geology and the Solar Energy Institute of Aegean University and, the Mineral Research and Exploration Institute of Ministry of Energy and Natural Sources have shown that the Amasra coal field is suitable with certain restrictions for the underground coal gasification. In the present work, the suitability of the Amasra - coal field for underground coal gasification will be discussed and the "Controlled Retraction of the Injection Point; CRIP"- Method which was successfully used and tested in the American field experiments will be described briefly. A brief thermodynamic analysis of the gasification process will be given which should help, as a tool, to the theoretical prediction of the underground coal gasification.Conference Object Energy Losses From Outdoor Located Air Handling Unit and Connection Duct(Universita degli Studi di Padova, 2007) Erdoğmuş, Abdullah Berkan; Mobedi, Moghtada; Özerdem, BarışIn the present study, energy losses due to heat transmission and air leakage from outdoor located air handling unit and connection duct are investigated based on EN 1886 and NEN-EN 1507 standard. The EN 1886 standard classifies air handling unit according to heat transmission and air leakage, while NEN-EN 1507 standard specify air leakages of rectangular ducts. In this study, air leakage and heat transmission fluxes for three cities in different regions of Turkey are determined and the economical value of energy losses for a building located in the city of Izmir and services 24 hours is calculated. The ambient air temperatures are taken from Turkish State Meteorological Service. The daily average values are considered for ambient temperature. The energy losses are determined for the variable and constant supply temperatures. Tables and charts are provided to show the variation of energy losses due to transmission and air leakage for the whole year. The total amounts of heat transmission and air leakage energy losses for different classes of air handling unit and connection duct are compared and discussed.Conference Object Si-Geothermometry Applied for the Interpretation of Three-Components Mixtures in Marine Geothermal Systems -Exploration of the Gülbahce Geothermal Field, Western Anatolia/ Turkey(Wydawnictwo Uczelniane Politechniki Szczecinskiej, 2000) Giese, L.B.; İlken, Zafer; Çetiner, Levent; Yıldırım, NazımThe geothermal field of Gülbahce is located in western Anatolia/Turkey near Izmir. The University of Izmir IYTE is building-up a campus there. A pre-study was done to investigate whether the campus can be supplied with geothermal heat. Based on hydrogeochemical data, mixing calculations and a modified version of the SiO2-enthalpy diagram were applied to evaluate the reservoir temperature of three-components-mixtures. The temperature of the mixed outcrop water is 35°C. It consists of geothermal sea water, freshwater, and cold sea water. The fraction of freshwater was estimated to be 8%, The contents of Li and Si were interpreted to be generated by the reservoir temperature of 60°C in minimum - lower limit for low-temperature space heating - but to be maybe more than 100°C. This geothermal resource seems to be suitable, but exploitation will be difficult. One production well should satisfy the heat supply. Problems with scaling and corrosion are expected.Article Citation - WoS: 171Characteristics of Brick Used as Aggregate in Historic Brick-Lime Mortars and Plasters(Elsevier Ltd., 2006) Böke, Hasan; Akkurt, Sedat; İpekoğlu, Başak; Uğurlu, ElifMortars and plasters composed of a mixture of brick powder and lime have been used since ancient times due to their hydraulic properties. In this study, raw material compositions, basic physical, mineralogical, microstructural and hydraulic properties of some historic Ottoman Bath brick-lime mortars and plasters were determined by XRD, SEM-EDS, AFM, TGA and chemical analyses. The mineralogical and chemical compositions, microstructures, morphologies and pozzolanicities of the brick powders and fragments used as aggregates in the mortars and plasters were examined to find out the relationship between hydraulic properties of the mortars and the bricks. The characteristics of bricks used in the bath domes were also determined to investigate whether the brick aggregates used in mortar and plasters were prepared from these bricks. The results indicated that the mortars and plasters were hydraulic owing to the presence of crushed brick powders that have good pozzolanicity. The brick powders bad high pozzolanicity because they contained high amounts of calcium-poor clay minerals in their raw materials that were fired at low temperatures. On the other hand, bricks used in the domes had poor pozzolanicity with different mineralogical and chemical compositions from bricks used in mortars and plasters. Based on the results of the analysis, it was thought that the bricks manufactured with high amounts of clays were consciously chosen in the preparation of hydraulic mortars and plasters. (C) 2006 Elsevier Ltd. All rights reserved.Article Fireproofing the Firefighting Robot(Laurin Publishing Co. Inc., 2009) Keçeci, Emin FarukResearchers at the Institute of Technology in Izmir, Turkey, have successfully developed a mechanical firefighter robot that will work inside the flames. The robot uses both passive and active cooling systems that, for a limited time, keep the inner temperature at a safe level for the electronic components inside the device, to survive the flame. The body of the robot is made of aluminum and comprises two shells attached to each other with rods. The robot is controlled with a remote unit by an operator, who can observe the fire via a CCD camera. Control and cooling subsystems will allow the robot to work in these rough conditions. The control system allows the robot to use the navigation system as well as the sensory and cooling systems. The robot will be controlled with radiofrequency communications and is able to break doors and climb stairs to work in upper-level fires.