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Öğe Application of genetic algorithms (GA) for the optimization of riveted joints(Carl Hanser Verlag, 2013) Başkal, Tamer; Nursoy, Mustafa; Esme, Uğur; Külekçi, Mustafa KemalGenetic algorithms have an effective search technique in a predefined research space based on natural selection theory. They use the same combination of selection, recombination, and mutation to evolve a solution to a problem. In this study, it has been demonstrated how to determine the optimal diameter, sheet thickness, and sheet width in riveted joints by means of genetic algorithms (GA). In this study the optimization of objective function for the variables in predetermined limit ranges was applied. Since the algorithms developed by this way are based on a principle to find out the best within a range like genetic process, it is becoming possible to predict the most suitable values for riveted junction dimensions in the defined limit range. The algorithms were restrained considering rivet diameter, thickness and width of the sheet, shear strength, tensile strength, and tear hazard of the sheet.Öğe Değişen ve gelişen endüstrinin nitelikli teknik eleman ihtiyaçlarının karşılanması için mesleki ve teknik eğitim sisteminde model arayışları(2008) Nursoy, MustafaEndüstrinin gereksinim duyduğu meslek elemanlarının ve mühendislerin eğitim ve öğretim süreçlerinde edinmesi gereken nitelikler konusunda çeşitli görüşler öne sürülmektedir. Endüstrinin yapısı gibi, gereksinim duyduğu teknik elemanların niteliği de sürekli değişmektedir. Ülkemizdeki değişmeleri, mesleki ve teknik yüksek öğretimdeki sorunları göz önüne alarak yapılan bu alan çalışmasında, sanayicinin beklentileri ve ülkemiz koşullarına uygun bir organizasyonla bu beklentilerin en iyi şekilde nasıl karşılanabileceği ortaya konulmaya çalışıldı. Üniversite düzeyindeki mesleki ve teknik eğitim sistemimizin hem daha verimli hâle getirilmesi hem de endüstrinin gereksinimlerini daha verimli olarak karşılaması için, AB, ABD ve diğer gelişmiş ülkelerde yıllardır uygulanan bir sistemin ülkemiz koşullarına uyup uymayacağı ve bu sisteme sanayicilerimizin gereksinim duyup duymadığı da belirlenmeye çalışıldı. Ankara çevresindeki sanayi kuruluşlarıyla yüz yüze görüşerek yapılan anket ve araştırma sonuçlarının değerlendirilmesi sanayicilerin değişen isteklerini ortaya koyduğu gibi yeni bir sistemin hayata geçirilmesi zamanının geldiğini ve gerekli düzenlemelerin yapılmasının şart olduğunu göstermektedir. Araştırma sonuçlarına ve dünyadaki gelişmelere uyumlu olarak ülkemiz koşullarına uygun olduğu düşünülen bir model önerilmektedir.Öğe Effect of Cr content on microstructure and abrasive wear behaviour of Co-based alloys(Taylor & Francis Ltd, 2011) Somunkıran, İlyas; Nursoy, Mustafa; Çelik, H.In this study, a series of Co-Cr-Mo alloys with varying Cr contents were produced by powder metallurgy technique, and the effects of Cr content on microstructure and abrasive wear behaviour were studied. Seven different powder compositions having 15-35 wt-%Cr were used in the experiments. Homogeneously blended powders were cold compacted in a 120 kN single action press. The sintering process was carried out at 1200 degrees C for 60 min in an argon atmosphere. The effects of Cr on the microstructure and abrasion wear performance of the produced powder metallurgy alloys were investigated using SEM, energy dispersive spectroscopy and abrasion wear tests. Abrasive wear resistances were observed to have been increasing up to 27.5 wt-%Cr addition and decreasing subsequently.Öğe Effects of CrN coating of cylinders on engine performance(Sila Science, 2009) Hazar, Hanbey; Öner, Cengiz; Nursoy, MustafaIn an experimental study performed on a single cylinder four stroke diesel engine, the cylinder was coated with CrN by PVD and its surface behaviors were investigated. Performance improvements of the engine with CrN coated cylinder and with uncoated cast iron cylinder were compared. Exhaust emission values, exhaust gas temperatures, specific fuel consumptions (SFC), and torque and power outputs were taken into account as performance indicators. CrN coated engines were performed better at almost all categories. The test results evidenced that, No. 2D fuel can be used in ceramic coated diesel engines successfully.Öğe Hardfacing behavior of Cr-Ni stainless steel with Co-based super alloys(Carl Hanser Verlag, 2008) Nursoy, Mustafa; Yaz, Mehmet; Çelik, HalisIn this study, the hardfacing behavior of Cr-Ni stainless steel was studied by depositing of Stellite 1, Stellite 6, and Stellite 12 superalloys on Cr-Ni stainless steel specimens using electric arc welding and tungsten inert gas welding. The cobalt base alloys were hardfaced on stainless steel plates as a single layer. The samples taken from the hardfaced materials were studied by optical microscopy, scanning electron microscopy, X-ray diffraction, and micro-hardness measurements. The hardness and wear resistance values of the layer obtained after the hardfacing processes are satisfactory and the process seem to be suitable for application.Öğe Hardfacing behavior of Cr-Ni stainless steel with Co-based super alloys(Carl Hanser Verlag, 2008) Nursoy, Mustafa; Yaz, Mehmet; Celik, HalisIn this study, the hardfacing behavior of Cr-Ni stainless steel was studied by depositing of Stellite 1, Stellite 6, and Stellite 12 superalloys on Cr-Ni stainless steel specimens using electric arc welding and tungsten inert gas welding. The cobalt base alloys were hardfaced on stainless steel plates as a single layer. The samples taken from the hardfaced materials were studied by optical microscopy, scanning electron microscopy, X-ray diffraction, and microhardness measurements. The hardness and wear resistance values of the layer obtained after the hardfacing processes are satisfactory and the process seem to be suitable for application.Öğe Influence of annealing temperature on the microstructure and mechanical properties of MgB2(Institute of Physics Publishing, 2009) Görür, Osman; Nursoy, Mustafa; Terzioğlu, Cabir; Varilci, Ahmet; Belenli, İbrahimWe have investigated the effect of annealing temperature on the microstructure, magnetic and mechanical properties of MgB2 superconducting samples employing X-ray diffraction (XRD), scanning electron microscopy (SEM), ac susceptibility and Vickers microhardness measurements. XRD patterns and SEM micrographs are used to obtain information about lattice parameters and grain size, respectively. These measurements indicate that MgB2 grain size, lattice parameters, and critical temperature are increased, and grain connectivity is improved, with increasing the sintering temperature up to 850°C. It is also observed that the Vickers microhardness of the samples is dependent of the sintering temperature and applied load. In addition, we calculate the load dependent mechanical properties of MgB 2 samples such as the Young's modulus, yield strength, and fracture toughness. The possible reasons for the observed improvements in microstructure, superconducting and mechanical properties due to annealing temperature are discussed. © 2009 IOP Publishing Ltd.Öğe The influence of cooling rates on microstructure and mechanical properties of Bi1,6Pb0,4Sr2Ca2Cu 3Oy superconductors(Institute of Physics Publishing, 2009) Çetinkara, Hacı Ali; Yılmazlar, Mustafa; Öztürk, Özgür; Nursoy, Mustafa; Terzioğlu, CabirWe investigated the effect of cooling rates on the microstructure and mechanical properties of Bi1,6Pb0,4Sr2Ca 2Cu3Oy superconductors prepared by standard solid state reaction methods. The samples were annealed under identical condition and cooled with different cooling rates. The investigations consisted of Vickers microhardness, SEM and XRD measurements. XRD examination of the samples showed that high percentage of Bi-2212 phase was observed and low-T c phase increased with increasing the cooling rates. From SEM analysis, flake-like grains were more pronounced with increasing cooling rates. The indentation load versus diagonal length of the samples under different indentation loads in the range of 0.245-2.940 N were presented. We calculated Vickers hardness, Young's modulus, yield strength, fracture toughness values. These mechanical properties of the samples were found to be load and cooling rate dependent. In addition, we calculated the load independent microhardness, Young's modulus, and yield strength and fracture toughness of the samples using different models. The possible reasons for the observed changes in microstructure and mechanical properties of the samples due to cooling rates were discussed. © 2009 IOP Publishing Ltd.Öğe A Novel Model Investigation for Turkish Vocational and Technical Higher Education System(Edam, 2008) Nursoy, MustafaThe skills necessary for the training of technical staff during their training and education vary according to the viewpoint of the employees. Like the nature of the industry, the skills of the staff arc evolving continuously. The conformity of training institutions to this evolution is always among current issues; however, the implementation is not as easy as it may seem. According to the results of this study which was held to determine the applicability of a training system applied by the EC, USA, and other developed countries for decades and to make our vocational technical training system more efficient for meeting the requirement of the industry. This study is aimed to determine the needs of the industry on this issue. The industrial plants around Ankara were chosen as the sample of the study. The need for a new system and regulations is clearly seen to be necessary. A novel model thought to be suitable for Turkey's conditions and the developments over the world is proposed after the results of the study.Öğe The potential of wind energy as an alternative source in Turkey(Taylor & Francis Inc, 2010) İlkılıç, Cumali; Nursoy, MustafaDevelopment in wind energy systems and the potential of wind energy in Turkey were studied; the wind energy potential of various regions was investigated in this study. A power equation was derived by a mathematical approach using the characteristics of wind energy, including rotor diameter, wind speed, and density of the wind power. The maximum power obtainable at each location with the wind speed of the location and the diameter of the rotor used has been calculated with this power equation. Nurdagi, Karabiga, Datca, Bandirma, Antakya, Mardin, and Kumkoy areas were found to be the most suitable areas for wind energy systems by their wind densities; Sinop, Gokceada, and Siverek are following these areas.Öğe Surface properties of CrN coated engine cylinders(Elsevier Sci Ltd, 2009) Öner, Cengiz; Hazar, Hanbey; Nursoy, MustafaIn an experimental study performed on a single cylinder four stroke diesel engine, the cylinder was coated with CrN by PVD and its surface behaviors were investigated. The wear behaviors of the engine with CrN coated cylinder and with uncoated, cast iron, cylinder were compared. The effect of hardness, surface topography, microstructure, and running conditions were studied. With X-ray analysis, the structural changes on the surface due to thermal and mechanical shocks were examined. (C) 2008 Elsevier Ltd. All rights reserved.Öğe Thermal expansion and vickers hardness measurements on Bi1.6Pb0.4Sr2Ca2-xSmxCu3Oy superconductors(Elsevier Science Bv, 2006) Yılmazlar, Mustafa; Çetinkara, Hacı Ali; Nursoy, Mustafa; Öztürk, Özgür; Terzioğlu, CabirIn this work, Bi1.6Pb0.4Sr2Ca2-SmxCu3Oy (x = 0.0000, 0.0005, 0.0010, 0.0050, 0.0100, 0.1000, 0.5000, 1.0000, 1.5000) superconductors were prepared by conventional solid-state reaction method. The effect of the substitution of Sm for Ca in the high-T-c phase Bi-2223 was investigated by DTA, thermal expansion coefficient, Vickers microhardness, XRD and SEM analysis. The lattice constants and volume fractions are estimated from XRD analysis. The thermal expansion coefficient, the microhardness, the volume fraction, and the lattice constants strongly depend on the Sm content of the samples. XRD data show that the high-Tc phase decreases and the low-T-c phase increase as the Sm substitution changes from x = 0.0 to 1.5. The coefficients of thermal expansion (in the range of 30-800 degrees C) of the pure (x = 0.0) and high doped (x = 1.5) samples were 7.90 x 10(-7) and 5.70 x 10-7 degrees C-1, respectively. The results of Vickers hardness measurements varied between 0.254 and 0.623 GPa as increasing the Sm concentration.Öğe Transport, microstructure and mechanical properties of Au diffusion-doped Bi-2223 superconductors(Elsevier B.V. All, 2008) Nursoy, Mustafa; Yılmazlar, Mustafa; Terzioğlu, Cabir; Belenli, İbrahimWe have investigated the effect of the Au-diffusion on the mechanical and transport properties of the (Bi,Pb)(2)Sr(2)Ca(2)Cu(3)Oy (Bi-2223) superconducting samples with different annealing times of 10, 20 and 50 It. The samples are prepared by the conventional solid-state reaction method in the polycrystalline bulk form. Doping of Bi-2223 was carried out by means of Au diffusion during sintering from an evaporated An film on pellets. The experimental works in this study consist of dc electrical resistivity and critical current density measurements for electrical and superconducting properties, microhardness measurements for mechanical properties, powder X-ray diffraction (XRD) for phase analyses (phase ratio) and lattice parameters, and scanning electron microscopy (SEM) for microstructure examination. These measurements showed that Au-doping, in comparison with the undoped samples, increased the critical transition temperature, critical current density and enhanced formation of high-T-c, phase. Additionally, microhardness and grain size were also improved with increasing amount of diffusion. Moreover, the diffusion-annealing time decreased the number and size of voids and increased the transition temperature. The experimental results of microhardness measurements were analyzed using the Kick's law, modified proportional specimen resistance (MPSR) model and the Hays-Kendall (HK) approach. Kick's law did not give useful knowledge of the origin of the indentation size effect. It was observed that the load independent microhardness values were determined based on the MPSR and HK models, and found to be similar with each other. The possible reasons for the observed enhancement in transport and mechanical properties due to An diffusion are discussed. (C) 2007 Elsevier B.V. All rights reserved.Öğe Wear behavior of a crankshaft journal bearing manufactured by powder spraying(Elsevier Sci Ltd, 2008) Nursoy, Mustafa; Öner, Cengiz; Can, İbrahimA new crankshaft bearing material that can be an alternative to the traditional material has been improved and its wear behavior studied experimentally. Crankshaft main bearings are subjected to various stresses. A new material supposed to be adapted these operating conditions was designed composing of Pb-Sn-Cu-ZrO(2) and manufactured by HVOF spraying technique. Wear behavior of the bearing was tested with the simulation of real operating conditions. An original bearing was used for comparison. After a trial of 500 h, the weight losses were measured. SEM micrographs of both original and new bearings were examined. The effect of microhardness was discussed. The new composition was seen as promising as a bearing material for automotive engines. (C) 2008 Elsevier Ltd. All rights reserved.
