Salamcı, Elmas

Diğer | 2001 | Turkish Journal of Engineering and Environmental Sciences25 ( 6 ) , pp.681 - 686

Aytekin, Hüseyin | Baldık, Rıdvan

Diğer | 2008 | Turkish Journal of Engineering and Environmental Sciences32 ( 2 ) , pp.101 - 105

This paper presents a study performed on the radiological character of the Çatalağzı Thermal Power Plant (ÇTPP/ÇATES), on the west Black Sea coast of Turkey. Natural radioactivity distribution of the terrestrial radionuclides $^{238}U$, $^{232}Th$, and $^{40}K$ of surface soil samples around the ÇTPP was analyzed. The average radioactivity concentrations for $^{232}Th$, $^{238}U$, and $^{40}K$ for soil samples were 39.7, 30.5, and 378.7 Bq $kg^{-1}$, respectively. $^{238}U$ and $^{40}K$ concentrations are lower than the world average values, 35 Bq $kg^{-1}$ and 400 Bq $kg^{-1}$, respectively, and the $^{2 . . .32}Th$ concentration is higher than the world average value, 30 Bq $kg^{-1}$. This paper presents a study performed on the radiological character of the Çatalağzı Thermal Power Plant (ÇTPP/ÇATES), on the west Black Sea coast of Turkey. Natural radioactivity distribution of the terrestrial radionuclides $^{238}U$, $^{232}Th$, and $^{40}K$ of surface soil samples around the ÇTPP was analyzed. The average radioactivity concentrations for $^{232}Th$, $^{238}U$, and $^{40}K$ for soil samples were 39.7, 30.5, and 378.7 Bq $kg^{-1}$, respectively. $^{238}U$ and $^{40}K$ concentrations are lower than the world average values, 35 Bq $kg^{-1}$ and 400 Bq $kg^{-1}$, respectively, and the $^{232}Th$ concentration is higher than the world average value, 30 Bq $kg^{-1}$ Daha fazlası Daha az

Kopaç, Mehmet | Arıkol, Mahir

Makale | 1997 | Turkish Journal of Engineering and Environmental Sciences21 ( 3 ) , pp.149 - 154

Bu çalışmada literatürde mevcut olan bazı bünye denklemlerinden faydalanılarak deneysel sonuçlara göre başarılı olabilecek türev tipli bir bünye denklemi geliştirilmeye çalışılmıştır. Kullanılan hesaplama yöntemi Marquardt metodu olarak bilinen lineer olmayan regresyon yöntemidir. Çalışmalar kanalın simetri ekseni boyunca olan akım dikkate alınarak yapılmıştır. Bu çalışmada önerilen bünye denkleminin tansörel ifadesi, akım kinematiği ve modele ait türev operatörü karteziyen koordinatlar için yazılarak simetri ekseni üzerine indirgenmiştir. 1- ve 2- doğrultularındaki normal gerilme bileşenlerinin farkı oluşturularak normal gerilme fa . . .rkına ait lineer olmayan bir adi diferansiyel denklem elde edilmiştir. Simetri ekseni üzerine indirgenmiş olan bu diferansiyel denklem, lineer olmayan regresyon yöntemiyle çözüldüğünde model parametreleri, simetri ekseni boyunca olan normal gerilme farkı değerleri ve deneysel gerilme farkına göre olan hata karelerinin toplamı aynı anda belirlenmiştir. Başarılı bulunan mevcut bünye denklemleri ile önerilen bünye denkleminin karşılaştırılması yapıldığında önerilen modelin simetri ekseni boyunca olan akımda daha başarılı olduğu saptanmıştır. In this study using some constitutive equations present in the literature, a rate-type constitutive equation is developed which is successful with the experimental results. The method being used is a nonlinear regression method that is known as Marquardt Method. Studies were done considering flow along the centerline of the flow channel. In this study the general form of the proposed constitutive equation was reduced on the centerline by using the flow kinematics and derivative operator for cartesian coordinates. Developing the difference of the normal stress components in the 1- and 2- directions a nonlinear ordinary differential equation was obtained for the normal stress difference. When this differential equation that was reduced on the centerline was solved by this nonlinear regression method, model parameters, normal stress difference values along the centerline and sum of squares were determined simultaneously. When the proposed constitutive equation was compared with the existing equations, the proposed equation was found to be more successful in the flow along the centerline Daha fazlası Daha az

Salamcı, Elmas

Diğer | 2002 | Turkish Journal of Engineering and Environmental Sciences26 ( 4 ) , pp.345 - 352

Mechanical properties of spray deposited and extruded 7xxx series aluminium alloys were investigated in peak aged condition. To study the influence of Zn additions on the mechanical behaviour of spray deposited materials, three alloy compositions were selected, namely: SS70 (11.5% Zn), N707 (10.9% Zn) and 7075 (5.6% Zn). After ageing treatment, notched and unnotched specimens of spray deposited alloys were subjected to tensile tests at room temperature. Experimental results showed that the SS70 alloy exhibited the highest strength. Spray deposited Al alloys showed a very high strength as compared to conventionally processed 7xxx ser . . .ies Al alloys. Compared with the PM processed 7xxx series Al alloys, fracture toughness values of these alloys were higher. Mechanical properties of spray deposited and extruded 7xxx series aluminium alloys were investigated in peak aged condition. To study the influence of Zn additions on the mechanical behaviour of spray deposited materials, three alloy compositions were selected, namely: SS70 (11.5% Zn), N707 (10.9% Zn) and 7075 (5.6% Zn). After ageing treatment, notched and unnotched specimens of spray deposited alloys were subjected to tensile tests at room temperature. Experimental results showed that the SS70 alloy exhibited the highest strength. Spray deposited Al alloys showed a very high strength as compared to conventionally processed 7xxx series Al alloys. Compared with the PM processed 7xxx series Al alloys, fracture toughness values of these alloys were higher Daha fazlası Daha az

Müftüoğlu, Fisun | Keskinel, Tuna

Makale | 2007 | Turkish Journal of Engineering and Environmental Sciences31 ( 3 ) , pp.183 - 187

This study examined the effect of coating thickness on electrode life and nugget strength. Uncoated and galvanized steel sheets supplied from Ere˘gli Iron and Steel Factories Co. (Erdemir) with similar chemical compositions having different coating weights (100, 180, and 275 g/m2) were welded using resistance spot welding under constant welding parameters. Electrode force used during spot welding operation was 7.3 kN under 6.5 kA of constant welding current and 2 s welding time. After welding operations, shearing tests were applied to selected specimens and the nugget diameters were measured. Experimental results showed tha . . .t as the coating thickness increased the electrode life and the strength of the weld nugget decreased. This study examined the effect of coating thickness on electrode life and nugget strength. Uncoated and galvanized steel sheets supplied from Ere˘gli Iron and Steel Factories Co. (Erdemir) with similar chemical compositions having different coating weights (100, 180, and 275 g/m2) were welded using resistance spot welding under constant welding parameters. Electrode force used during spot welding operation was 7.3 kN under 6.5 kA of constant welding current and 2 s welding time. After welding operations, shearing tests were applied to selected specimens and the nugget diameters were measured. Experimental results showed that as the coating thickness increased the electrode life and the strength of the weld nugget decreased Daha fazlası Daha az

Acarer M. | Gülenç B.

Makale | 2003 | Turkish Journal of Engineering and Environmental Sciences27 ( 6 ) , pp.431 - 434

High Mn steel containing about 16% Mn was cladded to a low C steel by explosive welding. The experimental results showed that the bonding interface has a wavy morphology; the welding interface has the characteristics of both sharp transition and local melted zones between 2 metals. Hardness increased near the welding interface due to excess plastic deformation in the explosion area and phase transformation from ? (f.c.c.) to ? (b.c.c.).

Karabulut H. | Yücesu H.S. | Koca A.

Makale | 2000 | Turkish Journal of Engineering and Environmental Sciences24 ( 2 ) , pp.71 - 80

An air charged V-type Stirling engine, having 260 cm3 swept volume, was manufactured and tested. Speed-torque characteristics of the engine were obtained for different temperature and charge pressure values in the range of 600°C to 1100°C and 1 to 4 bars. The experiments intended to determine the performance characteristics of the engine at different set up values of pressure and hot source temperature. Maximum output power was obtained at 1100°C and 2.5 bars charge pressure as 65 W. The results are presented in diagrams.

Salamcı, Elmas

Diğer | 2003 | Turkish Journal of Engineering and Environmental Sciences27 ( 3 ) , pp.169 - 176

Three 7xxx series aluminium SS70, N707 and 7075 alloys have been produced by the spray deposition process. The alloys were extruded and subsequently heat treated in the T6 and T7 temper conditions. Texture analysis of as-received and solution treated alloys revealed and fibre textures leading to higher mechanical properties in the longitudinal direction. Anisotropic behaviour was observed in these alloys. In addition, the influence of recrystallizing, heat treatment, stretching, and processing techniques (IM, PM and spray casting) as well as techniques of forming (extrusion, rolling and forging) on the anisotropic behaviour of the . . . 7xxx series aluminium alloys was examined. Three 7xxx series aluminium SS70, N707 and 7075 alloys have been produced by the spray deposition process. The alloys were extruded and subsequently heat treated in the T6 and T7 temper conditions. Texture analysis of as-received and solution treated alloys revealed and fibre textures leading to higher mechanical properties in the longitudinal direction. Anisotropic behaviour was observed in these alloys. In addition, the influence of recrystallizing, heat treatment, stretching, and processing techniques (IM, PM and spray casting) as well as techniques of forming (extrusion, rolling and forging) on the anisotropic behaviour of the 7xxx series aluminium alloys was examined Daha fazlası Daha az

Müftüoglu F. | Keskinel T.

Makale | 2007 | Turkish Journal of Engineering and Environmental Sciences31 ( 3 ) , pp.183 - 187

This study examined the effect of coating thickness on electrode life and nugget strength. Uncoated and galvanized steel sheets supplied from Eregli Iron and Steel Factories Co. (Erdemir) with similar chemical compositions having different coating weights (100, 180, and 275 g/m2) were welded using resistance spot welding under constant welding parameters. Electrode force used during spot welding operation was 7.3 kN under 6.5 kA of constant welding current and 2 s welding time. After welding operations, shearing tests were applied to selected specimens and the nugget diameters were measured. Experimental results showed that as the c . . .oating thickness increased the electrode life and the strength of the weld nugget decreased. © TÜBİTAK Daha fazlası Daha az

Yücesu, Hüseyin Serdar

Makale | 1999 | Turkish Journal of Engineering and Environmental Sciences23 ( 2 ) , pp.105 - 120

Bu araştırmada bir Stirling motorunun ısıtıcı ve soğutucusunda hız ve sıcaklık dağılım eğrileri sonlu farklar yöntemiyle incelenmiştir. Kararlı çalışma şartlarında, 300 K soğuk kaynak ve 1000 K sıcak kaynak sıcaklığı ve 750 d/d motor hızı için motorun termodinamik analizleri yapılarak sıkıştırma ve genişleme periyodu boyunca ısıtıcı ve soğutucu içerisine giren iş gazı kütlesi miktarları hesaplanmış, yoğunluk ve kütle miktarı değişimi kullanılarak hız ve sıcaklık profilleri oluşturulan bir Fortran bilgisayar programı yardımı ile belirlenmiştir. Peryodik akış şartlarında yapılan hesaplamalarda sıkıştırma ve genişleme periyotları süres . . .ince ortalama gaz sıcaklığı ve ısı taşınım katsayıları da hesaplanmıştır. Deneysel çalışmalarda ölçülen sıcaklıklar hesaplamalarda sınır şartları olarak kullanılmıştır. Yapılan hesaplama sonucunda lmm kanal genişliği için ısıtıcı boyu 12 cm ve soğutucu boyu 14 cm olarak belirlenmiştir. In this study the dimensions of the heater and cooler of a Stirling engine are estimated by simulating the velocity and temperature fields in the heater and cooler using finite difference method. For an engine working at steady conditions, at the 300 K cold and 1000 K hot sources temperatures and 750 rpm engine speed a thermodynamic analysis is performed and the local values of mass, density and pressure are determined relative to crank angle. The cyclic period is divided into 10 degree sub periods and using the mass flow obtained from thermodynamic analysis, the velocity profiles, temperature profiles, average temperature and heat transfer coefficient distribution are calculated for each sub period. In the calculations the gas temperature measured at the inlet and outlet of heater are used as boundary condition. As the result considering 1 mm channel width, 12 cm length for heater and 14 cm length for cooler were determined Daha fazlası Daha az

Gökkaya, Hasan | Nalbant, Muammer

Makale | 2006 | Turkish Journal of Engineering and Environmental Sciences30 ( 5 ) , pp.307 - 316

The effects of a number of cutting tool coating materials on the surface quality of workpieces, depending on various cutting parameters, were investigated. AISI 1015 steel was processed without cooling on a lathe using 4 different cemented carbide cutting tools, i.e. uncoated, coated with AlTiN and coated with TiAlN using the PVD technique, and one with 3-layer coatings (outermost being TiN) applied by the CVD technique. Among the cutting parameters, the depth of cut was kept constant (2.5 mm) while the cutting speed and feed rate were changed. Five cutting speeds (50, 73, 102, 145, 205 m/min) and 2 feed rates (0.24 and 0.32 mm/rev) . . . were used during the machining process. Coating type, feed rate and cutting speed have different effects on surface roughness. In the experiments, less average surface roughness was obtained by using a 3-layer coated tool coated outermost with TiN. The lessening of cutting speed by about 33% improves the surface roughness by about 26%, and increasing the cutting speed by about 310% resulted in an improvement of about 69%. The effects of a number of cutting tool coating materials on the surface quality of workpieces, depending on various cutting parameters, were investigated. AISI 1015 steel was processed without cooling on a lathe using 4 different cemented carbide cutting tools, i.e. uncoated, coated with AlTiN and coated with TiAlN using the PVD technique, and one with 3-layer coatings (outermost being TiN) applied by the CVD technique. Among the cutting parameters, the depth of cut was kept constant (2.5 mm) while the cutting speed and feed rate were changed. Five cutting speeds (50, 73, 102, 145, 205 m/min) and 2 feed rates (0.24 and 0.32 mm/rev) were used during the machining process. Coating type, feed rate and cutting speed have different effects on surface roughness. In the experiments, less average surface roughness was obtained by using a 3-layer coated tool coated outermost with TiN. The lessening of cutting speed by about 33% improves the surface roughness by about 26%, and increasing the cutting speed by about 310% resulted in an improvement of about 69% Daha fazlası Daha az

Gündüz S.

Makale | 2002 | Turkish Journal of Engineering and Environmental Sciences26 ( 4 ) , pp.353 - 359

The internal friction of a C-Mn-Al-V-N steel was investigated using a dynamic mechanical thermal analyser (DMTA) under different austenitisation time, cooling and tempering conditions. Internal friction measurements using a DMTA instrument showed energy loss peaks at different temperatures for a frequency of 1 Hz. For example, as well as the normal nitrogen peak, other broader loss peaks were observed centred on 100°C in the case of air-cooled samples austenitised at 900°C for 1 h. This is most probably due to carbon or nitrogen atom jumps associated with Fe-N-V sites, since the energy barrier which must be overcome for a carbon or . . .nitrogen atom to break away from the foreign atom such as vanadium will be larger than that in a normal interstice. In addition, this abnormal damping peak disappeared after tempering at 450°C for 72 h. This indicates the precipitation of carbon and/or nitrogen Daha fazlası Daha az