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Öğe Aging Effect on Microstructure and Machinability of Corrax Steel(Dr D. Pylarinos, 2020) Guldibi, A.S.; Demir, H.In this paper, the influence of the aging process on the microstructure and machinability of Corrax Steel was investigated for four samples: a solution heat-treated (A0) and three samples aged at 400ºC (A4), 525ºC (A5.25) and 600ºC (A6) for four hours. The effect of aging temperature on hardness was examined. Machining tests were carried out using a CNC lathe with a multi-layer coated PVD (AlTiN) cutting tool, at various cutting speeds (50, 100, 150, 200, 250, 300, 350m/min) with constant feed rate (0.1mm/rev) and 1mm constant cutting depth. The microstructure was investigated using an optical microscope and EDS attached SEM. The effect of aging on reverted austenite formation was also evaluated. In order to understand the changes in surface topology, cutting forces and vibrations were measured. With increasing aging temperature, the lath martensite was transformed to plate martensite because of the formation of precipitates and reverted austenite. Aging at different temperatures increased hardness up to 58%, cutting forces up to 117% and surface roughness up to 450%. The results describe the effect of the aging treatment on cutting forces, surface topology, tool wear and vibrations. © 2020, Dr D. Pylarinos. All rights reserved.Öğe Comparison of PID and FUZZY Controller in the Cascade Tank System in Matlab/Simulink(Kaunas Univ Technology Press, 2013) Bayir, R.; Ertunc, H. M.; Demir, H.In this study present comparison of PID and FUZZY controller in the cascade tank system. In order to control cascade tank system, fuzzy and pid controller was simulated in Matlab /Simulink. The system has two tanks. The water level in the tanks and the stream provided by pump are the system parameters. The current which is applied to the motor is the only control variable in the system. In this system fuzzy controller are compared with pid controller. The signals of the system's output are observed in matlab.Öğe Comparison of PID and FUZZY controller in the cascade tank system in Matlab/Simulink(Kaunas University of Technology, 2013) Bayir, R.; Ertunç, H.M.; Demir, H.In this study present comparison of PID and FUZZY controller in the cascade tank system. In order to control cascade tank system, fuzzy and pid controller was simulated in Matlab/Simulink. The system has two tanks. The water level in the tanks and the stream provided by pump are the system parameters. The current which is applied to the motor is the only control variable in the system. In this system fuzzy controller are compared with pid controller. The signals of the system's output are observed in matlab.Öğe Effect of Deep Cryogenic Treatment on Microstructure, Mechanical Properties, and Residual Stress of AISI 52100 Bearing Steel(Engineered Science Publisher, 2023) Kara, F.; Çiçek, A.; Demir, H.This study covers tensile, fatigue, and material characterization tests on AISI 52100 material. In this study, the effects of deep cryogenic treatment (DCT) applied to the material at different holding hours on the mechanical properties (macro-hardness, micro-hardness, yield and tensile strength), microstructure, change in residual austenite volume ratio and residual stress values were examined. Five different holding times (12, 24, 36, 48 and 60h) were employed to the bearing steel to compare the effect of holding time in the deep cryogenic temperature. The metallographic findings showed that the deep cryogenic treatment (DCT) decreased the retained austenite and hence improved the micro-hardness, due to more homogenized carbide distribution and the elimination of the retained austenite, compared with the conventional heat treatment (CHT). The improvements in the maximum tensile strength of DCT specimens were 5.2%, 3.6%, 3.35%, 2.9% and 1.7% for DCT-36, DCT-48, DCT-60, DCT-24 and DCT-12, respectively. The highest value in macro and micro-hardness was obtained with the DCT-36 sample. It was observed that the best fatigue performance was obtained with the DCT-12 sample. In addition, the fatigue life of DCT-12, DCT-36, DCT-24, DCT-48 and DCT-60 samples increased by 122%, 108%, 100%, 40% and 12%, respectively, compared to the CHT sample. The lowest stress values for both axial and circumferential tensile residual stresses were obtained in the DCT-12 sample. © Engineered Science Publisher LLC 2023.Öğe The effects of cutting tool coating and machining parameters in drilling of steel AISI H13 and AISI D2(Gazi Universitesi Muhendislik-Mimarlik, 2015) Tekaüt, I.; Demir, H.In drilling, temperature is an important factor for the tool and the machining performance. For this reason, analysis of the temperature in the cutting zone is essential for predicting the machining performance. In this study, commonly used AISI H13 and AISI D2 steels were drilled using uncoated and (AlCrN monolayer) coated carbide drills of 14 mm diameter on a vertical machining centre. The cutting zone temperatures were determined using the thermocouples inserted into the coolant holes of the drills. The tests were carried out at four different cutting speeds (60, 75, 90 and 108 m/min) and three different feed rates (0.15, 0.20 and 0.25 mm/rev). The experimental results showed that increasing feed rate and cutting speed led to decrease in the temperature. The lower heat conduction of the coated drills resulted in the higher temperature. In all the tests, drilling of AISI H13 caused higher temperature than that of AISI D2. It is considered that this was caused by the structural and chemical differences of the materials.Öğe The effects of microalloyed steel pre-heat treatment on microstructure and machinability(2008) Demir, H.An extensive study was performed in finish turning of the following microalloyed steels: as received (14.3 HRc), water-cooled (44.9 HRc), air-cooled (14.41 HRc) and furnace-cooled (9.1 HRc). The turning tests were carried out using multi-layer coated cemented carbide tools at four different cutting speeds (60, 90, 120, and 150 m/min) while feedrate and depth of cut were kept constant at 0.1 mm/rev and 1 mm, respectively. The influences of workpiece microstructure and cutting speed on cutting forces and workpiece surface roughness were investigated. The worn parts of the cutting tools were also examined under a scanning electron microscope (SEM). The results showed that cutting speed significantly affected the machined surface roughness values. However, cutting forces were not influenced significantly by workpiece microstructure and cutting speed except for water cooled specimen. © 2007 Springer-Verlag London Limited.Öğe ESTIMATION of SURFACE ROUGHNESS and FLANK WEAR in MILLING of INCONEL 625 SUPERALLOY(World Scientific, 2021) Akgün, M.; Demir, H.The main objective of this work is to experimentally investigate and statistically evaluate the effects of the milling parameters on surface roughness (Ra) and flank wear (Vb) in the milling of Inconel 625. Thus, milling experiments on different cutting conditions with Physical vapor deposition (PVD) and Chemical vapor deposition (CVD) coated inserts have been conducted on CNC milling machine according to Taguchi L18 orthogonal array. The effect levels of the milling conditions on Ra and Vb have been determined with analysis of variance (anova) at 95% confidence level. The analysis results indicate that the cutting tool is the most significant parameter affecting Ra while the feed rate is the most significant parameter affecting Vb. Then the linear and quadratic regression models have been applied in order to estimate Ra and Vb. The results show that a higher correlation coefficient (R2) is obtained via the quadratic regression model with a value of 0.97 for both Ra and Vb. Finally, the verification results are in excellent agreement with experimental findings, regarding the surface roughness (Ra), and tool wear (Vb). © 2021 World Scientific Publishing Company.Öğe Examining the machinability of 38MnVS6 microalloyed steel, cooled in different mediums after hot forging with the coated carbide and ceramic tool(SAGE Publications Ltd, 2021) Özlü, B.; Demir, H.; Türkmen, M.; Gündüz, S.In this study, the effect of the microstructure, hardness, and cutting speed on main cutting force and surface roughness in medium carbon microalloyed steel cooled in different mediums after hot forging, was investigated. As-received sample, which was not hot forged, and the samples cooled in the sand, air, oil, and polymerized water after hot forging were used for the experimental studies. The machinability tests were performed via turning method by using coated carbide and coated ceramic cutting tools with five cutting speed (120, 150, 180, 210, and 240 m/min), constant feed rate (0.04 mm/rev), and constant depth of cut (0.6 mm). The microstructure examinations of the samples were carried out and their hardness values were determined. Also, the wear of cutting tools were examined with scanning electron microscope. In the experimental study, it was revealed that the microstructure, hardness and cutting speed had a significant effect on the surface roughness values of the samples cooled in dissimilar environments following forging. Moreover, the samples cooled in air and polymerized water, whose hardness increased depending on the increase in the cooling rate, had the highest cutting force after machining by using the coated carbide and ceramic tool. © IMechE 2021.Öğe Experimental and numerical analysis of the effect of cutting parameters on cutting force and chip formation in turning process(TUBITAK, 2021) Akgün, M.; Demir, H.In this study, the influences of cutting parameters on the main cutting force (Fc) and the chip morphology in turning of the Inconel 625 superalloy by using uncoated cutting tools are evaluated by experimental and numerical analysis. The turning tests were performed without coolant on a CNC lathe at five different cutting speeds (60, 90, 120 and 180 m/min), three different feed rates (0.12 0.18 and 0.24 mm/rev) and three different depth of cut (0.5, 1 and 1.5 mm). Kistler 9257B type dynamometer and equipment’s were used to measure the main cutting force (Fc). Finite element modelling of the cutting forces have been performed using Deform 3D software. The lowest main cutting force value was measured as 120 N in the experiments conducted at 180 m/min cutting speed, 0.12 mm/rev feed rate and 0.5 mm depth of cut. Comparing experimental and numerical analysis results, it was found that there is a deviation of approximately 12% between the experimental and numerical results of the main cutting force (Fc). © 2021, TUBITAK. All rights reserved.Öğe FRICTION STIR SPOT WELDABILITY OF Al-Cu-Al MATERIAL COUPLE(Gazi Univ, Fac Engineering Architecture, 2011) Kacar, R.; Emre, H. Ertek; Demir, H.; Guenduez, S.Recently joining of metallic materials has gained a big importance. The problem can arise joining of advanced and new materials especially in industry. Thus, the solid state bonding methods have become much more popular effective in joining such materials. One of them is friction stir spot welding. In this study, 5754 quality aluminum couple using interlayer copper were joined by friction stir spot welding method using 1000 and 1600 rpm pin rotation for 3 and 5 second time intervals. The mechanical and metallurgical properties of weldment determined. The finding from this study compared with result that was obtained from FSSW Al-Al couple. The mechanical properties of FSSW welded Al-Cu-Al couple found better than Al-Al weldment.Öğe Friction stir spot weldability of Al-Cu-Al material couple(2011) Kaçar, R.; Emre, H.E.; Demir, H.; Gündüz, S.Recently joining of metallic materials has gained a big importance. The problem can arise joining of advanced and new materials especially in industry. Thus, the solid state bonding methods have become much more popular effective in joining such materials. One of them is friction stir spot welding. In this study, 5754 quality aluminum couple using interlayer copper were joined by friction stir spot welding method using 1000 and 1600 rpm pin rotation for 3 and 5 second time intervals. The mechanical and metallurgical properties of weldment determined. The finding from this study compared with result that was obtained from FSSW Al-Al couple. The mechanical properties of FSSW welded Al-Cu-Al couple found better than Al-Al weldment.Öğe Heating/Cooling Block System Design with Thermoelectric Module(Institute of Electrical and Electronics Engineers Inc., 2020) Kavsaoglu, A.R.; Demir, H.; Sungur, H.The aim of this study is to design and develop a system for polymerase chain reaction devices. Temperature is an important criterion for the realization of polymerase chain reactions, which is a simple and precise technique. Equal temperature stability must be achieved on the hopper aluminum block used for the placement of PCR tubes in equal time. By using the Peltier effect of the thermoelectric module, electric energy is converted to heat energy due to the temperature difference between the surfaces. In the study, the Peltier effect is to ensure that the samples placed in the aluminum block are kept at the desired temperature during the desired time. The thermoelectric modules used for this system were operated in heating/cooling modes and the values obtained with the temperature sensor used were drawn as temperature-time graph on the interface screen designed momentarily. PCR devices are commonly used in the areas of DNA amplifications, activation of incubation and cultures, serum coagulation, melting/boiling points, nucleic acid hydridizations, and PCR testing. © 2020 IEEE.Öğe An investigation into the influences of grain size and grinding parameters on surface roughness and grinding forces when grinding(2010) Demir, H.; Gullu, A.; Ciftci, I.; Seker, U.This study was carried out to investigate the effects of grain size on workpiece surface roughness and grinding forces when surface grinding AISI 1050 steel. A previously designed and constructed dynamometer was used to measure and record the forces developed during grinding. Grinding tests were carried out using different grinding wheels of different grains. Ground surface roughness measurements were also carried out. The results showed that grain size significantly affected the grinding forces and surface roughness values. Increasing grain size and depth of cut increased the grinding forces and surface roughness values. For different grain sizes, depth of cuts of 0.01 and 0.02 mm did not result in any significant variations in the grinding forces but further increase in depth of cut led to variations of up to 50% in grinding forces. © 2010 Journal of Mechanical Engineering. All rights reserved.Öğe An investigation into the influences of grinding wheel hardness and grinding parameters on surface roughness and grinding forces(2008) Demir, H.; Güllü, A.This study was carried out in order to examine the influences of grinding wheel hardness on surface roughness and grinding forces during surface grinding. Grinding tests were carried out using Al2O3 grinding wheels with I, M and Q hardness grades at different table speeds and at different depth of cuts. AISI 1050 (50 HRc) and AISI 4140 steels (52 HRc) were used as the workpiece materials. In order to measure the grinding forces generated during grinding, the dynamometer previously designed and manufactured was used. This dynamometer was also connected to a personal computer to save the grinding force data. The roughness of surfaces were also measured. It is seen significant increases on surface roughness by increasing wheel hardness and grinding forces. The grinding operations carried out using grade I grinding wheels produced higher surface roughness and mean grinding force values by 53.5 % and 59.8 %, respectively, than those obtained by grade Q grinding wheel.Öğe An investigation into the influences of grinding wheel structure on surface roughness and grinding forces(2008) Demir, H.; Güllü, A.This study was carried out in order to examine the influences of grinding wheel structure on surface roughness and grinding forces during surface grinding. Grinding tests were carried out using Al2O3 grinding wheels at different table speeds and at different depth of cuts. The structures of the grinding wheels were 3, 5 and 7. AISI 1050 steel (50 HRc) was used as the workpiece material. For measurement of the grinding forces developed during grinding, a previously designed and constructed dynamometer was used. This dynamometer was also connected to a personal computer to save the grinding force data. The ground surface roughness values were also measured. Increasing grinding wheel structure resulted in significant increases in surface roughness values. However, its influence on grinding forces was marginal. The highest cutting force was obtained when grinding using grinding wheel having the lowest structure at the highest depth of cut.Öğe An investigation of cutting speed effects on geometric tolerances in turning of AA 7075 aluminum alloy(Institute of Physics Publishing, 2018) Bozkurt, S.; Tekaüt, I.; Demir, H.; Seker, U.The main purpose is to produce the machine parts within the defined geometric limits for performing their functions where they are assembled. Production between the tolerance values stated in the technical drawing is very important for rapid assemblying of the shaft-hub connections working with the longevity of the moving mechanisms accurately. Because, production of machine parts at geometric tolerances is required in order to minimize the error-free assembly and undesirable conditions (heating, vibration, wear etc.). For this purpose, AA 7075 T651 aluminum alloy, which is frequently used in aviation, defense, automotive industry where desired geometric tolerance values are so important, is used as workpiece. It was machined by four different coating speeds (100, 200, 300 and 400 m/min), 0.1 mm / 0.5, 1.5 and 3 mm cut depths. The effects of cutting speed on geometric tolerances (cylindricality, circularity, linearity) after processing were investigated. It was observed that the increase of cutting speed is an effective parameter for increasing or decreasing the geometric tolerance values obtained. Increasing cutting speed was resulted in increase of tool vibration, and so increased vibration led to an increase in geometric tolerance values. © 2018 Institute of Physics Publishing. All rights reserved.Öğe MULTIPLE REGRESSION AND ANN MODELS FOR SURFACE QUALIFICATION OF CRYOGENICALLY-TREATED AISI 52100 BEARING STEEL(Scibulcom Ltd, 2013) Kara, F.; Cicek, A.; Demir, H.This paper focuses on 2 different models, the multiple regression method and the artificial neural network (ANN), for predicting surface roughness (R-a). Experiments were conducted to measure surface roughness in the cylindrical grinding of AISI 52100 bearing steel which had been conventionally heat-treated and deep cryogenically treated (-145 degrees C). In order to compare the effects of holding time at the deep cryogenic temperatures, 5 different holding times (12, 24, 36, 48 and 60 h) were employed to obtain the optimum R-a. The cylindrical grinding test results showed that optimum R-a values were obtained on specimens cryogenically treated for 36 h. In addition, the prediction results showed that the ANN was superior to the multiple regression method in terms of prediction capability. Moreover, due to a higher determination coefficient (R-2) and lower root-mean-square error (RMSE) and mean error percentage (MEP), the ANN was notably successful in predicting the R-a.Öğe Multiple regression and ANN models for surface quality of cryogenically-treated AISI 52100 bearing steel(2013) Kara, F.; Cicek, A.; Demir, H.This paper focuses on 2 different models, the multiple regression method and the artificial neural network (ANN), for predicting surface roughness (Ra). Experiments were conducted to measure surface roughness in the cylindrical grinding of AISI 52100 bearing steel which had been conventionally heat-treated and deep cryogenically treated (-145°C). In order to compare the effects of holding time at the deep cryogenic temperatures, 5 different holding times (12, 24, 36, 48 and 60 h) were employed to obtain the optimum Ra. The cylindrical grinding test results showed that optimum R a values were obtained on specimens cryogenically treated for 36 h. In addition, the prediction results showed that the ANN was superior to the multiple regression method in terms of prediction capability. Moreover, due to a higher determination coefficient (R2) and lower root-mean-square error (RMSE) and mean error percentage (MEP), the ANN was notably successful in predicting the Ra.
