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https://hdl.handle.net/20.500.12684/6775

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Evaluation of machinability of hardened and cryo-treated AISI H13 hot work tool steel with ceramic inserts
(Elsevier Sci Ltd, 2013) Çiçek, Adem; Kara, Fuat; Kıvak, Turgay; Ekici, Ergün
The positive effects of deep cryogenic treatment on the wear resistance of cutting tools and workpiece material are well known; however, no information has been reported about the effect on the machinability of cryo-treated tool steel in hard turning. In order to investigate the effects of cryogenic treatment on the machinability of hardened and cryo-treated tool steel, a number of investigations were performed on the hard turning of cryo-treated AISI H13 hot-work tool steel with two ceramic inserts under both dry and wet cutting conditions. Three categories of the hot-work tool steel were turned in the machinability studies: conventional heat treated (CHT), cryo-treated (CT) and cryo-treated and tempered (m). Experimental results showed that the lowest wear and surface roughness (Ra) values were obtained in the turning of the CTT samples. Additionally, in terms of main cutting force (Fc), surface roughness (Ra) and tool wear, Ti[C, N]-mixed alumina inserts (CC650) showed a better performance than SiC whisker-reinforced alumina inserts (CC670) under both dry and wet cutting conditions. The use of cutting fluid slightly improved the machinability of the tool steel. (C) 2013 Elsevier Ltd. All rights reserved.
Experimental analysis of maximum valve lift effects in cam-follower system for internal combustion engines
(Korean Soc Mechanical Engineers, 2014) Sarıdemir, Suat; Saruhan, Hamit
Designing valve lift of cam-follower system is very important for improving dynamic performance of internal combustion engines. Potential problems due to unwanted vibrations in high-speed engine are the follower jump, colliding surface of the valves, and seats which cause collide in a cam-follower system. The degree of collide depends on the valve lift value and valve closing velocity. Large forces and stresses are introduced when the cam and follower collide. This might cause early failure of the system due to unwanted vibration. The main purpose of present experimental study was to investigate and analyze the dynamic behavior of the cam-follower system for different valve lift values and operating speeds using time domain and frequency domain analysis technique. Two cases for maximum valve lift values of 8 and 10 mm were tested with corresponding operating speeds of 450, 930, 1440, 1950 and 2430 rpm. From the results, it was observed that the higher the operating speed, the higher amplitude values were obtained. Statistical analysis of obtained data showed that the 10 mm valve lift produced much more power than the 8 mm valve lift.
Experimental investigation of combustion, performance and emission characteristics of a diesel engine fuelled with diesel-biodiesel-alcohol blends
(Springer Heidelberg, 2019) Ağbulut, Ümit; Sarıdemir, Suat; Albayrak, Serdar
The purpose of this study is to investigate the impacts of diesel-biodiesel-alcohol blends on the combustion, performance and emissions characteristics of a single-cylinder diesel engine. Tests were conducted at different engine speeds of 1750, 2250, 2750 and 3250 rpm and under full load. In this study, different fuels [called as reference diesel (D100), 20 vol% cottonseed methyl ester (D80C20), 10 vol% ethanol (D90E10) and finally the ternary type of their derivations (D70C20E10)], were used. The experimental results showed that the highest reduction values were observed on CO emission by 42%, 30% and 8% for the D90E10, D70C20E10 and D80C20 fuels, respectively. These reductions for HC emission were achieved as 40%, 31% and 23% for the D90E10, D70C20E10 and D80C20, respectively. On the other hand, the reductions of NOx and CO2 emissions were not sharp and varied between 2-7%. Besides the reductions on the exhaust emissions, biodiesel-ethanol blend presented better results in terms of HRRmax and CPmax than using biodiesel alone. Additionally, ignition delay of the biodiesel blends was longer than that of D100 fuel owing to their low cetane numbers. Combustion duration was shortened with the increment in engine speed because the turbulence increased in the combustion chamber at high engine speed. This case also improved the homogeneity of test fuels and increased the quality of the combustion process. As a consequence, this paper clearly reported that it is possible to achieve fewer emissions, the highest CPmax values with the presence of ethanol in biodiesel fuels rather than using biodiesel alone for diesel engines.
Effects of Deep Cryogenic Treatment on the Wear Resistance and Mechanical Properties of AISI H13 Hot-Work Tool Steel
(Springer, 2015) Çiçek, Adem; Kara, Fuat; Kıvak, Turgay; Ekici, Ergün; Uygur, İlyas
In this study, a number of wear and tensile tests were performed to elucidate the effects of deep cryogenic treatment on the wear behavior and mechanical properties (hardness and tensile strength) of AISI H13 tool steel. In accordance with this purpose, three different heat treatments (conventional heat treatment (CHT), deep cryogenic treatment (DCT), and deep cryogenic treatment and tempering (DCTT)) were applied to tool steel samples. DCT and DCTT samples were held in nitrogen gas at -145 degrees C for 24 h. Wear tests were conducted on a dry pin-on-disk device using two loads of 60 and 80 N, two sliding velocities of 0.8 and 1 m/s, and a wear distance of 1000 m. All test results showed that DCT improved the adhesive wear resistance and mechanical properties of AISI H13 steel. The formation of small-sized and uniformly distributed carbide particles and the transformation of retained austenite to martensite played an important role in the improvements in the wear resistance and mechanical properties. After cleavage fracture, the surfaces of all samples were characterized by the cracking of primary carbides, while the DCT and DCTT samples displayed microvoid formation by decohesion of the fine carbides precipitated during the cryo-tempering process.
Effect of hard chrome plating parameters on the wear resistance of low carbon steel
(Carl Hanser Verlag, 2019) Kır, Hasan; Apay, Serkan
Electrolytic hard chrome plating is applied to improve the surface properties of metals and add a decorative look. In this study, hard chrome plating was applied to low carbon steel in various parameters by means of an electrolytic method. The plating and metal surface of the specimen were analysed using a scanning electron microscope (SEM). Following SEM analyses, microhardness measurements from the plating to the base metal in the samples were conducted at 100 g. The wear resistance in the plated samples was determined by the pin-on-disc method. Moreover, the surface morphology was examined by SEM and optic profilometer subsequent to the wear experiment. The results showed that the hard chrome plating, which was applied at 0.4 A x m(-2) current density, 100 mm anode-cathode distance and 60 degrees C bath temperature, yielded the highest wear resistance and hardness.
EFFECT OF CRYOGENIC TREATMENT APPLIED TO M42 HSS DRILLS ON THE MACHINABILITY OF Ti-6Al-4V ALLOY
(Inst Za Kovinske Materiale I In Tehnologie, 2015) Kıvak, Turgay; Şeker, Ulvi
This study investigated the effects of deep cryogenic treatment applied to M42 HSS drills on the tool wear, the tool life and the surface roughness during the drilling of a Ti-6Al-4V alloy under dry and wet cutting conditions. Drilling tests were carried out using untreated, cryogenically treated, cryogenically treated and tempered, and multi-layered TiAlN/TiN-coated HSS drills. Four different cutting speeds ((6, 8, 10, 12) m/min) and a constant feed rate of 0.06 mm/r were used as the cutting parameters and holes with a depth of 15 mm were drilled. At the end of the drilling tests, it was seen that the use of a coolant increased the tool life and decreased the surface roughness. Among the four tools, the best results in terms of the tool life and surface roughness were obtained with the multi-layered TiAlN/TiN-coated tool. The cryogenically treated and tempered drills exhibited an increase of 87 % in the tool life compared to the untreated drills. Scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses showed that by reducing the size of the carbide particles in the microstructure, cryogenic treatment resulted in a more uniform carbide distribution and in the transformation of retained austenite to martensite. This played an important role in the increase in the hardness and wear resistance of the cutting tools.
Effect of Deep Cryogenic Treatment on Wear Resistance of AISI 52100 Bearing Steel
(Springer India, 2014) Güneş, İbrahim; Çiçek, Adem; Aslantaş, Kubilay; Kara, Fuat
In this study, the effects of deep cryogenic treatment (DCT) on the wear resistance of AISI 52100 bearing steel were investigated. For this purpose, a number of bearing steel samples were held for different times (12, 24, 36, 48, 60 h) at deep cryogenic temperatures (-145 degrees C). The wear experiments were carried out in a ball-disk arrangement, by applying loads of 10 and 20 N and a sliding velocity of 0.15 m/s. After conducting the experimental studies, 36 h was found to be the optimal holding time. At this holding time, the wear rate and friction coefficient were decreased, while the hardness reached to maximum values. It was observed that DCT led to significant microstructural changes, which resulted in improved tribological properties.
Determination of the heat transfer coefficient of PV panels
(Pergamon-Elsevier Science Ltd, 2019) Ceylan, İlhan; Yılmaz, Sezayi; İnanç, Özgür; Ergün, Alper; Gürel, Ali Etem; Acar, Bahadır; Aksu, Ali İlker
In this study, the efficiency of the rear-panel air velocity in cooling was investigated based on the temperature and solar radiation in the environment where the panels are located. During the cooling of the panels, the rear-panel temperature decreases, and accordingly, the open-circuit voltage of the panels increases. At present, the most important losses in panels are due to the increase in panel temperature depending on the solar radiation and outdoor air temperature. In this study, the rear-panel temperature changes were observed at 0-5 m/s air velocities and 10-40 degrees C. The calculations reveal that in winter weather conditions, the temperature of the panels did not increase at a level that would require cooling. This study investigated the heat transfer from the surface depending on the outdoor air temperature of the rear-panel air velocity and the changing rear-panel temperature. The effect of different outdoor air temperatures on the rear-panel heat transfer is minimal. When the air velocity was 5 m/s and the outdoor air temperature was 10-40 degrees C, the heat transfer in the Poly Crystal Solar panel was calculated as 11.6 W/m(2)K. (C) 2019 Elsevier Ltd. All rights reserved.
Determination of MQL Parameters Contributing to Sustainable Machining in the Milling of Nickel-Base Superalloy Waspaloy
(Springer Heidelberg, 2017) Yıldırım, Çağrı Vakkas; Kıvak, Turgay; Sarıkaya, Murat; Erzincanlı, Fehmi
In addition to reducing production costs, minimum quantity lubrication (MQL) aims to minimize the adverse effects of conventional cutting fluid usage on the environment and human health. Because of the positive effect of the MQL system on both health and production efficiency, sustainable production is increasing daily. Therefore, optimum MQL parameters must be determined in order to obtain maximum efficiency in the manufacturing process. In this study, unlike similar studies in which MQL parameters were evaluated, the scope was widened and the main parameters affecting the efficiency of the system were tested at the same time. For this aim, nickel-base superalloy Waspaloy was machined under MQL using a CNC milling machine with uncoated carbide inserts. In the machining process, the MQL parameters selected were cutting oil type (mineral-, synthetic-, mineral-synthetic-and vegetable-based oils), fluid flow rate (25, 50, 75 and 100 ml/h), milling method (up milling and down milling), spray distance (25 and 50 mm) and nozzle type (Type 1 and Type 2). In order to analyze the effect of MQL parameters on the quality characteristics of tool life and cutting force, the cutting parameters, including cutting speed, feed rate and depth of cut, were kept constant for all experiments. Taguchi's L16 (4(2) x 2(3)) orthogonal array was employed to minimize the number of experiments. As a result, both maximum tool life and minimum cutting force were attained via a combination of vegetable-based cutting oil, 100 ml/h flow rate, opposite-direction (up) milling, Type 1 nozzle and a 25-mm spray distance.
Design optimization of rotor-bearing system considering critical speed using Taguchi method
(Sage Publications Ltd, 2017) Yücel, Emre; Saruhan, Hamit
The purpose of this study is to utilize Taguchi method, which can prove to be a handy and effective tool for determining minimum vibration response of rotor-bearing system set to avoid running at critical speed. In the study, three test cases considering different coupling type (elastic, jaw, and solid) and disc location (disc location A, B, and C) were conducted to observe behavioral changes of the shaft system considering vibration signatures. Each test case was conducted for three different shaft running speeds of 12, 18, and 24Hz. To find the minimum peak amplitude values by experimenting different combinations of the rotor-bearing system set needs a lot of experiments for reaching solution. Moreover, the solution proves costly because of the time consumed in doing many experiments. This fact depicts the importance of an efficient optimization method to be used. Taguchi method can determine the design parameters, which have the greatest influence on the solution through a very limited number of experiments, for finding optimum set of rotor-bearing system. The method is performed using an iterative procedure to gain an optimum design.
CUTTING TOOL GEOMETRY IN THE DRILLING OF CFRP COMPOSITE PLATES AND TAGUCHI OPTIMISATION OF THE CUTTING PARAMETERS AFFECTING DELAMINATION
(Yildiz Technical Univ, 2018) Sur, Gökhan; Erkan, Ömer
It is possible to improve the hole quality by reducing the delamination which occurs in the drilling of carbon fibre reinforced plastic (CFRP) composite plates. For this study, carried out under dry machining conditions, the parameters included three different cutting speeds, three different feed rates and drill geometry involving three different point angles. The Taguchi L-9 orthogonal array experimental design was selected and the optimum cutting parameters and drill geometry for reducing the damage factor to a minimum were determined. The optimum test conditions were achieved using the parameter combination of 118 degrees point angle, 30 m/min cutting speed and 0.06 mm/rev feed rate (A1B1C1). In addition, variance analysis (ANOVA) was conducted to determine the effect rate of the parameters on the damage factor. The variable having the greatest effect on the damage factor was found to be the point angle (47.66%), followed by the cutting speed (24.44%) and feed rate (19.82%). The conditions for minimising delamination damage in the drilling of the CFRP plates were optimised successfully by using the Taguchi test design.
Weldability of Zinc Coated Automotive Steel Sheets by Resistance Spot Welding
(Natl Acad Sciences Ukraine, Inst Metal Physics, 2012) Durgutlu, A.; Erik, M.; Gülenç, B.; Sarıdemir, Suat; Apay, Serkan
In a given study, resistance spot welding of automotive steel sheets, which are widely used in the house-goods and car manufacturing industry, is studied. The shear strength, hardness and microstructure of the welded parts are measured in order to find the effects of welding period, welding current, and thickness of the galvanizing under constant applied electrode force pressure. Welding periods are chosen as 22 and 27 cycles, and welding current increased from 4.5 kA to 5.5 kA. The electrode-applied forces are kept constant at 3.5 Bar. The samples are exposed to tensile shear tests, hardness tests and metallographic examinations, and suitable welding parameters are advised to users. The results show that, increasing welding period and thickness of coating, the tensile shear strength and hardness of the welding nugget are increased.
Turkey's electricity generation problem and nuclear energy policy
(Taylor & Francis Inc, 2019) Ağbulut, Ümit
Energy is undoubtedly the most key to sustainability of the economic growth of a country. Turkey is today dependent on energy approximately at a rate of 75%. The country is able to meet approximately half of its total electricity demand owing to its own limited resources. Over the past 10 years period, Turkey paid nearly half a trillion dollars for its energy bill. On the other hand, the official reserve assets are equal to 93 billion dollars in the central bank of Turkey in November 2018. New power plants are being installed and planned to decrease the energy dependency in the country, particularly for electricity generation. Of these plants, nuclear energy is currently one of the newest and the most debated issues for the country. Hence, this study mainly focused on the possible outputs of the transiting to nuclear energy such as carbon dioxide emissions, radiation doses, energy demand, economic growths, etc., in the country. Additionally, new shares on electricity generation by the new sources were foreseen with this study after the nuclear plants to be operated in Turkey.
Tool wear and surface roughness analysis in milling with ceramic tools of Waspaloy: a comparison of machining performance with different cooling methods
(Springer Heidelberg, 2019) Yıldırım, Çağrı Vakkas; Kıvak, Turgay; Erzincanlı, Fehmi
Ceramic cutting tools are widely used particularly in high-speed machining of difficult-to-machine materials. However, using cutting fluid with these ceramic tools significantly reduces tool life. Therefore, the inclusion of a cooling/lubrication method into the process to improve the machining performance of ceramic tools will make machining efficiency much more effective. The aim of this study is to analyze the effect of cutting parameters and cooling/lubricating conditions on tool wear and surface roughness in the milling of nickel-based Waspaloy with ceramic tools. The cutting tools selected for the study were Ti[C, N]-mixed alumina inserts (CC650), SiC whisker-reinforced alumina inserts (CC670) and alumina and SiAlON ceramic inserts (CC6060). The machining parameters comprised three different cooling/lubricating methods (dry, wet and MQL), three different cutting speeds (500, 600 and700m/min) and three different feed rates (0.02, 0.04 and 0.06mm/rev). Analysis of variance was used to determine the effects of the machining parameters on tool wear and surface roughness. In addition, a regression analysis was conducted to identify the relationship between the dependent and independent variables. According to the experimental results, the minimum quantity lubrication method was identified as the best cooling method for minimum tool wear and surface roughness. In terms of ceramic grades, the SiAlON inserts provided better results in all experimental trials. The dominant wear types observed in all cutting tools were flank wear and notch wear.
Tool life and wear mechanism of coated and uncoated Al2O3/TiCN mixed ceramic tools in turning hardened alloy steel
(Elsevier Science Sa, 2012) Aslantaş, Kubilay; Ucun, İrfan; Çiçek, Aydan
The focus of this paper is the continuous turning of hardened AISI 52100 (similar to 63HRc) using coated and uncoated ceramic Al2O3-TiCN mixed inserts, which are cheaper than cubic boron nitride (CBN) or polycrystalline cubic boron nitride (PCBN). The machinability of hardened steel was evaluated by measurements of tool wear, tool life, and surface finish of the workpiece. Wear mechanisms and patterns of ceramic inserts in hard turning of hardened AISI 52100 are discussed. According to the results obtained, fracture and chipping type damages occur more frequently in uncoated tools, whereas crater wear is the more common type of damage in TiN coated tools. Most important result obtained from the study is that TiN coating and crater wear affect chip flow direction. In uncoated ceramic tool, the crater formation results in decrease of chip up-curl radius. Besides, uncoated cutting tool results in an increase in the temperature at the tool chip interface. This causes a thermal bi-metallic effect between the upper and lower sides of the chip that forces the chip to curl a smaller radius. Chips accumulate in front of the tool and stick to the workpiece depending on the length of the cutting time. This causes the surface quality to deteriorate. TiN coating not only ensures that the cutting tool is tougher, but also ensures that the surface quality is maintained during cutting processes. (C) 2011 Elsevier B.V. All rights reserved.
The effects of ethanol-unleaded gasoline blends in a single cylinder SI engine performance and exhaust emissions
(Sila Science, 2012) Sarıdemir, Suat
Ethanol has the potential to be used as an alternative fuel to gasoline in the spark-ignited (SI) engines. In this study, ethanol was used as a fuel to reduce the fuel consumption and emissions and to improve the performance of a single cylinder SI engines. The tests were performed for a maximum torque speed (2500 rpm) and maximum engine speed (3250 rpm) at a wide open throttle (WOT) conditions. The results obtained from the use of ethanol gasoline fuel blends (E10, E20, E30, E40 containing 10%, 20%, 30%, 40% of ethanol by volume) were compared to unleaded gasoline fuel. The results indicated that when ethanol gasoline fuel blends were used, the engine torque, power and brake specific fuel consumption (BSFC) were increased; the exhaust gas temperature, the carbon monoxide (CO), carbon dioxide (CO2) and hydrocarbon (HC) emissions were decreased. Also, the flame speed was increased by presence of oxygen in the ethanol fuel molecule. Thus, process of combustion and stability were increased and engine efficiency was improved.
The effect of the CO2 ratio in biogas on the vibration and performance of a spark ignited engine
(Elsevier Sci Ltd, 2018) Karagöz, Mustafa; Sarıdemir, Suat; Deniz, Emrah; Çiftçi, Burak
Being a renewable fuel, biogas can be produced either through anaerobic digestion from animal manure, inedible seed residue, food waste, agricultural waste, domestic waste and sewage sludge or through thermo-chemical processes. Along with thermal applications, by means of combustion inside an engine, biogas can produce both mechanical and electric energy. Depending on the inertia forces of the active parts and the characteristics of the in-cylinder combustion of the engine, vibration can be quite a big problem because it leads to rapid breakdown of engine parts, noisy operation and decreased performance and power output. The CO2 in biogas is an important compound that affects its lower heating value (LHV), burning characteristics and exhaust emissions. There are a limited number of studies in the literature on the effect of biogas CO2 content on engine vibration. In the present study, a four-cylinder diesel engine was modified to operate with a spark plug and used to detect the effect of the biogas CO2 content on the vibration of the engine. The experiments were carried out with biogas containing 13% and 49% CO2 at 1.5-9 kW with 1.5 kW load increments at a steady 1500 rpm speed. The amplitude of the engine vibration at all three axes increased as the CO2 ratio in the biogas and the engine load increased. On the other hand, by decreasing the CO2 ratio and increasing the engine load, cylinder pressure increased and brake specific fuel consumption decreased. The highest amplitude of engine vibration for all loads was observed at the lateral axis.
THE EFFECT OF THE MOISTURE CONTENT OF WOOD ON THE LAYER PERFORMANCE OF WATER-BORNE VARNISHES
(North Carolina State Univ Dept Wood & Paper Sci, 2011) Sönmez, Abdullah; Budakçı, Mehmet; Pelit, Hüseyin
The test panels obtained from Scots pine (Pinus sylvestris L.) and Eastern beech (Fagus orientalis L.) were initially adjusted to have 8%, 10%, and 12% moisture content in this study. One-component semi-matte and two-component water borne varnishes were applied on the surfaces in order to investigate the effect of the type and the moisture content of the wood on the hardness and the gloss values as well as the adhesion strength of the varnishes. The hardness of the test samples was evaluated based on the standard ANS/ISO1522, the gloss based on TS.4318 EN ISO 2813, and the adhesive strength based on ASTM D-4541. The results indicated that variations in the moisture content of the wood material adversely affected the layer performance of water-borne varnishes and that the best performance was obtained for the wood with moisture contents of 8% and 10%.
The effect of dwell angle on vibration characteristics of camshaft bearing housings
(Korean Soc Mechanical Engineers, 2013) Sarıdemir, Suat
Cam-follower mechanisms are affected by undesired dynamic forces which may disrupt the accuracy of the follower motion. These undesired dynamic forces create vibrations which cause noise, wear, and increasing operating costs for cam-follower mechanisms. Journal bearings are the most widely-used mechanical parts in internal combustion engines under high load and high operating speeds. In this study, the effect of the dwell angle on the vibration characteristics of camshaft bearing housings was investigated. Two camshafts having a 6 mm lift and different dwell angles were tested at operating speeds of 450, 900, 1350, 1920, and 2400 rpm. The collected data were analyzed in detail. It was observed that with the increasing of the camshaft rotational speed, vibration responses of greater magnitude were obtained. In general, the first and second peak values of the low dwell angle camshaft were higher than those of the high dwell angle camshaft.
The effect of addition of hBN nanoparticles to nanofluid-MQL on tool wear patterns, tool life, roughness and temperature in turning of Ni-based Inconel 625
(Elsevier Sci Ltd, 2019) Yıldırım, Çağrı Vakkas; Sarıkaya, Murat; Kıvak, Turgay; Şirin, Şenol
Nickel-based Inconel 625 is employed in critical applications because of its excellent properties. But the machinability of this material is very poor. In recent years, the use of minimum quantity lubrication has gained prominence to improve machining performance without increasing the oil. However, pure-MQL may be insufficient for machining of difficult-to-machine materials. This paper focused on the development of nano-MQL by adding ISBN nanoparticles compared to pure-MQL and dry machining in turning of Inconel 625. Tool life, surface roughness, tool wear and tool-chip interface temperature were analyzed. Wear mechanisms were evaluated by SEM photographs and EDX analysis. The results showed that; 0.5 vol% hBN nanofluid has produced promising results for low tool wear and roughness and high tool life.

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