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Öğe Evaluation of drilling performances of nanocomposites reinforced with graphene and graphene oxide(Springer Nature, 2018-09-16) Çelik, Yahya Hışman; Kılıçkap, Erol; Koçyiğit, NihayetThe use of graphene (G) and graphene oxide (GO) reinforced nanocomposites have a great importance since G and GO improve the interface conditions of composite materials. However, the effects of G and GO on some mechanical properties and machinability in nanocomposites are still a research topic. In this study, G was converted to GO by Hummers’ method. G and GO nanoparticles were added to epoxy at different ratios and the tensile strengths of nanocomposites were determined. By taking into account, the reinforcement ratio of nanocomposites having the highest tensile strength, epoxy with G and GO, and unreinforced epoxy were added to carbon fiber (CF) fabric by hand lay-up. Thus, fabrication of the carbon fiber-reinforced plastic (CFRP) composite, and the G/CFRP and GO/CFRP nanocomposites was carried out. The effects of the G and GO on the fabricated nanocomposites, and the effect of different drilling parameters (cutting speed and feed rate) on the cutting force, cutting torque, temperature, and delamination factor were investigated. In the drilling of these composites, drills with the different bit point angles and the diameter of 5 mm were used. As a result, it was observed that GO was successfully synthesized, and G and GO positively affected the tensile strength, and GO exhibited a more effective feature than G on the tensile strength. It was also seen that the increase of the cutting speed, feed rate, bit point angle caused the increase in the cutting forces, cutting torque, and delaminations.Öğe Investigating the effects of cutting parameters on the hole quality in drilling the Ti-6Al-4V alloy(Materiali in Tehnologije, 2014-10) Çelik, Yahya HışmanIn this study, the effects of cutting parameters on the surface roughness, burr height, hole-diameter deviation, cutting temperature and structure of a chip formation were investigated during the drilling of the Ti-6Al-4V alloy. For this purpose, the Ti-6Al-4V alloy was drilled at different cutting parameters, longitudinally in the 10 mm depth with Ø = 10 mm high-speed-steel (HSS) drills, having 90°, 118°, 130° and 140° point angles on the CNC vertical machining centre. Experiments were carried out at the (12.5, 18.75 and 25) m/min cutting speeds and the (0.05, 0.1 and 0.15) mm/r feed rates without using the cutting fluid. As a result, as the feed rate and the drill-point angle were increased, the surface roughness increased as well; however, as the cutting speed increased, the surface roughness decreased. When the feed rate and drill-point angle increased, the burr height decreased. On the other hand, an increase in the cutting speed increased the burr height. In general, an increase in the feed rate and drill-point angle increased the hole diameters, and the hole diameters obtained were close to the nominal size when the cutting speed was increased.Öğe Evaluation of drilling performances of nanocomposites reinforced with graphene and graphene oxide(Springer Nature, 2019-02-25) Çelik, Yahya Hışman; Kılıçkap, Erol; Koçyiğit, NihayetThe use of graphene (G) and graphene oxide (GO) reinforced nanocomposites have a great importance since G and GO improve the interface conditions of composite materials. However, the effects of G and GO on some mechanical properties and machinability in nanocomposites are still a research topic. In this study, G was converted to GO by Hummers’ method. G and GO nanoparticles were added to epoxy at different ratios and the tensile strengths of nanocomposites were determined. By taking into account, the reinforcement ratio of nanocomposites having the highest tensile strength, epoxy with G and GO, and unreinforced epoxy were added to carbon fiber (CF) fabric by hand lay-up. Thus, fabrication of the carbon fiber-reinforced plastic (CFRP) composite, and the G/CFRP and GO/CFRP nanocomposites was carried out. The effects of the G and GO on the fabricated nanocomposites, and the effect of different drilling parameters (cutting speed and feed rate) on the cutting force, cutting torque, temperature, and delamination factor were investigated. In the drilling of these composites, drills with the different bit point angles and the diameter of 5 mm were used. As a result, it was observed that GO was successfully synthesized, and G and GO positively affected the tensile strength, and GO exhibited a more effective feature than G on the tensile strength. It was also seen that the increase of the cutting speed, feed rate, bit point angle caused the increase in the cutting forces, cutting torque, and delaminations.Öğe Evaluation of drilling parameters in gas hydrate exploration wells(Elsevier, 2018-08-31) Merey, ŞükrüGas hydrates are crystalline ice-like structures formed from water and gas molecules at high pressure and low temperature conditions. They are considered as near-future energy resources. Recently, there have been many drilling activities in gas hydrates in both permafrost regions (mainly Mallik wells, Canada; Ignik Sikumi #1 well, Alaska; Mount Elbert #1, Alaska) and marine sediments (the wells drilled in Gulf of Mexico and India drilling expeditions). In this study, it is aimed to evaluate and analyze logging-while drilling data (LWD) and other drilling data of these drilling activities. Initially, all drilling parameters (i.e. rate of penetration, weight on bit, torques, mud logs, etc.) of these wells were collected and drawn to see the change in parameters with depths. In order to indicate the changes in drilling parameters in the sediments containing gas hydrates, gas hydrate saturations were estimated from resistivity logs and NMR logs in this study. High resistivity log values and methane peaks in drilling fluid were good indicators of gas hydrate existence. During the drilling of permafrost formations and gas hydrates deposited in coarse sands as pore filling, the rate of penetration generally decreased. Differently, there was not almost any change in the rate of penetration during the drilling of fracture-filling gas hydrates within silts/clay in India. Borehole enlargements (washouts) were commonly seen in the wells drilled in marine sediments (Gulf of Mexico and Indian expeditions). However, this effect was minimum during the drilling of the wells in permafrost regions. This difference is due to the loose sediments in marine environment. Furthermore, gamma and density logs were seriously affected by washouts, mainly in marine sediments. It was observed that pore-filling gas hydrates affect the rate of penetration and keep the sediments stable because well collapses mainly occurred in the sediments without any gas hydrates. However, the temperature of drilling fluid should be close to the temperature of gas hydrate zones to reduce the effect of drilling on gas hydrate dissociation for the wells both in permafrost and marine sediments. In Gulf Mexico and Indian drilling expeditions, riser and wellhead equipment were not used. However, the usage of surface casing might decrease the risk of borehole collapses due to very loose sediments close to sea floor. Another important outcome of this study is that the pressure gradient follows hydrostatic pressure gradients according to the pressure analysis within gas hydrate stability zones of marine sediments. Finally, the analyses of drilling parameters revealed that drilling through gas hydrate bearing strata is not as risky as it might have been considered. The key is hidden in appropriate drilling design.
