Person: KENTLİ, AYKUT
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KENTLİ
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AYKUT
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Publication Metadata only Experimental observation of tool wear, cutting forces and chip morphology in face milling ofcobalt based super-alloy with physical vapour deposition coated and uncoated tool(ELSEVIER SCI LTD, 2007) KENTLİ, AYKUT; Aykut, Seref; Bagci, Eyup; Kentli, Aykut; Yazicioglu, OsmanCobalt base superalloys are used extensively in applications requiring good wear, corrosion and heat resistance. The main goal of this study is to examine the effect of machining conditions (cutting speed, feed rate and depth of cut) on tool wear, chip morphology and cutting forces in symmetric face milling of cobalt base superalloy with physical vapour deposition coated and uncoated inserts. with the aim of achieving to achieve this goal, 90 milling experiments were carried out with different cutting speeds, feed rate and depth of cut under dry cutting conditions. The settings of machining parameters were determined by using general full factorial design method. Chip morphology, cutting forces and tool wear were compared by using PVD coated and uncoated hard metal inserts which are obtained dependent on feed rate, cutting speed and cutting depth. The cutting forces increase as the feed rate and depth of the cut increases, but cutting speeds' effect on cutting forces has not been observed for symmetric face milling. (C) 2006 Elsevier Ltd. All rights reserved.Publication Metadata only Novel SPD Method: Twisted Variable Channel Angular Extrusion(KOREAN INST METALS MATERIALS) KENTLİ, AYKUT; Ozbeyaz, Kerim; Kaya, Hasan; Kentli, AykutDifferent types of SPD techniques are applicable and have been studied by various researchers. All of them have several advantages and disadvantages. Equal Channel Angular Pressing (ECAP) is one of the most popular SPD techniques and is still being developed. The aim of this paper is to improve the efficiency of ECAP process by putting forward a novel design (Twisted Variable Channel Angular Pressing (TV-CAP)) and also to achieve higher mechanical properties when compared to conventional ECAP processes. For this purpose, a new TV-CAP die was designed by combining three different methods: ECAP, Twist Extrusion, and Direct Extrusion. The new design was able to integrate the advantages of each method to the workpiece material. In this context, the design parameters of the TV-CAP die were first identified by finite element analysis (FEA) in Deform-3D. The TV-CAP die was produced according to the determined parameters and AA5083 alloy was pressed with this novel die. Hardness and tensile tests were carried out to compare mechanical properties. In addition, Optical Microscope, SEM, TEM images were taken, and XRD and EBSD analyses were carried out to examine the changes in grain structure. As a result of this experimental study, an increase of 197.3% was observed in the hardness value and an increase of 144.7% was achieved in the tensile strength value by using the novel TV-CAP die. These results also agreed with the effective strain values obtained from the FEA.Publication Metadata only Comparative assessment of support plates' influences on delamination damage in micro-drilling of CFRP laminates(ELSEVIER SCI LTD, 2017) KENTLİ, AYKUT; Dogrusadik, A.; Kentli, A.In this study, drilling induced delamination damage which occurs during micro-drilling of CFRP laminates was investigated experimentally under variable cutting speeds and feed rates. Unlike the previous studies, the delamination factors in micro-drilling of CFRP laminates were precisely calculated and compared for supported and unsupported cases. Using support plates which are placed front and rear sides of the CFRP laminate is one of the methods which limits the delamination damage. Two different setups of support plates were used in the experiments. In the first setup, the entry board was aluminum plate and the backing board was phenolic plate. In the second setup, the entry board was brass plate and the backing board was wooden plate. Hole pictures were taken from each CFRP laminate by using a digital microscope. The first, the middle and the last three holes were inspected from the front and rear sides of the CFRP laminate. Minitab was used to evaluate the experiments' outputs, and response surface method was used to optimize the process parameters. It has been revealed that the delamination damage in micro-drilling differs from the delamination damage in conventional drilling of CFRP laminates. Obviously, the process exhibits unusual delamination behavior as process size decreases. (C) 2017 Elsevier Ltd. All rights reserved.Publication Metadata only Microstructure development and mechanical behaviour of pure copper processed by the novel TWO-CAP procedure(2023-01-01) KENTLİ, AYKUT; ÖĞÜT, SERKAN; KAYA H., UÇAR M., Ş Ahbaz M., KENTLİ A., Özbeyaz K., ÖĞÜT S.In this study, thin-walled open channel angular pressing (TWO-CAP) technique was applied to pure copper specimens as a novel severe plastic deformation (SPD) method. The TWO-CAP process was applied to the specimens up to four passes. After each pass, the microstructural and mechanical characterization of the material was investigated by tensile and hardness tests along with OM, SEM, EDS, TEM and XRD analyses. As a result, a highly increase in the mechanical properties was obtained, in addition satisfactory grain refinement was observed in microstructures. Strength and hardness values were positively affected from the minimizing the grain sizes after TWO-CAP process. Another reason of the improvements in mechanical properties can be explained as the increase in dislocation density. Furthermore, the effect of the TWO-CAP process on the dislocation density of the material has been demonstrated by XRD and TEM analyses in nanoscale. Moreover, the strain equation has been developed analytically and the effect of each pass on strain was calculated. Finally, the effect of the process on the stress-strain properties of the material was examined by the numerical analysis method and the study was verified.Publication Metadata only Influence of injection molding parameters on electrical resistivity of carbon nanotube reinforced polycarbonate(WALTER DE GRUYTER GMBH, 2016) KENTLİ, AYKUT; Donmez, Sinan; Kentli, AykutElectrical properties of plastic products can be adjusted by adding a certain amount of carbon nanotubes (CNT) in the injection molding process. However, injection molding parameters should be arranged carefully due to their influence on electrical properties of CNT-reinforced plastic composites. In this study, polycarbonate/CNT nanocomposites, having three different CNT concentrations (1, 3 and 5 wt%), were produced and injection molded by using three different injection temperatures and speeds to investigate their influence on electrical resistivity. It was found that the electrical resistivity was influenced greatly by the injection temperature when 1 wt% amount of CNT was used in the nanocomposite. However, the effect of injection speed was negligible.Publication Metadata only Performance of Novel TWO-CAP (Thin-Walled Open Channel Angular Pressing) Method on AA5083(KOREAN INST METALS MATERIALS, 2021) KENTLİ, AYKUT; Sahbaz, Mehmet; Kentli, Aykut; Kaya, HasanNewly developed severe plastic deformation (SPD) method TWO-CAP was applied to AA5083 to increase its mechanical properties. The method was developed to obtain the structural beams which have a thin-walled open-cross section area in high strength to weight ratio. During the TWO-CAP process, the annealed U-profile specimens will be pressed along the specifically designed die channel with the help of the hydraulic press machine. After the expansion and narrowing processes, the specimen leaves the die with initial dimensions at the end of each pass. Therefore, the material gains strength, hardness, and toughness while the microstructure of the material was improved as a result of the SPD. In order to determine the effect of the TWO-CAP on the mechanical properties of the material, the hardness and tension tests were carried out on the all passed specimens. Also, the characteristic investigations were performed on the specimens by using optical microscopy, SEM-EDS, and XRD analyses. Graphic AbstractPublication Metadata only Mechanical property improvement of a AA6082 alloy by the TV-CAP process as a novel SPD method(2023-02-01) KENTLİ, AYKUT; KAYA H., Özbeyaz K., KENTLİ A.© 2023 Walter de Gruyter GmbH, Berlin/Boston.Twisted variable channel angular pressing (TV-CAP) is a novel method. While it combines the advantages of equal channel angular pressing (ECAP), twist extrusion and direct extrusions, also it eliminates the disadvantages of these methods. Finite element analysis was also carried out in order to examine the design parameters, material flow and examine the effective strain values. Hardness and tensile tests were performed to examine the effect of TV-CAP on the mechanical properties of AA6082. In addition, optic microscope, SEM and TEM images were taken respectively and XRD, EDS and EBSD analyses were accomplished in order to investigate the microstructural analysis. As a result of this study, it has been observed that the material has hardened approximately 3 times compared to the annealed material and became 1.5 times stronger in terms of ultimate tensile strength. It was also concluded that, this new method is more efficient than twist extrusion and multi-pass equal channel angular pressing processes.Publication Metadata only INVESTIGATION OF STRAIN INHOMOGENEITy IN HExA-ECAP PROCESSED AA7075(POLSKA AKAD NAUK, POLISH ACAD SCIENCES, INST METALL & MATER SCI PAS, 2021) KENTLİ, AYKUT; Ogut, Serkan; Kaya, Hasan; Kentli, Aykut; Ozbeyaz, Kerim; Sahbaz, Mehmet; Ucar, MehmetSevere Plastic Deformation (SPD) techniques have been used by researchers for last three decades in order to obtain UltraFine Grained (UFG) materials. Equal Channel Angular Pressing (ECAP) is preferred more than other SPD techniques thanks to its high performance and practicability. Hexa Equal Channel Angular Pressing (Hexa-ECAP) - modified ECAP technique which enables to apply ECAP routes for cylindrical samples properly - was preferred in this study. Within the objective of this study, the effects of coefficient and ram velocity on the mean effective strain and strain inhomogeneity of Hexa-ECAP processed Al7075 aluminium alloy were investigated. Also, the effects of ram velocity and friction coefficient on hardness homogeneity were investigated benefitting from the similarity between the hardness distribution and the strain distribution.Publication Metadata only Applying hybrid equal channel angular pressing (HECAP) to pure copper using optimized Exp.-ECAP die(SPRINGER LONDON LTD, 2021) KENTLİ, AYKUT; Ogut, Serkan; Kaya, Hasan; Kentli, Aykut; Ucar, MehmetEqual channel angular pressing (ECAP), expansion equal channel angular pressing (Exp.-ECAP), and hybrid equal channel angular pressing (HECAP) or (Hybrid ECAP) processes were applied to pure copper specimens within this study. After the application of ECAP, the die used in the application of the Exp.-ECAP process was optimized considering the strain inhomogeneity in the specimen and the maximum load that occurred during the process. Finite element method (FEM), artificial neural network (ANN), and genetic algorithm (GA) were utilized together for the optimization process. The optimized die equally minimizes the pressing load and the strain inhomogeneity that occurred in the specimen. Using the optimized die, Exp.-ECAP and HECAP processes were applied to pure copper. The Exp.-ECAP process was previously applied only for aluminum alloys and magnesium alloys. With the application of the Exp.-ECAP process to pure copper, this gap in the literature was removed. In addition, with the application of the HECAP process, the effects of the Exp.-ECAP passes applied after ECAP were also examined which was not done earlier. The specimens, on which ECAP, Exp.-ECAP, and HECAP processes were applied, were subjected to microstructure analysis and mechanical tests, and the effects of these processes were examined. The results obtained showed that the Exp.-ECAP process gave better results in grain refinement and mechanical properties. The Exp.-ECAP passes applied after the ECAP process within the scope of the HECAP process provided a more homogeneous distribution for the microstructure and the hardness.Publication Metadata only Effect of support plates on the micro-drilled hole form quality in CFRP laminates(WALTER DE GRUYTER GMBH, 2019) KENTLİ, AYKUT; Dogrusadik, Ahmet; Kentli, AykutHole diameter, roundness error, and fiber overlap determine the form quality of a drilled hole on a fiber reinforced composite material. Using support plates is one of the methods to ensure hole form quality. In this study, the effects of support plates on hole form quality in the micro-drilling of CFRP laminates have been investigated. A comprehensive experimental study was carried out under variable cutting speeds and feeds. Three different setups were employed to inspect the effects of the support plates. In the first setup, bare CFRP laminates were drilled. In the second setup, aluminum entry board and phenolic backing board were used. In the third setup, brass entry board and wooden backing board were preferred to inspect the effect of different support plate materials. A large number of holes was drilled per experiment to be able to identify the tool wear effect on the process outputs. Diameter, roundness error, and fiber overlap were measured by using the hole images. Finally, variations of diameter, roundness error, and fiber overlap were evaluated for each setup. It was concluded that support plates improved the process outputs and made the process less sensitive to a change of process variables and tool wear.