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KENTLİ, AYKUT

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    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, Osman
    Cobalt 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.
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    Novel SPD Method: Twisted Variable Channel Angular Extrusion
    (KOREAN INST METALS MATERIALS) KENTLİ, AYKUT; Ozbeyaz, Kerim; Kaya, Hasan; Kentli, Aykut
    Different 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.
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    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, Mehmet
    Equal 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.