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    An Experimental and Statistical Evaluation of The Cutting Parameters on The Machinability of Hadfield Steel
    (Gazi Univ, 2016) Kivak, Turgay; Uzun, Gultekin; Ekici, Ergun
    The effects of cutting tool coatings and cutting parameters (cutting speed, feed rate) on the cutting forces and surface roughness during the turning of Hadfield steel were investigated in this study. Cutting experiments were made on a CNC lathe under dry cutting conditions by employing CVD TiCN/Al2O3/TiN-, PVD TiAlN- and PVD TiAlN/AlCrO-coated cementite carbide inserts. Four different cutting speeds (100, 140, 180, 220 m/min), two different feed rates (0.2, 0.3 mm/rev) and a constant cutting depth of 0.8 mm were used as the cutting parameters. At the end of the tests, cutting force and surface roughness results were subjected to variance (ANOVA) and multiple regression analyses. The experimental results showed that the PVD TiAlN coating was superior to the CVD TiCN/Al2O3/TiN and PVD TiAlN/AlCrO coatings with respect to cutting force and surface roughness. The correlation coefficients of the statistical model developed at the end of the analysis were R-2=0.994 and R-2=0.996 for the cutting forces and surface roughness, respectively. The feed rate was found to be the most effective parameter on the cutting forces and surface roughness, with contribution ratios of 91.31% and 94.79% respectively.
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    An investigation of the effects of cutting parameters and graphite reinforcement on quality characteristics during the drilling of Al/10B4C composites
    (Elsevier Sci Ltd, 2017) Ekici, Ergun; Motorcu, Ali Rıza; Uzun, Gultekin
    This study investigated the effects of cutting parameters on the quality characteristics of thrust force (Ft), surface roughness (Ra), dimensional accuracy (Da) and burr height (Bh) during the drilling of Al/10B(4)C and Al/10B(4)C/5Gr composites. Machinability experiments were carried out with uncoated carbide twist drills at three different cutting speeds (18, 25 and 35 m/min) and three different feed rates (0.08, 0.112 and 0.16 mm/rev) under dry cutting conditions. The percent contribution of the cutting/drilling parameters/variables to the quality characteristics was determined using analysis of variance (ANOVA), and predictive linear equations were developed for the estimation of all the quality characteristics. As a result of the experimental study, it was determined that during the drilling of the composites, the 5% graphite reinforcement of Al/10B(4)C/5Gr decreased the thrust force and the burr height, improved the surface quality and brought the composite closer to its ideal diameter value. (C) 2016 Published by Elsevier Ltd.
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    Delamination and thrust force analysis in GLARE: Influence of tool geometry and prediction with machine learning models
    (Sage Publications Ltd, 2024) Ekici, Ergun; Pazarkaya, Ibrahim; Uzun, Gultekin
    The multi-layered (fiber/metal) structure of glass fibre aluminium reinforced epoxy (GLARE) makes it difficult to obtain acceptable damage-free holes that meet aerospace standards. This paper investigated the effects of tool geometry and drilling parameters on reducing delamination damage and uncut fibers at the hole exit surface in drilling GLARE. The hole surfaces were examined by scanning electron microscope (SEM) at various magnifications. In addition, deep neural network (DNN) and long-short-term memory (LSTM) machine learning models were used to predict delamination (Fda), uncut fiber (UCF), and thrust forces using experimental data. No positive contribution of the special geometry tool was observed, while the standard geometry tool was found to be ideal for drilling conditions. Analysis of variance (ANOVA) revealed that feed rate contributed 57.83% to delamination damage, while tool geometry contributed 74.31% and 92.33% for uncut fiber and thrust force, respectively. SEM analysis revealed high deformation zones in the aluminum layers and fiber fracture and separation in the glass fibre reinforced polymer (GFRP) layers. DNN and LSTM models were found to provide accurate predictions with R2 values greater than 95% and 98%, respectively.
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    Effect of lapping process on axis misalignment and surface roughness in elliptical gear pairs
    (Elsevier Sci Ltd, 2024) Pazarkaya, Ibrahim; Yazar, Mehmet; Karabulut, Sener; Uzun, Gultekin; Ozdemir, Ahmet
    This study aims to investigate the effect of application of the lapping process on the amount of axis misalignment in elliptical spur gears. Using a Taguchi L9 experimental design, nine distinct pairs of elliptical spur gears were manufactured, each featuring three distinct modules (m), number of teeth (z), and ratio of major and minor radius of the pitch ellipse (a/b). Specialized hardware and software were developed to determine inter-axis misalignment in the gear pairs. The hardware measured the misalignment, while the software collected data from a digital indicator, recording changes in inter-axis alignment at different angular positions of the gear pairs. Three diverse parameters were utilized in the lapping processes: rotational speed of 120 rpm, 170 rpm, and 220 rpm; duration of 10 min, 20 min, and 30 min; and mass of 0.5 kg, 1 kg, and 1.5 kg. Axial misalignment of the gear pairs was evaluated both before and after the lapping process. The most significant change in misalignment was observed at 76 mm for gear pairs with parameters m = 2.0, z = 25, a/b = 1.60, while the smallest misalignment change was recorded at 5 mm for gear pairs with parameters a/b = 1.60, m = 1.60, z = 40. After lapping process, the average surface roughness values of all gear pairs improved by an average of 27.64%, and no significant weight loss was noted. The optimal lapping parameters were determined based on post-lapping average surface roughness values, and they were found to be 220 rpm, 10 min, and a 1 kg weight. Although the rotational speed and duration varied, it was observed that a constant 1 kg weight parameter was the optimal lapping weight for all gear modules.
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    Effects on machinability of cryogenic treatment applied to carbide tools in the milling of Ti6AI4V with optimization via the Taguchi method and grey relational analysis
    (Springer Heidelberg, 2022) Ekici, Ergun; Uzun, Gultekin
    The effects of processing parameters and cryogenic treatment on cutting force and surface roughness in the milling of Ti6AI4V alloy were investigated in this study. The effects of cutting speed, feed rate, and the treatments applied to the tools were evaluated through the Taguchi method and grey relational analysis. Control factors in the experiments performed under dry cutting conditions were based on two different cutting speeds and three different feed rates and tool properties. It was observed that the cutting force values decreased with increased cutting speed and significantly increased parallel to the feed rate. In terms of surface roughness, they were observed to change based on cutting parameters. Whereas the most effective parameter for cutting force was feed rate, with a 81.9% contribution, for surface roughness it was cutting speed, with a 48.8% contribution. Optimum machining conditions were determined as A(1)B(3)C(2) following the grey relational analysis performed for both responses.