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    CUTTING TOOL GEOMETRY IN THE DRILLING OF CFRP COMPOSITE PLATES AND TAGUCHI OPTIMISATION OF THE CUTTING PARAMETERS AFFECTING DELAMINATION
    (Yildiz Technical Univ, 2018) Sur, Gokhan; Erkan, Omer
    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.
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    INVESTIGATION OF SURFACE MORPHOLOGY OF DRILLED CFRP PLATES AND OPTIMIZATION OF CUTTING PARAMETERS
    (World Scientific Publ Co Pte Ltd, 2020) Erkan, Omer; Sur, Gokhan; Nas, Engin
    In this study, the carbon fiber reinforced polymer (CFRP) composite material was drilled using different parameters (118 degrees and 140 degrees Point Angle, 30, 60 and 90 m . min(-1) cutting speed and 0.06, 0.08 and 0.10 mm . rev(-1) feed rate). Experimental parameters were designed according to full factorial design method and the results were analyzed using Taguchi L18 experimental design. The results of the study show that the lowest surface roughness values are 0.1958 and 0.1945 mu m with the cutting speed of 90 m . min(-1) and feed rate of 0.06 m . rev(-1) in the Point angles of 118 degrees and 140 degrees, respectively. When the results of Anova analysis were evaluated, parameters (feed speed, cutting speed and end point angle) according to the effect ratios on surface roughness were formed at the rates of 41.06%, 33.13% and 5.07%, respectively. The most suitable parameters according to S/N ratios were determined using A2B3C1 factors for the average surface roughness.
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    Optimization of Cutting Conditions, Parameters, and Cryogenic Heat Treatment for Surface Roughness in Milling of NiTi Shape Memory Alloy
    (Springer, 2022) Altas, Emre; Erkan, Omer; Ozkan, Dervis; Gokkaya, Hasan
    This study discusses the milling of Nickel-Titanium (NiTi) alloy, one of the innovative and widely used shape memory alloy (SMA). During the face milling operations, the average surface roughness (R-a) was investigated depending on the change in machining parameters, cutting conditions, and cryogenic heat treatment. Experiments were carried out with uncoated and two different coated (PVD, CVD) cutting tools with untreated, shallow (- 80 degrees C) and deep (- 196 degrees C) cryogenic heat treatment. In addition, experiments were carried out using Ethylene Glycol (EG), and boron added Ethylene Glycol (EG+5%BX) cutting fluids as well as dry cutting condition. In the cutting experiments, three different cutting speeds (20-35-50 m/min), three different feeds (0.03-0.07-0.14 mm/tooth), and 0.7 mm fixed cutting depth was used as machining parameters. In the milling mechanism of NiTi shape memory alloys, how the cutting parameters affect the surface quality is discussed in detail. In this context, the cutting parameters were successfully optimized using Taguchi and ANOVA methods. The study is innovative in terms of evaluating the effect of different cutting fluids and cryogenic heat treatment. The results showed that CVD-coated cutting tool, - 196 degrees C cryogenic heat treatment, EG+5%BX cutting fluid, 50 m/min cutting speed, and 0.03 mm/tooth feed are the optimal parameters for the minor surface roughness. In addition, it has been determined that progress is the most influential parameter. On the other hand, ANOVA results showed that the most significant variable on the R-a was feed rate with 42.99%, and then cutting tool type 20.27%, cutting fluid 20.25%, cutting speed 11.68%, and cryogenic heat treatment 1.95%, respectively.
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    Prediction of Damage Factor in end Milling of Glass Fibre Reinforced Plastic Composites Using Artificial Neural Network
    (Springer, 2013) Erkan, Omer; Isik, Birhan; Cicek, Adem; Kara, Fuat
    Glass fibre reinforced plastic (GFRP) composites are an economic alternative to engineering materials because of their superior properties. Some damages on the surface occur due to their complex cutting mechanics in cutting process. Minimisation of the damages is fairly important in terms of product quality. In this study, a GFRP composite material was milled to experimentally minimise the damages on the machined surfaces, using two, three and four flute end mills at different combinations of cutting parameters. Experimental results showed that the damage factor increased with increasing cutting speed and feed rate, on the other hand, it was found that the damage factor decreased with increasing depth of cut and number of the flutes. In addition, analysis of variance (ANOVA) results clearly revealed that the feed rate was the most influential parameter affecting the damage factor in end milling of GFRP composites. Also, in present study, Artificial Neural Network (ANN) models with five learning algorithms were used in predicting the damage factor to reduce number of expensive and time-consuming experiments. The highest performance was obtained by 4-10-1 network structure with LM learning algorithm. ANN was notably successful in predicting the damage factor due to higher R-2 and lower RMSE and MEP.
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    Surface quality optimization of CFRP plates drilled with standard and step drill bits using TAGUCHI, TOPSIS and AHP method
    (Emerald Group Publishing Ltd, 2021) Sur, Gokhan; Erkan, Omer
    Purpose Drilling of carbon fiber reinforced plastic (CFRP) composite plates with high surface quality are of great importance for assembly operations. The article aims to optimize the drill geometry and cutting parameters to improve the surface quality of CFRP composite material. In this study, CFRP plates were drilled with uncoated carbide drill bits with standard and step geometry. Thus, the effects of standard and step drill bits on surface quality have been examined comparatively. In addition, optimum output parameters were determined by Taguchi, ANOVA and multiple decision-making methods. Design/methodology/approach Drill bit point angles were selected as 90 degrees, 110 degrees and 130 degrees. In cutting parameters, three different cutting speeds (25, 50 and 75 m/min) and three different feeds (0.1, 0.15 and 0.2 mm/rev) were determined. L18 orthogonal sequence was used with Taguchi experimental design. Three important output parameters affecting the surface quality are determined as thrust force, surface roughness and delamination factor. For each output parameter, the effects of drill geometry and cutting parameters were evaluated. Input parameters affecting output parameters were analyzed using the ANOVA method. Output parameters were estimated by creating regression equations. Weights were determined using the analytic hierarchy process (AHP) method, and multiple output parameters were optimized using technique for order preference by Similarity to An ideal solution (TOPSIS). Findings It has been determined from the experimental results that step drills generate smaller thrust forces than standard drills. However, it has been determined that it creates greater surface roughness and delamination factor. From the Taguchi analysis, the optimum input parameters for Fz step tool geometry, 90 degrees point angle, 75 m/min cutting speed and 0.1 mm/rev feed. For Fd, are standard tool geometry, 90 degrees point angle, 25 m/min cutting speed and 0.1 mm/rev feed and for Ra, are standard tool geometry, 130 degrees point angle, 25 m/min cutting speed and 0.1 mm/rev feed. ANOVA analysis determined that the most important parameter on Fd is the tip angle, with 56.33%. The most important parameter on Ra and Fz was found to be 40.53% and 77.06% tool geometry, respectively. As a result of the optimization with multiple criteria decision-making methods, the test order that gave the best surface quality was found as 4-1-9-5-8-17-2-13-6-16-18-15-11-10-3-12-14. The results of the test number 4, which gives the best surface quality, namely, the thrust force is 91.86 N, the surface roughness is 0.75 mu m and the delamination factor is 1.043. As a result of experiment number 14, which gave the worst surface quality, the thrust force was 149.88 N, the surface roughness was 3.03 mu m and the delamination factor was 1.163. Practical implications Surface quality is an essential parameter in the drilling of CFRP plates. Cutting tool geometry comes first among the parameters affecting this. Therefore, different cutting tool geometries are preferred. A comparison of these cutting tools is discussed in detail. On the other hand, thrust force, delamination factor and surface roughness, which are the output parameters that determine the surface quality, have been optimized using the TOPSIS and AHP method. In this way, this situation, which seems complicated, is presented in a plain and understandable form. Originality/value In the experiments, cutting tools with different geometries are included. Comparatively, its effects on surface quality were examined. The hole damage mechanism affecting the surface quality is discussed in detail. The results were optimized by evaluating Taguchi, ANOVA, TOPSIS and AHP methods together.