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Öğe An Evaluation on the Reproducibility of Composite Materials Produced(Zonguldak Bülent Ecevit Üniversitesi, 2013) Nas, Engin; Gökkaya, Hasan; Sur, GökhanResearchers unceasingly continuetrying to improve the strength features of industrial materials to meet day to day increasing industrial needs. Most of these studies are on the improvement of composite materials. These materials constitute a group of materials which can not be separated from traditional ones. Composite is a mixed-structured material which is created by the addition of fiber, whisker, flake, particle etctothetraditional materials like metal, ceramic, plasticand refractor. Composites a reproduced in three ways depending on anaphases’ state; liquid, solidand solid-liquid. Today, powder metallurgy- one of the solids tatefabricationtechniques- is commonly used for the production of composites. In this study, the effects of hot pressingmethod used in powder metallurgy on the producibility of composites are evaluated.Öğe THE EFFECT OF CORE CONFIGURATION ON THE COMPRESSIVE PERFORMANCE OF METALLIC SANDWICH PANELS(Inst Za Kovinske Materiale I In Tehnologie, 2019) Zurnacı, Erman; Gökkaya, HasanThe compressive performance of metallic sandwich panels signifies a key mechanical behaviour under compression loading. This paper describes the compressive performance of metallic corrugated core sandwich panels having different core configurations under quasi-static compression loads. Two different sandwich panel core configurations were studied: the corrugated monolithic core and the corrugated sliced core. The corrugated cores were fabricated using a sheet-metal bending technique with trapezoidal geometry and then bonded to surface plates. Aluminium 1050 1114 sheets were used as the core and surface materials. Sandwich panel samples were prepared and tested experimentally under a quasi-static compression load (compression rate of 2 mm/min). The force-displacement curves of the sandwich panels with different core configurations were obtained from the experimental tests. The compressive performance parameters included the maximum compression load, the average compression load, the energy absorption and the specific energy absorption. It was found that the core configuration played a key role in the compressive performance. Finally, when the compressive performance of these two different core configurations was compared, the corrugated sliced-core configurations exhibited better performance.Öğe The effects of cryogenic-treated carbide tools on tool wear and surface roughness of turning of Hastelloy C22 based on Taguchi method(Springer London Ltd, 2016) Akıncıoğlu, Sıtkı; Gökkaya, Hasan; Uygur, İlyasIn this study, Taguchi method has been applied to evaluate the effect of cryogenically treated tools in turning of Hastelloy C22 super alloy on surface roughness. The optimum parameters (cryogenic treatment, cutting speed, and feed rate) of turning were determined by using the Taguchi experimental design method. In Taguchi method, L9 orthogonal array has been used to determine the signal noise (S/N) ratio. Analysis of ANOVA was carried out to identify the significant factors affecting surface roughness. The statistical analysis indicated that feed rate, with a contribution percentage as high as 87.64 %, had the most dominant effect on machining performance, followed by the cryo-treated tools treatment and cutting speed, respectively. The confirmation tests indicated that it is possible to improve surface roughness significantly by using the Taguchi method. Surface roughness was improved by 28.3 and 72.3 % by shallow (CT1) cryogenic treatment and deep cryogenic treatment (CT2) applied on cementite carbide tools (UT). It found that wear resistance of tungsten carbide insert was increased by shallow and deep cryogenic treatments.Öğe Effects of cryogenically treated physical vapor deposition-coated tools on the turning performance of nickel-based superalloy(Sage Publications Ltd, 2022) Gökkaya, Hasan; Akıncıoğlu, SıtkıIn recent years, cryogenic treatment has been applied to improve the performance of cutting tools. Improving the performance of cutting tools can improve the surface qualities of workpiece and reduce costs. Nickel-based superalloys are difficult to machine. It is necessary to improve the machinability properties of these hard-to-machine alloys and to increase the product quality. In this study, the effects of cryogenically treated physical vapor deposition-coated tools on the turning performance of nickel-based Hastelloy C22 superalloy were investigated. Deep cryogenic treatment (-145 degrees C) and shallow cryogenic treatment (-80 degrees C) were applied to the physical vapor deposition-coated tools. Experiments were carried out under dry conditions. The cutting parameters selected for the machining were cryogenically treated cutting tools, cutting speed, and feed rate. The deep cryogenic treatment had a favorable influence on the performance of the physical vapor deposition-coated carbide inserts. Thanks to the deep cryogenic treatment applied to the cutting tools, 99.5% and 19.7% improvement in surface roughness and cutting forces were achieved, respectively, compared to the untreated tool. The deep cryogenic treatment contributed more to the wear resistance of the tools than the shallow cryogenic treatment. A slight increase in the hardness and electrical conductivity of the tools was detected thanks to the cryogenic treatment.Öğe Experimental and Statistical Study on Machinability of the Composite Materials with Metal Matrix Al/B4C/Graphite(Springer, 2017) Nas, Engin; Gökkaya, HasanIn this study, four types of Al/B4C/Graphite metal matrix composites (MMCs) were produced by means of a hot-pressing technique with reinforcement elements, B4C 8 wt pct and graphite (nickel coated) 0, 3, 5, and 7 wt pct. Machinability tests of MMC materials thus produced were conducted using four different cutting speeds (100, 140, 180, and 220 m/min), three different feed rates (0.1, 0.15, and 0.20 mm/rev), and a fixed cutting depth (0.5 mm), and the effects of the cutting parameters on the average surface roughness were examined. After the machinability tests, the height of the built-up edge (BUE) formed on the cutting tools related to the cutting speed and feed rate was measured. The test results were examined by designing a matrix according to the full factorial design and the average surface roughness, and the most important factors leading to formation of the BUE were analyzed by the analysis of variance (ANOVA). As a result of analysis, it was found that the lowest surface roughness value was with 7 wt pct graphite MMC material, while the highest was without graphite powder. Based on the statistical analysis results, it was observed that the most important factor affecting average surface roughness was the type of MMC material, the second most effective factor was the feed rate, and the least effective factor was the cutting speed. Furthermore, it was found that the most important factor affecting the formation of the BUE was the type of MMC material, the second most effective factor was the cutting speed, and the least effective factor was the feed rate.Öğe Investigation of the effect of AWJ drilling parameters for delamination factor and surface roughness on GFRP composite material(Emerald Group Publishing Ltd, 2022) Altın Karataş, Meltem; Gökkaya, Hasan; Akıncıoğlu, Sıtkı; Biberci, Mehmet AliPurpose The purpose of this study is to optimize processing parameters to get the smallest average surface roughness (Ra) and delamination damage (F-d) values during drilling via abrasive water jet (AWJ) of the glass fiber-reinforced polymer composite material produced at [0 degrees/90 degrees](s) fiber orientation angles. Design/methodology/approach Drilling experiments were done via AWJ with three-axis computer numerical control (CNC) control system. Machine processing parameters such as water pressure of 3,600, 4,300, 4,800 and 5,300 bar; stand-off distance of 1, 2, 3 and 4 mm; traverse rate of 750, 1,500, 2,000 and 3,000 mm/min; and hole diameters of 8, 10, 12 and 14 mm have been selected. The effects of processing parameters in drilling experiments were investigated in conformity with the Taguchi L-16 orthogonal array and the data obtained were analyzed using Minitab 17 software. The signal/noise (S/N) ratio was taken as a basis for evaluating the test results. Optimum processing conditions were determined by calculating the S/N ratio for both Ra and F-d in conformity with the smaller is better approximation. The effects of processing parameters on Ra and F-d were statistically investigated using analysis of variance, S/N ratio and Taguchi-based gray relational analysis. Ra and F-d were predicted by evaluating with the ANN model and were predicted with the least amount of error. Findings It has been determined that the most effective parameter for Ra and F-d is the water pressure and then the stand-off distance. Originality/value The novel approach is to reduce cost and the time spent by using Taguchi optimization as a result of AWJ drilling the material in this fiber orientation [0 degrees/90 degrees](s).Öğe Mechanical and physical properties of hybrid reinforced (Al/B4C/Ni(K)Gr) composite materials produced by hot pressing(Carl Hanser Verlag, 2015) Nas, Engin; Gökkaya, HasanIn this study, the mechanical and physical properties of hybrid reinforced (Al/B4C/Ni(K)Gr) metal matrix composite (MMC) materials were investigated. The MMC materials were produced using the powder metallurgy (PM) production method of hot pressing (HP). The aluminum alloy Alumix 13 was used as matrix material and boron carbide (B4C) and nickel-coated graphite (Ni(K) Gr) as reinforcement elements. The microstructural characteristics, hardness, 3-point bending strength and density values of the produced hybrid reinforced MMC materials were determined. The reinforcement element B4C was kept at constant concentration of 8 wt.-%. Four different MMC materials were produced with the addition of 0, 3, 5 and 7 wt.-% Ni(K) Gr in the B4C. From the SEM images of the MMC materials produced by the HP technique, it was observed that the reinforcement element exhibited a uniform distribution. Moreover, the particles showed an approach to each other depending on the particle size and the amount (wt.-%) of the reinforcement element. With increasing graphite content in the structure density, hardness and 3-point bending test values decreased.Öğe Optimization of Cutting Conditions, Parameters, and Cryogenic Heat Treatment for Surface Roughness in Milling of NiTi Shape Memory Alloy(Springer, 2022) Altaş, Emre; Erkan, Ömer; Özkan, Derviş; Gökkaya, HasanThis 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.Öğe A review of cryogenic treatment on cutting tools(Springer London Ltd, 2015) Akıncıoğlu, Sıtkı; Gökkaya, Hasan; Uygur, İlyasEnhancing the performance of cutting tools is an important factor in reducing production costs. Cutting tools are subjected to processes such as heat treatment and coating in order to improve their performance. Cryogenic treatment, which is also known as sub-zero heat treatment, has made significant contributions to the improvement of wear resistance, tool life, dimensional integrity, and product quality of cutting tools. The mode of application of cryogenic treatment and the type of cutting tool both affect tool performance. Therefore, it is necessary to examine the way cryogenic treatment is applied to cutting tools and its effects on their performance. This study reviews the literature on the performance of cryo-treated cutting tools.Öğe Three-Point Bending Response of Corrugated Core Metallic Sandwich Panels Having Different Core Configurations - An Experimental Study(Eos Assoc, 2019) Zurnacı, Erman; Gökkaya, Hasan; Nalbant, Muammer; Sur, GökhanBending response of corrugated core metallic sandwich panels was studied experimentally under three-point bending loading. Two different core configurations were used: the corrugated monolithic core and the corrugated sliced core. The trapezoidal corrugated cores were manufactured from aluminum sheets via a sheet metal bending mould. After the sandwich panel samples were prepared, they were subjected to three-point bending tests. The load and displacement responses of the sandwich panels having different core configurations were obtained from the experimental testing. The influence of the core configuration on the three-point bending response and failure modes was then investigated. The experimental results revealed that the corrugated sliced core configuration exhibited an improved bending performance compared to the corrugated monolithic core configuration.
