Yazar "Karatas, Meltem Altin" seçeneğine göre listele

Listeleniyor 1 - 6 / 6
  • Küçük Resim Yok
    Öğe
    Analysis of Surface Roughness and Flank Wear Using the Taguchi Method in Milling of NiTi Shape Memory Alloy with Uncoated Tools
    (Mdpi, 2020) Altas, Emre; Gokkaya, Hasan; Karatas, Meltem Altin; Ozkan, Dervis
    The aim of this study was to optimize machining parameters to obtain the smallest average surface roughness (Ra) and flank wear (Vb) values as a result of the surface milling of a nickel-titanium (NiTi) shape memory alloy (SMA) with uncoated cutting tools with different nose radius (r(epsilon)) under dry cutting conditions. Tungsten carbide cutting tools with different r(epsilon) (0.4 mm and 0.8 mm) were used in milling operations. The milling process was performed as lateral/surface cutting at three different cutting speeds (V-c) (20, 35 and 50 m/min), feed rates (f(z)) (0.03, 0.07 and 0.14 mm/tooth) and a constant axial cutting depth (0.7 mm). The effects of machining parameters in milling experiments were investigated based on the Taguchi L18 (2(1) x 3(2)) orthogonal sequence, and the data obtained were analyzed using the Minitab 17 software. To determine the effects of processing parameters on Ra and Vb, analysis of variance (ANOVA) was used. The analysis results reveal that the dominant factor affecting the Ra is the cutting tool r(epsilon), while the main factor affecting Vb is the f(z). Since the predicted values and measured values are very close to each other, it can be said that optimization is correct according to the validation test results.
  • Küçük Resim Yok
    Öğe
    Optimization of machining parameters for abrasive water jet drilling of carbon fiber-reinforced polymer composite material using Taguchi method
    (Emerald Group Publishing Ltd, 2020) Karatas, Meltem Altin; Gokkaya, Hasan; Nalbant, Muammer
    Purpose The aim of this paper is to optimize the machining parameters to obtain the smallest average surface roughness values during drilling of the carbon fiber-reinforced polymer (CFRP) composite material with abrasive water jet (AWJ) and analyze the damage of the delamination. Design/methodology/approach CFRP composite material had been fabricated having fiber orientations frequently used in the aerospace industry (0 degrees/45 degrees/90 degrees/-45 degrees). Three different stand-off distances (1, 2 and 3 mm), three different water pressures (1,800, 2,800 and 3,800 bar) and three different hole diameters (4, 8 and 12 mm) were selected as processing parameters. The average surface roughness values were obtained, and delamination damage was then analyzed using Taguchi optimization. Drilling experiments were performed using the Taguchi L-27 orthogonal array via Minitab 17 software. The signal/noise ratio was taken into account in the evaluation of the test results. Using the Taguchi method, the control factors giving the mean surface roughness values were determined. Analysis of variance was performed using the experimental results, and the effect levels of the control factors on the average surface roughness were found. Findings It was found that water pressure and hole diameter had a higher effect on average surface roughness, while water pressure and stand-off distance were effective on delamination. Originality/value The novel approach is to reduce cost and spent time using Taguchi optimization as a result of AWJ drilling the material in this fiber orientation ([0 degrees/45 degrees/90 degrees/-45 degrees](s), which is often used in the aerospace industry).
  • Küçük Resim Yok
    Öğe
    Optimization of machining parameters for kerf angle and roundness error in abrasive water jet drilling of CFRP composites with different fiber orientation angles
    (Springer Heidelberg, 2020) Karatas, Meltem Altin; Motorcu, Ali Riza; Gokkaya, Hasan
    In this study, carbon fiber-reinforced polymer (CFRP) composites with three different fiber orientation angles (M1: [0 degrees/90 degrees](s), M2: [+ 45 degrees/- 45 degrees](s), and M3: [0 degrees/45 degrees/90 degrees/- 45 degrees](s)) were drilled (with and without pilot holes) on an abrasive water jet (AWJ) machine and the effect of the drilling parameters on the kerf angle (K) and roundness error (Re) of selected holes was investigated to determine quality characteristics. The first aim of the study was the single-objective optimization of drilling parameters for minimum K and Re individually. The second aim was the multi-objective optimization of drilling parameters for the simultaneous minimization of both K and Re. The Taguchi method was applied for single-objective optimization, while all steps of the Taguchi-based gray relational analysis were used for multi-objective optimization. Drilling experiments were performed using the L16 (4(4)) orthogonal array. Four levels each for water pressure, stand-off distance, traverse feed rate, and hole diameter were selected as control factors. Analysis of experimental findings revealed that pilot drilling improved the kerf angle of the hole by 12.4% and the roundness error by 22.87%. Minimum kerf angle and roundness error were realized in the AWJ drilling of the M3 CFRP. The most effective parameter on kerf angle and roundness error in AWJ drilling of M1, M2, and M3 CFRP materials was water pressure (80.6%, 76.9%, and 73.8%, respectively), followed by stand-off distance (11.7%, 12.0%, and 13.5%),while other drilling parameters remained below 10%. The statistical evaluation and optimization results in this study can contribute to the evaluation of the AWJ machinability of CFRP composites.
  • Küçük Resim Yok
    Öğe
    A review on machinability of carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) composite materials
    (Elsevier Science Bv, 2018) Karatas, Meltem Altin; Gokkaya, Hasan
    Fiber reinforced polymer (FRP) composite materials are heterogeneous and anisotropic materials that do not exhibit plastic deformation. They have been used in a wide range of contemporary applications particularly in space and aviation, automotive, maritime and manufacturing of sports equipment. Carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) composite materials, among other fiber reinforced materials, have been increasingly replacing conventional materials with their excellent strength and low specific weight properties. Their manufacturability in varying combinations with customized strength properties, also their high fatigue, toughness and high temperature wear and oxidation resistance capabilities render these materials an excellent choice in engineering applications. In the present review study, a literature survey was conducted on the machinability properties and related approaches for CFRP and GFRP composite materials. As in the machining of all anisotropic and heterogeneous materials, failure mechanisms were also reported in the machining of CFRP and GFRP materials with both conventional and modern manufacturing methods and the results of these studies were obtained by use of variance analysis (ANOVA), artificial neural networks (ANN) model, fuzzy inference system (FIS), harmony search (HS) algorithm, genetic algorithm (GA), Taguchi's optimization technique, multi-criteria optimization, analytical modeling, stress analysis, finite elements method (FEM), data analysis, and linear regression technique. Failure mechanisms and surface quality is discussed with the help of optical and scanning electron microscopy, and profilometry. ANOVA, GA, FEM, etc. are used to analyze and generate predictive models. (c) 2018 The Authors. Published by Elsevier Ltd.
  • Küçük Resim Yok
    Öğe
    Study on delamination factor and surface roughness in abrasive water jet drilling of carbon fiber-reinforced polymer composites with different fiber orientation angles
    (Springer Heidelberg, 2021) Karatas, Meltem Altin; Motorcu, Ali Riza; Gokkaya, Hasan
    Carbon fiber-reinforced polymer (CFRP) composites are used in aerospace applications because of their superior mechanical properties and light weight. Avoiding damage in the machining of CFRP composites is difficult using traditional methods. Abrasive water jet (AWJ) has recently become one of the preferred machining methods for CFRP composites. This study evaluated the AWJ machinability of CFRP composites having three different fiber orientation angles (M1: [0 degrees /90 degrees ]s, M2: [+45 degrees/- 45 degrees ]s, and M3: [0 degrees /45 degrees /90 degrees/- 45 degrees ]s) according to the delamination factor (D-f), and the average surface roughness (R-a) as quality characteristics of the drilled holes. The aim of the study was to investigate the effects of different levels of AWJ drilling parameters on the delamination factor and surface roughness and to determine the optimum drilling parameter levels that provide minimum delamination formation and surface roughness values. For this purpose, AWJ drilling experiments were carried out using the Taguchi L16 (4(4)) orthogonal array. Water pressure (WP), stand-off distance (L), traverse feed rate (F), and hole diameter (D) were chosen as process parameters. Analysis of variance was used to determine the percentage effects of the AWJ drilling process parameters. The microscopic surface roughness and delamination formation properties of the machined surfaces were revealed using a scanning electron microscope and an optical microscope, respectively. The most effective parameters on D-f and R-a in the AWJ drilling of M1, M2 and M3 CFRP materials were determined to be water pressure, and stand-off distance. Minimum D-f and R-a values were obtained when AWJ drilling the M3 CFRP composite with a fiber orientation angle of [0 degrees /45 degrees /90 degrees/- 45 degrees ]s. Minimum delamination formation and very good surface quality can be obtained when the optimum process parameters determined in this study are used in the planning process for the AWJ drilling of CFRP composites having different fiber orientation angles.
  • Küçük Resim Yok
    Öğe
    A Study on Optimum Machinability of NiTi Shape Memory Alloy Via AWJ
    (Korean Soc Precision Eng, 2024) Guven, Sedat; Karatas, Meltem Altin; Gokkaya, Hasan
    The high ductility behaviour and high hardening of Nickel-Titanium (NiTi) alloys during cutting make them one of the alloys with low machinability. In addition, poor chip breakage and high tool wear are observed when machining these materials with conventional manufacturing methods. One of the unconventional processing methods, abrasive water jet (AWJ), is an alternative method for cutting low machinability materials. In this study, NiTi shape memory alloy (SMA) was subjected to AWJ drilling under different machining parameters. The aim of the research is to determine the optimum kerf (K), surface roughness (Ra) and material removal rate (MRR) variables resulting from the drilling process by examining the effect of process variables such as water pressure (WP), stand-off distance (SoD) and feed rate used in AWJ machining of NiTi SMAs. Taguchi-based Gray Relational Analysis (GRA), one of the multi-criteria decision-making methods, was used to optimise machining parameters in the drilling of NiTi SMAs with AWJ. The effect percentages of the test levels in the drilling operations were determined using Analysis of Variance (ANOVA). As a result of the experimental study, optimum levels were obtained for K, MRR and Ra at low WP, medium SoD and high feed rate. According to the result obtained from ANOVA, the parameter with the highest effect on K, MRR and Ra was determined as feed rate with 34.65%.