Browsing by Author "Pinar, AM"

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    Examination of the Methods Used in Circularity Error Measurement
    Pinar, AM; Güllü, A
    Circular motions in CNC machining centres are achieved by circular interpolation motions. The errors in these movements are called circularity errors. In this study circularity error measurement system is introduced. Having described the circularity error the algorithms in which this error is evaluated are introduced. Furthermore, the measurement devices in this system are discussed by a detailed literature survey.
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    Microstructural Properties of Particle-Reinforced Polytetrafluoroethylene Composite Bearings After Wear
    Ünlü, BS; Uzkut, M; Pinar, AM; Özdin, K
    High-performance engineering polymers that ensure the desired properties of journal bearings and give good wear results are investigated. We determine the microstructural properties of polymer-based particle-reinforced polytetrafluoroethylene composite bearings by analyzing the optical and SEM surface wear images.
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    A comparison of cooling methods in the pocket milling of AA5083-H36 alloy via Taguchi method
    Pinar, AM; Filiz, S; Ünlü, BS
    In this study, classical and vortex tube cooling methods are compared in the pocket machining of AA5083-H36 alloy with uncoated cemented carbide cutting tool. The effects of cutting speed, feed rate, axial/radial depth of cut and nose radius and their two-way interactions on the surface roughness, and the optimization of surface roughness are investigated via Taguchi method. The experiments conducted based on Taguchi's L16 orthogonal array (OA) are assessed with analysis of variance (ANOVA) and signal to noise (S/N) ratio. As a result, in both cooling methods, it is obtained that roughness correlates negatively with cutting speed and radial depth of cut and positively with feed rate and axial depth of cut. While in the cooling with vortex tube, lower average R (a) values are observed in the experiments with the nose radius of 0.8 mm, in the classical cooling almost no change is obtained. Lastly, optimum roughnesses for the classical and vortex tube cooling are obtained as 0.164 and 0.188 mu m, respectively.
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    STATISTICAL ASSESSMENT OF COUNTER-FLOW VORTEX TUBE PERFORMANCE FOR DIFFERENT NOZZLE NUMBERS, COLD MASS FRACTIONS, AND INLET PRESSURES VIA TAGUCHI METHOD
    Pinar, AM; Uluer, O; Kirmaci, V
    In this article, the effect and optimization of process parameters in a counter-flow vortex tube on temperature difference were investigated through the Taguchi method. The experiments were planned as per Taguchi's L27 orthogonal array with each experiment performed under different conditions of inlet pressure, nozzle number, and cold mass fraction. By means of analysis of variance and regression analysis, the effects of factors and their interactions on temperature difference were determined and modeled with a correlation coefficient of 93.5%. Accordingly, it was observed that temperature difference goes up with the increase in inlet pressure, and the cold mass fraction and decreases with the increase in nozzle number. In addition, the optimum settings of process parameters maximizing the temperature difference are an inlet pressure of 650 kPa, a nozzle number of 2, and a cold mass fraction of 0.7. Finally, confirmation tests verified that the Taguchi method was successful in the assessment of vortex tube parameters for temperature difference.
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    Corrosion resistance and mechanical properties of quenched and tempered 28MnCrB5 steel in two acidic environments
    Yazici, A; Zeybek, MS; Güler, H; Pinar, AM; Tücer, R
    Microstructure, hardness distribution, tensile properties and fracture behavior of the quenched and tempered steel 28MnCrB5 were investigated before and after corrosion tests. The corrosion behavior of the quenched and tempered steel 28MnCrB5 was examined in two different acidic environments, namely a hydrochloric acid solution and fertilizer-containing soil. The specimens were immersed in corrosive environments for 24, 48, 72, 96, 120, 144 and 168 hours, and additionally into fertilizer-containing soil for 240 days. The corrosion losses were determined by measuring the weight changes and the respective corrosion rates were calculated. Ductile fracture was observed in the sample of the quenched and tempered material before and after 168 hours of exposure to the hydrochloric acid solution and fertilizer-containing soil environment. But, in the sample subjected to corrosion in the fertilizer-containing soil environment for 240 days, brittle fracture took place and the fracture topography on the surface exhibited inter-granular cleavage. After 240 days of corrosion test in the fertilizer-containing soil environment, the ductility of the material decreased to a very great extent. The surface of the quenched and tempered 28MnCrB5 samples was covered by corrosion pits, cracks and peelings at the end of 168 h tests in the hydrochloric acid solution environment. At the end of 240 day tests in the fertilizer-containing soil environment, the surface of the samples showed deep peelings and cracks.
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    Optimization of counter flow Ranque-Hilsch vortex tube performance using Taguchi method
    Pinar, AM; Uluer, O; Kirmaci, V
    This study discusses the application of Taguchi method in assessing maximum temperature gradient for the Ranque-Hilsch counter flow vortex tube performance. The experiments were planned based on Taguchi's L27 orthogonal array with each trial performed under different conditions of inlet pressure, nozzle number and fluid type. Signal-to-noise ratio (SIN) analysis, analysis of variance (ANOVA) and regression analysis were carried out in order to determine the effects of process parameters and optimal factor settings. Finally, confirmation tests verified that Taguchi method achieved optimization of counter flow Ranque-Hilsch vortex tube performance with sufficient accuracy. (C) 2009 Elsevier Ltd and IIR. All rights reserved.
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    Machinability evaluation of multi-directional turning tools
    Pinar, AM; Firat, K
    Multi directional turning tools can perform various operations such as cutting, grooving and profile turning with high performance on their own. Tool change and setting times are reduced considerably with the use of these tools. This study discusses surface roughness and wear behavior for different cutting speeds, chip breaker types and nose radii in the rough turning of AISI 4140 steel with physical vapor deposition coated cemented carbide multi directional turning tool. Experimental results based on Taguchi's L8 orthogonal array are assessed through the analysis of variance, main effects and interaction plots. As a result, optimum roughness and an roughness increase percentage are obtained at 0.803 mu m and 19.92 %, respectively.
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    Biomechanical effects of three different configurations in Salter Harris type 3 distal femoral epiphyseal fractures
    Gok, K; Inal, S; Gok, A; Pinar, AM
    In this study, the biomechanical effects of three different configurations (K-wire, stainless steel screws, and titanium screws), which are used for stabilizing Salter-Harris (SH) type 3 epiphyseal fracture of distal femur after reduction process, on the epiphyseal plate and fracture line have been investigated under axial, rotational, and bending forces to determine the most advantageous configuration. Three different configurations have been modeled using SolidWorks, and computer-aided numerical analyses were performed by finite-element analysis software. For each configuration, mesh process, boundary conditions, and material model have been applied in finite-element analysis software. In addition, von Mises stress values on growth of epiphyseal plate and K-wire have been calculated. According to the results obtained, it has been found particularly advantageous to use the fixation shape of configuration with screw. In addition, the fixation shape of K-wire configuration was found to be disadvantageous in the SH type 3 epiphyseal fractures.
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    OPTIMIZATION OF NUMERICAL CONTROLLED HYDRAULIC DRIVEN POSITIONING SYSTEM VIA TAGUCHI METHOD
    Pinar, AM; Güllü, A
    This study, investigates the positioning accuracy of the hydraulic system that is controlled by FM-357 function module used in the control of CNC machine tools. The system consists of two axes driven by two cylinders directed by proportional directional valves. The effects of feed rate, motion distance, direction and inertia load on the positioning accuracy and the determination of their optimum levels are achieved via Taguchi method. According to this, minimum positioning error is obtained in the motion distance of 5mm, in - direction and at the inertia load of 5kg. Lastly, the confirmation experiments showed that Taguchi method achieves the optimization of the system with sufficient accuracy.
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    Statistical investigation of hydraulic driven circular interpolation motions
    Pinar, AM; Gullu, A; Taskin, S
    In this study, a twin-axis gantry has been structured to examine hydraulic driven positioning skills of the curvilinear motions based on ISO 230-4 standard entitled 'Circular tests for numerically controlled machine tools'. The system is controlled by a path and position control module of a PLC device. As a result of the experiments conducted based on the full factorial design, the effects of piston diameter, feed rate, radius and their two-way interactions on the circularity error are determined through analysis of variance. Accordingly, minimum circularity error is obtained with the piston diameter of 63 mm, inertia load of 12.5 kg, radius of 5 mm and feed rate of 50 mm/min as 0.345 mm. Circularity error increases with the increase of inertia load, radius and feed rate, and declines with the increase of piston diameter. Lastly, piston diameter has the greatest effect on the circularity error change and followed by radius, feed rate, piston diameter-radius, radius-feed rate, piston diameter-feed-rate, inertia load, piston diameter-inertia load, and inertia load-radius factors and interactions.
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    Mechanical properties of heat treated iron based compacts
    Çavdar, U; Ünlü, BS; Pinar, AM; Atik, E
    In this study, powder metal (PM) compacts were prepared by mixing iron powder with 1-6 wt.% ratio of Cu and 0.2-0.8 wt.% ratio of graphite. The 20 different PM compacts compositions were prepared with a 0.8 wt.% ratio of zinc striate as the lubricant. The dimension of compacts were 10 x 10 x 55 mm. All the compacts were pressed at 600 MPa and, sintered at 1120 degrees C for 30 min using a conventional sintering furnace and then boronizing, steaming and carbo-nitriding heat treatments were applied. The results of all compacts for the bending test, microstructure images and HV microhardness results were compared. As a result of the experiments, it was concluded that, the highest bending strength was obtained at carbo-nitrided samples, the highest surface hardness was measured at boronized samples and all these heat treatments increase the densities of iron based samples. (C) 2014 Elsevier Ltd. All rights reserved.
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    Optimization of Process Parameters with Minimum Surface Roughness in the Pocket Machining of AA5083 Aluminum Alloy via Taguchi Method
    Pinar, AM
    This paper aims at determining the effects of process parameters (cutting speed, feed rate, tool path pattern and depth of cut) on surface roughness and the factor levels with minimum surface roughness in pocket machining. The experiments conducted based on Taguchi's L27 orthogonal array are assessed with analysis of variance and signal-to-noise ratio. According to this, it is observed that surface roughness correlates negatively with cutting speed and positively with feed rate and cutting depth. Minimum surface roughness is predicted as 0.5413 mu m with the cutting speed of 300 m/min, feed rate of 150 mm/min, spiral tool path pattern and 1 mm depth of cut. Finally, confirmation tests verify that Taguchi method achieves the optimization of the system with sufficient accuracy at 95 % confidence level.
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    Modelling of Surface Roughness Performance of Coated Cemented Carbide Groove Cutting Tool Via Artificial Neural Networks
    Pinar, AM
    The objective of the presented study is to model the effects of cutting speed, feed rate and depth of cut on the surface roughness (roughness average, Ra) in the turning process carried out by the grooving cutting tool by using Artificial Neural Network (ANN). To realize this aim, twenty seven specimens are machined at the cutting speeds of 100, 140 and 180m/min, feed rates of 0.05, 0.15 and 0.25mm/rev, and cutting depth of 0.6, 1.3 and 2mm in wet conditions. Data from these experiments are used in the training of ANN. When we compare the experimental results with the ANN ones, it is observed that proposed method is applied with an error rate of 8.14% successfully.
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    Optimization of Surface Roughness Performance in The Turning of AISI 4140 Steel With Multi Directional Cutting Tool
    Pinar, AM; Firat, K
    Presented study discusses the turning of AISI 4140 steel with groove cutting tool at the rough machining conditions ( high feed rate and depth of cut). Experiments based on Taguchi's L8 orthogonal array at the different levels of cutting speed, chip breaker type and nose radius conducted. As a result of the analyses carried out at the confidence level of 95%, nose radius has the most significant effect on the roughness followed by chip breaker type and chip breaker type-nose radius interaction, and optimum roughness is obtained as 0,572 mu m. Furthermore, tool wear performances are observed for each experiment condition.
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    Comparison of Biomechanical Effects of Different Configurations of Kirschner Wires on the Epiphyseal Plate and Stability in a Salter-Harris Type 2 Distal Femoral Fracture Model
    Inal, S; Gok, K; Gok, A; Pinar, AM; Inal, C
    Background: We sought to investigate the different configurations of Kirschner wires used in distal femur Salter-Harris (SH) type 2 epiphyseal fracture for stabilization after reduction under axial, rotational, and bending forces and to define the biomechanical effects on the epiphyseal plate and the fracture line and decide which was more advantageous. Methods: The SH type 2 fracture was modeled using design software for four different configurations: cross, cross-parallel, parallel medial, and parallel lateral with two Kirschner wires, and computer-aided numerical analyses of the different configurations after reduction were performed using the finite element method. For each configuration, the mesh process, loading condition (axial, bending, and rotational), boundary conditions, and material models were applied in finite element software, and growth cartilage and von Mises stress values occurring around the Kirschner wire groove were calculated. Results: In growth cartilage, the stresses were highest in the parallel lateral configuration and lowest in the cross configuration. In Kirschner wires, the stresses were highest in the cross configuration and lowest in the cross-parallel and parallel lateral configurations. In the groove between the growth cartilage and the Kirschner wire interface, the stresses were highest in the parallel lateral configuration and lowest in the cross configuration. Conclusions: The results showed that the cross configuration is advantageous in fixation. In addition, in the SH type 2 epiphyseal fracture, we believe that the fixation shape should not be applied in the lateral configuration.