Browsing by Author "Atik, E"

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    Mechanical Properties and Hardness Results of the Medium Frequency Induction Sintered Iron Based Powder Metal Bushings
    Çavdar, U; Atik, E; Ataç, A
    In this study; iron based powder metal (PM) bushing compacts were sintered via medium frequency induction heating system. Iron based powders were mixed with 2 wt.% copper (Cu), 0.3 wt.% carbon (C) and 1 wt.% zinc stearat (Zn-st) via V-Type mixer. PM compacts were sintered by 2 different sintering processes. One of them was conventional sintering method other was medium frequency induction sintering method. In conventional sintering process, PM bushing compacts were sintered under inert environmental at 1120 degrees C for 30 minutes. In medium frequency induction sintering process, PM bushing compacts were sintered between 30-50 kHz frequency (Medium frequency) at 2 kW, 1120 degrees C for 1 or 3 minutes under atmospheric environmental. Mechanical properties, densities and micro hardness' were investigated for all sintered processes. SEM and micro structural images were taken from polished broken surface of the sintered PM bushing compacts. 3 minutes induction sintered compacts were reached the compressive strength, microhardness and density values of the conventional sintered PM bushing compact.
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    Quenching and tempering of 51CrV4 (SAE-AISI 6150) steel via medium and low frequency induction
    Civi, C; Yurddaskal, M; Atik, E; Celik, E
    Mechanical and microstructural properties of quenched steel are directly related to tempering time and temperature. In many applications, conventionally quenched and tempered steel is widely used for acquiring high strength and toughness. The present study was carried out to investigate the variation in mechanical properties, observation of diminished energy consumption and evaluation of the microstructural properties in SAE-AISI 6150 steel components by induction heating, compared with those of steel tempered by conventional method. Induction quenched and tempered steel provides a shorter process time, less energy consumption and improved mechanical properties through the inhibition of grain growth. In this study, quenching and tempering processes were carried out on medium and low frequency induction units and by using a conventional electrical resistance furnace for the sake of comparison. It was observed that cementite particles began changing their shape from spherical to fine-grained in the induction tempered samples. The sample tempered by low frequency induction manifests superior mechanical properties and offers a potential advantage for significant cost savings.
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    The effect of surface roughness and carburized depth on wear resistance in 16MnCr5 case hardening steel
    Baykara, C; Atik, E
    Purpose - Today, wear and tear is a metaphor whose cost cannot be ignored by real sector. For this reason, many sectoral and academic studies are carried out to minimize the wear effect. This study aims to create a perspective against wear problems for the automotive industry as well. Design/methodology/approach - The 16MnC5 material, which is used as the U-joint material in the powertrain of the automotive industry, was subjected to heat treatment such as normalization and carburization at certain temperatures and duration. By subjecting the resulting carbide thickness to the abrasion process, the maximum effective heat treatment parameters against wear were determined. Findings - It has been determined that the ideal cementation condition for 16MnCr5 steel to be used in the wear system is carburized samples at 900 degrees C for 3.5 h with a hardness depth of 1.04 mm. Originality/value - The variation in which the surface hardness thickness and surface roughness obtained by different heat treatment variations of the U-joint part, which is one of the cardan shaft components that provide power transmission of heavy commercial vehicles, show the best wear resistance, were investigated. As a result of this study, the study is to prevent the waste of limited materials in the world and to reduce the repair and maintenance costs of commercial vehicles.
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    Determination of hardness of AA 2024 aluminium alloy under ageing conditions by means of artificial neural networks method
    Atik, E; Meric, C; Karlik, B
    As known, 2XXX and 7XXX Aluminium wrought alloys can have high strength values by means of precipitation hardening heat treatment. Determination of the precipitation hardening conditions, which can give the most suitable strength values of an alloy, requires numerous tests. But the results of this process which require long time and high cost can be obtained in a shorter time and at a lower cost with less data by means of Artificial Neural Networks method. Since this method is used, less number of experiments and therefore less data are needed. Then other values are found by means of Artificial Neural Networks (ANN) method. This paper, presents the feed forward ANN to determine hardness of alloy for different temperatures. For this purpose, a classic Back-Propagation Algorithm was used that is structure as 1:2:4.
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    Tribological Behaviors of Polymer-based Particle-reinforced PTFE Composite Bearings
    Ünlü, BS; Uzkut, M; Atik, E
    In this study, tribological behaviors of polymer-based particle-reinforced PTFE bearings have been investigated and evaluated. Tribological properties of these particle-reinforced PTFE composite bearings have improved two- or three-fold.
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    Tribological behaviors of polymer based journal bearings manufactured from particle reinforced bakelite composites
    Ünlü, BS; Atik, E; Yilmaz, SS
    Polymer based materials are widely used do to their good corrosion resistance, self lubrication, and wear resistance properties at low speeds, but are not suitable for lubrication in journal bearings. High performance engineering polymers offer desired properties for journal bearings and give good tribological results. In this study, tribological behaviors of polymer based composite bearings manufactured from particle reinforced bakelite have been investigated and evaluated. Reinforcement significantly improved wear resistance of bronze-bakelite composite bearings. (C) 2009 Published by Elsevier Ltd.
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    Investigation of Conventional- and Induction-Sintered Iron and Iron-Based Powder Metal Compacts
    Çavdar, U; Atik, E
    Induction sintering was developed as an alternative method to conventional sintering to sinter iron-based powder metal (PM) compacts. Several compositions of compact such as pure iron, 3 wt.% copper mixed iron, or 3 wt.% bronze mixed iron were sintered by using induction sintering machines with 12 kW power and 30 kHz frequency. The mechanical properties, microstructural properties, densities, and microhardness values were investigated for both processes. Iron-based PM compacts sintered at 1120A degrees C by induction in 8.33 min (500 s) were found to be similar to those sintered conventionally in 30 min. The results were compared with the experimental studies.
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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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    Investigation of tribological properties of boronised pure Cu journal bearings
    Ünlü, BS; Atik, E
    Cu based materials are widely used as journal bearings. These materials have a good tribological performance in journal bearings. Pure copper is not generally used due to its low mechanical and wear properties. It is generally used as alloys. In this study, tribological properties of copper bearings manufactured from pure copper were investigated by boronising at 950 degrees C. The SAE 1050 steel shaft was used as counter abrader. Experiments were carried out at 20 N load and 1500 rev min(-1) speed every 30 min for 2.5 h using radial journal bearing wear test rig. As a result, boronising increased wear resistance.
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    Tribological properties of journal bearings manufactured from particle reinforced Al composites
    Ünlü, BS; Atik, E
    In this study, journal bearings were manufactured from composite structures by casting method reinforcing 3% (Al2O3 and SiC) and (3% Al2O3 + 3% SiC) into pure Al. Tribological properties of these bearings were investigated by wear experiments at lubricated conditions under 20 N load and 1500 rpm on the radial journal bearing wear test rig. Effects of these composites on wear properties were investigated. Consequently, tribological properties of these particle reinforced composite bearings have significantly improved. In addition, particle reinforced Al composites were used to produce journal bearing. (C) 2008 Elsevier Ltd. All rights reserved.
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    Experimental microhardness for AA 1030, Cu, CuSn7, CuZn30 and 6114 alloys and a correlation with the Hall-Petch relation
    Meriç, C; Atik, E; Engez, T
    In this experimental study, the strip-formed specimens made from aluminum alloy 1030, pure Cu, CuSn7, CuZn30, and low-carbon steel 6114 were cold worked to different ratios. To determine the microhardness values of the materials, microhardness tests were applied. The grain sizes of the materials were determined by the Heyn method, using a metal microscope. The hardness of materials, H, is dependent on the grain diameter, d, in a way similar to the yield stress in the Hall-Fetch relation H = H-0 + K(H)d(-1/2), where H-0 and K-H are constants. The microhardness of the materials was found, with reasonable accuracy, to vary with grain size according to the Hall-Fetch equation. (C) 2000 Elsevier Science Ltd.
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    Investigation of tribological properties of boronized Fe-based SAE 1020 and TS-DDK 40 journal bearings at high loads
    Ünlü, BS; Atik, E
    In practice, ferrous based materials are not used because they show similar properties to shaft material and are known to cause adhesive wear in journal bearings. With boronizing process, adhesive wear can significantly be decreased. In this study, boronizing has been applied to some ferrous based (SAE 1020, TS-DDK 40) journal bearings. Wear experiments were done on SAE 1050 steel shaft as counter abrader with 100 N loads, and 1500 rpm for 5 h by using a radial journal bearing test rig. Boronizing treatment increased wear resistance of SAE 1020, TS-DDK 40 about 10-25, and 5-7 times respectively. (C) 2009 Elsevier Ltd. All rights reserved.
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    Magnetic-Thermal Analysis and Rapid Consolidation of FE-3 wt.% CU Powder Metal Compacts Sintered by Medium-Frequency Induction-Heated System
    Cavdar, U; Atik, E; Akgul, MB
    In this paper, the results of numerical and experimental studies concerning the effect of mediumfrequency induction sintering of Fe-3 wt.% Cu powder metal (PM) compacts are discussed. Several sintering durations from 30 to 180 sec are studied. The mixed powders are compacted at 600 MPa and sintered by medium-frequency induction system (30-50 kHz frequency and 12 kW power). Magnetic and thermal analysis, mechanical properties, and densities of copper-iron PM compacts are presented.
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    EFFECT OF THE COPPER AMOUNT IN IRON-BASED POWDER-METAL COMPACTS
    Çavdar, U; Ünlü, BS; Atik, E
    In this study, iron-based powder-metal (PM) compacts were sintered using a medium-frequency induction-heating system. The effects of copper amounts on mechanical properties were investigated. Iron-based powders were mixed with mass fractions w = 1 % to 6 % copper (Cu) and 0.8 % zinc stearate in a V-type mixer. During the sintering process, PM compacts were sintered at a frequency of 30-50 kHz (medium frequency), at 12 kW and 1120 degrees C for 400 s in an atmospheric environment. Mechanical properties, microstructural properties, densities and microhardness values were investigated for the sintered material. The highest mechanical properties were obtained for the iron-based PM compacts including 3 % Cu.
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    Tribological properties of polymer-based journal bearings
    Ünlüe, BS; Atik, E; Köksal, NS
    Polymer-based materials are widely used due to their good corrosion resistance, self lubrication, and wear resistance properties at low speeds and but are not suitable for lubrication in journal bearings. High performance engineering polymers ensure desired properties for journal bearings and give good tribological results. In this study, tribological behaviors of polymer-based PE, PA, POM, PTFE, and Bakelite bearings have been investigated and evaluated. As a result, the highest wear resistance has occurred in PA and POM bearings. (C) 2008 Published by Elsevier Ltd.
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    Evaluation of effect of alloy elements in copper based CuSn10 and CuZn30 bearings on tribological and mechanical properties
    Ünlü, BS; Atik, E
    Brass and especially bronze in copper based alloys are widely used as journal bearing material. Pure copper materials are not used as journal bearing material due to their low mechanical and hardness properties. These materials having acceptable tribological and mechanical performance give satisfactory results in journal bearings. In this study, tribological and mechanical properties of journal bearings manufactured from copper based CuSn10 bronze and CuZn30 brass were investigated. Moreover, the effect of alloy elements of Cu, Sn and Zn on tribological and mechanical properties of journal bearings was evaluated. SAE 1050 steel shaft (journal) was used as counter abrader. Wear experiments were carried out at 20 N loads, 1500 rpm for 2.5 h by using radial journal bearing wear test rig. (C) 2009 Elsevier B.V. All rights reserved.
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    Mechanical properties and wear strengths in aluminium-alumina composites
    Atik, E
    In this study, after producing metal matrix composite materials reinforced with ceramic particles by adding hard Al2O3 particles into a selected ageable aluminum alloy, the wear strengths were investigated. Composites of aluminum alloys containing 2 to 10 wt of Al2O3 particles in the size range of 23.4 to 108 mu m were prepared by adding alumina particles to a partially-solid vigorously-agitated matrix alloy. For a given tribologic system, the sizes and ratios of optimum particles were determined from the point of the wear strengths of these materials, of which the wear strengths greatly increased according to the matrix materials. Alumina particles were subjected to preheating at 500 degrees C for 8 hours. Particles were added into the alumina alloy heated up to semi-solid/ semi-liquid phase interval in an argon medium by using a mixer. Then furnace temperature was raised up to 800 degrees C step by step. Later the composite materials were die cast and solidified and aged. The behavior of the composites was studied by using a pin-on-disk type machine. The largest wear strengths were obtained at an average particle size of 76.5 mu m and percentage of 4% wt Al2O3. Increase in the wear strength of the composites was obtained as 3.85 times the wear strength of the matrix material.
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    Effect of aging on abrasive wear of deformable aluminum alloy AA6351
    Meriç, C; Atik, E; Kaça, H
    Special features of abrasive wear of deformable aluminum alloy AA6351 are studied as a function of aging conditions and modes of friction tests. After aging in different modes the specimens are tested for wear in a special installation by the method of brad against disk with the use of abrasives with different grain sizes. The effects of different speeds of sliding and loads on the wear resistance and surface roughness are studied.
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    Effect of loading capacity (pressure-velocity) to tribological properties of CuSn10 bearings
    Ünlüe, BS; Atik, E; Meriç, C
    Bronze is widely used as a journal bearing material for copper-based alloys. These alloys ensure that journal bearings possess the expected properties. These materials that possess tribological properties give good results at journal bearings. In this study, friction and wear properties of journal bearings manufactured by CuSn10 bronze and the effect of p.v. (pressure-velocity) parameter have been examined and compared. SAE 1050 steel shaft has been used as counter abrader. Experiments have been carried out for p. v. values of 0.0125, 0.025 and 0.05 (N/mm s) and for every half an hour totalling to 2.5 h by using radial journal bearing wear test rig. As a result, depending on p.v. values, high friction coefficient and weight loss have been obtained under dry condition more than those obtained under lubricated condition. (c) 2006 Elsevier Ltd. All rights reserved.