Browsing by Publisher "Institute of Metals Technology"

Now showing 1 - 11 of 11
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    Effect of the copper amount in iron-based powder-metal compacts
    (Institute of Metals Technology, 2014) Çavdar U.; Ünlü B.S.; Atỳk 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 °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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    Investigation of induction and classical-sintering effects on powder-metal parts with the finite-element method
    (Institute of Metals Technology, 2014) Akpinar G.; Çivi C.; Atik E.
    Induction sintering provides large time and energy savings because the components heat up rapidly and the sintering time is lower than in classical sintering in a furnace. Therefore, induction sintering is an important alternative to classical sintering. In this study, mechanical properties of induction-sintered Fe-based components including Cu and carbon (graphite) were compared with those sintered in a classical furnace. For this purpose, microstructure photographs of both samples were taken. A tensile analysis of the sintered powder-metal samples was carried out with the finite-element method, and the micro-stress values were found to change depending on the amount and distribution of the porosity.
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    Finite element modelling of submerged arc welding process for a symmetric T-beam
    (Institute of Metals Technology, 2014) Culha O.
    Metallurgical welding joints are extensively used in the fabrication industry, including ships, offshore structures, steel bridges and pressure vessels. The merits of such welded structures include a high joint efficiency, water and air tightness, and low fabrication costs. However, residual stresses and distortions can occur near the weld bead due to localized heatin by the welding process and subsequent rapid cooling. This paper is focused on deriving a simulation solution to predict the design parameters, such as the temperature-stress distribution,the approximate gradient and the nodal displacement on the plates during the process of submerged arc welding (SAW). During the construction of an AH 36 quality T-beam profile using the SAWprocess, thermal residual stress and distortion occurs due to heat fusion from the source to the joint part of the symmetric T-beam. The value of the design parameter is achieved by performing a thermal elasto-plastic analysis using finite-element techniques. Furthermore, this investigation provides an available process analysis to enhance the fabrication process of welded structures.
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    Wear behavior of Al/SiC/graphite and Al/FeB/graphite hybrid composites
    (Institute of Metals Technology, 2014) Şahin S.; Yüksel N.; Durmuş H.; Irizalp S.G.
    Silicon carbide is often the preferred reinforcement in the production of aluminium-powder composites. In this study, aluminium composites were produced with 10 % and 20 % silicon-carbide and ferroboron reinforcements and (0, 0.5, 1 and 1.5) % graphite additions using powder metallurgy. The effects of the reinforcement type, the amount and the graphite content on the wear resistance were investigated. When compared with the unreinforced aluminium sample, it was clear that the increasing reinforcement increased the wear resistance. It was determined that the increasing graphite content negatively affects the wear resistance. The sample including 20 % ferroboron and 0 % graphite showed the minimum wear rate.
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    Effect of preheating on mechanical properties in induction sintering of metal-powder material Fe and w(Cu) = 3 %
    (Institute of Metals Technology, 2015) Akpinar G.; Atik E.
    In this study, the sintering process of iron-based powder-metal parts through induction and in a classic resistance furnace was analyzed experimentally and theoretically. Within the scope of the study, the Högenas ASC 100.29 iron powder containing mass fractions w(Cu) = 3%, 0.5% graphite and, as a lubricant, 0.8% Kenolub was used. The effects of preheating, sintering time, conveyor-belt speed and gradual cooling on the sintering with induction, and the effects of the sintering parameters on the mechanical properties of the samples were analyzed experimentally and numerically. In the study, preheating with the induction adjustable at a low or mid (2.5-5kHz) frequency was tested. By means of applying preheating and sintering in an atmosphere of argon gas, the thermal shock on the samples was blocked and superior physical and mechanical properties were achieved.
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    Prediction of the elastic moduli of chicken-feather-reinforced pla and a comparison with experimental results
    (Institute of Metals Technology, 2016) Özmen U.; Baba B.O.
    The purpose of this study is to obtain the elastic moduli, the key material property, of random discontinuous fiber composites with experiments and micromechanical models and to compare them. The proposed study makes it possible to assess the elastic moduli of chicken-feather fiber (CFF)/PLA green composites with different CFF mass fractions and to determine the feasibility of the micromechanical models for the CFF/PLA composites. For this purpose, initially, CFF/PLA composites including 2, 5 or 10 % chicken-feather mass fractions were extruded and standard tensile specimens for ISO 527 were formed with the injection-molding method. Tensile tests were carried out in accordance with the standards and the elastic moduli were calculated using the stress-strain curve. Then, using six different micromechanical models, the elastic moduli of the CFF/PLA composites with different mass fractions were calculated and compared with the experimental results. The results of the experiments and the models indicated that the presence of chicken feather increased the elastic moduli of all the composites in comparison with the pure PLA. According to the experimental data, the maximum increase in the elastic moduli of the composites with the presence of CFF was found to be 5.4 %. The maximum error in the prediction is about 16.8 % for the composite with a chicken-feather rate of 10 % when Manera's model is used. Among the micromechanical models, the ones that gave more converging results for the prediction of the elastic moduli of the CFF/PLA composites are Pan's 2-D, IROM (the inverse rule of mixtures), Nielsen-Chen and Halpin-Tsai models. A comparison of the results of these six models shows that the maximum deviation (the percentage error in prediction) is the smallest (1.4 %) for the Nielsen-Chen model. Therefore, the Nielsen-Chen model is the most appropriate model for the prediction of the elastic moduli of the CFF/PLA composites.
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    Effects of cutting parameters and tool-path strategies on tool acceleration in ball-end milling
    (Institute of Metals Technology, 2017) Gök A.; Gök K.; Bilgin M.B.; Alkan M.A.
    The determination of the cutting-parameter values that cause increases in vibration values is important to minimize the errors that can occur. Thus, the first aim of this study was to investigate the optimum cutting-parameter values and tool-path strategies in ball-end milling of the EN X40CrMoV5-1 tool steel with three coated cutters using the Taguchi method. The parameters taken into consideration are the cutting speed, feed rate, step over and tool-path strategies. The second aim of the study, a model for the tool acceleration as a function of the cutting parameters, was obtained using the response-surface methodology (RSM). As a result, the most effective parameter within the selected cutting parameters and cutting strategies for both inclined surfaces and different coatings was the step over. In terms of tool coatings, the most deteriorating coating for the tool acceleration on both inclined surfaces was the TiC coating. In addition, the response-surface methodology is employed to predict the tool-vibration values depending on the cutting parameters and tool-path strategy. The model generated gives highly accurate results.
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    Investigation of the geometrical accuracy and thickness distribution using 3D laser scanning of AA2024-T3 sheets formed by SPIF
    (Institute of Metals Technology, 2017) Bayram H.; Köksal N.S.
    Incremental sheet forming (ISF) is developed in order to meet the increasing demand for sheet metal forming and because it is a more economical method. First of all, this method gains attention become it is a die-less method. Furthermore, process flexibility and higher formability are other advantages of this method. In this study, AA2024-T3 sheets with a determined geometry and parameters were formed using the ISF method. Among the forming process parameters, tool path, step size and lubrication parameters were changed. The tool diameter, feed rate, spindle speed, angle of the wall and the tool coating parameters were kept constant. The thickness distributions and geometrical accuracy of the processed samples with the three-dimensional laser scanning method were examined accurately. It is clear from the results that the tool path that spirals and always keeps in touch is more successful than the tool path that makes it an incremental process. ISF is preferable to die production for limited production runs because it is more economic and the processing time is short.
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    Simulation-aided investigation of the effect of a pre-forming process on the initiation of cracks, the required forging forces and material flowlines for mining ground support clamps' manufacture using the hot-forging technique
    (Institute of Metals Technology, 2018) Kilerci I.; Culha O.
    In this study, the influence of the number of forging stages on the crack formation and forging forces in the hot-forging process for mining support clamps that were produced from 31Mn4 material was investigated. In this context, a single-stage process has been considered and a multiple-stage forging process that included a pre-forming stage was fictionalized with the aim of preventing crack formation by obtaining crack-formation zones. It is aimed to improve the toughness properties of the final product by ensuring that the material flow lines are obtained in accordance with the product geometry as well as preventing the formation of cracks by the forging process design, including the preforming step of the mining support clamp. Designed dies and workpieces were simulated using the finite-volume method. According to the simulation results of forging process, the stress and strain variation of materials is obtained as max. 229 MPa and 3.969 MPa. Damage analysis of the sample with effective stress and strain is exposed as 0.438-1.0 flash surface of material. The increase in the forming step decreased the forging forces per step and the crack formation was prevented and the material flowlines can be arranged in accordance with the product geometry in the presence of the preforming stage in the hot-forging process and that this regulation has a reducing effect on the forging forces. The material flowlines of the samples obtained from real production were examined and validation of the simulations and actual production was provided. © Institute of Metals and Technology, Ljubljana, Slovenia.
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    Fabrication And Characterization Of Nanoclay-Reinforced Thermoplastic Composite Films; [Izdelava In Karakterizacija Nanogline, Oja^Ane S Termoplasti^Nimi Kompozitnimi Filmi]
    (Institute of Metals Technology, 2019) Erba S.Ç.; Baştürk S.B.
    A number of nanoclay/poly(methyl methacrylate) (PMMA) composite films were prepared with three different clay concentrations (0.5 %, 1 % and 2 % (w/%)) via a solution-casting process. The nanoclay was modified by applying different compatibilization techniques: mere silane surface treatment and surfactant application with the addition of a silane agent. The interlayer distances of the clay galleries were determined using X-ray diffraction (XRD) and the modifications were verified with Fourier-transform infrared spectroscopy (FTIR) analysis. The dynamic mechanical analyses (DMA) were performed to clarify the viscoelastic properties of the produced films. Morphological characterizations were carried out with a scanning electron microscope (SEM). The neat clay/PMMA composites and pure PMMA film were also used to compare the effects of the compatibilization methods. The silane-modified clay/PMMA composites exhibited the best performance, as compared to neat PMMA, by considering the storage modulus (17.7 % increase) and the glass-transition temperature (20 % increase). However, in terms of the dynamic mechanical properties, the joint implementation of these two modification techniques did not satisfy the expectations, probably due to the excess modifier and the plasticizing effect. © 2019 Materials and technology.; Avtorji so s tako imenovanim raztopno-ulivnim procesom pripravili {tevilne kompozitne filme (tanke prevleke) na osnovi nanogline/polimetil metakrilata (PMMA) s tremi razli~nimi koncentracijami gline (0,5, 1 in 2 masnih dele`ev). Nanoglino so modificirali z razli~nimi kompatibilizacijskimi tehnikami: s povr{insko obdelavo s silanom (SiH4) ter z aplikacijo povr{insko aktivne snovi z dodatkom za tvorbo silana. Razdalje med galerijami plasti gline so dolo~ili z rentgensko difrakcijo (XRD) in modifikacije so verificirali z infrarde~o spektroskopijo s Fourierjevo transformacijo (FTIR). Dinami~ne mehanske analize (DMA) so izvedli, da bi razjasnili viskoelasti~ne lastnosti izdelanih filmov. Morfolo{ke lastnosti filmov pa so okarakterizirali z vrsti~nim elektronskim mikroskopom (SEM). Med seboj so primerjali izdelane kompozite glina/PMMA in ~isti PMMA ter s tem ugotavljali u~inkovitost kompatibilizacijskih metod. S silanom modificirani kompoziti glina/PMMA ka`ejo bolj{e lastnosti v primerjavi s ~istim PMMA; meritev modula shranjene energije je pokazala 17,7 % izbolj{anje in temperatura prehoda v steklasto stanje se je povi{ala za 20 %. Vendar pa implementacija obeh tehnik modifikacije z vidika dinami~nih lastnosti ni izpolnila pri~akovanj, verjetno zaradi prebitka modifikatorja in u~inka plastificiranja. © 2019 Materials and technology.
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    Effects Of Air-Cooling-Hole Geometries On A Low-Pressure Die-Casting Process; [Vpliv Geometrije Kanalov Za Zračno Hlajenje Na Proces Nizko Tlačnega Litja]
    (Institute of Metals Technology, 2021) Pehlivanoglu U.; Yagci T.; Culha O.
    A significant precondition for the production of high-quality castings is keeping an optimum temperature of the respective parts of the die cavity surface. This temperature depends on the temperature of the material, the quantity of metal, the method of cooling the casting die, the thermal conductivity of the die material, and the time during which the casting remains in the die. In addition, the cooling characteristics of alloy steel dies, used in the production of aluminum-alloy wheels with the low pressure die casting (LPDC) method, have critical effects on the mechanical and metallurgical properties of the product. Ducted air coolers are widely used for the cooling of these alloy steel dies. However, the geometrical designs of the air-cooling holes are limited. In this study, we define the effects of the geometry of the cooling holes on the cooling power of the die, the efficiency of the air consumption with the Full Factorial Experimental Design method and to determine the optimum values for LPDC. Pilot production has been carried out on an industrial scale to verify the data obtained by experimental design. The experimental and real data were compared based on the values of the yield strength and the secondary dendrite arm spacing in the microstructure. © 2021, Materiali in Tehnologije. All Rights Reserved