Browsing by Author "Durmuş H."
Now showing 1 - 20 of 27
Results Per Page
Sort Options
Item Determination of hardness of pre-aged AA 6063 aluminum alloy by means of artificial neural networks method(Association for Scientific Research, 2004) Durmuş H.; Ünlü B.S.; Meriç C.A lot of experiments must be conducted in order to find an appropriate technology for the calculation of strength of the materials, which wastes both man power and money. For this reason artificial neural networks (ANNs) have been used to search the optimum technology proper for pre-aged AA 6063 aluminum alloy. In this study, ANNs were used to compare experimental results and test data were used for teaching of the ANNs. This paper examines the changes in the hardness of AA 6063 alloys when heat treated at different pre-aging treatments. The alloy was solution treated for 1 hour at 525±3 °C and quenched in water. After quenching, samples were subjected to five different pre-aging times, 2 hours, 1 day, 3 days, 7 days. On the other hand, some specimens were not pre-aged. Artificial age temperatures were selected as 160 °C and 180 °C. The hardness values of these under-aged alloys were measured. When the pre-aging time was 7 days, the hardness values of the specimens increased. An excellent correlation was found between experimental hardness results and ANNs hardness results.Item Determination of friction coefficient at journal bearings by experimental and by means of artificial neural networks method(Association for Scientific Research, 2004) Ünlü B.S.; Durmuş H.; Meriç C.; Atik E.Knowing friction coefficient is important for determination of wear loss conditions at journal bearings. Tribological events that influence wear and its variations affect experimental results. In this study, friction coefficient at CuSn10 Bronze radial bearings has been determined by a new approach as experimental and artificial neural networks method. In experiments, effects of bearings have been examined at dry and lubricated conditions and at different loads and velocities.Item Tribological and mechanical properties of Al alloyed bearings(2009) Ünlü B.S.; Durmuş H.; Akgün S.Aluminum based alloys are widely used as journal bearing materials in tribological applications. Duralumines, AlMgSi are widely used as journal bearing materials for aluminum based alloys. These alloys provide properties expected from journal bearings. In this study, tribological and mechanical properties of these journal bearings manufactured from aluminum alloys were investigated. SAE 1050 steel shaft was used as counter abrader. Experiments were carried out in every 30 min for the total of 150 min by using radial journal bearing wear test rig. Wear resistance of Al alloyed bearings increased about 2-3 times and journal wear resistance increased about 2-8 times. The highest bearing wear rate occurred in pure Al bearings while the lowest bearing wear rate occurred in AlMgSi bearing. © 2009 Elsevier B.V. All rights reserved.Item Pin-on-disc characterization of 2xxx and 6xxx aluminium alloys aged by precipitation age hardening(2010) Meyveci A.; Karacan I.; Çaligülü U.; Durmuş H.In this study, wear behaviors of aged aluminium AA 2024 and AA 6063 alloys were investigated. AA 2024 and AA 6063 aluminium alloys were solution treated at two different temperatures of 490 and 520 °C. Then all samples were cooled to room temperature. After this process, the samples were aged at three different temperatures (140 °C, 180 °C and 220 °C) for five different periods of time (2, 4, 6, 8, 10). The microstructures of the aged samples were examined by optical microscope, SEM-EDS and X-ray analysis. The hardness values of the aged samples were measured by microhardness tests. Wear tests were carried out on the pin-on-disc model wear test apparatus under sliding velocity at 2 m s-1 speed, 400, 800, 1200 and 1600 m sliding distances for 10, 20 and 30 N variable loads. The mass-loss values of the aged samples were tested by wear tests. As a result of this study, the hardness of the second phase precipitated samples was found to be higher than that of the as-cast samples and it increased with increasing the solution temperature and aging periods. The study also revealed that the wear rate and friction coefficient can be decreased with increasing the solution temperatures and aging periods. Crown Copyright © 2009.Item A study of wear of aged aluminum alloys 2XXX and 6XXX within the manova statistical analysis(2011) Meyveci A.; Karacan Í.; FIrat E.H.; ÇalIgülü U.; Durmuş H.Statistically processed data on the microstructure and wear of aged aluminum alloys AA2024 and AA6063 are presented. Results of wear tests are analyzed using multidimensional analysis of variance (MANOVA) with 95% confidence interval for statistically significant deviations. It is shown that the temperature and the duration of the aging are statistically significant factors affecting wear of aluminum alloys 2XXX and 6XXX. © 2011 Springer Science+Business Media, Inc.Item Optimization of multi-process parameters according to the surface quality criteria in the end milling of the AA6013 aluminum alloy(2012) Durmuş H.In the study the effects of multi-process parameters on the surface roughness during the machining of the AA6013 aluminum alloy with non-coated cemented carbide milling cutters were investigated by using Taguchi's experimental design method. Experiments were conducted on the basis of Taguchi's L16 orthogonal array (OA) at different levels of the factors relating to the aging process, the cutting speed, the feed rate, the axial depth of a cut and the radial depth of a cut; then they were evaluated through the signal/noise ratio (S/N), ANOVA and the main effects' graphic. Accordingly, the lowest surface roughness was estimated to be 0.436 μm and, finally, Taguchi's method allowed the optimization of the system for the verification of the tests.Item Determination of tribological properties at CuSn10 alloy journal bearings by experimental and means of artificial neural networks method(2012) Ünlü B.S.; Durmuş H.; Meriç C.Purpose - It is important to know the friction coefficient and wear loss for determination of tribological conditions at journal bearings. Tribological events that influence wear and its variations affect experimental results. The purpose of this paper is to determine friction coefficient and wear loss at CuSn10 alloy radial bearings by a new approach. In experiments, effects of bearings have been examined at dry and lubricated conditions and at different loads and velocities. Design/methodology/approach - In this study, friction coefficient and wear losses of journal and bearing have been determined by a new approach with a radial journal bearing test rig and artificial neural networks (ANNs) method. The ANN typifies a learning technique that enables the hidden input-output relationship to be mapped accurately. Bronze-based materials have been used as bearing material. Effects of friction coefficient and wear losses have been examined at same load and velocity and at dry and lubricated conditions. Findings - The results obtained in ANN application are close to friction test results for dry and lubricated conditions. Therefore, by using trained ANN values, the intermediate results that were not obtained in the tests can be calculated. Experimental studies will be increased and research with ANN will be continued. Originality/value - By using trained ANN values, the intermediate results that were not obtained in the tests can be calculated. The training finished on 30 min whereas experimental study had continued day after day. Copyright © 2012 Emerald Group Publishing Limited. All rights reserved.Item 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.Item Effect of mill type on morphology of AA6013 aluminium powder(Universidade Federal do Rio de Janeiro, 2016) Uzun R.O.; Durmuş H.In conventional recycling method, metal chips are cast after pressing and melting in electric arc furnace. Material loss occurs during the recycling from liquid metal due to the several reasons. Direct recycling method which produces the aluminium powder from aluminium chips using mechanical mill can be an alternative to conventional recycling method. Thus material and energy losses, and labour cost will be reduced by direct recycling method without melting. In this study, the particle morphology of powder direct recycled from AA6013 aluminium alloy chips with cryogenic, disc and ball type grinders is investigated. Mechanical milling resulted flaky and irregular shaped AA6013 particles. It was ascertained that the chips did not break sufficiently in despite of the long duration milling mechanisms by ball mill. Cryogenic mill provides the energy required for milling mechanisms to act. Disc mill has the highest impact energy was determined. Consequently, efficiency of ball mill is lower than the efficiency of cryogenic and disc type mills. Shape factors of powders produced with ball and cryogenic mills were found greater than that of the powder produced by disc mill. Disc mill has the most efficient and effective impact energy which produces the smaller particles per minute, was determined. © 2016 Universidade Federal do Rio de Janeiro. All rights reserved.Item Cold metal transfer welding of AA1050 aluminum thin sheets(Universidade Federal do Rio de Janeiro, 2016) İrizalp A.O.; Durmuş H.; Yüksel N.; Türkmen İ.This study was aimed to investigate the welding parameters on mechanical behavior of 2 mm thick AA1050 sheet materials joined by cold metal transfer (CMT) method. Macro structural examination showed that decreasing heat input decreased the pore size in the weld metal. Tensile test was applied and failure occurred in heat affected zone of aluminum sheet metal. Maximum tensile strength was found in the sample with minimum heat input. Heat affected zone was observed explicitly in the sample produced with the maximum heat input. Decreasing joint gap affected the bending strength positively. Bending strength was found superior with maximum bonding line length. © 2016 Universidade Federal do Rio de Janeiro. All rights reserved.Item Consideration of cold metal transfer welding of AA5754 to galvanized steel from mechanical and microstructural aspects(Centro Nacional de Investigaciones Metalurgicas, 2018) Çömez N.; Durmuş H.In this study, overlap welding of AA5754 and galvanized steel sheets was carried out by cold metal transfer (CMT) method using ER4043 (AlSi5) filler wire. The effect of heat input on the formation of intermetallic compound (IMC) layer between steel and aluminum was investigated. Mechanical properties of the joints were determined by tensile and hardness tests and also applying nano indentation test to intermetallic layer. Chemical compositions of IMC were analyzed by EDX and the formation of Al7.2Fe1.8Si and Fe2Al5 phases was detected. Formation of Fe2Al5 phase was found detrimental for reliability of joint, although it’s superior mechanical strength. © 2018 CSIC.Item Wear performance of Fe-Cr-C-B hardfacing coatings: Dry sand/rubber wheel test and ball-on-disc test(Elsevier Ltd, 2018) Durmuş H.; Çömez N.; Gül C.; Yurddaşkal M.; Yurddaşkal M.Minimizing wear would ensure reduced loss of material, labor and time for numerous branches of industry. Hardfacing coating method is a promising application to overcome this loss. The purpose of the the hardfacing application is to support, repair or improve the surface that is susceptible to abrasion by forming hard phases. The present study was aimed to investigate the wear resistance of iron-based hardfacing coatings which were produced with Fe-Cr-C-B and Fe-Cr-C based filler wires, according to ball-on-disc and dry sand rubber wheel wear tests. During the open arc welding process powder compositions of 100% FeB and 40% FeB + 60% FeCr were transferred to the weld pool, in order to enrich the coating with boron and chromium. Increased FeB content ensured the formation of boride phases such as Fe2B, CrB2, B6Fe23, Cr5B3. Minimum wear loss was obtained in a sample which was coated with Fe-Cr-C-B based filler wire reinforced with 40% FeB + 60% FeCr powder. Formation of massive carbide/boride phases and a tough matrix protected by the high amount of secondary carbides increased the wear resistance. The outcomes showed that the wear resistance is not only correlated with hardness but also affected by the morphology of microstructural constituents. © 2018 Elsevier LtdItem An investigation into the wear behavior of aged Alumix321/SiC composites fabricated by hot pressing(CSIC Consejo Superior de Investigaciones Cientificas, 2019) Durmuş H.; Gül C.; Çömez N.; Yurddaşkal M.Aerospace or automobile industries need materials that have a combination of several features such as lightness, high strength, corrosion and wear resistance. With ceramic particulates reinforcement, the properties of aluminum alloys can be greatly improved. The aim of this study is to investigate the effect of precipitation age hardening and the mass percentage of SiC particles on hardness and wear resistance of the 6061 aluminum matrix composites produced by hot pressing. Composites were solution treated at 530 °C for 1.5 h and then artificially aged at 160 °C for 18 h. The ball-on-disc wear test was carried out under 2N load using an alumina ball as the counterpart. The density of the composites was calculated according to Archimedes principle. Porosity tended to increase with increasing SiC reinforcement. Hardness and wear resistance of composites were improved by SiC particles and aging. Maximum hardness and minimum wear loss was obtained heat treated sample that contains 20 wt.% SiC reinforcement. © 2019 CSIC. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License.Item Reliability Analysis of Brinell Hardness Results for Aged Alumix321/SiC Composites(Springer, 2019) Gül C.; Çömez N.; Çivi C.; Durmuş H.Aluminum/SiC composites are widely employed in the automotive industry. Aluminum composites can be produced by hot pressing which forms a final product with a low porosity level and a denser structure. Homogeneous distribution of reinforcement particles, the level of porosity, and heat treatment not only affect the mechanical properties of the composites but also the reliability of their mechanical test results. In this study, Brinell hardness test reliability analyses of the hot-pressed Alumix321/SiC composites were carried out. The effects of increasing SiC amount and aging treatment on the reliability of hardness test results were discussed. Reliability analysis revealed that the aging treatment and increasing amount of SiC reinforcement decreased the reliability of the hardness test results. The reason for this was researched and resulting cases were discussed. © 2019, The Indian Institute of Metals - IIM.Item Effect of Heat Input on the Microstructure, Strength and Corrosion Behavior of Sheets of Alloy AA6061 After Cold Metal Transfer Welding(Springer, 2019) Çömez N.; Durmuş H.The effect of the parameters of welding conducted by the method of cold metal transfer on the geometry of the welding pool, the ultimate tensile strength, and the corrosion rate of welded joints of sheets from aluminum alloy AA6061 is studied. The influence of the current, voltage, and heat input rate during welding on the properties of the welded joints is analyzed. The welding parameters providing maximum ultimate strength and high corrosion resistance of welded joints of alloy AA6061 are determined. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.Item Reliability evaluation of hardness test methods of hardfacing coatings with hypoeutectic and hypereutectic microstructures(University of Science and Technology Beijing, 2019) Çömez N.; Çivi C.; Durmuş H.Hardfacing coatings involve hard carbide/boride phases dispersed in a relatively soft steel matrix. For the hardness measurements of hardfacing coatings, depending on the micro structure, both the hardness test method and the applied load affect the hardness results; therefore, they affect the wear performance predictions of the coating. For this reason, the proper hardness test method should be determined according to the microstructure of the coating, and the reliability of the obtained hardness data should be established. This study aimed to determine the most suitable hardness test method for hypoeutectic and hypereutectic microstructures of hardfacing coatings by analyzing the reliability of Rockwell-C and Vickers hardness test results. Reliability analyses showed that Rockwell-C is not a suitable hardness test method for hypereutectic hardfacing coatings. Based on the relationship between wear resistance and hardness, Vickers hardness method was found more suitable for the considered materials. © 2019, University of Science and Technology Beijing and Springer-Verlag GmbH Germany, part of Springer Nature.Item Mechanical Properties and Corrosion Behavior of AA5754-AA6061 Dissimilar Aluminum Alloys Welded by Cold Metal Transfer(Springer New York LLC, 2019) Çömez N.; Durmuş H.The trend of using lightweight materials in the automotive industry brings along the necessity of dissimilar welding of aluminum alloys such as AA5754 and AA6061. Hybrid structures in automobiles are subjected not only to mechanical forces but also corrosive effects of the environment. In this study, cold metal transfer welding, which is suitable for welding thin sheets and dissimilar materials, was applied to join AA5754 to AA6061. It was aimed to investigate the effect of weld heat input on mechanical properties and corrosion rate measured by the Tafel extrapolation method in 3.5 wt.% NaCl solution at room temperature. The tensile strength of AA5754-AA6061 joints tended to reduce with increasing heat input. Corrosion test results showed that the increased heat input decreased the corrosion resistance and caused intergranular corrosion besides pitting corrosion. © 2019, ASM International.Item Corrosion behavior and mechanical properties of cold metal transfer welded dissimilar AA7075-AA5754 alloys; [不同种类 AA7075-AA5754 合金冷态金属转移焊的腐蚀行为和力学性能](Central South University of Technology, 2020) Çömez N.; Durmuş H.Cold metal transfer (CMT) welding is a brand-new arc welding technique which shows adequate results for welding of thin sheets and dissimilar materials. Corrosion behavior of dissimilar aluminum joints should be determined in terms of predicting the effect of welding process on the possible failures in their constructions caused by corrosive agents. The present study investigates the effect of heat input on mechanical properties and corrosion rate of AA5754-AA7075 joints welded by CMT using ER5356 filler wire. Pore formation was observed not only in the weld metal but also in the partially melted zone of AA7075 base metal due to the vaporization of zinc. Increased heat input caused over aging and zinc vaporization in AA7075 base metal, and grain coarsening in AA5754 base metal consequently decreased the tensile strength. The average tensile strength of AA7075-AA5754 joints varies between 235 and 240 MPa. The ductile fracture occurred at the AA5754 base metal side in all samples. Pitting was observed as the dominant corrosion mechanism. Corrosion resistance tended to increase with increasing heat input. Heat input values between 95 and 110 J/mm are recommended for the optimization of corrosion resistance and strength. © 2020, Central South University Press and Springer-Verlag GmbH Germany, part of Springer Nature.Item From metal chips to composite: Effect of age-hardening on mechanical and wear properties of al2 o3 reinforced aa7075 composites(International Institute for the Science of Sintering (IISS), 2020) Durmuş H.; Gül C.; Çömez N.; Uzun R.Aluminum metal matrix composites were used in various fields such as aircraft, underwater, automobile, aerospace. Several fabrication techniques were used for the production of these composites. Among the various methods, the powder metallurgy route provides dimensional accuracy and high production rates. In this paper, metal matrix composites that include 7075 aluminum alloy chips and Al2O3 particles were produced by using a hot pressing. The effect of reinforcement amount and T6 heat treatment on the mechanical and wear properties of the composites were investigated. Al2O3 particles were added by weight of 5, 10 and 15 % and the composites were produced by hot pressing. T6 heat treatment consisted of a solution treatment at 480 °C for 2 h and artificially aging process at 120 °C for 24 h. Wear resistance of the composites was determined by a ball-on-disc dry sliding wear test. Brinell Hardness of the composites tended to increase with the increasing Al2O3 reinforcement up to 10 wt.% and with T6 treating. Particle reinforcement improved the wear resistance up to 10 wt.% Al2O3. In addition, volumetric material loss tended to decrease after the aging process. © 2020 Authors.Item A Comparative Study On Deep Drawing Process And Autoform Simulations Of DX54D + Z And DX56D + Z Steels; [Dx54d + z ve dx56d + z çeliklerinin derin çekme işlemi ve autoform simülasyonları hakkında karşılaştırmalı bir çalışma](TUBITAK, 2021) Durmuş H.; Güneşgörmez G.; Çömez N.; Gül C.A Sheet Metal Forming (SMF) process, especially deep drawing, is one of the manufacturing processes that commonly used in the automotive industry. Compared with casting and forging, the SMF process has several advantages, including lesser weight materials and broader variations in shape that can be made. The most important of the problems in the SMF process is the wrinkling phenomenon and tearing of sheet products. The wrinkle and tear occurs because of the mechanical properties of the material, product geometry, and blank holder force. The finite element based Computer-Aided Engineering (CAE) program AutoForm Plus R7 used in this article was used for analysis. Solidworks software was used during mold design. AutoForm is a highly productive software that provides high accuracy and reliable results, specially developed for the sheet metal forming mold industry, especially for the automotive industry. With AutoForm, multiple analyses were made by computational calculations, even before the mold production started, and with the help of these analyses, the closest to perfect mold outputs were obtained. In addition, optimum drawbead geometry and springback effect were analysed. The most suitable material was selected for the deep drawing product. DX54D + Z and DX56D + Z from continuously hot-dip coated steel flat products selected as analysis materials. As a result, the simulation reports obtained from this study were compared with many results in the literature. It is concluded that DX56D + Z sheet material can be used in deep drawing products without negative consequences such as tearing, wrinkling and shrinkage marks. © 2021, TUBITAK. All rights reserved.