Yazar "Akata, H. Erol" seçeneğine göre listele

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    An approach for calculation of press loads in closed - die upsetting of gear blanks of gear pumps
    (Elsevier Sci Ltd, 2007) Altinbalik, Tahir; Akata, H. Erol; Can, Yilmaz
    Some results of an industrial research and development project aimed to develop the manufacturing technologies of gear pumps were presented. Gear blanks of gear pumps that have traditionally been produced by machining from round bars in an industrial company were closed-die forged as an alternative. A comparison method of mechanical properties of the manufacturing methods was published formerly. A classical method was applied to calculation of press loads in closed-die upsetting of gear blanks of gear pumps and results were compared with those of measured in the experimental part of the work. Commercially pure lead was used as test material. In addition to comparison of calculated and measured loads, contributions of the method applied on the manufacturing costs of gear blanks were also discussed in the study. (c) 2005 Elsevier Ltd. All rights reserved.
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    Characterization of mechanical properties in AISI 1040 parts welded by friction welding
    (Elsevier Science Inc, 2007) Sahin, Mumin; Akata, H. Erol; Gulmez, Turgut
    This study deals with the importance of welding in manufacturing methods. There are various welding methods that have been developed to obtain suitable joints in various applications. However, friction welding, which is an alternative manufacturing method, is one of the methods that has been widely used for many years. In the present study, an experimental friction welding setup, which is a continuous drive friction welding set-up, was used in the experiments. Firstly, optimum parameters were obtained to join parts having equal diameter: Secondly, the effects of welding parameters on welding strength were investigated. Later, the mechanical properties of joints were examined by using tensile tests, fatigue tests, notch-impact tests and hardness tests. Finally, the results obtained were shown and discussed. (C) 2006 Elsevier Inc. All rights reserved.
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    Effect of surface roughness on friction coefficients during upsetting processes for different materials
    (Elsevier Sci Ltd, 2007) Sahin, Mumin; Cetinarslan, Cem S.; Akata, H. Erol
    Presented study is focused on the investigation of the effect of the surface roughness on the frictional properties for different materials and conditions. Three types of steel, commercially pure aluminium and annealed CuZn40Pb2 brass were used as the test materials in the experimental part of the study. Ring compression test procedure was applied to the specimens using flat end upsetting dies. Dimensional changes of the specimens after the tests were measured in order to obtain the variations of the increments in the inner diameters versus upset ratios. Experimental results were placed into ring compression calibration curves for each of the material type and surface conditions. Roughness measurements were carried out using a digital roughness meter. Upsetting tests were carried out using a hydraulic press of 150 metric tons with 5 mm/s ram speed. (c) 2005 Elsevier Ltd. All rights reserved.
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    An experimental study on joining of severe plastic deformed aluminium materials with friction welding method
    (Elsevier Sci Ltd, 2008) Sahin, Mumin; Akata, H. Erol; Ozel, Kaan
    In this study, 5083 aluminium alloys, which were exposed to severe plastic deformation, were joined with friction welding method and the variation in mechanical properties of the joints was experimentally investigated. Severe plastic deformation methods can be classified as equal channel angular pressing (ECAP) (in other words, equal cross section lateral extrusion-ECSLE) and cyclic extrusion-compression. Aluminum alloy as test material 5083 and square cross-sectional equal channel angular pressing die for severe plastic deformation were used in the study. Firstly 5083 alloys, as purchased, were joined with friction welding method. The optimum parameters for friction time, upset time, friction pressure and upset pressure, which are necessary for welding, were obtained. Afterwards, 5083 aluminium materials as purchased were prepared as square cross-section and then I-pass severe plastic deformation was applied to specimen by equal channel angular pressing die. The obtained parts as square form were prepared as cylindrical form by machining and then the parts were joined by continuous drive friction welding equipment that was designed and produced in laboratory conditions before. Later, the tensile strengths of the parts, obtained at optimum conditions, were compared with those of the joined parts as purchased form. Then, hardness variations and microstructures of joints were examined. Finally, the obtained results were commented on. (C) 2006 Elsevier Ltd. All rights reserved.
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    An investigation into reutilizing of waste materials using friction welding and upset manufacturing methods
    (Emerald Group Publishing Limited, 2007) Akata, H. Erol; Sahin, Mumin; Ipekci, M. Turan
    Purpose - The present study seeks to examine the possibilities of combined usage of friction welding and plastic forming in recycling of bar-shaped waste materials. Design/methodology/approach - if the waste materials can be reproduced using various manufacturing methods without melting, their economic values could be increased economically. For this reason, using a combination of friction welding and plastic forming was chosen as an alternative recycling method. Upsetting was chosen as the plastic forming method due to its ease of application. Findings - In the present study, dimensional changes, hardness variations in heat affected zone (HAZ), variations of torsion and tensile strengths with upsetting ratio of specimens were examined. Hardness values of test material are raised to higher levels within the HAZ by the local hardening. The maximum shear stress in torsion and the tensile strengths of specimens are closely harmonious with hardness values of test material. Research limitations/implications - Although it was observed in general that the increasing upsetting ratio increased the torsion and tensile strengths, experimental study must be improved and extended in order to obtain more precise results. Practical implications - It can be concluded that combined usage of just welded and additional cold deformation can be considered as an alternative recycling method owing to obtained positive results. Originality/value - This paper helps individuals reutilize waste materials because of the small lengths of the bars. Furthermore, it can be observed that the combination of friction welding and plastic|forming produces savings in the material and the cost in this study.
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    On properties at interfaces of friction welded near-nanostructured Al 5083 alloys
    (Springer London Ltd, 2012) Sahin, Mumin; Balasubramanian, N.; Misirli, Cenk; Akata, H. Erol; Can, Yilmaz; Ozel, Kaan
    Equal-channel angular pressing is a material processing method that allows very high strains to be imposed, which leads to extreme work hardening and micro-structural refinement, with minimal change of external sample dimensions. It offers possibilities of good mechanical properties, such as high strength and ductility, while allowing flexibility of choice of alloy composition for better corrosion behavior, lower materials costs, and so on. This study characterizes for the first time the microstructure and properties of aluminum friction welded after severe plastic deformation via the equal-channel angular pressing method. In this study, 5,083 aluminum alloys, which were exposed to severe plastic deformation using square cross-sectional equal-channel angular pressing die, were joined with friction welding method. It was found that tensile and fatigue strengths of severe plastic deformed and welded specimens were higher than those of the purchased specimens. Hardness values were also consistent with the strength results. However, the refining of grain size as shown from microstructures results in a significant increase in hardness and mechanical properties.