Yazar "Halkaci, Mehmet" seçeneğine göre listele

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    Comparison of Flow Curves of AA 5457-O Sheet Material Determined by Hydraulic Bulge and Tensile Tests at Warm Forming Temperatures
    (AMER SOC TESTING MATERIALS, 2016) Sukur, Emine Feyza; Turkoz, Mevlut; Dilmec, Murat; Halkaci, Huseyin Selcuk; Halkaci, Mehmet
    The deformation behavior of sheet materials changes according to temperature. It is possible that the formability of a material for different temperatures is investigated and the flow curves are obtained by using a hydraulic bulge test. Generally, biaxial stress state occurs in real forming processes. Flow curves can be derived from the hydraulic bulge test for the biaxial stress state, and the higher strain values can be achieved in comparison to the tensile test without extrapolation. Hydraulic bulge tests are preferred instead of tensile tests on account of presuming the problems can occur during the formation process of sheet material, being informed about the formability of material at the current pressure and temperature states, and obtaining flow curves to perform more accurate process simulations. In this study, the flow curves for the material AA5754-O were obtained using the warm bulge test and by considering the strain rates. The sections of the curves that can be used in simulation were identified, and these curves were comparatively investigated with respect to the curves obtained from the tensile test. In addition, case studies were performed in order to conduct more realisitic simulations using the results of the flow curves obtained from the bulge and tensile tests.
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    Design of Sheet Hydroforming Press Body
    (IEEE, 2017) Turkoz, Mevlut; Avci, Semih; Dilmec, Murat; Ozturk, Ekrem; Halkaci, Mehmet; Halkaci, H. Selcuk
    In this research, the body of a sheet hydroforming press, which can produce an industrial product, was designed and dimensioned. Initially, the required pressure and forces to produce the industrial product were determined by finite element analysis. Then, structural analysis of the press body was conducted by using these forces in Solidworks Premium simulation module. The strain gauges were bonded on various critical areas of the press body. The strains were measured for various loading conditions and compared with the analysis results. According to the results obtained, the strain values obtained from the analysis and measured experimentally are in good agreement with each other.
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    Design, Fabrication, and Experimental Validation of a Warm Hydroforming Test System
    (ASME, 2016) Turkoz, Mevlut; Halkacr, Huseyin Selcuk; Halkaci, Mehmet; Dilmec, Murat; Avci, Semih; Koc, Muammer
    In this study, a hydroforming system was designed, built, and experimentally validated to perform lab-scale warm hydromechanical deep drawing (WHDD) tests and small-scale industrial production with all necessary heating, cooling, control and sealing systems. This manuscript describes the detailed design and fabrication stages of a warm hydroforming test and production system for the first time. In addition, performance of each subsystem is validated through repeated production and/or test runs as well as through part quality measurements. The sealing at high temperatures, the proper insulation and isolation of the press frame from the tooling and synchronized control had to be overcome. Furthermore, in the designed system, the flange area can be heated up to 400 degrees C using induction heaters in the die and blank holders (BH), whereas the punch can be cooled down to temperatures of around 10 degrees C. Validation and performance tests were performed to characterize the capacity and limits of the system. As a result of these tests, the fluid pressure, the blank holder force (BHF), the punch position and speed were fine-tuned independent of each other and the desired temperature distribution on the sheet metal was obtained by the heating and cooling systems. Thus, an expanded optimal process window was obtained to enable all or either of increased production/test speed, reduced energy usage and time. Consequently, this study is expected to provide other researchers and manufacturers with a set of design and process guidelines to develop similar systems.
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    A Study on DOE Methods for Hydromechanical Deep Drawing Process Parameters
    (TRANS TECH PUBLICATIONS LTD, 2012) Halkaci, Mehmet; Halkaci, H. Selcuk; Turkoz, Mevlut; Daghan, Behcet
    Formability of sheet metals can be increased by Hydromechanical Deep Drawing (HDD) process. Formability of the deep drawn cups is generally assessed by Limiting Drawing Ratio (LDR) which is the ratio of the blank diameter to punch diameter. In order to increase LDR by HDD, process parameters of the HDD should be arranged properly. Arranging of the process parameters requires a great knowledge about the effects of the process parameters to certain performance criteria of the process. Determining of the effects of the process parameters by full factorial experiments is a hard duty. Hence certain statistical methods that decrease the number and the cost of the experiments and reduce the time should be used to find effective parameters and their appropriate levels. In this study orthogonal experimental array was applied and effective process parameters were determined by analyzing predicted data with Taguchi's robust parameter design method and ANOVA method. Then the results were compared with each other to evaluate differences between the methods. By using the appropriate levels of the parameters the LDR of AA 5754 aluminum alloy which uses in automotive industry intensely was determined.