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    Design, Fabrication and Performance Tests of a Double-sided Sheet Hydroforming Test System
    (Natl Inst Science Communication-Niscair, 2023) Urmamen, Mustafa Kemal; Atas, Gurkan; Dilmec, Murat; Turkoz, Mevlut; Ozturk, Osman; Halkaci, Huseyin Selcuk
    In this study, a double-sided sheet hydroforming (DSH) test system, which contains dies, sealing, pressure intensifiers, and a control unit, has been designed, built, and tested. The hydraulic numerical control system, which is currently used, has been modified as afour-axis where parameters are forming pressure, back pressure, punch position, and blank holder force. A hydromechanical deep drawing press has been modified in terms of die and sealing. New sealing components have been used to prevent leakage during the forming process because one side of the sheet is exposed to the forming pressure, and the other side is exposed to both the back pressure and the moving punch. Performance tests have been carried out to determine the limitations and capacity of the system. After the performance tests, it has been concluded that; the higher forming rates all along the process curve, the higher the pressure and force differences. However, the resultant error of the corresponding points has been only higher at the beginning of the process curve. In addition, the higher slopes in process curves have increased the pressure and force differences. A conical industrial part has been deformed by using hydromechanical deep drawing and DSH processes to test the performance of the DSH press. The wrinkling defect that occurred in previous hydroformed parts has been reduced remarkably by using back pressure in the DSH process. As a result, a double-sided sheet hydroforming test press has been successfully designed and manufactured. Finally, this study provides technical knowledge and can be used as a guideline for the design and performance evaluation of similar manufacturing systems.
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    Öğe
    Formability improvement in Ti-6Al-4 V sheet at room temperature by pulsating hydraulic bulging: experimental and numerical investigations
    (Springer London Ltd, 2023) Ozturk, Osman; Korkmaz, Habip G.; Atas, Gurkan; Aydin, Mevlut; Turkoz, Mevlut; Toros, Serkan; Dilmec, Murat
    Ti-6Al-4 V sheets possess limited formability at room temperature due to low ductility with almost no strain hardening. Pressure pulsation during hydroforming may bring significant improvement as an alternative to the widespread solution hot forming. However, much uncertainty exists on the deformation mechanism and effects of pulsating on difficult-to-form materials. In this study, the effect of pulsating pressure on the hydraulic bulge test was investigated to increase the limited formability of the Ti-6Al-4 V sheet at room temperature. Experimental results of thickness distribution and bulge height obtained from the bulge tests were compared with the finite element simulation results. The results show that the tests with pulsation allow a higher thickness reduction with a slightly more homogenous thickness distribution. Pulsation causes a delay in the material's failure resulting in a 15.4% increase in the dome height with a 17% increased burst pressure compared to monotonic loading. The underlying microstructural phenomena of increased formability were elaborated using dislocation estimations, fracture surface analysis, and hardness. Test results suggest that pulsation improves formability by 47% in terms of maximum elongation due to stress relaxation.