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    An Experimental Investigation of the Lubrication Effects on Formability In Warm Deep Drawing
    (Gazi Univ, 2016) Sen, Nuri; Kurgan, Naci; Karaagac, Ibrahim; Uluer, Onuralp
    The lubrication reduces to effects of friction forces that it is between die and blank holder in deep drawing process. The affecting factors to friction forces are material, surface quality of die and blank holder, temperature, blank holder force and lubrication properties. In this study, the effects of lubricant type on drawing ratio (DR) and forming force have been investigated experimentally. Graphite spray and composition of graphite spray-Teflon (PTFE) materials were used as lubricant materials. Compared with the use of spray, in case of using graphite and Teflon spray composition as lubrication type, it was observed that friction force was decreased. As a result of this decrease, the forming force decreased. The depending on lubrication type, the DR increased maximum 11.26 % for HC300LA sheet material. Also, The DR increased maximum 11.51 % for HC420LA sheet material.
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    Improving deep drawability of HC300LA sheet metal by warm forming
    (Springer London Ltd, 2016) Sen, Nuri; Kurgan, Naci
    The formability of high-strength sheet materials is limited at room temperatures. In this study, the first of its kind to be conducted, experimental research was performed on the formability of HC300LA-grade sheet material using the warm deep drawing (WDD) method. Temperature control is among the most important parameters in the WDD method. To increase the limiting drawing ratio (LDR) of HC300LA-grade sheet material, a new warm deep drawing method featuring sensitive temperature control was designed and manufactured. With this new method, the formability of HC300L-grade sheet material was considerably increased by heating the flange zone of the blanks under blank-holder force (BHF). Before the experimental study, unidirectional tensile tests were applied at room temperature (RT), 150 degrees C, and 300 degrees C. At the completion of the test conducted at 300 degrees C, dynamic strain aging (DSA) was seen in the test specimen. As a result of DSA, the HC300LA-grade sheet material became brittle and its formability decreased. Experimental studies were therefore conducted in the temperature range of 170 and 295 degrees C. LDR for a 1.2-mm sheet thickness of HC300LA-grade sheet material, which is 2.14 at RT, increased to 2.61 after applying this method. In experimental studies on LDR involving 1.5-mm sheet thickness, which is 2.15 at RT, the ratio increased to 2.59. The drawing ratio (DR) increased by 21.96 and 20.45 % for 1.2 mm sheet thickness and 1.5 mm sheet thickness, respectively. Moreover, the microstructures of the warm cup's punch corner region, and wall and bottom regions were investigated under an optical microscope. The results showed whether any changes occurred in the microstructures.
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    Investigation of tribological performance of hydrothermal carbon by pin-on-disc test and warm deep drawing process
    (Iop Publishing Ltd, 2024) Yurt, Ozgur Erdem; Sen, Nuri; Simsir, Hamza; Kucuk, Yilmaz; Altas, Emre; Gok, M. Sabri; Civek, Tolgahan
    In this study, the synthesis of hydrothermal carbon (HTC) lubricant and its usability as a lubricant under hot industrial conditions were investigated. In this context, the characterization of HTC produced from organic sources at low cost and in a short time was performed, and its tribological performance was analysed in detail. HTC produced by the hydrothermal carbonization method was characterized through SEM images and EDS analysis. To determine the effect of HTC on friction at different temperatures, HTC was subjected to a pin-on-disc wear test with AA5754 material. The effect of various lubricants, temperatures, blank holder pressure, and forming speed parameters on the forming force for the analysis of the tribological effect of HTC on deep drawing processes were statistically analysed. The performance of HTC was compared with Teflon, fullerenes, graphene, and carbon nanotube (CNT) materials. According to the results obtained from wear tests, the lowest friction coefficient value was achieved in the presence of fullerenes as the lubricant, and as the temperature increased, the friction coefficient decreased. It was observed that HTC exhibited lower performance in the wear test compared to fullerenes due to oxidation. When the effect of deep drawing parameters on the forming force was analysed, it was concluded that the most effective parameters were temperature (72.32%) and lubricant (20.89%). According to the S/N analysis results, the minimum forming force was obtained under the conditions of solid Teflon lubricant, 250 degrees C temperature, 15-bar blank holder pressure, and 2 mm/s forming speed. The tribological performance difference between HTC and Teflon is at the 1% level. The results demonstrate the potential industrial usability of HTC as a lubricant.
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    Prediction of Flow Behavior and Deformation Analysis of AA5754 Sheet Metal at Warm and Hot Temperatures
    (Springer, 2024) Sen, Nuri; Civek, Tolgahan; Ilhan, Omer; Yurt, Ozgur Erdem; Cetin, M. Huseyin; Simsir, Hamza
    The utilization of lightweight materials such as AA5754 aluminum alloys in the inner body panel parts of vehicles has been significantly important for automotive manufacturers to minimize the high fuel consumption by reducing the overall weight. In this study, the flow behavior of AA5754 sheet metal has been discussed by conducting uniaxial tensile tests at five different temperatures (RT, 200, 250, 300, 350 degrees C) and three strain rates (0.001, 0.01, 0.05 s(-1)). Additionally, the capability of Fields and Backofen (F&B) and Voce hardening rules in describing the flow behavior of AA5754 at different temperatures and strain rates has been investigated by conducting uniaxial tensile tests in finite element analysis. It has been found that the main deformation mechanisms for the AA5754 are the strain hardening mechanism up to 250 degrees C, strain hardening and dynamic recovery mechanisms at 300 degrees C, dynamic recrystallization and strain hardening mechanisms at 350 degrees C. While the F&B hardening rule has been able to successfully capture the flow behavior of AA5754 up to 250 degrees C with a 14.36% error, its capability has significantly reduced after 250 degrees C due to its incapability of describing the effects of dynamic recovery and recrystallization. Voce hardening model has been better able to describe the flow behavior of AA5754 at all the temperature levels than F&B model due to its saturation behavior.