Yazar "Kilic, Suleyman" seçeneğine göre listele

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    Effects of Aging Temperature, Time, and Pre-Strain on Mechanical Properties of AA7075
    (Univ Fed Sao Carlos, Dept Engenharia Materials, 2019) Kilic, Suleyman; Kacar, Ilya; Sahin, Mevlut; Ozturk, Fahrettin; Erdem, Oguz
    Aluminum alloys of the 7xxx series (AA7075) are preferred in the aerospace and automotive industries due to their low densities, high strength, good corrosion resistance properties. Additionally, these alloys show the most effective aging properties among aluminum alloys. For this reason, it is very important to determine the most appropriate aging parameters for microstructural development. Literature review reveals that the effect of pre-strain on springback has not been studied yet. In this study, the effects of aging temperature, time, and pre-strain on mechanical properties are investigated for AA7075. Precipitates present in solid solutions of AA7075 and their effects are examined. Results reveal that MgZn2 precipitation is not observed at aging temperatures of 120 and 160 degrees C. After the formation of MgZn2 precipitates, microstructure becomes softer when aging continues at a higher temperature or longer period of time. It is clearly seen that pre-strain causes Portevin-Le Chatelier (PLC) effect after aging at 120 and 160 degrees C for aging times of 30 and 90 minutes.
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    Effects of anisotropic yield functions on prediction of forming limit diagrams of DP600 advanced high strength steel
    (ELSEVIER SCIENCE BV, 2014) Ozturk, Fahrettin; Toros, Serkan; Kilic, Suleyman; Ishikawa, T; Mori, KI
    In recent years, numerous researchers have reported that the predicted forming limit diagrams strongly depend on the method of determining the material parameters used in the yield functions and the corresponding the shape of the yield surface. In this study, the capability of different yield functions to predict the forming limit diagram of DP600 advanced high strength steel sheet is investigated. Additionally, the effects of determination method of the anisotropic parameters on the forming limit diagram are studied. The yield functions proposed by Hill-48, Barlat-89, and YLD2000-2d are considered and the forming limit diagrams are constructed using the Marciniak Kuczynski model. Results reveal that predictions using different yield functions are lower than the experimental forming limits. In terms of shape and tendency, the YLD2000-2d curve is best suited for representing experimental curve. (C) 2014 Published by Elsevier Ltd.
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    EVALUATION OF TENSILE PROPERTIES OF HIGH STRENGTH STEELS AT WARM TEMPERATURES AND VARIOUS STRAIN RATES
    (VERLAG STAHLEISEN MBH, 2008) Ozturk, Fahrettin; Toros, Serkan; Bas, M. Hakan; Kilic, Suleyman
    The use of advanced high strength steels in automotive industry has been increased recently. Dual-phase (DP) high-strength steel, which is an advanced high strength steel, has gained great attention due to its high strength and good formability. In this study, uniaxial tensile deformation of DP600 and DP800 advanced high strength steels were studied at temperatures between room temperature (RT) and 300 degrees C and at strain rates between 0.008 s(-1) and 0.16 s(-1). Results indicate that the formability of the materials is lower after the testing at 200 degrees C and 300 degrees C than the testing at RT. Moreover, the formability decreases with the increasing strain rate. Finally, the forming should be done at RT and low strain rates to get good formability.
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    Evaluation of tensile properties of high strength steels at warm temperatures and various strain rates
    (Wiley-VCH Verlag, 2008) Ozturk, Fahrettin; Toros, Serkan; Hakan Bas, M.; Kilic, Suleyman
    The use of advanced high strength steels in automotive industry has been increased recently. Dual-phase (DP) high-strength steel, which is an advanced high strength steel, has gained great attention due to its high strength and good formability. In this study, uniaxial tensile deformation of DP600 and DP800 advanced high strength steels were studied at temperatures between room temperature (RT) and 300 °C and at strain rates between 0.008 s-1and 0.16 s-1. Results indicate that the formability of the materials is lower after the testing at 200 °C and 300 °C than the testing at RT. Moreover, the formability decreases with the increasing strain rate. Finally, the forming should be done at RT and low strain rates to get good formability. © 2008 Verlag Stahleisen GmbH, Düsseldorf.
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    Parameter determination and calibration of the combined plasticity model through inverse analysis for cold forging simulation of 7075-T6 aluminum alloy
    (Gazi Univ, Fac Engineering Architecture, 2022) Kacar, Ilyas; Kilic, Suleyman
    In this study, plasticity models have been developed to be used in cold forging simulations of AA7075-T6 alloy which is widely used in aviation industry. In addition, the coefficients of the obtained models have been calibrated using genetic algorithm optimization method. As the hardening rule in models; bilinear isotropic is combined with Chaboche's nonlinear kinematic hardening rule (three-termed). Plasticity models have been obtained by using the associated flow rule and Hill48 yield criterion in addition to the hardening rules. Experimental stress values have been compared with those obtained from the models. As a result, the most suitable hardening model for monotonic/cyclic loading deformation conditions is presented and the effects of the model parameters on the simulation results are shown.
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    Prediction of Strain Limits via the Marciniak-Kuczynski Model and a Novel Semi-Empirical Forming Limit Diagram Model for Dual-Phase DP600 Advanced High Strength Steel
    (Assoc Mechanical Engineers Technicians Slovenia, 2020) Kacar, Ilyas; Ozturk, Fahrettin; Toros, Serkan; Kilic, Suleyman
    The prediction capability of a forming limiting diagram (FLD) depends on how the yield strength and anisotropy coefficients evolve during the plastic deformation of sheet metals The FLD predictions are carried out via the Marciniak-Kuczynski (M-K) criterion with anisotropic yield functions for DP600 steel of various thicknesses. Then, a novel semi-empirical FLD criterion is proposed, and prediction capabilities of the criterion are tested with different yield criteria. The results show that the yield functions are very sensitive to anisotropic evolution. Thus, while the FLD curves from the M-K model and the proposed model are not the same for each thickness, the proposed model has better prediction than the M-K model.
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    Tensile deformation behavior of AA5083-H111 at cold and warm temperatures
    (CARL HANSER VERLAG, 2010) Ozturk, Fahrettin; Toros, Serkan; Kilic, Suleyman
    The effects of strain rate and temperature on the deformation behavior of hardened 5083-H111 aluminum magnesium alloy sheet were investigated by performing uniaxial tensile tests at various strain rates from 0.0083 to 0.16 s(-1) and temperatures from -100 to 300 degrees C. Results from the prescribed test ranges indicate that the formability of this material at cold and warm temperatures is better than at room temperature. The improvement in formability at cold temperatures is principally due to the strain hardening of the material. However, the improvement at warm temperature and low strain rate is specifically due to the high strain rate sensitivity characteristic of the material. Results indicate that this alloy should be formed at temperatures higher than 200 C and at low strain rates.
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    THE EFFECTS OF MATERIAL THICKNESS AND DEFORMATION SPEED ON SPRINGBACK BEHAVIOR OF DP600 STEEL
    (TRANS TECH PUBLICATIONS LTD, 2011) Toros, Serkan; Kilic, Suleyman; Ozturk, Fahrettin; Hashmi, MSJ; Mridha, S; Naher, S
    There is an increase trend in the use of advanced high strength steels in automotive industry due to a combination of high strength and good formability in order to achieve substantial weight reduction. Lightening by using thinner advanced high strength steel sheets is effective to provide better performance than current structures. In recent years, the usage of DP600 steel in automotive industry has been increased remarkably. However, high strength usually increases the springback behavior which creates serious problem in the assembly line. Springback is a very complex behavior and not easy to be eliminated. This problem limits the usage of these types of steels, increases part cost and reduces part quality. Springback free or minimum springback observed parts are one of the important goals of automotive industry in terms of cost and quality. In this study, the effects of deformation speeds, sheet thickness, and widths on the springback were investigated experimentally and numerically using a 60 degrees V-shaped bending for DP600 steel. Results reveal that the springback was significantly decreased with increasing thicknesses and deformation speed except for 500mm/min deformation speed. The effects of widths on springback were found to be inconsiderable.