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Öğe Assessment of Electrical Resistance Heating for Hot Formability of Ti-6Al-4V Alloy Sheet(TRANS TECH PUBLICATIONS LTD, 2011) Ozturk, Fahrettin; Ece, Remzi Ecmel; Polat, Naki; Koksal, Arif; Duflou, JR; Clarke, R; Merklein, M; Micari, F; SHirvani, B; Kellens, KTi-6Al-4V (Ti64) is the most commercially used heat treatable high strength/weight ratio, high corrosion, and thermal resistance alloy in titanium alloys. However, room temperature (RT) formability of this alloy is very poor and springback after forming is very severe due to the high yield strength and low elasticity modulus. In this research, the applicability of electrical resistance heating process which is a new and rapid heating process for hot forming application is investigated in order to improve formability and eliminate springback. The electrical resistance heating method is found to be effective for T64 alloy. Results reveal that the changes in hardness and grain size of the alloy have been found inconsiderable when the method is used. Springback compensation is achieved at high temperatures and springback free part is almost produced.Öğe EFFECT OF PRE-STRAINING ON THE SPRINGBACK BEHAVIOR OF THE AA5754-0 ALLOY(INST ZA KOVINSKE MATERIALE I IN TEHNOLOGIE, 2011) Toros, Serkan; Alkan, Mahmut; Ece, Remzi Ecmel; Ozturk, FahrettinThis study presents the effect of pre-straining on the springback behavior of the AA5754-0 aluminum-magnesium (Al-Mg) alloy sheet under V bending by an experimental and finite-element simulation studies. Pre-straining ranges from 0 To to 11 % were applied to the samples, which were bent on a 60 degrees V-shaped die for the springback evaluation. Commercially available finite-element software, ETA/Dynaform, was used to simulate the 60 degrees V-die bending process. The dynamic explicit finite-element method for pressing and the static implicit finite-element method for the unloading phase were used for the simulations. The results from both the experiment and the simulation indicate that the pre-straining has no positive effect on the springback compensation.Öğe Effect of pre-straining on the springback behavior of the AA5754-0 alloy(2011) Toros, Serkan; Alkan, Mahmut; Ece, Remzi Ecmel; Ozturk, FahrettinThis study presents the effect of pre-straining on the springback behavior of the AA5754-0 aluminum-magnesium (Al-Mg) alloy sheet under V bending by an experimental and finite-element simulation studies. Pre-straining ranges from 0 % to 11 % were applied to the samples, which were bent on a 60°V-shaped die for the springback evaluation. Commercially available finite-element software, ETA/Dynaform, was used to simulate the 60°V-die bending process. The dynamic explicit finite-element method for pressing and the static implicit finite-element method for the unloading phase were used for the simulations. The results from both the experiment and the simulation indicate that the pre-straining has no positive effect on the springback compensation.Öğe Effect of Warm Temperature on Springback Compensation of Titanium Sheet(TAYLOR & FRANCIS INC, 2010) Ozturk, Fahrettin; Ece, Remzi Ecmel; Polat, Naki; Koksal, ArifIn the present study, the effect of warm temperature on springback compensation of commercially pure grade 2 (CP2) titanium sheet is investigated. The results reveal that the springback is substantially reduced with increasing temperature. The elastic energy and the ratio of tensile strength/yield strength (TS/YS) of the material are measured at various temperatures under tensile loading condition. A gradual decrease of elastic energy is observed with increasing temperature. The change in the ratio of TS/YS is left diminutive with increasing temperature.Öğe Investigation of thermoforming processes of aerostructures: Simulation and microstructural analysis(Springer London Ltd, 2024) Cobanoglu, Merve; Ece, Remzi Ecmel; Unlu, Busra; Oz, Yahya; Toros, Serkan; Ozturk, FahrettinA series of experimental and numerical studies were carried out on the mechanical and geometric performance of an aerostructural part produced by a material out-of-autoclave stamp forming process using unidirectional (UD) carbon fiber (CF) reinforced polyetherketoneketone (PEKK), which provides advantages like reshaping, recycling, welding, and low serial manufacturing costs. As a novelty, initial part geometry, different types of springs, and their attachment type were examined experimentally and compared with simulations. Compression tests were performed to determine mechanical strengths which reach levels up to 550 MPa. In addition, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were conducted to determine the crystallinity which occurs depending on the cooling regimes of the material. The crystallinity has been observed to vary regionally ranging from 16 to 21%. However, the crystallinity of the part towards the cold mold region decreased from 20 to 17%. In addition, simulations were performed to observe and control the occurrence of wrinkles and other defects.Öğe Mechanical and microstructural evaluations of hot formed titanium sheets by electrical resistance heating process(ELSEVIER SCIENCE SA, 2013) Ozturk, Fahrettin; Ece, Remzi Ecmel; Polat, Naki; Koksal, Arif; Evis, Zafer; Polat, AytekinIn this study, effect of temperature in the electrical resistance heating process on mechanical properties and microstructures of commercially pure titanium grade 2 (CP2) and Ti-6Al-4V (T64) alloy sheets was investigated. Sheets were successfully heated by the electric resistance heating process, and their mechanical properties and microstructures were evaluated. Ductilities of both materials were increased significantly after 400 degrees C. Results indicate that no significant change was observed in grain sizes and microhardness of the materials. XRD analysis revealed that presence of secondary phases regarding oxidation of Ti was observed for 164 alloy above the manufacturer specified temperature ranges. However, no secondary phase was observed even above the manufacturer specified temperature ranges for CP2. (c) 2013 Elsevier B.V. All rights reserved.Öğe Titanyum sac malzemelerin elektrikli ısıtma yöntemi ile şekillendirilebilme kabiliyetinin iyileştirilmesi(Niğde Üniversitesi / Fen Bilimleri Enstitüsü, 2011) Ece, Remzi Ecmel; Öztürk, FahrettinBu tezde, özellikle havacılıkta en çok kullanılan ve şekillendirme güçlüğü yaşanan iki farklı titanyum malzemenin (CP2 ve Ti6Al4V) yüksek sıcaklıklarda şekillendirilerek şekillendirme sorunlarının ortadan kaldırılması hedeflenmiştir. İlk olarak malzemenin mekanik davranışlarını tespit etmek için deneyler yapılmıştır. Daha sonra yeni bir sıcak şekillendirme tekniği olan `Elektrik Akımı ile Isıtma' yöntemi kullanılarak laboratuar ölçekli ve endüstriyel ölçekli olmak üzere tasarlanan ve imal ettirilen iki farklı sistemde şekillendirme denemeleri gerçekleştirilmiştir. Sonuç olarak yeni teknikle yüksek sıcaklıkta şekillendirmenin malzemenin mekanik özelliklerini ve mikro yapısını değiştirmediği ve yöntemin uygulanabilir olduğu tespit edilmiştir.
