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Öğe A Review of and Current State-of-the-Art in Laser Beam Welding in the Automotive Industry(OLD CITY PUBLISHING INC, 2016) Kacar, I.; Ozturk, F.; Yilbas, B. S.Laser beam welding is an indispensable and preferable method which is widely used in the automotive industry. It satisfies the requirements of low cost, short processing time, and high quality. Although laser welding finds applications in different industries, its application in the automotive industry requires further investigation. In this paper, the current status of laser beam welding applications in automotive industry is reviewed and recent developments are discussed. This review study reveals that LASER BEAM WELDING is an important process for automotive industry, therefore it will become a more prominent method in upcoming years.Öğe A review of and current state-of-the-art in laser beam welding in the automotive industry(Old City Publishing, 2016) Kacar, I.; Ozturk, F.; Yilbas, B.S.Laser beam welding is an indispensable and preferable method which is widely used in the automotive industry. It satisfies the requirements of low cost, short processing time, and high quality. Although laser welding finds applications in different industries, its application in the automotive industry requires further investigation. In this paper, the current status of laser beam welding applications in automotive industry is reviewed and recent developments are discussed. This review study reveals that LASER BEAM WELDING is an important process for automotive industry, therefore it will become a more prominent method in upcoming years. © 2016 Old City Publishing, Inc. Published by license under the OCP Science imprint, a member of the Old City Publishing Group.Öğe Aluminum Alloys with Identical Plastic Flow and Different Strain Rate Sensitivity(SPRINGER, 2010) Picu, R. C.; Ozturk, F.; Esener, E.; Li, R.Mg-rich and Si-rich aluminum alloys from the AA6XXX class are considered to demonstrate that standard heat treatments can be used to produce materials with identical plastic flow (yield stress and strain hardening) and different strain rate sensitivity. The Mg-rich alloy exhibits lower strain rate sensitivity and a different variation of this parameter with the stress (Haasen plot) relative to the Si-rich alloy. This is due to the instantaneous component of the strain rate sensitivity being smaller in the Mg-rich alloy. Hence, the underlying mechanism is not related to the presence of free, fast diffusing Mg atoms, but rather to the different nature of precipitates forming in the two alloys. A simple model is used to demonstrate that it is possible to tailor the strain rate sensitivity while preserving the flow stress by controlling the nature of precipitates and that of the dislocation-precipitate interaction.Öğe ANALYSIS OF TEMPERATURE DISTRIBUTION ON WARM FORMING OF ALUMINUM-MAGNESIUM ALLOY(TRANS TECH PUBLICATIONS LTD, 2011) Ozturk, F.; Arslan, M. A.; Hashmi, MSJ; Mridha, S; Naher, SWarm forming of lightweight materials has become very important issue in automotive industry due to their energy saving potential. Although there have been a lot of ongoing researches on this subject, there is no well-accepted technique is available describing how this process is going to be used in stamping. Designing optimal temperature distribution on the blank is directly affecting the overall success of the warm forming process. In this study, a temperature distribution of 5083-O aluminum-magnesium (Al-Mg) alloy was analyzed at various die and blank initial temperature conditions using finite element analysis approach. Temperature distribution results of the blank reveal that the dies must be heated to predetermined temperatures for successful warm forming, even the blank is kept at room temperature.Öğe Analysis of Yield Criteria and Flow Curves on FLC for TWIP900 Steel(Springer, 2020) Kilic, S.; Ozturk, F.; Toros, S.In this study, the applicability of yield criteria and flow curve models to predict forming limit curve (FLC) via the Marciniak-Kuczynski (M-K) model is investigated for TWIP900 steel. Forming limit characteristics of TWIP900 are determined experimentally and numerically. The yield criteria of Hill48, Barlat89, YLD2000-2d, and BBC2000 are tested and compared with each other. Results indicate that the YLD2000-2d and the BBC2000 yield criteria are found to be more accurate than the other criteria. The YLD2000 criterion has the best prediction capability with the Krupskowsky flow curve while the BBC2000 model has the best prediction with the Ludwick flow curve model.Öğe Determination of anisotropy parameters via the optimization process of V-bending(American Society of Mechanical Engineers (ASME), 2015) Ozturk, F.; Toros, S.In recent years, the use of optimization methods in sheet metal forming has been increased remarkably. In the finite element simulation of the sheet metal stamping operations, the model parameters are determined from the several tests like tensile, compression, and biaxial stretching tests (bulge test). In this study, Yld2000-2d anisotropic yield function parameters are determined for DP800 advanced high strength steel using a 60o V-shaped die bending process. The difference between the simulation and experiment is found to be 1 degree using the classical determination method of the anisotropy parameters. The difference is 0.1 degree using the optimization method. Copyright © 2015 by ASME.Öğe DETERMINATION OF ANISOTROPY PARAMETERS VIA THE OPTIMIZATION PROCESS OF V-BENDING(AMER SOC MECHANICAL ENGINEERS, 2016) Ozturk, F.; Toros, S.In recent years, the use of optimization methods in sheet metal forming has been increased remarkably. In the finite element simulation of the sheet metal stamping operations, the model parameters are determined from the several tests like tensile, compression, and biaxial stretching tests (bulge test). In this study, Yld2000-2d anisotropic yield function parameters are determined for DP800 advanced high strength steel using a 60 degrees V-shaped die bending process. The difference between the simulation and experiment is found to be 1 degree using the classical determination method of the anisotropy parameters. The difference is 0.1 degree using the optimization method.Öğe Effects of cold and warm temperatures on springback of aluminium-magnesium alloy 5083-H111(SAGE PUBLICATIONS LTD, 2009) Ozturk, F.; Toros, S.; Kilic, S.; Bas, M. H.Springback is one of the most common problems in sheet metal forming processes. It causes improper fit, which creates serious problems during assembly of the parts. Based on material strength, a considerable amount of elastic recovery during unloading can be observed. in this study, springback behaviour of a hardened 5083-H111 aluminium-magnesium (Al-Mg) alloy with a thickness of 3 mm using a 600 angle V-shape die bending process at various temperatures ranging from -50 to 300 degrees C was investigated. The effects of temperature on springback behaviour were identified. Results indicate that springback increased with decreasing temperature. The same amount of springback was measured at 0, 25, and 100 degrees C. It was observed that the amount of springback increased between 100 and 200 degrees C and then started to decrease beyond 200 degrees C. The lowest springback was obtained at 300 degrees C.Öğe Evaluation of tensile behaviour of 5754 aluminium-magnesium alloy at cold and warm temperatures(TAYLOR & FRANCIS LTD, 2009) Ozturk, F.; Toros, S.; Pekel, H.Cost effective lightweight vehicles have recently become a key target for automotive manufactures due to increasing concerns about minimising environmental impact and maximising fuel economy without sacrificing the vehicle performance and comfort. Aluminium-magnesium alloys are the most important candidate materials due to their excellent high strength to weight ratio, good formability, good corrosion resistance and recycling potential. Although their deformations leave undesirable traces on the surface of the final product and their formability are not very favorable at room temperatures, the formability can be improved by changing the forming temperature to either cryogenic or warm. In this study, uniaxial tensile deformation behaviour of 5754 aluminium-magnesium alloy sheet was extensively studied at cold (-60 to 0 degrees C) and warm (room to 250 degrees C) forming temperatures and a strain rate range of 0.0016-0.042 s(-1). Results indicate that the formability of this material at cold and warm temperatures is better than at room temperature. Stretching lines were eliminated at both cold and warm temperatures especially above 175 degrees C and 0.0016 s(-1) strain rate. The most suitable forming conditions were obtained at 250 degrees C and 0.0083 s(-1) or 175 degrees C and 0.0016 s(-1).Öğe Evaluation of tensile properties of 5754-O type aluminum- magnesium alloy at cold and warm temperature(Hanrimwon Publishing Co., 2008) Ozturk, F.; Toros, S.; Pekel, H.In this research, uniaxial tensile deformation behavior of 5754-O type aluminum-magnesium (Al- Mg) alloy sheets which are used widely in diverse applications ranging from automotive bodies to food processing due to their excellent high strength to weight ratio, corrosion resistance, and weldability were investigated at temperature range between -60 to 250oC and at the range of strain rates 0.0016-0.04 s-1. Mechanical properties such as yield strength (YS), ultimate tensile strength (UTS), strain hardening coefficient (n), strain rate sensitivity (m), total elongation (TE) and reduction of area (RA) were determined. In addition, the elimination of Luder's band (stretcher marks or line) elimination was investigated. The ductility of the alloy was calculated by two different methods. As a result, the ductility was found to increase with increasing temperature and to decrease with increasing strain rate. Luder's band elimination was observed with increasing temperatures and strain rates. The test results at cold temperatures indicated that an increase in total elongation and strain hardening coefficient were observed. Optimum formability condition was obtained at high temperature and low strain rate.Öğe Finite-element modelling of two-disc shrink fit assembly and an evaluation of material pairs of discs(PROFESSIONAL ENGINEERING PUBLISHING LTD, 2011) Ozturk, F.In this study, a two-disc shrink fit assembly was modelled in two dimension using ABAQUS/Standard to determine the interfacial pressures with respect to the interferences. Steel-steel and steel-aluminium material pairs were considered. Inner disc of the assembly was considered as hollow and solid shafts, respectively. The results indicate that the finite-element results were in good agreement with the analytical results. In the hollow shaft assembly, both the hollow shaft and the outer disc had non-uniform stress distribution. In the solid shaft assembly, uniform stress distribution for the solid shaft and non-uniform stress distribution for the outer disc were determined. It was pointed out that same pressure can be obtained by different interference with different material pairs. If the assembly has complex shapes, the finite-element method gives more comprehensive and accurate results than the analytical method.Öğe Formability and springback characterization of TRIP800 advanced high strength steel(ELSEVIER SCI LTD, 2012) Toros, S.; Polat, A.; Ozturk, F.Springback is one of the most common problems in the sheet metal forming operation. In the literature there have been numerous studies about springback and its compensation for many material groups. Illustrations of these phenomena for the sheet metals have still been going on by using the numerical and the experimental tools. Nowadays, the finite element method is the most powerful tool for determining of the springback characterization of the sheet metals. The selection of the material models which are used in the finite element software for the simulation of the forming operation and springback are very important in terms of accurate predictions. In the present study, formability and springback characterization of the TRIP800 steel are investigated by finite element analysis method using different material models, i.e. Hill-48, Barlat-89, and YLD2000. Additionally, the capability of the Hill-48 and Barlat-89 on predicting the variation of the yield stress and anisotropy values with respect to the angle from rolling direction is investigated for different methods like Lankford parameters and ErrMin approaches. Results reveal that the variation of the yield stress and anisotropy values that obtained from experiments at different directions like 0 degrees 45 degrees, 90 degrees can be predict better with ErrMin method. Among the studied anisotropic yield criteria, YLD2000-2d has the best fit to the yield stress and anisotropy values. According the finite element simulation of V-die bending processes YLD2000-2d has the best prediction capability of the springback. (C) 2012 Elsevier Ltd. All rights reserved.Öğe Influence of aging treatment on mechanical properties of 6061 aluminum alloy(ELSEVIER SCI LTD, 2010) Ozturk, F.; Sisman, A.; Toros, S.; Kilic, S.; Picu, R. C.Aluminum-magnesium-silicon (Al-Mg-Si) alloys show medium strength, excellent formability, good corrosion resistance and are widely used in extruded products and automotive body panels. The major advantage of these alloys is their age hardening response during the paint baking process as well as the fact that they exhibit no yield point phenomenon and Ludering. In this study, the mechanical properties of a commercially available AA6061 alloy aged to various levels were studied. Peak-aged conditions were reached in this particular alloy after a 2 h heat treatment at 200 degrees C. The variation of the yield stress, ultimate tensile strength, ductility and strain hardening rate with aging time is measured and discussed in relation to the microstructural changes induced by the heat treatment. (C) 2009 Elsevier Ltd. All rights reserved.Öğe Investigation of tensile strength of hydroxyapatite with various porosities by diametral strength test(MANEY PUBLISHING, 2008) Evis, Z.; Ozturk, F.It is appropriate to administer the diametral test to biomedical materials used in dental applications because stresses formed on dental implants are similar to those that formed in this test. To show this similarity, an experimental study of diametral strength testing of hydroxyapatite was performed. The influence of porosity on hydroxyapatite was investigated experimentally to determine how the diametral strength was affected. Hydroxyapatite was air sintered at 1100 degrees C for 1 h with porosities ranging from 1 to 32%. The results indicated that hydroxyapatite with improved densification had higher diametral strength values. X-ray diffraction analysis showed that sintered samples were pure hydroxyapatite.Öğe Modeling uniaxial, temperature and strain rate dependent behavior of Al-Mg alloys(ELSEVIER SCIENCE BV, 2010) Toros, S.; Ozturk, F.The mechanical properties of 5083-H111 and 5754-O Al-Mg alloys at various testing temperatures (between room temperature (RT) and 300 degrees C) and strain rates (0.0016-0.16 s(-1)) were determined. A new mathematical model which is based on temperature and strain rate is developed and named as "softening model". The model is used to simulate the recorded strain softening behavior of the 5083-H111 and 5754-O Al-Mg alloys at warm temperatures and modeling capabilities of softening model are shown. (C) 2010 Elsevier B.V. All rights reserved.Öğe Modeling Uniaxial, Temperature, and Strain Rate Dependent Behavior of AZ31 Alloy by Softening Model(TRANS TECH PUBLICATIONS LTD, 2011) Toros, S.; Ozturk, F.; Kaya, M.; Duflou, JR; Clarke, R; Merklein, M; Micari, F; SHirvani, B; Kellens, KIn the present study, a softening model proposed for warm forming behavior of Al-Mg alloys is applied to AZ31 alloy in order to determine the applicability of the model to magnesium alloys AZ31 alloy is tested at several temperatures (room temperature to 300 degrees C) and strain rates (0.0083-0.17 s(-1)). The results indicate that the model shows good agreement with experimental flow curves for different temperatures and strain rates for AZ31 alloy.Öğe Strain Hardening and Strain Rate Sensitivity Behaviors of Advanced High Strength Steels(JOURNAL IRON STEEL RESEARCH EDITORIAL BOARD, 2013) Ozturk, F.; Polat, A.; Toros, S.; Picu, R. C.The mechanical properties of commercial dual phase (DP), transformation induced plasticity (TRIP), and high strength low alloy (HSLA-340) steel sheets are investigated and compared at various strain rates ranging from 0.0017 to 0.17 s(-1) at ambient temperature. TRIP steel outperforms the other two materials, having comparable ductility and twice as large strength relative to DP steel. TRIP has larger strength and much larger ductility than HSLA-340. The exceuent ductility of TRIP800 is due to its high strain hardening capability, which promotes stable plastic deformation. It is observed that the strain hardening rate in TRIP800 does not decrease to zero at failure, as common in most materials in which failure is preceded by necking.Öğe Tensile and Spring-Back Behavior of DP600 Advanced High Strength Steel at Warm Temperatures(SPRINGER, 2009) Ozturk, F.; Toros, S.; Kilic, S.In recent years, the use of advanced high strength steels in automotive industry has been increased remarkably. Among advanced high strength steels, dual phase (DP) steels have gained a great attention owing to a combination of high strength and good formability. However, high strength usually increases the spring-back behavior of the material, which creates problems for the parts during the assembly. Thus, the uniaxial tensile deformation and spring-back behaviors of DP600 advanced high strength steel were investigated in rolling (0 degrees), diagonal (45 degrees), and transverse (90 degrees) directions in the temperature range from room temperature (RT) to 300 degrees C. All tests were performed at a deformation speed of 25 mm/min. A V-shaped die (60 degrees) was used for the spring-back measurements. The results indicated that the formability and spring-back of the material were decreased with increasing the temperatures. The material showed complex behaviors in different directions and at different temperatures.
