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Conference Object Citation - Scopus: 9Modeling Flexforming (fluid Cell Forming) Process With Finite Element Method(Trans Tech Publications Ltd, 2007) Ali Hatipoǧlu,H.; Polat,N.; Köksal,A.; Erman Tekkaya,A.In this paper, the flexforming process is modeled by finite element method in order to investigate the operation window of the problem. Various models are established using explicit approach for the forming operation and implicit approach for the unloading one. In all analyses the rubber diaphragm has been modeled revealing that the modeling of this diaphragm is essential. Using the material Aluminum 2024 T3 alclad sheet alloy, three basic experiments are conducted: Bending of a straight flange specimen, bending of a contoured flange specimen and bulging of a circular specimen. By these experiments the effects of blank thickness, die bend radius, flange length and orientation of the rolling direction of the part have been investigated. Experimental results are compared with finite element results to verify the computational models.Conference Object Citation - WoS: 11Modeling Flexforming (fluid Cell Forming) Process With Finite Element Method(Trans Tech Publications Ltd, 2007) Hatipoglu, H. Ali; Polat, Naki; Koeksal, Arif; Tekkaya, A. ErmanIn this paper, the flexforming process is modeled by finite element method in order to investigate the operation window of the problem. Various models are established using explicit approach for the forming operation and implicit approach for the unloading one. In all analyses the rubber diaphragm has been modeled revealing that the modeling of this diaphragm is essential. Usine the material Aluminum 2024 T3 alclad sheet alloy, three basic experiments are conducted: Bending of a straight flange specimen, bending of a contoured flange specimen and bulging of a circular specimen. By these experiments tile effects of blank thickness, die bend radius, flange length and orientation of the rolling direction of the part have been investigated. Experimental results are compared with finite element results to verify the computational models.Conference Object Citation - Scopus: 2Influence of Heat Treatment and Grinding Conditions on Surface Residual Stresses in the Production of Rollers(Trans Tech Publications Ltd, 2006) Güley,V.; Tekkaya,A.E.; Savaş,T.; Özhan,F.The aim of this study is to investigate surface residual stresses after heat treatment and grinding processes in the production of rollers. The residual stresses were measured using the X-ray diffraction method utilizing chromium radiation, which has an average penetration depth of 5 μm incident on AISI-E52100 (100Cr6) ball bearing steel. Taguchi design of experiments (DOE) is applied to define the set of experiments for grinding, which facilitates evaluation of the individual influences of process parameters on residual stresses and also eliminates unnecessary experiments. Response of residual stresses to each parameter is evaluated with the help of the results of residual stress measurements by X-ray diffraction. In grinding with aluminum oxide wheels, it was concluded that the lower the cutting speed and the higher the workpiece speed the higher the magnitude of surface compressive residual stresses. Higher compressive stresses were measured in axial direction compared to the circumferential direction after the grinding process.Conference Object Citation - WoS: 1Experimental Investigation of Residual Stresses After Heat Treatment and Grinding Processes in the Production of Ball Bearing Rings(Trans Tech Publications Ltd, 2008) Gueley, Volkan; Tekkaya, A. Erman; Savas, Turhan; Ozhan, FeridunExperimental investigation of residual stresses after heat treatment and grinding processes in the production of ball bearing rings has been carried out. The residual stresses were measured by X-ray diffraction method utilizing chromium radiation, which has an average penetration depth of 5 mu m incident on 100Cr6 (AISI-E52100) ball bearing steel. The process parameters of heat treatment and grinding processes were varied so as to represent the extreme values that can be applied in the respective processes. Hardness and percent retained austenite limit the heat treatment process parameters; while roundness, surface roughness and form the grinding process. Tensile surface residual stresses on the raceway of ball bearing rings changes to compression after grinding in both circumferential and axial directions. In grinding relatively higher compressive stresses were measured in axial direction compared to the circumferential direction. This experimental investigation also showed that the influence of heat treatment process parameters on the magnitude and distribution of residual stresses survived even after grinding process; i.e. heat treatment and grinding processes cannot be evaluated independently in process design for favourable residual stresses.Conference Object Citation - Scopus: 1An Ontology Based Semantic Machine Tool Selection for Multi Scale Wire Edm Processes(Trans Tech Publications Ltd, 2017) Sadigh,B.L.; Oliaei,S.N.B.; Dadvandipour,S.Manufacturing high-tech complex products which contain multi-scale complex features without outsourcing considering company's capabilities is quite difficult. Outsourcing some processes to other independent companies is a crucial step toward fabricating a product. To find the most suitable partner company several critical parameters should be considered including company machine-park, skilled personnel, infrastructure etc. Having comprehensive information about necessary machine tool(s) to outsourcing related manufacturing process is essential. Focusing on Wire Electro Discharge Machining (WEDM) process, the objective of this paper is to introduce a platform to store and analyze information and data about part(s) and machine tools and show out coming results as a list of capable machine tools to produce the desired parts with multi-scale features.Conference Object Citation - Scopus: 3Experimental Investigation of Residual Stresses After Heat Treatment and Grinding Processes in the Production of Ball Bearing Rings(Trans Tech Publications Ltd, 2008) Güley,V.; Tekkaya,A.E.; Savaş,T.; Özhan,F.Experimental investigation of residual stresses after heat treatment and grinding processes in the production of ball bearing rings has been carried out. The residual stresses were measured by X-ray diffraction method utilizing chromium radiation, which has an average penetration depth of 5 μm incident on 100Cr6 (AISI-E52100) ball bearing steel. The process parameters of heat treatment and grinding processes were varied so as to represent the extreme values that can be applied in the respective processes. Hardness and percent retained austenite limit the heat treatment process parameters; while roundness, surface roughness and form the grinding process. Tensile surface residual stresses on the raceway of ball bearing rings changes to compression after grinding in both circumferential and axial directions. In grinding relatively higher compressive stresses were measured in axial direction compared to the circumferential direction. This experimental investigation also showed that the influence of heat treatment process parameters on the magnitude and distribution of residual stresses survived even after grinding process; i.e. heat treatment and grinding processes cannot be evaluated independently in process design for favourable residual stresses.Conference Object Citation - WoS: 10Production of Anorthite From Kaolinite and Caco3 Via Colemanite(Trans Tech Publications Ltd, 2004) Mergen, A; Kayed, TS; Bilen, M; Qasrawi, AF; Gürü, MBoron oxide has been found to be useful flux for the preparation of dense anorthite ceramics (CaO.Al2O3.2SiO(2)). Inexpensive starting materials of kaolinite, calcium carbonate and silica were used for anorthite ceramic production. Colemanite (2CaO.3B(2)O(3).5H(2)O) was added into the mixtures and the effects of colemanite upon the transformation towards anorthite and on the densification were investigated between 900-1400 degreesC. Single phase anorthite ceramic formed at lower temperatures in boron containing mixtures. Boron containing powder compacts were sintered above 90% theoretical density at 1350 degreesC.Conference Object Citation - Scopus: 1Direct Evaluation of Coulomb Friction Coefficient From Sheet Strip Stretch Test on a Cylinder Surface(Trans Tech Publications Ltd, 2014) Karadoǧan,C.; Hatipoǧlu,H.A.Knowing the flow curve of a sheet metal, strain distribution on a sheet strip may be used to roughly but quickly evaluate the Coulomb friction coefficient. Strain distribution on the strip being stretched on a cylindrical surface of interest may be measured by an optical strain measurement system. This could be used to estimate the stresses on the specimen. The capstan equation is then used to roughly evaluate the coefficient of friction acting between the sheet strip and the cylindrical surface. Validation of the approach is done using the simulation of the process. The corresponding experiments can be performed easily on a sheet metal testing device equipped with an optical strain measurement system, which is commonly used for the experimental evaluation of FLCs. © (2014) Trans Tech Publications, Switzerland.Conference Object Citation - Scopus: 1Determination of Tool Motions in Stretch Forming Process for Aerospace Applications by Using Finite Element Method(Trans Tech Publications Ltd, 2013) Hatipoǧlu,H.A.; Alkaş,C.O.; Karadoǧan,C.Stretch forming process is commonly used in the aircraft industry for the manufacturing of large sheet panels. The success of this process is highly dependent on the tool motions during forming. These motions are determined by trial - error procedure and it is costly. This study aims to improve the design of the stretch forming process by determining the necessary tool motions with numerical analysis. For this purpose, realistic finite element model (FEM) of the process is established. Material characterization and friction tests of mostly used aluminum alloys are conducted for input to the model. In order to improve the model and validate the numerical results, experimental work is performed in which the deformation of the sheet is measured optically. Copyright © 2013 Trans Tech Publications Ltd.Conference Object Influence of Heat Treatment and Grinding Conditions on Surface Residual Stresses in the Production of Rollers(Trans Tech Publications Ltd, 2006) Güley,V.; Tekkaya,A.E.; Savaş,T.; Özhan,F.The aim of this study is to investigate surface residual stresses after heat treatment and grinding processes in the production of rollers. The residual stresses were measured using the X-ray diffraction method utilizing chromium radiation, which has an average penetration depth of 5 μm incident on AISI-E52100 (100Cr6) ball bearing steel. Taguchi design of experiments (DOE) is applied to define the set of experiments for grinding, which facilitates evaluation of the individual influences of process parameters on residual stresses and also eliminates unnecessary experiments. Response of residual stresses to each parameter is evaluated with the help of the results of residual stress measurements by X-ray diffraction. In grinding with aluminum oxide wheels, it was concluded that the lower the cutting speed and the higher the workpiece speed the higher the magnitude of surface compressive residual stresses. Higher compressive stresses were measured in axial direction compared to the circumferential direction after the grinding process.
