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Article Citation - WoS: 113Citation - Scopus: 147Experiments and Finite Element Simulations on Micro-Milling of Ti-6al Alloy With Uncoated and Cbn Coated Micro-Tools(Elsevier, 2011) Oezel, T.; Thepsonthi, T.; Ulutan, D.; Kaftanoglu, B.This paper presents experimental investigations and finite element simulations on micro-milling of Ti-6Al-4V alloy with fine grain uncoated and cBN coated micro-end mills. Micro-milling of Ti-6Al-4V using uncoated and cBN coated tungsten carbide micro-end mills are conducted; surface roughness, burr formation and tool wear are measured. Effects of machining parameters on surface roughness, burr formation, and tool wear for uncoated and cBN coated micro-tools are investigated. Finite element modelling is utilized to predict forces, temperatures, and wear rate for uncoated and cBN coated micro-tools. Predicted temperature and tool wear contours for uncoated and cBN coated micro-tool edges reveal advantages of cBN coatings. Optimization studies on the experimental results are also conducted to identify the optimum process parameters which minimize both surface roughness and burr formation concurrently. (C) 2011 CIRP.Article Citation - WoS: 13Citation - Scopus: 13Analysis of Non-Isothermal Warm Deep Drawing of Dual-Phase Dp600 Steel(Springer France, 2019) Pepelnjak, T.; Kayhan, E.; Kaftanoglu, B.Improving the formability of the material is a key issue in the deep drawing process. Heating the material above its recrystallization temperature drastically increases formability, but in the case of dual phase (DP) steels, it results in a loss of their mechanical properties. To improve the drawing ratio, only the heating of the flange region in the warm temperature range up to 573K was studied on DP600 sheet steel by numerical simulation. A thermo-elastic-plastic finite element method (FEM) analysis of deep drawing at several drawing ratios was performed and compared with experimental results. During the experiments, the flange area of the blank was heated by induction heating, and the central part over the punch was cooled with spray water. Experimental results showed that limiting drawing ratio could be increased by 25.58%. The microstructure of the DP 600 steel was analyzed before and after the warm forming process. No significant changes were observed, and the high strength properties of the DP 600 steel remained intact. There was good agreement between numerical and experimental results.Conference Object Citation - WoS: 176Citation - Scopus: 220Investigations on the Effects of Multi-Layered Coated Inserts in Machining Ti-6al Alloy With Experiments and Finite Element Simulations(Elsevier Science Bv, 2010) Ozel, T.; Sima, M.; Srivastava, A. K.; Kaftanoglu, B.This paper presents investigations on turning Ti-6Al-4V alloy with multi-layer coated inserts. Turning of Ti-6Al-4V using uncoated, TiAlN coated, and TiAlN + cBN coated single and multi-layer coated tungsten carbide inserts is conducted, forces and tool wear are measured. 3D finite element modelling is utilized to predict chip formation, forces, temperatures and tool wear on these inserts. Modified material models with strain softening effect are developed to simulate chip formation with finite element analysis and investigate temperature fields for coated inserts. Predicted forces and tool wear contours are compared with experiments. The temperature distributions and tool wear contours demonstrate some advantages of coated insert designs. (C) 2010 CIRP.Article Citation - WoS: 13Citation - Scopus: 13Surface Characterization and Corrosion Resistance of Boron Nitride Coated Titanium Dental Implants(Maik Nauka/interperiodica/springer, 2019) Cakal, G. O.; Gokmenoglu, C.; Kaftanoglu, B.; Ozmeric, N.Surface modifications of dental implants are of vital importance to enhance osseointegration and improve their corrosion resistance. This study characterized the surface properties of boron nitride (BN) coated titanium implants and their corrosion behaviors. Pretreated implant surfaces were coated successfully with BN by RF-magnetron sputtering system. Surface morphology and elemental composition of uncoated and BN-coated implant surfaces were examined by using X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) coupled with energy dispersive X-ray spectrometer (EDS). The corrosion tests were performed by use of artificial saliva. The tri-dimensional topography of the uncoated sandblasted, large-grit, acid-etched (SLA) implant surface showing sponge-like characteristics, revealed characteristic differences at micro level after BN-coating. It had more holes and peaks in addition to the sponge-like characteristics which further improved its surface microroughness. Boron-to-nitrogen ratio of the coated surface was obtained in the range of 0.8-1.6. The BN-coated SLA implant had no weight loss in the corrosion test. However, the surface characteristics of implants before coating had an impact on corrosion behavior of other implant types. The results demonstrated that titanium implants can be coated with BN successfully and this coating improves the surface properties of dental implants.
