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Yayın Effect of magnesium and osteoblast cell presence on hydroxyapatite formation on (Ti,Mg)N thin film coatings(Springer, 2016-07-19) Önder, Sakip; Çalıkoğlu Koyuncu, Ayşe Ceren Eren; Köse, Gamze Torun; Kazmanlı, Kürşat Muhammet; Kök, Fatma Neşe; Ürgen, MustafaTiN and (Ti,Mg)N thin film coatings were deposited on Ti substrates by an arc-physical vapor deposition technique. The effect of cell presence on hydroxyapatite (HA) formation was investigated using surfaces with four different Mg contents (0, 8.1, 11.31, and 28.49 at.%). Accelerated corrosion above 10 at.% Mg had a negative effect on the performance in terms of both cell proliferation and mineralization. In the absence of cells, Mg-free TiN coatings and low-Mg (8.1 at.%)-doped (Ti,Mg)N surfaces led to an early HA deposition (after 7 days and 14 days, respectively) in cell culture medium (DMEM), but the crystallinity was low. More crystalline HA structures were obtained in the presence of the cells. HA deposits with an ideal Ca/P ratio were obtained at least a week earlier, at day 14, in TiN and low-Mg (8.1 at.%)-doped (Ti,Mg)N compared with that of high-Mg-containing surfaces (>10 at.%). A thicker mineralized matrix was formed on low-Mg (8.1 at.%)-doped (Ti,Mg)N relative to that of the TiN sample. Low-Mg doping (<10 at.%) into TiN coatings resulted in better cell proliferation and thicker mineralized matrix formation, so it could be a promising alternative for hard tissue applications.Yayın Transient multi-domain thermal modeling of interrupted cutting with coated tools(Springer Science and Business Media Deutschland GmbH, 2021-09) Karagüzel, UmutInterrupted cutting operations, such as milling, produce fluctuating tool temperatures which directly affect the process outputs. Thus, prediction of cutting tool temperatures enables process planning, selection of materials for tool substrate and coating layers, and tool geometric design for improved productivity in machining operations. Theoretical analysis of temperature is a cost effective way to predict the tool temperatures. Considering the industrial needs, a theoretical model should be fast, easy to implement, and reliable. To that end, a novel hybrid model, which assembles analytical and numerical methods, is proposed in this study. This novel transient thermal model simulates the interrupted cutting with coated cutting tools. The proposed model includes an analytical heat flux calculation at the tool-chip interface considering the sticking-sliding contact behavior. The determined heat flux is, then, used to perform a numerical solution of the transient heat conduction problem in the cutting tool geometry with temperature-dependent thermal properties. The developed model is validated with experimental results found in literature under different cutting conditions. The results show that the model can predict the maximum temperatures generated in a thermal cycle with an accuracy of 2–10%. Thus, the proposed model can be further used to determine the process parameters, properties of coating layers, and tool geometric design.
