Browsing by Author "Ozturk K."

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Analysis of indentation size effect (ISE) behavior in low-load Vickers microhardness testing of (Sm123) 1-x (Nd123) x superconductor system
(2013-01-01) Celik S.; Ozturk O.; Coşkun E.; Sarıhan M.; Asikuzun E.; Ozturk K.; Terzioglu C.
Indentation size effect (ISE) for (Sm123) 1-x (Nd123) x superconducting samples which were fabricated by the solid state reaction technique for values of x = 0.00, 0.05, 0.10, 0.20, and 0.30 was investigated by analyzing the theoretical models. When the experimental data of a number of single crystals which have the different crystal structure and different chemical bonding inside the polycrystallined samples were analyzed with the ISE models, the sample encountering with resistance and elastic deformation was observed as well as plastic deformation. The microhardness values on different surfaces of materials were calculated by using Meyer Law, proportional specimen resistance model, modified proportional specimen resistance model, elastic/plastic deformation model and the Hays-Kendall (HK) approach. The results showed that the HK approach was determined as the most successful model. Furthermore, X-ray powder diffraction and scanning electron microscope measurements were analyzed for superconducting properties of (Sm123) 1-x (Nd123) x superconductor system. The results showed that microhardness values at the minimum load and averaged plateau region of load increased with increase of Nd123 concentration. Nd123 content can be used as to be estimated the microhardness value of (Sm123) 1-x (Nd123) x superconducting sample in the range of 0.878-2.717 GPa. The control of the microhardness value by using Nd123 content in (Sm123) 1-x (Nd123) x superconducting structure can be useful in technological applications in superconductivity industry. © 2013 Springer Science+Business Media New York.
Nanoindentation study on Gd-deposited YBaCuO superconductor
(2013-01-01) Yilmaz F.; Uzun O.; Kolemen U.; Kilicaslan M.; Basman N.; Ergen S.; Ozturk K.; Yanmaz E.
Nanoindentation technique was used to characterize the mechanical properties of Gd-deposited bulk YBaCuO superconductors fabricated by solid-state reaction method. In order to determine the hardness and reduced modulus of the samples, load-displacement data were analysed by using the Oliver-Pharr method. The hardness values exhibited significant peak load-dependence especially at lower peak loads, while the reduced modulus values were found to be nearly constant at studied loading range. In order to find true hardness of the samples, the peak load-dependency of hardness was analysed by using Meyer's law,minimum resistance model, elastic/plastic deformation model, energy balance model, Nix-Gao model and Mukhopadhyay approach. Of the aforementioned models, energy balance model and Mukhopadhyay approach were found to be the most effective models to explain the load-dependency of hardness. © Indian Academy of Sciences.