Malzeme Bilimi ve Mühendisliği Bölümü

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Citation - WoS: 20
Citation - Scopus: 21
Effect of electrical discharge machining on dental Y-TZP ceramic-resin bonding
(Elsevier Ireland Ltd, 2017) Çoğun, Can; Rona, Nergiz; Yenisey, Murat; Esen, Ziya; Kucukturk, Gokhan; Gurun, Hakan; Cogun, Can; Esen, Ziya; 3837; 52373; Mekatronik Mühendisliği; Ortak Dersler Bölümü
Purpose: The study determined (i) the effects of electrical discharge machining (EDM) on the shear-bond strength (SBS) of the bond between luting resin and zirconia ceramic and (ii) zirconia ceramic's flexural strength with the three-point bending (TPB) test. Methods: Sixty 4.8 mm x 4.8 mm x 3.2 mm zirconia specimens were fabricated and divided into four groups (n = 15): SBG: sandblasted + silane, TSCG: tribochemical silica coated + silane, LTG: Er:YAG laser treated + silane, EDMG: EDM + silane. The specimens were then bonded to a composite block with a dual-cure resin cement and thermal cycled (6000 times) prior to SBS testing. The SBS tests were performed in a universal testing machine. The SBS values were statistically analyzed using ANOVA and Tukey's test. To determine flexural strength, sixty zirconia specimens were prepared and assigned to the same groups (n = 15) mentioned earlier. After surface treatment TPB tests were performed in a universal testing machine (ISO 6872). The flexural strength values were statistically analyzed using ANOVA and Tukey's test (a = 0.05). Results: The bond strengths for the four test groups (mean SD; MPa) were as follows: SBG (Control), 12.73 +/- 3.41, TSCG, 14.99 +/- 3.14, LTG, 7.93 +/- 2.07, EDMG, 17.05 +/- 2.71. The bond strength of the EDMG was significantly higher than those of the SBG and LTG (p < 0.01). The average flexural strength values for the groups SBG (Control), TSCG, LTG and EDMG were 809.47, 800.47, 679.19 and 695.71 MPa, respectively (p > 0.05). Conclusions: The EDM process improved the SBS. In addition, there was no significant adverse effect of EDM on the flexural strength of zirconia. (C) 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.
Citation - WoS: 17
Citation - Scopus: 22
Experimental Investigation on Wire Electric Discharge Machining of Biodegradable AZ91 Mg Alloy
(Springer, 2021) Çoğun, Can; Urtekin, Levent; Ozerkan, Haci Bekir; Esen, Ziya; Cogun, Can; Genc, Asim; Esen, Ziya; Bozkurt, Fatih; 3837; 52373; Mekatronik Mühendisliği; Ortak Dersler Bölümü
The AZ91 magnesium alloy, used commonly as a biodegradable material in biomedical applications, is generally formed by conventional casting method (CCM) and high-pressure die casting method (HPDCM). The AZ91 alloys exhibit poor machinability with conventional chip removal methods since they degrade at elevated temperatures. In this study, the wire electric discharge machining (WEDM) was presented as a candidate process to machine the AZ91 alloy since no cutting stresses and plastic deformations were applied by the cutting tool to the part causing elevated temperatures. In this context, the WEDM machinability of the AZ91 alloy samples produced by cold chamber HPDCM and CCM at different process parameters, was experimentally investigated. The machining performance outputs (the machining current (I), the machining rate (MR), the average surface roughness (R-a), and surface topography) were found for the varying process parameters [pulse time (t(s)), pulse-off time (t(off)), dielectric flushing pressure (P-d), and wire speed (V-w)]. The present study revealed that the I and the MR were significantly dependent on the density, the porosity, and the micro structure of the samples, and the HPDCM samples gave the higher MR and the smoother surface than that of the CCM.

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