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Reliability and fatigue life evaluation of railway axles
Meral Bayraktar,Necati Tahrali,Rahmi Guclu 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.3
The axle is one of the most important components of a rail vehicle which transmits the weight of the vehicle to the wheels, meets the vertical and horizontal loads formed during static and dynamic moving, and carries the driving moment and braking moment. The prediction of fatigue failure of axles plays an important role in preventing fatigue fractures. Varying loads on components lead to cumulative failure in the mechanism. In this study, failures in axles of rail vehicles serving the Istanbul Transportation Co. have been investigated. Statistical evaluation of real life values has been performed by taking into account the kilometer and load cycle. Equivalent stresses have been used to derive life equations and diagrams by using one of the cumulative life theories known as the Palmgren-Miner method. Finally,theoretical and practical Wohler diagrams S-N (σ-N: stress-life) have been plotted to reveal error calculation.
Melahat Çelik Güven,Meral Tuna,Ergun Bozdağ,Gizem Nur Öztürk,Gulsen Bayraktar 대한치과보철학회 2017 The Journal of Advanced Prosthodontics Vol.9 No.6
The article ‘Comparison of retention forces with various fabrication methods and materials in double crowns’ authored by Melahat Çelik Güven, Meral Tuna, Ergun Bozdağ, Gizem Nur Öztürk, and Gulsen Bayraktar, published in August issue [Vol 9, No 4] of The Journal of Advanced Prosthodontics (2017), has an erratum. In the above article, the financial grant has been erroneously omitted, so it would be disclosed as below. Funding: This study was supported by the Research Fund of Istanbul University. Project No. 50058. The Journal of Advanced Prosthodontics apologizes to the readers for this error.
Comparison of retention forces with various fabrication methods and materials in double crowns
Guven, Melahat Celik,Tuna, Meral,Bozdag, Ergun,Ozturk, Gizem Nur,Bayraktar, Gulsen The Korean Academy of Prosthodonitics 2017 The Journal of Advanced Prosthodontics Vol.9 No.4
PURPOSE. The purpose of this study was to analyze the retention force changes and wear behaviours of double-crown systems over long-term use. MATERIALS AND METHODS. Ten groups, each consisting of six samples, were evaluated. Specifically, casting gold alloy primary crown - casting gold alloy secondary crown (AA), laser sintering primary crown - laser sintering secondary crown (LL), casting Cr alloy primary crown - casting Cr alloy secondary crown, (CC) zirconia primary crown - electroformed secondary crown (ZA), and CAD/CAM titanium alloy primary crown - CAD/CAM titanium alloy secondary crown (TT) groups were evaluated at cone angles of $4^{\circ}$ and $6^{\circ}$. The samples were subjected to 5,000 insertion-separation cycles in artificial saliva, and the retention forces were measured every 500 cycles. The wear levels were analyzed via SEM at the beginning and end of the 5,000 cycles. RESULTS. In all samples, the retention forces increased when the conus angle decreased. The highest initial and final retention force values were found in the $LL-4^{\circ}$ group (32.89 N-32.65 N), and the lowest retention force values were found in the $ZA6^{\circ}$ group (5.41 N-6.27 N). The ZA groups' samples showed the least change in the retention force, and no wear was observed. In the other groups, wear was observed mostly in the primary crowns. CONCLUSION. More predictable, clinically relevant, and less excursive retention forces can be observed in the ZA groups. The retention force values of the LL groups were statically similar to those of the other groups, except the ZA groups.
Comparison of retention forces with various fabrication methods and materials in double crowns
Melahat Çelik Güven,Meral Tuna,Ergun Bozdağ,Gizem Nur Öztürk,Gulsen Bayraktar 대한치과보철학회 2017 The Journal of Advanced Prosthodontics Vol.9 No.4
PURPOSE. The purpose of this study was to analyze the retention force changes and wear behaviours of doublecrown systems over long-term use. MATERIALS AND METHODS. Ten groups, each consisting of six samples, were evaluated. Specifically, casting gold alloy primary crown - casting gold alloy secondary crown (AA), laser sintering primary crown - laser sintering secondary crown (LL), casting Cr alloy primary crown - casting Cr alloy secondary crown, (CC) zirconia primary crown - electroformed secondary crown (ZA), and CAD/CAM titanium alloy primary crown - CAD/CAM titanium alloy secondary crown (TT) groups were evaluated at cone angles of 4° and 6°. The samples were subjected to 5,000 insertion-separation cycles in artificial saliva, and the retention forces were measured every 500 cycles. The wear levels were analyzed via SEM at the beginning and end of the 5,000 cycles. RESULTS. In all samples, the retention forces increased when the conus angle decreased. The highest initial and final retention force values were found in the LL-4° group (32.89 N-32.65 N), and the lowest retention force values were found in the ZA6° group (5.41 N-6.27 N). The ZA groups’ samples showed the least change in the retention force, and no wear was observed. In the other groups, wear was observed mostly in the primary crowns. CONCLUSION. More predictable, clinically relevant, and less excursive retention forces can be observed in the ZA groups. The retention force values of the LL groups were statically similar to those of the other groups, except the ZA groups.