Browsing by Author "Celik, Gokhan"
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Article Citation Count: 8Biomechanical evaluation of a fiber-reinforced composite prosthesis supported by implants with and without a microthread collar design(Elsevier Taiwan, 2010) Meric, Gokce; Erkmen, Erkan; Kurt, Ahmet; Eser, Atilim; Celik, GokhanBackground/purpose: A fiber-reinforced composite (FRC) resin system was introduced as an alternative for implant-retained fixed dental prostheses (FDPs); however, the stress distribution in the bone around the implants which support the FRC-FDP has so far not been reported. The aim of this study was to investigate the biomechanical behavior of FRC-FDPs supported by implants with different collar geometries. Materials and methods: A 3-dimensional finite element analysis method was selected to evaluate the stress distribution. FRC-FDPs were supported by 2 different dental implant systems with 2 distinct collar geometries: a microthread collar structure (MCS) and a non-MCS (NMCS). In separate load cases, 300-N vertical, 150-N oblique, and 60-N horizontal forces were simulated. Tensile and compressive stress values in the cortical and cancellous bone and von Mises stresses in the fixture-abutment complex, the framework, and veneer material were calculated. Results: The MCS model revealed higher compression stresses at the cortical bone than did the NMCS model under all 3 load conditions. Moreover, higher tensile stresses under the oblique loads at the cortical bone were shown with the MCS model. In each model, stresses were much higher in the implant abutment complex than in the cortical bone, and they were very low in the cancellous bone. Conclusion: Although additional experimental and clinical studies are needed, FRC-FDPs can be considered a suitable and alternative treatment choice for an implant-supported prosthesis. The implant design and geometry affect the load-transmission mechanisms. Implants with an MCS that supports FRC-FDPs were shown to be superior in terms of the stress distribution in the bone around the implant compared to implants with an NMCS. Copyright (C) 2010, Association for Dental Sciences of the Republic of China. Published by Elsevier Taiwan LLC. All rights reserved.Conference Object Citation Count: 0Investigation of Influence Parameters on Forming Limit Diagrams of Aluminum Alloy-AA2024(Trans Tech Publications Ltd, 2011) Kaftanoğlu, Bilgin; Kaftanoglu, Bilgin; Karadoğan, Celalettin; Manufacturing EngineeringSheet metal forming technology is the keyword for many industries such as aerospace, aeronautics and automobile industries. Customer expectations, quality and safety requirements and market competitions require sheet metal forming operations to be well analyzed before the process to fulfill all these requirements. In this study, combination of FEA (finite element analysis) and mechanical material characterization were used in order to improve sheet metal forming operations while considering cost and quality. On the material characterization side of the studies, simple uniaxial tensile tests were conducted to obtain anisotropy parameters and yield points along different directions and hydraulic bulge test (HBT) was performed to obtain plastic behavior of the material up to 0.7 strains. Deformation measurements were conducted using optical measurement system GOM-ARAMIS while a 60-ton hydraulic press; Zwick/Roell BUP600 was used to deform the sheet part AA2024-0 aluminum alloy. Effects of process parameters, which are initial material thickness, lubrication and punch speed, on sheet metal formability and forming limit diagrams (FLDs) were investigated. On the study of thickness effects, sheet metals those having 0.81mm, 1.27mm and 1.60mm thickness were tested. Punch velocities of 250mm/min, 500mm/min and 750mm/min were used to investigate effect of punch speed on formability of sheet metals. Finally, PTFE (Polytetrafluoroethylene), paraffin lubricated and dry conditions were presented to obtain friction effects. FE analyses were performed to simulate experiments and to obtain friction coefficients of different lubricants. Good correlations were observed between numerical simulations and experimental results.