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Öğe The effect of weld parameters on friction stir welding of brass plates(Wiley-V C H Verlag Gmbh, 2008) Cam, G.; Serindag, H. T.; Cakan, A.; Mistikoglu, S.; Yavuz, H.More successful results have been obtained in butt- and overlap-joining of Al-alloy plates by a recently developed solid state joining technique, namely friction stir welding (FSW), than in more conventional fusion welding processes. In this joining technique, no fusion takes place in the joint area of the plates welded. This novel joining method also offers the potential to weld some other materials rather than Al-alloys, such as Mg-alloys, brasses and low strength steels. In this study, the applicability of friction stir welding to brasses, namely 90%Cu-10%Zn and 70%Cu-30%Zn alloys, has been investigated. The joint performance was determined by conducting optical microscopy, microhardness mesurements and mechanical testing (e.g. tensile and bend tests). The effect of welding speed on the joint quality at a given rotational speed of the stirring pin (i.e. 1600 rpm) was also determined for both alloys. The highest joint performances were obtained at a welding speed of 210 mm/min for both alloys.Öğe For how many times can a partially absorbable monofilament mesh be sterilized? In vitro experimental study(Springer Wien, 2013) Ozkan, O. V.; Aydogan, A.; Akkucuk, S.; Aydin, M.; Nacar, E.; Ozer, B.; Mistikoglu, S.We investigated the effects of hydrogen peroxide gas plasma resterilization (HPS) on partially absorbable monofilament meshes in terms of their mechanical properties and risk of infection. A mesh was divided into small pieces which were categorized as HPS-1, HPS-2 and HPS-3 according to the number of HPS. To assess the strength of specimens, maximum load, elongation at maximum load and quantity of energy required for complete failure of the specimens were measured. Microbiological and ultrastructural analyses were also performed. There was not a significant relationship between control and HPS-1, HPS-2 groups in terms of maximum load and quantity of energy required for complete failure of the specimens. However, those parameters were statistically different between HPS-3 and control groups. We observed minor morphological changes in the HPS-3 group when compared to those of the control group. No risk of infection was detected by microbiological tests. It is advisable to apply HPS to partially absorbable monofilament meshes no more than twice since sterilization for three times leads to degeneration in mesh structure and strength.Öğe Microstructural and Mechanical Characterization of Friction Stir Butt Joint Welded 63% Cu-37% Zn Brass Plate(Amer Welding Soc, 2009) Cam, G.; Mistikoglu, S.; Pakdil, M.A recently developed solid-state joining technique, namely friction stir welding (FSW), has been well demonstrated to produce joints with better joint performances in Al alloys, particularly in difficult-to-weld grades, than those obtained in more conventional fusion welding processes. The technique has already been implemented with joining Al alloys in various production lines such as shipbuilding, automobile, high-speed train manufacturing, and aviation industries. In this study, the applicability of friction stir welding to 63% Cu-37% Zn brass plate has been investigated. The joint performance values were determined by conducting optical microscopy, microhardness measurements, and mechanical testing (e.g., tensile and bend tests). The effects of the tool rotational speed (i.e., 1250 and 1600 rev/min) and the welding speed on the joint performance were determined. The best joint performances were obtained at a rotational speed of 1600 rev/min with a welding speed of 225 mm/min.Öğe Processing irregular wave measurements to enhance point absorber power capture performance(Pergamon-Elsevier Science Ltd, 2011) Yavuz, H.; Mistikoglu, S.; Stallard, T.The paper aims at introducing practical methods for power capture performance enhancement of a heaving wave energy converter in irregular seas. The optimum control solution requires tuning to wave frequency based on wave force information. However, identification of the wave frequency in irregular seas is considered to be a complex and difficult task. This is partly due to technical difficulties in determination of the wave force. Besides, there are no clear guidelines for identification of wave frequency from an irregular sea state based wave force information. In a typical application, one of the available sources of information about the wave properties is the wave elevation record. The proposed approach presents a method for estimation of the wave frequency information from the wave elevation data by using signal processing and filtering techniques. The proposed method uses filters to generate an estimation of wave force information, which is used to identify the local wave frequency by method of a time-series analysis of the data. This wave frequency information is then used in tuning the device. The details of the proposed techniques, the model of the wave energy converter, the simulated sea states and the related simulation results are also presented. (C) 2011 Elsevier Ltd. All rights reserved.
