Browsing by Publisher "Trans Tech Publications Ltd"
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Item Calculation of temperature and thermal stress in refractory materials quenched in water using finite element methods(Trans Tech Publications Ltd, 2004) Köksal N.S.; Toparli M.In this study, temperature and thermal stress distribution calculated using a finite element method for magnesia and magnesia-chromite content of chromite between 6% and 15%. The thermal and mechanical properties of the materials were measured using standard laboratory procedure. The samples were dried at 110°C and then transferred into electric furnace at 400, 600 and 800°C and held there for 30 min. Samples were then moved into water and left there for 3 minutes. A quenching simulation was made for three different temperatures (400, 600 and 800°C) using ANSYS 6.0 package. The finite element study was carried out using two-dimensional models. The refractory material was assumed to be homogenous and isotropic. Time dependence of temperature and thermal stress were calculated in surface and center of the plate specimen subjected to the thermal shock by quenching in water.Item Mechanical properties of magnesia and magnesia-chromite refractory materials(Trans Tech Publications Ltd, 2004) Köksal N.S.; Toparli M.; Altun I.A.In this study, modulus of rupture, elastic modulus and fracture toughness values were investigated at elevated temperature for magnesia and magnesia-chromite content of chromite between 6% and 20%. Modulus of rupture and elastic modulus values were calculated by three point bending test at temperatures 400, 600, 800 and 1400°C. Modulus of rupture and Young's modulus values decreased when temperature and content of chromite increased. Modulus of rupture and Young's modulus values at room temperature were compared to the values at 400, 600, 800 and 1400°C. Young's modulus values decreased to about 40% and modulus of rupture values decreased to about 25% of the values at room temperature. The samples were notched as a/h = 0.3 by cutting tool of 0.2 mm thickness. Fracture toughness values were calculated at each temperature. Fracture toughness value at room temperature was compared to the values at 400, 600, 800 and 1400°C. It was seen that fracture toughness values had decreased by the increase at temperature.Item Microstructural evolution of ETIAL 160 aluminium alloy feedstock produced by cooling slope casting(Trans Tech Publications Ltd, 2008) Saklakoglu N.; Birol Y.; Kasman Š.Owing to its superior flow and mould-filling capability, a fully globular structure is essential for semisolid processing technologies. The present work was undertaken to identify the cooling slope casting process parameters that, upon heating to the semisolid state, gives the required globular structure for the ETIAL 160 alloy. Of the two pouring temperatures investigated, 605 °C and 615 °C, the lower pouring temperature was found to provide more globular grains surrounded by liquid phases.Item The influence of toolpath strategy on geometric accuracy in incremental forming(Trans Tech Publications Ltd, 2013) Malyer E.Incremental sheet metal forming is a new process to manufacture sheet metal parts and it is becoming a remarkable technology for fast prototyping and small lot production because of the advantages of this technology such as process flexibility, product independent tooling and higher formability. On the other hand, limited maximum drawing angle, relatively coarse surface roughness, low geometrical accuracy and long forming time are common disadvantages of the process. Furthermore, it is affected by process parameters which are tool diameter, forming velocity, spindle speed, forming geometry and depth, etc. Toolpath strategy which is used to form sheet metal by CNC machine has a key role among these parameters. The present study has been undertaken in order to investigate the suitable toolpath strategy which is developed for metal cutting by commercial CAD/CAM software to increase geometrical accuracy and decrease thinning and forming time. For the intended purpose, seven different toolpath strategies which are rough and finish strategies were used to form a truncated frustum by using one millimeter thick S235JR steel alloy. The effect of each strategy on the surface roughness, geometrical accuracy and thinning distribution of formed product was studied by measuring thickness, drawing angle and depth of formed parts. Therefore, formed parts scanned by 3D laser scanner and STL files of parts were generated then STL files were converted into CAD file. CAD data of parts was used for measurements. The measurements showed that not only forming movements but also transition movements along the tool path affected the geometric accuracy and thinning distribution, surface roughness and forming time of formed parts. On the other hand it was observed that rough strategies were given good results as finish strategies and tool paths generated by CAM software need to be editing for better geometric accuracy, thinning, forming time and surface quality. Copyright © 2013 Trans Tech Publications Ltd.Item Ferrofluid convection in a lid-driven cavity(Trans Tech Publications Ltd, 2018) Selimefendigil F.; Chamkha A.J.This study numerically investigates the mixed convection of ferrofluids in a partially heated lid driven square enclosure. The heater is located to the left vertical wall and the right vertical wall is kept at constant lower temperature while other walls of the cavity are assumed to be adiabatic. The governing equations are solved with Galerkin weighted residual finite element method. The influence of the Richardson number (between 0.01 and 100), heater location (between 0.25 H and 0.75H), strength of the magnetic dipole (between 0 and 4), and horizontal location of the magnetic dipole source (between -2H and -0.5H) on the fluid flow and heat transfer are numerically investigated. It is found that local and averaged heat transfer deteriorates with increasing values of Richardson number and magnetic dipole strength. The flow field and thermal characteristics are sensitive to the magnetic dipole source strength and its position and heater location. © 2018 Trans Tech Publications, Switzerland.