• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.12
• /
• pp.513-518
• /
• 2019

Friction Stir Welding is a welding technique for metal materials that utilizes the heat generated by friction between the material to be welded and the welding tool that rotates at high speed. In this study, a numerical analysis method was used to analyze the change in the internal temperature of the welded material during friction stir welding. As the welding target material, AZ31 magnesium alloy was applied and the welding phenomenon was considered a flow characteristic, in which a melting-pool was formed. FLUENT was used as the numerical tool to perform the flow analysis. For flow analysis of the welding process, the welding material was assumed to be a high viscosity Newtonian fluid, and the boundary condition of the welding tool and the material was considered to be the condition that friction and slippage occur simultaneously. Analyses were carried out for various rotational speeds and the translational moving speed of the welding tool as variables. The analysis results showed that the higher the rotational speed of the welding tool and the slower the welding tool movement speed, the higher the maximum temperature in the material increases. Moreover, the difference in the rotational speed of the welding tool has a greater effect on the temperature change.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.36 no.4
• /
• pp.300-307
• /
• 2016

The faults in railway vehicle components may result in either the stoppage of the service and the derailment of the vehicle. Therefore, it is important to diagnose and monitor the main components of a railway vehicle. The use of temperature is one of the basic methods for the diagnosis of abnormal conditions in the rotational components of a railway vehicle, such as bearings, reduction gears, brake discs, wheels and traction motors. In the present study, the diagnose of the rotational components using infrared thermography and a pattern recognition technique was carried out and a field test was performed. The results show that this method of diagnosis using infrared thermography can be used to identify abnormal conditions in rotational components of a railway vehicle.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.9 no.5
• /
• pp.374-378
• /
• 2004

The effects of various environmental factors such as pH (5, 6, 7, 8 and 9), temperature (30, 37 and $40^{\circ}C$) and rotational speed (150, 200 and 250 rpm) on the growth and the hepatitis B core antigen (HBcAg) production of Escherichia coli W3110IQ were examined in the present Study. The highest growth rate is achieved at pH 7, $37^{\circ}C$ and at a rotational Speed of 250 rpm which is 0.927 $h^{-1}$. The effect of pH on cell growth is more substantial compared to other parameters; it recorded a $123\%$ different between the highest growth rate (0.927 $h^{-1}$) at pH 7 and lowest growth at pH 5. The highest protein yield is achieved at pH 9, rotational speed of 250 rpm and $40^{\circ}C$. The yield of protein at pH 7 is $154\%$ higher compared to the lowest yield achieved at pH 5. There is about $28\%$ different of the protein yield for the E. coli cultivated at 250 rpm compared to that at 150 rpm which has the lowest HBcAg yield. The yield of protein at $40^{\circ}C$ is $38\%$ higher compared to the lowest yield achieved at $30^{\circ}C$.

• The Korean Journal of Rheology
• /
• v.11 no.2
• /
• pp.73-81
• /
• 1999

The intention of this research is to give criteria of designing devices using ER fluids and MR fluids. The Properties of commercial ER fluids and MR fluids are compared using a rotational viscometer. The yield strength is compared upon changes of shear rate, temperature and applied fields. MR fluids seem less sensitive to temperature change than ER fluids. In cases of MR and ER fluid dampers, the time delay and damping force are measured in tension and compression mode when the applied field changes.

• Journal of Photoscience
• /
• v.12 no.3
• /
• pp.119-122
• /
• 2005

The photophysical properties of coumarin 6 laser dye have been studied in two solvents; ethanol and acetonitrile using steady-state fluorescence depolarization technique. The experimentally measured reorientation time of coumarin 6 is more or less the same in given solvents at particular temperature. It is found that coumarin 6 rotates slower in acetonitrile than in ethanol especially at higher values of viscosity over temperature. We also measure the ground and excited state dipole moments of coumarin 6 by solvent perturbation method. The results found that excited state dipole moment is greater than ground state dipole moment, which indicates that excited state is more polar than the ground state.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2005.10a
• /
• pp.358-361
• /
• 2005

The rotational barrel type equipment has been designed for the new rheology fabrication process. During the continuous rotation of barrel with a constant temperature, the shear rate is controlled with the rotation speed and rotation time of barrel. The barrel surface can be controlled the temperature by the induction heating and cooling system. Many experiments were widely examined by using this system with controlling the rotation speed and the rotation time. The possibility for the rheoforming process was investigated with microstructural characteristics.

• Solar Energy
• /
• v.18 no.4
• /
• pp.101-110
• /
• 1998

The purpose of this research is to study the charateristics and manufacture of a composite heat pipe system with rotational and static pipe. A composite heat pipe system were tested to obtain the relationship between the expansion injector and auxiliary expansion for the motion of the working fluid by the experimental results. In addition the heat transport characteristics were found based on wall temperature of rotor, expansion injector, storage tank and vapor temperature. Water is used as working fluid of heat pipes. As the results of experiments, the composite heat pipe was operated for long times, 10 hour above with various rotational speed in performance. There were a few unexpected data by the capillary pumped loop at small working fluid, but as a whole the testing was successful.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.10a
• /
• pp.645-648
• /
• 2005

The rotational barrel type equipment has been designed for the new rheology fabrication process. During the continuous rotation of barrel with a constant temperature, the shear rate is controlled with the rotation speed and rotation time of barrel. The barrel surface can be controlled the temperature by the induction heating and cooling system. Many experiments were widely examined by using this system with controlling the rotation speed and the rotation time. The possibility for the rheoforming process was investigated with microstructural characteristics.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.19 no.5
• /
• pp.111-117
• /
• 2020

Centrifugal casting is suitable for producing hollow-products using centrifugal force. Bush type metal bearings are the key parts that facilitate the rotational movement of various machinery. Metal bearings produced by conventional centrifugal casting machines show rotational imbalance. Therefore, after injecting a large amount of material, the product's precision is secured in the secondary processing. Rotational imbalance is caused by the force acting on the rotary disc plate. In order to minimize rotational imbalance, NASTRAN was used for the optimal design and structural analysis. It was concluded that the rotating plate of the conventional centrifugal casting machine should be prevented from tilting. For this purpose, the location & thickness of the stiffeners were obtained through the optimum design. In the conventional centrifugal casting machine, both ends of the product are lower in temperature than the center part, so internal stress occurs. This solves this problem by inserting a heating coil into the rotating plate.

• Publications of The Korean Astronomical Society
• /
• v.20 no.1 s.24
• /
• pp.7-10
• /
• 2005

We have calculated 2448 interstellar cloud models to investigate the formation and destruction of high rotational level $H_2$ according to the combinations of five physical conditions: the input UV intensity, the $H_2$ column density, cloud temperature, total density, and the $H_2$ formation rate efficiency. The models include the populations of all the accessible states of $H_2$ with the rotational quantum number J < 16 as a function of depth through the model clouds, and assume that the abundance of $H_2$ is in a steady state governed primarily by the rate of formation on the grain surfaces and the rates of destruction by spontaneous fluorescent dissociation following absorption in the Lyman and Werner band systems. The high rotational levels J = 4 and J = 5 are both populated by direct formation into these levels of newly created molecules, and by pumping from J = 0 and J = 1, respectively The model results show that the high rotational level ratio N(4)/N(0) is proportional to the incident UV intensity, and is inversely proportional to the $H_2$ molecular fraction, as predicted in theory.