• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.8
• /
• pp.1461-1471
• /
• 2002

Linear motor has a lot of advantages in comparison with conventional feed mechanisms: high velocity, high acceleration, good positioning accuracy and a long lifetime. An important disadvantage of linear motor is its high power loss and heating up of motor and neighboring machine components in operation. For the application of the linear motors to precision machine tools an effective cooling method and thermal optimizing measures are required. In this paper Finite-Element-Method for the thermal behavior of synchronous linear motor is introduced, which is useful for the design and manufacturing of linear motors. By modeling the linear motor the orthotropic physical properties of the sheet metal and windings were considered and convective coefficient in the water cooler and to the surroundings was defined by analytical and experimental method. The calculated isothermal lines could analyze the heat flow in the linear motor.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.05a
• /
• pp.78-81
• /
• 2002

To achieve high precision machine totals with high speed, it is needed to develop excellent rigidity statically, dynamically and thermally as well. In this view the chief things that thermal deformation of machine tool structure is directly related to high precision. And thermal behavior for transmission procedure have an effect on high precision. It is needed to exact temperature distribution of each members and all contact elements included for machine tool structure. This paper deals with thermal behavior caused by temperature variation in a high speed feeding process. At this procedure of temperature distribution is estimated using a Predictor-Corrector Method.

• Journal of Power System Engineering
• /
• v.10 no.2
• /
• pp.93-98
• /
• 2006

Metal matrix composites(MMCs) reinforced with ceramic particulates are receiving increasing attention because their high specific strength, low coefficient of thermal expansion and excellent wear resistance. Especially, Al-based composites(AMCs) have been widely applied for the aerospace and automotive industries. Such composites are mainly fabricated by the cast, powder metallurgy and infiltration process. In this study, SiC particulate reinforced Al-based composites were fabricated by thermal spray process and their wear behavior were investigated. Composites with different spray parameter were fabricated by using flame spray apparatus. Microstructure and wear behavior of the composites were observed by scanning electron microscope(SEM) and electron probe micro-analysis(EPMA).

• Nuclear Engineering and Technology
• /
• v.55 no.6
• /
• pp.2069-2087
• /
• 2023

In nuclear power plant (NPP) accidents, the containment is subject to high temperatures and high internal pressures, which may further trigger serious chain accidents such as core meltdown and hydrogen explosion, resulting in a significantly higher accident level. Therefore, studying the mechanical performance of a containment under high temperature and high internal pressure is relevant to the safety of NPPs. Based on similarity principles, the 1:3.2 scale model of a prestressed concrete containment vessel (PCCV) of a NPP was designed. The loading method, which considers the thermal-pressure coupling conditions, was used. The mechanical response of the PCCV was investigated with a simultaneous increase in internal pressure and temperature, and the failure mechanism of the PCCV under thermal-pressure coupling conditions was revealed.

• Journal of the Korean Ceramic Society
• /
• v.48 no.6
• /
• pp.617-620
• /
• 2011

Thermal shock behavior of porous ceramic nozzles with various pore sizes for continuous casting process of steel was investigated in terms of physical properties and microstucture. Porous nozzle samples with a composition of $Al_2O_3$-$SiO_2$-$ZrO_2$ were fabricatedby adding various sizes of graphite as the pore forming agent. As the graphite size increased from 45~75 to 150~180 ${\mu}m$, both the resulting pore size and the flexural strength also increased. A thermal shock test was carried out at temperatures (${\Delta}$T) of 600, 700, 800, and 900$^{\circ}C$. Microstructure analysis revealed a small number of cracks on the sample with the largest mean pore size of 22.32 ${\mu}m$. In addition, increasing the pore size led to a smaller decrease in both pressure drop and elastic modulus. In conclusion, controlling the pore size can enhance thermal shock behavior.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.30 no.12 s.255
• /
• pp.1543-1550
• /
• 2006

Since the performance of joints usually determines the structural efficiency of composite structures, an extensive knowledge of the behavior of adhesive joints and the related effect on joint strength is essential for design purposes. In this study, the torque capacity of adhesive joints was predicted using the combined thermal and mechanical analyses when the adherend was a composite tube. A finite element analysis was performed to evaluate residual thermal stresses developed in the joint, and mechanical s stresses in the adhesive were calculated including both the nonlinear adhesive behavior and the behavior of composite tubes. Three different joint failure modes were considered to predict joint failure: interfacial failure, adhesive bulk failure, and adherend failure. The influence of the composite adherend stacking angle on the residual thermal stresses was investigated, and how the residual thermal stresses affect the joint strength was also discussed. Finally, the predicted results were compared with experimental results available in literature.

• 한국태양에너지학회:학술대회논문집
• /
• 2008.11a
• /
• pp.273-279
• /
• 2008

The purpose of this study is not only to evaluate thermal performance but also to find the stress behavior of heat transfer tubes under the part load operation in Heat Recovery Steam Generator. Flow analysis was performed to know the behavior of exhaust gas from gas turbine and thermal performance was calculated using distribution of hot exhaust velocity. In addition, tubes temperature during operation were gathered from actual plant to verify the uneven flow distribution under part load operation. Stress analysis was performed using tubes temperature data gathered from actual plant under both part and full load operations to know the stress behavior of tubes.

• Korean Journal of Materials Research
• /
• v.14 no.5
• /
• pp.305-309
• /
• 2004

Mechanical alloying (MA) of Ti-25.0～37.5at%Si powders was carried out in a high-energy ball mill, and in situ thermal analysis was also made during MA. In order to classify the synthesis behavior of the powders with respect to at%Si, the synthesis behavior during MA was investigated by in situ thermal analysis and X-ray diffraction (XRD). In situ thermal analysis curves and XRD patterns of Ti-25.0～26.1at%Si powders showed that there were no peaks during MA, indicating $Ti_{5}$ $Si_3$ was synthesised by a slow reaction of solid state diffusion. Those of Ti-27.1～37.5at%Si powders, however, showed that there were exothermic peaks during MA, indicating $_Ti{5}$ $Si_3$ and$ Ti_3$Si phase formation by a rapid exothermic reaction of self-propagating high-temperature synthesis (SHS). For Ti-27.1～37.5at%Si powders, the critical milling times for SHS decreased from 38.1 to 18.5 min and the temperature rise, ΔT (= peak temperature - onset temperature) increased form $19.5^{\circ}C$ to $26.7^{\circ}C$ as at%Si increased. The critical composition of Si for SHS reaction was found to be 27.1at% and the critical value of the negative heat of formation of Ti-27.1at%Si to be -1.32 kJ/g.

• Korean Journal of Materials Research
• /
• v.14 no.5
• /
• pp.310-314
• /
• 2004

Mechanical alloying (MA) of Ti-50.0～66.7at%Si powders was carried out in a high-energy ball mill, and in situ thermal analysis was also made during MA. In order to classify the synthesis behavior of the powders with respect to at%Si, the synthesis behavior during MA was investigated by in situ thermal analysis and X-ray diffraction (XRD). In situ thermal analysis curves and XRD patterns of Ti-50.0～59.6at%Si powders showed that there were exothermic peaks during MA, indicating TiSi, $TiS_2$, and $Ti_{5}$ $Si_4$ phase formation by a rapid exothermic reaction of self-propagating high-temperature synthesis (SHS). Those of Ti-59.8～66.7 at%Si powders, however, showed that there were no peaks during MA, indicating any Ti silicide was not synthesised until MA 240 min. For Ti-50.0～59.6at%Si powders, the critical milling times for SHS increased from 34.5 min to 89.5 min and the temperature rise, $\Delta$T (=peak temperature-onset temperature) decreased form $26.2^{\circ}C$ to $17.1^{\circ}C$ as at%Si increased. The critical composition of Si for SHS reaction was found to be 59.6at% and the critical value of the negative heat of formation of Ti-59.6at%Si to be -1.48 kJ/g.

• Journal of the Korean Ceramic Society
• /
• v.49 no.1
• /
• pp.111-117
• /
• 2012

Dependencies of thermal properties on the crystallization behavior of $0.9CaMgSi_2O_6-0.1MgSiO_3$ glass-ceramics were investigated as a function of heat-treatment temperature from $750^{\circ}C$ to $950^{\circ}C$. The crystallization behavior of the specimens depended on the heat-treatment temperature, which could be evaluated by differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) analysis by the Rietveld-reference intensity ratio (RIR) combined procedure. With an increase of the heat-treatment temperature, the thermal conductivity and thermal diffusivity of the heat-treated specimens increased. These results could be attributed to the increase of crystallization with heat-treatment temperature. However, the specific heat capacity of the heat-treated specimens was not affected by the heat-treatment temperature. The thermal conductivities measured from $25^{\circ}C$ to $100^{\circ}C$ were also discussed for application to lighting-emitting diode (LED) packages and substrate materials.