• Journal of the Korean Society for Heat Treatment
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• v.29 no.5
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• pp.209-215
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• 2016

In this study, the effect of Nb contents and processing parameters on dynamic recrystallization behaviour of 0.15C-0.2Si-0.5Mn low-carbon steels was investigated. Three kinds of steel specimens with different Nb contents were fabricated and then high-temperature compressive deformation test was conducted by varying reheating temperature (RT), deformation temperature (DT), and strain rate (SR). The Nb2 and Nb4 specimens containing Nb had smaller prior austenite grain size than the Nb0 specimens, presumably due to pinning effect by the formation of carbides and carbonitrides precipitates at austenite grain boundaries. The high-temperature compressive deformation test results showed that dynamic recrystallization behavior was suppressed in the specimens containing Nb as the strain rate increased and deformation temperature decreased because of pinning effect by precipitates, grain boundary dragging effects by solute atoms, although the compressive stress increased with increasing strain rate and decreasing deformation temperature.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.4
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• pp.527-534
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• 2012

Thermal batteries are primary batteries that use molten salts as an electrolyte and employ an internal pyrotechnic source to heat the battery stack to operating temperatures, typically between 450 and $550^{\circ}C$. The unit cell of thermal batteries consists of an anode, an electrolyte, a cathode, a heat pellet and a current collector. The heat source for such batteries is typically heat pellets based on $Fe/KClO_4$. The elevated temperature by combustion of heat pellet is supposed to cause a flatness non-uniformity, buckling, with a lateral extension diameter of current collector. This paper mainly focused on the combustion and buckling model of current collector to simulate the effect of heat source. Mechanical stresses in the current collector caused by thermal stress is a critical design consideration of thermal batteries because the internal short circuit could be occurred.

• Journal of Ocean Engineering and Technology
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• v.17 no.1
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• pp.80-85
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• 2003

In this study, we developed an analysis method of plate forming by induction heating, verifying the effectiveness of the present method through a series of experiments. The phenomena of the induction heating involves a 3D transient problem, coupled with electromagnetic, heat transfer, and elastoplastic large deformation analyses. To solve the problem, or present an appropriate model and an integrated system. Using the present analysis model, or can estimate the plate deformation in heating without experiments and simulate the plate bending process of induction heating.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.66-68
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• 2004

Induction heating is a process that is accompanied with magnetic and thermal situation. When the high-frequency current flows in the coil, induced eddy current generates heat to conductor. To simulate an induction heating process, the finite element analysis program was developed. A coupling method between the magnetic and thermal routines was developed. In the process of magnetic analysis and thermal analysis, magnetic material properties and thermal material properties depending on temperature are taken into consideration. In this paper, to predict the angular deformation, temperature difference and the shape of heat affected zone were discussed. Also appropriate coil shape for maximum angular deformation were proposed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.6
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• pp.69-76
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• 2015

This study investigates the thermal efficiency and the efficiency of heat transfer through thermal analysis when the same heat is applied to a mortar frame by firing with various configurations of mortar. As the inside diameter of the mortar increases, the additional material must be reinforced. In comparison with the extent of getting cold due to models, a mortar with the strut under the gun barrel becomes cooler than one with no strut. The thermal deformation at firing becomes different. According to the configuration of mortar and its inside diameter, the extent of getting cold becomes different. This study result can be effectively applied for improving the efficiency of the heat transfer of mortar.

• Journal of the korean Society of Automotive Engineers
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• v.15 no.3
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• pp.55-67
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• 1993

In this study, the thermal behavior characteristics of the cylinder block of a small 3-cylinder, 4-stroke gasoline engine were analyzed, using the 3-dimensional finite element method. Before numerical analyses were conducted, the performance test and the heat transfer experiment of the engine were carried out in order to prepare the input data for the computations. Engine cycle simulation was performed to obtain the heat transfer coefficient and the temperature of the gas and the mean heat transfer coefficient of coolant. Temperature fields as a result of steady-state heat transfer were obtained and compared with experimental results measured at specific points of the inner and the outer walls of the cylinder block. The thermal stress and deformation characteristics resulting from the nonuniform temperature distributions of the block were investigated. The effects of the thermal behaviors of the cylinder block on the engine operations and the unfavourable aspects of excessive thermal loading were examined on the basis of the calculated results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1074-1077
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• 2004

This investigation is the result of a structural analysis by FEM and test to define the deformation mode of the Up-Right type Vacuum-Cleaner's Nozzle-Cover. In FEM analysis, 3 different conditions were considered separately, such as (1) Compressive force by Belt tension, (2) Friction heat between Belt and shaft and (3) Compressive force combined with heat. Throughout FEM analysis it was found that the deformation was caused by heat and it was proved through a simulation test with a real product.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.445-450
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• 2006

It is proposed that the electromechanical relation of the conductive materials with high electrical resistance may be used to estimate the current stress of prestressing tendons. To choose the best conductive material to this end, we studied the electromechanical relations of carbon fibers and metalic heat wires experimentally. It is found that the relation of carbon fibers can be modelled by a parabolic(or hyperbolic) function in the early stage of deformation. However because the relation is not consistent when it is unloaded and reload, carbon fibers are not suitable for this purpose. Metallic heat wires show a consistent linear relation during loading and unloading in the elastic deformation and are suitable for this purpose. To estimate the electromechanics relation of metallic wires, we developed a simple formula based on the rigid plasticity. We propose a new kind of prestressing tendons whose stress can be monitored.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.1
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• pp.1-9
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• 2016

Optimum cross-sectional shape of an automotive disc brake was developed based on FEM thermal analyses and the Taguchi method. Frictional heat flux and convection heat transfer coefficients were first calculated using equations and applied to the disc to calculate accurate temperature distribution and thermal deformations under realistic braking conditions. Maximum stress was generated in an area with highest temperature under pads and near the hat of ventilated disc and vanes. The SN ratio from Taguchi method and MINITAB was applied to obtain the optimum cross-sectional design of a disc brake on the basis of thermal deformations. The optimum cross-section of a disc can reduce thermal deformation by 15.2 % compared to the initial design.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.3
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• pp.113-117
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• 2019

The effects of severe plastic deformation and heat treatment on the mechanical properties of Al 5052 and 6005 alloys were investigated using the metallurgical technique and nano-indentation technique in nano-surface region. Equal channel angular pressing (ECAP) was used to apply severe plastic deformation to the aluminum alloys in order to obtain fine grain sized materials. The elastic modulus was measured and interpreted in relation to the metallurgical observation. The elastic modulus increased after ECAP process due to evolution of the fine grains. However, the elastic modulus decreased after heat treatment due to generation of coarsened precipitates on the grain boundaries.