• Korean Journal of Metals and Materials
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• v.47 no.2
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• pp.114-120
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• 2009

The viscosities of $CaO-SiO_2-Al_2O_3-MgO$ flux were measured under the condition of $CaO/SiO_2=1.0-1.3$ and 5-20 wt%MgO. Submerged arc welding flux with $5wt%Al_2O_3$ content had the lowest critical temperature and widest solid-liquid coexisting region at about 5 wt%MgO. It indicateds that both critical temperature and viscosity depend on the kind of primary phase of molten flux. Viscous behavior of the molten flux at 1773 K was analyzed in the view of silicate structure changed by FT-IR spectroscopy. Based on the critical temperature and the behavior of viscosity at a fixed temperature, it could be proposed that the contents of MgO and $Al_2O_3$ in SAW flux show a pronounced effect on preventing contamination in maintaining the liquid phase flux after welding process.

• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.5
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• pp.3-9
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• 2007

In this study, the effect of the purification materials is analyzed and tested by Flow 3D and Hydraulic model test. Three dimension numerical analysis led from the research that sees abnormal form and the size back of the water purification material conferred the flowing water conduct inside the test channel against the test condition. Comparison it analyzed the flux distribution, a water depth of the channel which establishes the water purification materials the cross section, an interval of the water purification material, a conference with general channel, it change executed. As a result, the cross section ratio of the purification materials against and a flux change from the test which it sees. The interval of the purification materials in order to prevent three dimension that follows in decrease of increase and flux must decide an interval.

• Journal of the Korean Society for Heat Treatment
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• v.26 no.5
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• pp.233-240
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• 2013

Rapid and homogeneous heating in heat treatment has been a challenging engineering issue throughout a heating temperature over $1,000^{\circ}C$. Induction heating has been widely used in field of heat treatment compared with conventional heating system. Advantages in homogeneous heating, simple fabrication, and repeatable use can be efficiently made with the induction heater. In this paper, numerical analysis of an induction coil system for heat flux gauge heating is performed. The effect of configuration on the heating performance was considered in various cases of the coil radius, distance between the winding, relative height difference between the heat flux gauge and the coil, and the applied current frequency. Temperature distribution within the heat flux gauge at frequency-steady state was calculated with a finite element method. Sensitivity analysis was also performed and the relative importance of 2 key parameters; coil radius, distance between the winding, were taken as main contributors for induction heating.

• Smart Structures and Systems
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• v.24 no.6
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• pp.759-768
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• 2019

In nuclear fusion reactors, the key structural component (i.e., the plasma-facing component) undergoes high heat flux cyclic loading. To ensure the safety of fusion reactors, an experimental study on the temperature-induced creep of stainless steel under heat flux cyclic loading was performed in the present work. The strains were measured using a stereo digital image correlation technique (3D-DIC). The influence of the heat haze was eliminated, owing to the use of a vacuum environment. The specimen underwent heat flux cycles ($500^{\circ}C-1000^{\circ}C$) with different mechanical preloads (0 kN, 10 kN, 30 kN, and 50 kN). The results revealed that, for a relatively large preload (for example, 50 kN), a single temperature cycle can induce a residual strain of up to $15000{\mu}{\varepsilon}$.

• Steel and Composite Structures
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• v.19 no.6
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• pp.1549-1560
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• 2015

This paper presents the characterization of fatigue crack in the A283 Grade C steel using the MMM method by identifying the effects of magnetic flux leakage towards the crack growth rate, da/dN, and crack length. The previous and current research on the relation between MMM parameters and fatigue crack effect is still unclear and requires specific analysis to validate that. This method is considered to be a passive magnetic method among other Non-Destructive Testing (NDT) methods. The tension-tension fatigue test was conducted with a testing frequency of 10 Hz with 4 kN loaded, meanwhile the MMM response signals were captured using a MMM instrument. A correlation between the crack growth rate and magnetic flux leakage produces a sigmoid shape curve with a constant values which present the gradient, m value is in the ranges of 1.4357 to 4.0506, and the y-intercept, log C in the ranges of $4{\times}10^{-7}$ to 0.0303. Moreover, a linear relation was obtained between the crack length and magnetic flux leakage which present the R-Squared values is at 0.830 to 0.978. Therefore, MMM method has their own capability to investigate and characterize the fatigue crack effects as a main source of fracture mechanism for ferrous-based materials.

• Agricultural and Biosystems Engineering
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• v.1 no.1
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• pp.49-53
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• 2000

A magnet assembly is a critical element of a nuclear magnetic resonance(NMR) based sensor. Magnetic flux density and homogeneity are essential to its optimum performance. Geometry and magnet material properties determine the magnetic flux density and homogeneity of the assembly. This study was carried out to develop the design for a magnet assembly. A 2-D finite element model for the magnetic assembly was developed using ANSYS and evaluated the effects of adding shimming frames and steel bars in the corners of the rectangular steel cover which surrounded the magnet. The assembly was manufactured and evaluated. According to the ANSYS model, modified pole frames increased magnetic flux density by 8.3% and increased homogeneity by 83%. Addition of steel bars in the corners increased the magnetic flux density by 1%, and improved homogeneity up to three times. The difference between simulated and measured magnetic flux densities at the center point of the air gap was within 2.4%.

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.134.1-134.1
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• 2007

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.37-37
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• 2008

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.5.1-5.1
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• 2010

One of the most important environmental problems is global warming. Global warming is caused by increase in the amounts of water vapor, methane, carbon dioxide and other gases being released into the atmosphere as a result of the burning of fossil fuels. It has thus become important to reduce fossil fuel use. Environmentally friendly preparation of functional materials has, therefore, attracted much interest for environmental problems. Furthermore, nature mimetic processes are recently been of great interest as environmentally friendly one. There have been many studies on fabrication of various functional nanocrystals. Among various nanocrystal fabrication techniques, flux growth is an environmentally friendly, very convenient process and can produce functional nanocrystals at temperatures below the melting points of the solutes. Furthermore, this technique is suitable for the synthesis of crystals having an enhedral habit. In flux growth, the constituents of the materials to be crystallized are dissolved in a suitable flux (solvent) and crystal growth occurs as the solution becomes critically supersaturated. The supersaturation is attained by cooling the solution, by evaporation of the solvent or by a transport process in which the solute is made to flow from a hotter to a cooler region. Many kinds of oxide nanocrystals have been grown in our laboratory. For example, zero- (e.g., particle), one- (e.g., whisker and tube) and two-dimensional (e.g., sheet) nanocrystals were successfully grown by flux method. Our flux-growth technique has some industrial and ecological merits because the nanocrystal fabrication temperatures are far below their melting points and because the used reagents are less harmless to human being and the environment.

• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.24-32
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• 2004

The characteristics of heat transfer from horizontal cylinder immersed in both a riser and downcomer of a circulating fluidized beds were investigated experimentally under different values of solids mass flux, superficial air velocity, particle size diameter, and different bed materials. The test results indicated that local heat transfer coefficients in both riser and downcomer are strongly influenced by angular position, and mass flux, as well as by particle size and bed materials. The local heat transfer coefficients around a circumference of the cylinder inside a riser and downcomer of a CFB exhibited a general tendency to increase with decreasing particle size and increasing solids mass flux and vary with different bed materials. Also the averaged heat transfer coefficient calculated from local heat transfer coefficient exhibited the same trend as a local i.e increase with decrease particle size and increasing solids mass flux and vary with varying bed materials. The general trend for a riser local heat transfer coefficient is decrease with increase angle until ${\Phi}$ = 0.5-0.6 (Where at angle =180$^{\circ}$ ${\Phi}$ =1). Also the general trend for a local heat transfer coefficient in downcomer is to increase with increase the angle until ${\Phi}$= ${\theta}/{\Pi}$ = 0.3-0.5 (Where at angle =180$^{\circ}$ ${\Phi}$ =1). Comparison the results of the heat transfer in the riser and downcomer of a circulating fluidized beds shows that they have approximately the same trend but the values of heat transfer coefficients in riser is higher than in downcomer.