• Nuclear Engineering and Technology
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• v.56 no.6
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• pp.2307-2316
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• 2024

A melting failure of W monoblock components of the upper divertor outer target in EAST occurred during the plasma campaigns in 2019. The failure characters and microstructure evolution of the failed W monoblock have been well investigated on one string (W436 string). Near the strike point region where heat flux density is highest, macroscopic cracks and severe surface damage such as dimensional change, melting and solidification are visible in several W monoblocks. At the same time, debonding, melting and migration of Cu/CuCrZr cooling tube components introduced fatal damage to the structure and function. The heat-induced microstructure evolution in the rest part has been examined via hardness tests and metallography. From the heat flux surface to the cooling tube, hardness increased gradually and the recrystallized grains could be found in the region with the highest temperature, while recrystallization grains also appear in some W monoblocks near the cooling tube area. The detailed microstructure has been investigated by metallography and EBSD. Such cases in EAST provide experiences on the extreme condition of accidental loss of coolant or higher discharge power in future devices.

• Design & Manufacturing
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• v.15 no.2
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• pp.30-35
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• 2021

The casting method uses a mold to solidify a liquid metal to make a solid metal. Since it uses a liquid metal with the least deformation resistance, it has the characteristic that it can easily manufacture even a complex shape. However, the process of solidifying a liquid metal into a solid metal inevitably involves a volume change and contains internal defects such as shrinkage holes. Therefore, in the design of the casting plan, an excess volume called a pressurization compensates for the volume shrinkage. in the product, and it induces the shrinkage hole defects to occur in parts other than the product1). In this study, casting analysis was performed using casting analysis software (anycasting) in order to optimize the design of the tilting gravity casting method for automobile brackets. In particular, the filling and solidification analysis according to the shape and volume of the pressurized metal was conducted, and applied to the actual product to study the effect of the pressurized metal on the shrinkage defect. Through this study, it is possible to understand the effect of the pressure metal on shrinkage defects in the actual product and propose a design of the pressure metal that improves reliability and productivity.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3909-3918
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• 2022

In the event of a severe accident, the reactor core may melt due to insufficient cooling. the high-temperature core melt will have a strong interaction (FCI) with the coolant, which may lead to steam explosion. Steam explosion would pose a serious threat to the safety of the reactors. Therefore, the study of steam explosion is of great significance to the assessment of severe accidents in nuclear reactors. This research focuses on the development of a two-dimensional steam explosion integrated analysis code called SEINA. Based on the semi-implicit Euler scheme, the three-phase field was considered in this code. Besides, the influence of evaporation drag of melt and the influence of solidified shell during the process of melt droplet fragmentation were also considered. The code was simulated and validated by FARO L-14 and KROTOS KS-2 experiments. The calculation results of SEINA code are in good agreement with the experimental results, and the results show that if the effects of evaporation drag and melt solidification shell are considered, the FCI process can be described more accurately. Therefore, it is proved that SEINA has the potential to be a powerful and effective tool for the analysis of steam explosions in nuclear reactors.

• Journal of Digital Contents Society
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• v.18 no.6
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• pp.1213-1216
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• 2017

Recently due to the increasing uncertainty of the disaster environment caused by climate change the effects of disasters have become larger due to the confluence and solidification diversification into disaster type and secondary damage. In this paper, we apply ICBMS through intelligent information technology and big data analysis to all processes of disaster safety management to minimize human, social, economic and environment damage from accidents or disasters, and prevention by control technology preparation by education and training expansion to remember by body, response by advanced technology of disaster response unmanned technology restoration by creation of local community environment ecosystem, investigation and analysis by intelligent information technology learn about disaster safety management 4.0. In addition, technical limitation and problems in the $4^{th}$ industrial revolution and the application of big data were analyzed and suggested alternatives and strategies to overcome.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.1
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• pp.82-88
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• 2015

Objectives: This study is designed to analyze the penetration performance into ceiling materials containing asbestos of scattering prevention agents and investigate the change in penetration depth and viscosity according to the dilution rate of anti-scattering agents diluted with distilled water. Methods: Five different types of scattering prevention agents were spread on plate-type asbestos ceiling materials. The penetration depth of each coated ceiling material was measured by energy dispersive spectroscopy (EDS) analysis, based on X-ray fluorescence (XRF) results of the non-coated ceiling materials. Test equipment installed the ceiling materials and 60 minutes were collected at a flow rate of $10{\ell}/min$ at a filter of 25 mm. Results: An EDS analysis of the cross-section of ceiling materials constructed with a scattering prevention agent revealed that potassium is detected in the process of penetrating hardener solidification and this element could be an indicator for infiltration. When anti-scattering agents with different viscosities were constructed and the penetration depth was analyzed by potassium detection assessment using EDS, the depth results with viscosities of 5.0, 2.5, and 1.9 cP were 98.5, 103, and $147{\mu}m$, respectively. Penetration performance improved with decrease in viscosity. Conclusions: For asbestos ceiling materials, it is concluded that a higher dilution rate of the scattering prevention agent leads to lower viscosity, and hence a deeper penetration depth from $156{\mu}m$ to 3 mm. The asbestos anti-scattering properties according to the penetration depth will be confirmed through further study.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1549-1554
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• 2010

Recently, plastic screws have replaced metal screws because of the former's light weight, thermal and electrical insulating properties, and anticorrosion characteristics. Plastic screws are usually produced by injection molding, which involves material shrinkage during the solidification of the polymer. This shrinkage results in the degeneration of the dimensional accuracy. In the present study, the effect of injection-molding conditions on the dimensional accuracy of plastic screws was investigated through a numerical simulation of injection molding; on the basis of this simulation, we could determine the mold-design parameters. The design of experiment was applied in accordance with the numerical analysis in order to optimize the injection-molding conditions with a view to improving the dimensional accuracy of the precision plastic screw.

• Journal of the Korean Geotechnical Society
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• v.27 no.6
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• pp.27-37
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• 2011

Recently, pressure grouting is widely being used in construction site for strength improvement of ground and water proof, reinforcement and so on. It is necessarily required to estimate an appropriate injection pressure and injection time for economical and reasonable construction in the site through the size and shape of the hardened grout measured according to ground condition. However, sampling for the hardened grout is time-consuming and needs high cost on preliminary test in the site. The system which could predict the size and shape of the hardened grout does not exist until now. Thus, numerical method based on VOF method and porous model was used for the calibration chamber injection test with injection pressure (50 kPa, 100 kPa, 150 kPa) in this study. The results indicate that the numerical technique based on VOF method and porous model among CFD analysis is expected to be a basic study for the prediction of the behavior and solidification of pressure grouting.

• Journal of Korea Foundry Society
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• v.29 no.5
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• pp.225-232
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• 2009

For comprehensive understanding of the formation behavior of $\beta-Al_5FeSi$ phase in Al-Si-Cu alloys with the existence of Fe element, microstructure characterizations were performed using combined analysis of OM, SEM-EDS, XRD. Especially, experimental and predictive works on solidification events of $\beta-Al_5FeSi$ phase as well as other phases formed together with $\beta-Al_5FeSi$ have been carried out by using DSC analysis and Java-based Materials Properties software (J. Mat. Pro.). Primary and eutectic $\beta-Al_5FeSi$ phases were able to distinguish from each other on microstructures by their morphological features. Primary $\beta-Al_5FeSi$ phase was seen to have rough surface perpendicular to growth direction, indicating free attachment of solute atoms in liquid state. On the other hand, the eutectic $\beta-Al_5FeSi$ phase was formed with plain and straight surface during eutectic reaction together with $\alpha$-Al phase. The eutectic reaction of $\beta-Al_5FeSi$ and $\alpha$-Al phases was seen to be able to separate into each formation depending on cooling rate.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.5
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• pp.589-596
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• 2021

In this study, the optimum gating system was designed, and the two zinc alloy worm gears were manufactured in single process by applying a symmetrical gating system with 2 runners. The SRG ratio is set to 1 : 0.9 : 0.6, and the cross-sectional shapes such as sprue, runner and gate are designed. In order to determine whether the design of the gating system is appropriate, casting analysis was carried out. It takes 4.380 s to charge the casting 100%, 0.55 to 0.6 m/s at the gates and solidification begins after the casting is fully charged. The amount of air entrapment is 2% in the left gear and 6% in the right gear. Hot spots occurred in the center hole of the gear, and pores were found to occur around the upper part of the hole. Therefore, the design of the casting method is suitable for worm gears. CT analysis showed that all parts of worm gear were distributed with fine pores and some coarse pores were distributed around the central hole of worm gear. The yield strength and tensile strength were 220 MPa, 285 MPa, and the elongation rate was 8%. Vickers hardness is 82 HV.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.1051-1057
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• 2010

This paper proposes a method that involves a combination of FDM and FEM for analyzing casting process. At present, many numerical analysis methods such as FDM, FEM, and BEM are used for solving engineering problems. For a given problem, a specific method that is suited to the problem is adopted; in general, FDM or FVM is favored for problems related to fluid flow or heat transfer, and FEM is adopted in stress analysis. However, there is an increasing need for using a combined method for complex and coupled phenomena analysis. Hence, we proposed a method in which FDM and FEM are coupled in three-dimensional space, and we applied this method to analyze casting process. In the proposed method, solidification and heat transfer was analyzed by using FDM. The field data such as temperature distribution were converted into a format suitable for FEM analysis that was used for calculating thermal stress distribution. Using the proposed method, we efficiently analyzed the analysis process from the viewpoints of work and time.