• 한국산학기술학회논문지
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• 제16권7호
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• pp.4375-4380
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• 2015

선박용 디젤엔진 부품인 블랭크 단조품 가열 시 생산성 및 품질을 향상시키기 위하여 새로운 가열공정을 제안하였다. 본 연구에서는 새로운 블랭크 가열공정을 평가하고 가열공정 설계기준을 정립하기 위하여 수치해석 전용 프로그램인 ANSYS를 사용하여 재료의 비선형을 고려한 온도분포, 열응력 해석을 수행하였다. 가열조건은 승온단계와 유지단계로 구성되어 총 32시간이며 가열 시 시간경과에 따른 블랭크 내 외부의 온도분포와 열응력 변화를 평가하였다. 그 결과 가열 시 승온단계에서 블랭크 내 외부 온도차는 시간이 경과함에 따라 점차 증가하여 최종 승온단계에서 최대 온도차가 발생하나 유지단계에서 온도차는 점진적으로 감소하는 반면에 가열이 시작되어 10시간 경과 후 블랭크 내부에는 최대 등가응력 $12.5kg/mm^2$가 발생한다는 것을 알 수 있다. 따라서 단조품 가열공정을 설계함에 있어서 가열 후 10시간 경과 시, 즉 노내 온도 $650^{\circ}C$에서 블랭크 내 외부 온도차는 $150^{\circ}C$이내가 되도록 관리해야 한다.

• Nuclear Engineering and Technology
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• 제51권1호
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• pp.257-262
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• 2019

The control of microstructure is critical for the porous fuel particles used for infiltrating actinide nuclides. This study concerns the effect of heating processes on properties and microstructure of the fuel particles. The uniform gel precursor beads were synthesized by a microfluidic sol-gel process and then the porous $CeO_2$ microspheres, as a surrogate for the ceramic nuclear fuel particles, were obtained by heating treatment of the gel precursors. The fabricated $CeO_2$ microspheres have a narrow size distribution and good sphericity due to the feature of microfluidics. The effects of heating processes parameters, such as heating mode and peak temperatures on the properties of microspheres were studied in detail. An optimized heating mode and the peak temperature of $650^{\circ}C$ were selected to produce porous $CeO_2$ microspheres. The optimized heating mode can avoid the appearance of broken or crack microspheres in the heating process, and as-prepared porous microspheres were of suitable pore size distribution and pore volume for loading minor actinide (MA) solution by an infiltration method that is used for fabrication of MA-bearing nuclear fuel beads. After the infiltration process, $1000^{\circ}C$ was selected as the final temperature to improve the compressive strength of microspheres.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2001년도 제23회 KOSCO SYMPOSIUM 논문집
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• pp.83-89
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• 2001

Most technologies of reduction process used in the heat treatment of existent metal products are related to metals applied to bolts and parts of automobiles, and nonmetal such as copper. Heating conditions and reduction gases produced in above processes depend on types of products to be treated thermally but heating systems employ electricity commonly and the reduction gases are separated into additional production equipment and a gas dryer and inefficiently provided into the system. Electrical heating system has the advantage of convenient temperature-control but is not economical because of disadvantages of high electricity-running cost and extra installation cost of a transformer. Accordingly, development of the system which has economical heating mode in which provision of reduction gas and heating conditions are unified is necessary for improvement of economy and efficiency in current reduction processes. This study aimed to develop a new advanced heat treatment furnace using catalytic combustion. thereby minimizing the cost during heating, supplying heat and reductive gas at the same time and controlling operating condition freely by changing electrical heating system to heating system by the gas combustion and regeneration of wasted heat.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.244-251
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• 2003

A two-dimensional BEM code, $FRACOD^{2D}$, was applied to simulate fracture initiation and propagation processes in a rock pillar during an in situ heater test of a rock pillar planned at the $\"{A}sp\"{o}$ Underground Rock laboratory of SKB, in Southern Sweden. To take the advantage of conventional BEM for simulating fracturing processes, but without efforts for domain integral transformation, a hybrid approach is developed to simulate the fracturing processes in rock pillar under coupled thermo-mechanical loading. The code FRACOD was used for simulating the fracture initiation and propagation processes with its boundary tractions reflecting the effects of the initial and redistributed thermomechanical stresses in the domain of interest at multiple excavation and heating steps were produced by a special algorithm of stress inversion, based on resultant thermo-mechanical stress fields at each excavation and heat loading step by a FEM code without considering fracturing processes. This hybrid approach can take the advantages of both types of numerical methods and avoids their shortcomings for fracturing process simulation and domain effects, respectively. In this paper, we present the hybrid approach for the stress, displacements, and fracturing processes at sequential excavation and heating steps of the in situ heater test as a predictive modelling, the formulation of the fracturing models and the predictive results. Two sections of borehole depth, 0.5 m and 1.5 m below the tunnel floor are considered. The pillar area is modelled with the FRACOD and the stress field produced by excavation and heating is transferred with corresponding boundary stresses. From the modelling results, the degree of fracturing and damage are evaluated for 120 days of heating. Dominated shear fracturing in the vicinity of the central pillar was observed from the models at both sections, but spalled area appears to be limited. Based on the modelling results, a sensitivity study for the effect of pre-existing fractures in the vicinity of the holes is also conducted, and the initiation and evolution of EDZ around the deposition holes are investigated using this particular numerical technique.

• 천문학회보
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• 제37권2호
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• pp.119.2-119.2
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• 2012

Charged particle energization is an outstanding problem in space physics. This paper investigates the nonlinear dynamics of Alfve'n-cyclotron waves accompanying particle heating processes and the drift Alfv'en-cyclotron (or EMIC) instability associated with a current disruption event on 29 January 2008 observed with THEMIS satellite by means of a particle-in-cell simulation. The simulation shows that the drift Alfv'en-cyclotron instabilities are excited in two regimes, a relatively low frequency mode propagating in a quasi-perpendicular direction while the second high-frequency branch propagating in a predominantly parallel propagation direction, which is consistent with observation as well as earlier theories. It is shown that parametric decay processes lead to an inverse cascade of Alfv'en-cyclotron waves and the generation of ion-acoustic waves by decay instability. It is also shown that the nonlinear decay processes are accompanied by small perpendicular heating and parallel cooling of the protons, and a pronounced parallel heating of the electrons.

• 한국안전학회지
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• 제26권5호
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• pp.65-72
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• 2011

The use of waste concrete can resolve the environmental pollution and shortage of natural aggregate. However, recycled aggregate includes substantial amount of cement paste. So, these aggregates are more porous, and less resistant to mechanical actions than natural aggregates. So, recently, the new manufacture processes of high quality recycled aggregates were suggested such as heating and solving to acid liquid. But the method of solving to acid liquid is not economical and produces additional environmental pollution. In this paper, for the purpose of manufacture of high quality recycled aggregates, the heating processes was added to the existing process of recycled aggregates. To find the optimum process, the experiment was performed by using the method of statistical experiment design, and the heating temperatures(4 levels : 300, 450, 600 and $750^{\circ}C$) and heating times(4 levels : 5, 20, 40, 60 minute) were main experimental variables. By the test results, the optimum manufacturing condition of coarse recycled aggregate was $600^{\circ}C$ and 40 minute, and for the fine recycled aggregate, a little heating made a satisfaction to the KS standard quality code.

• Journal of the Korean Wood Science and Technology
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• 제19권4호
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• pp.7-17
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• 1991

The feasibility of treating three softwood(Japanese larch pitch pine, and Korean pine) thinned logs by double-diffusion treatment processes was investigated. Some posts were incised before immersion, and others were imersed in hot copper sulfate solution. Comparison among species indicated that. in general, pitch pine was most treatable and Japanese larch least treatable. For all three species, almost all treatment schedules gave consistently good penetration and high net retention, but very steep gradient of preservative distribution. As expected, the treatability was increased by the extension of immersion time, increased concentration of treating solution, incising. and heating of the first solution. Of the variables tested, it appears that heating of the first solution is the most important. From the data in this paper, it may be concluded that, if the first solution is not heated, the best schedule is #3. If the first solution is healed. it appears the best schedules are #10 or #11. Since heating of the first solution improves the treatability. schedules # 10 or :#11 are recommended if the cost of heating might be justified. The data presented in this paper indicate that double-diffusion treatment processes seem to offer a promise as a comparatively effective and easy-operating method of treating thinned logs for the small-scale production of treated stock.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.137-140
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• 2002

The main objectives in the first year include selection of the MEMS bonding methods and feasibility study of selected methods. The ultrasonic bonding method is chosen for MEMS packaging, and the processes to provide localized heating are proposed. The ultrasonic bonding process is analyzed using a lumped model. Preliminary experiments using the eutectic solder and copper pin were performed to verify possibility to MEMS packaging. The preliminary results show possibility of the ultrasonic bonding method for MEMS packaging.

• 한국정밀공학회지
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• 제10권3호
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• pp.198-204
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• 1993

The study is concerned with finite element analysis and design of axisymmetric deep drawing by local heating. When the bottom shape of a cup is not flat but in complex-shaped, i.e., hemispherical, the cup cannot be drawn in one or two processes in the conventional deep drawing process and the limit drawing ratio is limited as well. By introducing local heating selectively with regards to the heating position, the formability of the sheet metal can be greatly increased with the reduced number of processes. In the Process analysisthe rigid- viscoplastic finite element method is employed and the temperature effect is incorporated. Bishop's step-wise decoupled method is employed to analyze the thermomechanical interaction between deformation and heat transfer. Axisymmetric deep drawing of a hemisphere-bottomed cup has been analyzed for various combinations of heat application in the punch and the die. At the first stage of deep drawing stretch forming is practically carried out by firmly pressing the blankholder with the punch and the die heated at various levels of temperature. Then at the second stage the same cup is drawn for the saame or different combination of temperature. From the computation, it has thus been shown that the fromability of a cup is greatly increased in two-stage deep drawing with increased limet drawing ratio.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.183-186
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• 2007

The injection molding process has high accuracy and good reproducibility that are essential for mass production at low cost. Conventional molding processes typically use the water-based mold heating and air cooling methods. However, in the nano injection molding processes, this semi-active mold temperature control results in the several defects such as air-flow mark, non-fill, sticking and tearing, etc. Therefore, in order to control temperature of the molds actively and improve the quality of the molded products, the novel nano injection molding system, which uses active heating and cooling method, has been introduced. By using the Peltier devices, the temperature of locally adiabatic molds can be controlled dramatically and the quality of the molded patterns can be improved.