• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.192-198
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• 2005

In this paper, a systematic attempt for estimating geometric dimensions of cold forgings is made by finite element method and a practical approach is presented. In the approach, the forging process is simulated by a rigid-plastic finite element method under the assumption that the die is rigid. With the information obtained from the forging simulation, die structural analysis and springback analysis of the material are carried out. In the springback analysis, both mechanical load and thermal load are considered. The mechanical load Is applied by unloading the forming load elastically and the thermal load is by cooling the increased temperature due to the plastic work to the room temperature. All the results are added to predict the final dimensions of the cold forged product. The predicted dimensions are compared with the experiments. The comparison has revealed that predicted results are acceptable in the application sense.

• 한국세라믹학회지
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• 제54권4호
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• pp.314-322
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• 2017

This study investigates changes in the mechanical behavior, such as changes in indentation load-displacement curve, wear resistance and contact fatigue resistance of thermal barrier coatings (TBCs) by thermal cycling test and thermal shock test. Relatively dense and porous TBCs on nickel-based bondcoat/superalloy are prepared; the highest temperature applied during thermal durability test is $1350^{\circ}C$. The results indicate that the porous TBCs have relatively longer lifetime during thermal cycling and thermal shock tests, while denser TBCs have relatively higher wear and contact fatigue resistance. The mechanical behavior is influenced by sintering of the TBCs by exposure to high temperature during tests.

• 한국기계가공학회지
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• 제8권4호
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• pp.34-40
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• 2009

The effect of frictional factors on thermal stress and deformation volume of motorcycle brake disk was studied by using a disk-on-pad type friction tester. It has an effect on the frictional factor such as applied load, sliding speed, sliding distance and number of ventilated disk hole. However, it is difficult to know the mutual relation of these factors. In this study, thermal stress and deformation volume by using design of experiment with 4 elements were investigated for thermal analysis with regression analysis. Thermal stress and thermal deformation are obtained by the application of temperature from mechanical test. From this study, the result showed that the motorcycle brake disk with ventilated hole 3 had the most excellent thermal stress and deformation volume. The regression equation had a trust rate of 95% for the prediction of thermal stress and deformation volume of motorcycle brake disk was composed.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2004년도 한국우주과학회보 제13권2호
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• pp.239-242
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• 2004

The fairing of the launch vehicles has a role of protecting the spacecraft from outer thermal, acoustical, and mechanical loads during flight. Among them, the thermal load is analyzed in the present study. The ascent thermal analyses include aerodynamic heating rate on every point of the fairing, heat transfer through the fairing and spacecraft, and the final temperature during ascent flight phase. A design code based on theoretical/experimental database is applied to calculate the aerodynamic heating rate, and a thermal math program, SINDA/Fluint, is considered for conductive heat transfer of the fairing. The results show that the present design satisfies the allowing temperature of the structure. Another important thermal problem, pyro explosive fairing separation device, is calculated because the pyro system is very sensitive to the temperature. The results also satisfies the pyro thermal condition.

• 한국산업융합학회 논문집
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• 제7권3호
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• pp.233-240
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• 2004

This paper presents a feasibility study of a fresh air load reduction system by using an underground double floor space The system was introduced into a real building and was examined by the field measurement Judging from the measurements during three years(1999~2001), the state of the system operation was very stable through this period and it was clear that the system contributes to reduction of energy consumption for air-conditioning. Futhermore, a simulation model used the simple heat diffusion equation Was developed to simulate its thermal characteristics and performances The simulations resulted m air temperature in good agreement with the measurements. Also, from the result of numerical analysis, It is clear that the amount of heat supply by using this system is more than the amount of energy loss to the room above it. Therefore, it is concluded that this systems is very useful and the proposed numerical model can be used for the prediction of system thermal performance.

• Journal of Welding and Joining
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• 제27권5호
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• pp.34-41
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• 2009

Thermal and mechanical characteristics in dissimilar SS400-STS304 steel weldment have been investigated by 3D thermal elastic-plastic analysis. Moreover, the influence of welding residual stresses on the mechanical behaviour of this welded joint, by applying superimposed external load (tension load) was determined. The residual stresses obtained by numerical simulation were compared with the experimentally measured results. The FE results were in good agreement with the measured values. The mechanical test (hardness, tensile test) and metallurgical analysis was carried out to ensure the weld integrity. Hence, possibility of applying SS400-STS304 dissimilar steels in industries has been established.

• 설비공학논문집
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• 제30권4호
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• pp.167-174
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• 2018

The geothermal heat pump systems were installed for heating and cooling of public buildings in Jincheon Eco-friendly Energy town. The heat pump system was operated at night to save on operational costs, and the cold heat was stored in thermal energy storage (TES). In this study, the performance of geothermal heat pump systems with the TES during the summer season was analyzed, and the operational costs with and without the TES were compared. The electric chiller model was used to simulate a heat pump applied without the TES system. Electric rates of each system were measured to calculate operational costs. When the TES is used in the air conditioning system, the electric load (30.4 MWh) calculated in the daytime can move to off-peak load time, and the operational cost is reduced by 36~54%.

• KIEAE Journal
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• 제3권1호
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• pp.31-36
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• 2003

Recently, buildings with transparent glazing on exterior walls have increased. The transparent glazing on exterior walls gives an impression of opening through introducing external environment's elements to inside of the building, and has various merits and so on, but has defects in controling indoor environments. Especially, the excess of solar radiation in summer increases cooling load causing discomforts to occupants providing radiant environment with high temperature. Cooling load mainly depends on electricity comparing to heating load and intents to centralize specific time. So it is necessary to work out a countermeasure. In this study, showed P building with transparent glazing on exterior walls as a case, investigated indoor thermal performance, numerical analysis of P building in summer through comparing dry-sauna which is represented as radiant environment with high temperature. In the results of this study, transparent glazing space has radiant environment with high temperature such as dry-sauna because of the excess of solar radiation. Accordingly countermeasures are considered in building planning. As concrete methods, there are adiabatic effects using double glazing, use of sunscreen, blind, ventilation facilitation using natural draft, decrease of surface temperature through evaporation cooling and cooling coils.

• KIEAE Journal
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• 제4권3호
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• pp.65-70
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• 2004

The purpose of this study is to analysis the thermal performance of the clayed hollow block wall. Its thermal performance was evaluated comparison with the cement block wall, it was generally used in building envelope. To that end, we conducted a insulation performance experiment and heating and cooling load simulation for a respective wall. In addition, we calculated a construction cost for each other's wall. The results of this study can be summarized as follows. (1) According to experiment of a insulation performance, coefficient of overall heat transmission of the cement block wall and clayed hollow block wall was calculated respectively $2.72W/^2K$ and $1.42W/^2K$. (2) The annular load saving of the clayed hollow block wall was evaluated 1.5% larger than its of the cement block wall. (3) The construction cost of the clayed hollow block wall was calculated 73% more expensive than its of the cement block wall. (4) The construction cost of the clayed hollow block composite wall was calculated 13.7% more expensive than its of the cement block composite wall.

• 한국항공우주학회지
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• 제35권9호
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• pp.826-835
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• 2007

발사체 열환경 설계를 위해서 여러 종류의 태양열 모델을 비교 검토하였으며, 측정된 태양열과 잘 일치하는 태양열 모델을 개발하였다. 기존의 태양열 모델은 태양 직사광 예측은 정확하지만 산란광에 대해서는 오차가 포함되어 있었다. 이에 반하여 새롭게 개발된 산란광 모델은 등방성, 이방성 산란을 고려하였으며 기존의 어느 모델보다 관측값과 잘 일치하였다. 우주 센터의 태양광 측정 데이터가 매우 적기 때문에 본 모델은 발사체 열하중 설계에 필요한 설계 데이터를 제공할 수 있었다. 또한 본 모델은 위도, 경도, 날짜, 고도에 대한 제한이 없는 일반적인 모델이기 때문에 추후 태양열에 민감한 반응을 보이는 비행기구 등의 개발에 효과적인 열환경 예측 수단을 제공할 수 있다.