• 전자공학회논문지SC
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• 제43권5호
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• pp.60-67
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• 2006

우주 비행체 전자장비의 신뢰도를 예측하고 최적화하기 위해 탑재장치 내 부품의 온도 예측이 필수적으로 요구된다. 본 논문에서는 전자장비 부품의 온도 예측방법에 관해 기술하고 있다. 본 예측 방법은 PCB 기판의 열전도도를 등방성모델로 설정하여 등가 열전도도를 계산하고 열력 모델을 이용하여 열 저항 행렬을 생성하였으며, 중첩의 원리를 이용하여 각 부품들의 온도를 예측하였다. 또한 본 논문의 온도 예측방법을 이용하여 전장품 소자의 열해석 결과와 상용 프로그램을 이용한 온도 계산 결과를 비교 분석하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.620-621
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• 2010

우주공간에서 임무를 수행하는 인공위성이 궤도상에서 원활하게 작동할 수 있도록 열모델의 보정과정을 통하여 열해석 모델을 검증하는 과정이 이루어진다. 본 연구에서는 열해석 모델을 검증하는 과정으로 지상 열진공시험결과를 이용하여 요구조건을 충족시키기 위하여 열모델의 보정을 수행하였다.

• Smart Structures and Systems
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• 제15권2호
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• pp.469-488
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• 2015

Thermal loads, especially thermal gradients, have a considerable effect on the behaviors of large-scale bridges throughout their lifecycles. Bridge design specifications provide minimal guidance regarding thermal gradients for simple bridge girders and do not consider transversal thermal gradients in wide girder cross-sections. This paper investigates the three-dimensional thermal gradients of arch bridge girders by integrating long-term field monitoring data recorded by a structural health monitoring system, with emphasis on the vertical and transversal thermal gradients of wide concrete-steel composite girders. Based on field monitoring data for one year, the time-dependent characteristics of temperature and three-dimensional thermal gradients in girder cross-sections are explored. A statistical analysis of thermal gradients is conducted, and the probability density functions of transversal and vertical thermal gradients are estimated. The extreme thermal gradients are predicted with a specific return period by employing an extreme value analysis, and the profiles of the vertical thermal gradient are established for bridge design. The transversal and vertical thermal gradients are developed to help engineers understand the thermal behaviors of concrete-steel composite girders during their service periods.

• Computers and Concrete
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• 제2권6호
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• pp.455-479
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• 2005

This paper describes a 2D nonlinear finite element analysis (NLFEA) platform that combines heat flow analysis with realistic analysis of cracked reinforced concrete structures. The behavior models included in the structural analysis are mainly based on the Modified Compression Field Theory and the Distributed Stress Field Model. The heat flow analysis takes into account time-varying thermal loads and temperature-dependent material properties. The capability of 2D nonlinear transient thermal analysis is then implemented into a nonlinear finite element analysis program VecTor2(C) for 2D reinforced concrete membranes. Analyses of four numerical examples are performed using VecTor2, and results obtained indicate that the suggested nonlinear finite element analysis procedure is capable of modeling the complete response of a concrete structure to thermal and mechanical loads.

• Nuclear Engineering and Technology
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• 제41권5호
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• pp.677-690
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• 2009

A previous study demonstrated that the two-row fuel assembly has much more favorable neutron-physical and thermal-hydraulic behavior than the conventional one-row fuel assemblies. Based on the newly developed two-row fuel assembly, an SCWR core is proposed and analyzed. The performance of the proposed core is investigated with 3-D coupled neutron-physical and thermal-hydraulic calculations. During the coupling procedure, the thermal-hydraulic behavior is analyzed using a sub-channel analysis code and the neutron-physical performance is computed with a 3-D diffusion code. This paper presents the main results achieved thus far related to the distribution of some neutronic and thermal-hydraulic parameters. It shows that with adjustment of the coolant and moderator mass flow in different assemblies, promising neutron-physical and thermal-hydraulic behavior of the SCWR core is achieved. A sensitivity study of the heat transfer correlation is also performed. Since the pin power in fuel assemblies can be non-uniform, a sub-channel analysis is necessary in order to investigate the detailed distribution of thermal-hydraulic parameters in the hottest fuel assembly. The sub-channel analysis is performed based on the bundle averaged parameters obtained with the core analysis. With the sub-channel analysis approach, more precise evaluation of the hot channel factor and maximum cladding surface temperature can be achieved. The difference in the results obtained with both the sub-channel analysis and the fuel assembly homogenized method confirms the importance of the sub-channel analysis.

• 한국항공우주학회지
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• 제39권5호
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• pp.466-473
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• 2011

인공위성의 열제어는 인공위성이 운용궤도상에서 겪는 고진공, 극한의 온도변화 환경에서 위성 구성품의 온도변화를 허용한계 온도 범위 내에서 유지하는데 목적이 있다. 본 연구에서는 저궤도 관측위성(LEO)의 광학탑재체에 대한 열해석 과정으로 열진공 시험 조건, 열진공 챔버의 형상, 위성 탑재체 내부의 열적 환경을 고려하여 열해석 모델을 구성하고 궤도 조건에 따른 열해석을 수행하였다. 또한 광학탑재체의 지상 열진공 시험 조건에 따른 열해석 수행하여 열진공 시험을 위한 시험조건을 정립하였다.

• 한국추진공학회지
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• 제23권6호
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• pp.59-71
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• 2019

고체 로켓용 삭마성 내열 시스템의 수치 해석은 1960년대부터 다양한 In-house 코드로 수행되어 왔으나 Fluent, Marc, ABAQUS 등 상용코드에 서브루틴, UDF 등을 추가하여 해석 범위를 확장함으로써 상용코드의 활용 범위가 넓어지고 있다. 또한 예전에는 내열 시스템의 유동, 열반응과 구조해석을 각각 수행하였으나 근래에는 이들을 서로 연동하여 해석하는 연구들이 진행되고 있다. 본 논문에서는 내열재의 열반응 특성, 열반응 해석용 In-house 코드 그리고 상용코드로 내열 시스템의 유동, 열반응과 구조 해석을 수행한 연구동향을 고찰하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.425-429
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• 2004

In real design of the high & interim pressure turbine casing, it is one of the important things to figure out its thermal strain exactly. In this paper, with the establishment of the new concept for the heat transfer coefficient of steam that is one of the factors in analysis of the thermal stress for turbine casing, an analysis was done for one of the high & interim pressure turbine casings in operating domestically. The sensitivity analysis of the heat transfer coefficient of steam to the thermal strain of the turbine casing was done with a 2-D simple model. The analysis was also done with switching of the material properties of the turbine casing and resulted in that the thermal strain of the turbine casing was not so sensitive to the heat transfer coefficient of steam. On the basis of this, 3-D analysis of the thermal strain for the high and interim pressure turbine casing was done.

• Journal of Welding and Joining
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• 제5권1호
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• pp.34-41
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• 1987

To explore the possible application of thermal analysis technique as a probe for finding weld defects, Hydrogen trapping phenomena in Heat Affected Zone (HAZ) of the AISI 5160 spring steel were investigated. HAZ was divided into five parts, which were used as thermal analysis specimens. Two types of trap sites were found in HAZ, ferrite/cementin interface and microvoid. The thermal analysis peak due to the ferrite/cementite interface increased its height toward the weld deposit. The thermal analysis peak due to the microvoid was the highest where the grain size was the smallest. The correspondence between the cold cracking and hydrogen trap nature is also discussed.

• Structural Engineering and Mechanics
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• 제69권1호
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• pp.69-75
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• 2019

The plates made of two materials joined to each other having the different coefficient of thermal expansions are frequently encountered in the industrial applications. The stress analysis of these members under the effect of high-temperature variation has great importance in design. In this study, the stress analysis of the experimental model developed for the problem considered here was performed by the method of photothermoelasticity. The thermal strains were formed by the mechanical way and these were fixed by the strain freezing method. For the stress measurements, the method of slicing is applied which provides three-dimensional stress analysis. The analytical solution in the literature was compared with the related stress distribution obtained from the model. Moreover, the axisymmetric finite element model developed for the problem was solved by ABAQUS and the results obtained here compared with those of the experimental model and the analytical solution. As a result of this study, this experimental method and numerical model can be used for these type of thermal stress problems which have not been comprehensively analyzed yet.