• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.4
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• pp.329-336
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• 2000

Welding is a important technological method in mechanical engineering. $CO_2$MAG(metal active gas) welding means that metal part in double capstan drum for the inshore and costal vessels are joined by melting(with or without a filler material) or that new material is added to a metal part by melting. The thermal stresses appear due to a non-uniform temperature field, inhomogeneous material properties, external restraint and volume changes during phase transformations. In this study analysis the elasto-plastic thermal stresses distribution of welding part in double capstan drum for the inshore and costal vessels using finite element method (FBM). Therefore it calculates the numerical value that can be applied to the optimum design of welding parts and the shapes. The significant results obtained in this study are summarized as fellows. At early stage of the cooling after welding process, the abrupt thermal stresses gradient has been shown in the vicinity of welding part. In the thermal stresses analysis due to temperature gradient and heat shocking maximum stress was occurred of welding part and stresses were distributed from 54MPa~48MPa.

• Journal of Energy Engineering
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• v.28 no.3
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• pp.1-9
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• 2019

A major stress determining the remaining life of the tube in feedwater heater of fossil fuel power plant is hoop stress by the internal pressure. However, thermal stress due to temperature difference across the wall thickness also contributed to reduce the remaining life of the tube. Therefore, thermal loading must be considered even though the contribution of internal pressure loading to the stresses of the tube was known to be much higher than that of the thermal loading. In this study, thermal stress of the tubes in the de-superheating zone was estimated, which was generated due to the temperature difference across the tube thickness. Analytic equations were shown for determining the hoop stress and the radial stress of the tube with uniform thinning and for the temperature across the tube thickness. Accuracy and effectiveness of the analytic equations for the stresses were verified by comparing the results obtained by the analytic equations with those obtained from finite element analysis. Using finite element analysis, the stresses for eccentric thinning were also determined. The effect of heat transfer coefficient on thermal stress was investigated using series of finite element analyses with various values of heat transfer coefficient for both inner and outer surface of the tube. It was shown that the effect of heat transfer coefficient at outer surface was larger than that of heat transfer coefficient at inner surface on the thermal stress of the tube. Also, the hoop stress was larger than the radial stress for both cases of uniformly and eccentrically thinned tubes when the thermal loading was only considered without internal pressure loading.

• Magazine of the Korea Concrete Institute
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• v.14 no.6
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• pp.82-87
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• 2002

매스 콘크리트 구조물에서는 콘크리트의 타설후 시멘트의 수화반응에 의해 발생하는 수화열로 인하여 적지 않은 크기의 인장응력이 유발되어 균열이 발생할 가능성이 크다. 토목분야에서 통용되고 있는 많은 범용구조해석 프로그램들은 유한요소법을 이용하여 수화열에 의한 온도분포해석 및 열응력해석을 수행할 수 있는 기능을 내장하고 있다. 그러나, 다른 모든 구조해석들이 그러하듯이 수화열 해석 역시 해석자가 적절한 입력자료를 프로그램에 제공하지 않았을 경우 예상과는 다른 결과를 산출할 수 있다.(중략)

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.1
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• pp.34-41
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• 2003

A Green's function approach is adopted for analyzing the thermoelastic deformation and stress analysis of a plate made of functionally graded materials (FGMs). The solution to the 3-dimensional steady temperature is obtained by using the laminate theory. The fundamental equations for thermoelastic problems are derived in terms of out-plane deformation and in-plane force, separately. The thermoelastic deformation and the stress distributions due to the bending and in-plane forces are analyzed by using a Green’Às function based on the Galerkin method. The eigenfunctions of the Galerkin Green's function for the thermoelastic deformation and the stress distributions are approximated in terms of a series of admissible functions that satisfy the homogeneous boundary conditions of the rectangular plate. Numerical examples are carried out and effects of material properties on thermoelastic behaviors are discussed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1999.10a
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• pp.12-12
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• 1999

온도에 따라 물성치가 변화하는 재료의 열응력 예측은 연속주조공정에 의한 제품 생산에서 중요하다. 연속주조공정에서 금속이 급속히 냉각됨으로 인하여 응력이 크게 발생될 뿐만 아니라 금속 내부에 크랙이 발생될 수 있으며, 이는 최종제품의 품질에 영향을 미칠 수 있다. 따라서 연속주조공정에서 양호한 주조제품을 얻기 위해서는 냉각조건 등과 같은, 주조시 수반되는 여러가지 주조결함의 원인을 제어해 주어야한다. 주조결함에는 주물 주입에 기인하는 결함과 주입 완료 후 응고과정에서 주물의 수축으로 기인하는 결함이 있다. 공기 및 가스의 포집, 개재물의 혼입 등이 전자에 속하며, 응고층 내부의 온도차, 응고수축(solidification shrinkage), 응력변형 등으로 인한 주물변형 및 표면결함 등이 후자에 속한다. 주물의 응고시에 고상화된 영역에서의 온도구배와 시간에 따른 온도변화는 금속내부에서의 열변형으로 인한 열응력을 발생시키고, 이것은 잔류응력이나 크랙 등과 같은 최종제품의 결함의 원인이 될 수 있다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.3
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• pp.229-235
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• 2016

In this paper, a methodology, which is able to predict the thermal stresses accurately yet efficiently, is presented for beam structures via Saint-Venant's principle. In general, higher-order beam theories have been known to be effective for the prediction of thermal stresses. In contrast to this, we propose the method to predict the thermal stresses of beam structures by post-processing the classical beam theory via Saint-Venant's principle. The approach includes an out-of-plane warping displacement to account for the through-the-thickness thermal deformation. With this, one can accurately recover the thermal stresses as compared to the elasticity solutions. In fact, they are identical for the beams made of isotropic materials. The effect of out-of-plane warping is also investigated, it turns out that the effect is negligible in mechanical stress analysis but not in thermal stress analysis.

• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.1
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• pp.110-120
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• 1999

Transient hygrothermal stresses in an infinitely long hollow cylinder subjected to heating in hygroscopic environments at the surfaces are studied. The equations of hygrothermoelasticity based on the plane strain assumption are formulated by considering the coupling effects between heat and moisture. A closed form solution for the transient hygrothermal stresses is obtained by using decoupling techniques and the method of separation of variables. Numerical results including distributions of temperature and moisture concentration are presented. Effects of transient hygrothermal characteristics are clearly shown in both displacements and stress distributions in the wall of hollow cylinder.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.283-290
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• 2005

제철용 고로구조물의 안전성 위협 요인으로는, 고로자중이나 철광석 낙하 둥과 같은 기계하중 외에도 구조물 내부 온도가 최대 $1700^{\circ}C$에 이르는 고온 환경을 들 수 있다. 이러한 고온의 작업 환경은 고로 구성부재들의 크립손상, 열피로 문제 등을 야기시키기 때문에 이들 고열에 의한 영향평가는 고로의 안전성 평가에 있어 필수요소로 거론되고 있다. 일반적으로 고로의 단면을 구성하고 있는 내화재, 냉각판, 철피 등의 냉각시스템을 거치면서 내부의 고온 환경은 고로 외피에 이르는 동안 온도강하가 이루어진다. 급격한 온도강하는 나타나지 않지만 장기간 고로 가동에 있어 상시하중으로 작용하는 이 열원에 의해 고로 각 구부위에는 열응력이 발생하고 이 열응력과 나머지 기계적 하중의 조합에 의해 크립이나 열피로 등과 같이 고로 구조물 안전성 위해요인들이 발생한다고 분석되어 진다. 따라서 본 연구에서는, 고로 안전성 평가를 위한 첫 번째 단계로서 범용유한요소해석 프로그램인 ANSYS를 이용한 열응력 해석을 수행하여 잠재적인 안전성 위해요인으로 알려진 열응력 발생 특성을 분석하고, 고로 건전설계 및 보수 유지 관리지침으로 활용할 수 있는 기반기술을 개발한다.

• Proceedings of the Korean Vacuum Society Conference
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• 1993.02a
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• pp.38-40
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• 1993

급속 열처리 시스템내에서의 비정상상태 온도분포, 가스유동형태, 웨이퍼내 열응력등을 여러 가지 작동조건하에서 2차원 유한 차분법으로 계산하였다. 계산결과는 실험에서 얻은 에피성장률 데이터와 비교 검증하였다. RTpp내 가스 유동이나 온도분포는 압력 및 주위 구성요소에 크게 의존하는 반면, 웨이퍼의 온도분포는 wafer edge loss가 큰 고온에서 온도 불균일도가 가장 크다. 저온에서는 대류에 의한 열 손실이 웨이퍼내의 온도 불균일도에 큰 영향을 미치고 있다. 웨이퍼상의 열응력을 가장 크게 받는 시점은 transient condition에서 나타났다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.1
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• pp.71-75
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• 1994

In this study, a thermoelastic stress index of (100) oriented single crystalline silicon wafer and a relationship between thermal stress and critical plastic deformation temperatures were simulated. The simulated results for the thermoelastic stress index indicated a maximum value on <110> direction and a minimum on <100>. Then, it could be predicted that silicon wafer is plastically deformable over 1000 K, based on the relationship between the thermal stress derived from the thermoelastic stress index and the critical plastic deformation temperature.