• 대한기계학회논문집A
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• 제20권1호
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• pp.172-179
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• 1996

For mechanical systems operating at high tempertature, thermal fatigue phenomenon has been recognized as a major cause of mechanical component failures. To evaluate cumulative fatigue damage as a conesquence of thermal fatugue on real time, the stress tranfer function(Green's function) approach is popularly used. The objective of this paper is to investigate the effect of thermophsical properties on the stress tranfer function. For this purpose a modified Green's function approach considering temperature-dependent thermophysical properties is proposed. Two case studies were performed and the proposed approach agrees well with full finite element analysis.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1994년도 춘계학술대회 논문집
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• pp.47-54
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• 1994

The study is concerned with the coupled analysis of heat transfer and thermoelastoplastic deformation. The thermoelastoplastic model is very useful for the analysis of residual stress and the analysis of thermal stress as well as the analysis of metal forming. Heat of deformation, phase transformation and contact heat transfer boundary are considered. The contact heat transfer boundary is treated by the interpolation of shape function. The analysis of deformation and the analysis of heat transfer are carried out for the could upsetting and the hot rolling. The computed results are found to be in good agreement with the experimental results.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.310-319
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• 2017

충격파 시험장치를 이용하여 추력을 측정하는 방법을 소개하였다. 충격파 시험장치를 이용하여 엔진의 추력을 측정하기 위해서는 일반적인 엔진시험 시설에서 추력을 측정하기 위해 사용하는 밸런스가 힘의 평형상태에 도달하지 못하기 때문에 응력파 힘 밸런스(Stress Wave Force Balance) 방법을 이용하여 측정한다. 본 논문에서는 모델 힘 밸런스(force balance)에 대해 충격하중을 주고 유한요소법(FEM)으로 변형률을 계산하였다. 충격하중과 변형률의 관계를 역합성곱(de-convolution)하여 천이함수를 도출하였다.

• 산업경영시스템학회지
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• 제19권40호
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• pp.291-299
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• 1996

This study is concerned with the evaluation model construction of Man-Machine System(MMS) using Transfer Function in order to improve the control characteristics of an operator in the system and the procedure for ergonomic system design, When man, as a subsystem, performs his allocated functions in a system, many physical and physiological problems such as fatigue, stress and error occur. And the imperfect design of a MMS may itself be a situational factor that accelerates stress as well as an idiosyncratic factor that causes errors. So, the economy of design should be considered together with the ergonomic characteristics on the evaluation of MMS.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.229-232
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• 2008

This study presents a numerical procedure to optimize the shape of stepped circular pin-fins to enhance turbulent heat transfer. The KRG method is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer with shear stress transport turbulent model. The objective function is defined as a linear combination of heat transfer and friction loss related terms with a weighting factor. Ten training points are obtained by Latin Hypercube Sampling for two design variables. Optimum shape has been successfully obtained with the increased objective function.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년 추계학술대회논문집
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• pp.229-232
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• 2008

This study presents a numerical procedure to optimize the shape of stepped circular pin-fins to enhance turbulent heat transfer. The KRG method is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer with shear stress transport turbulent model. The objective function is defined as a linear combination of heat transfer and friction loss related terms with a weighting factor. Ten training points are obtained by Latin Hypercube Sampling for two design variables. Optimum shape has been successfully obtained with the increased objective function.

• International Journal of Aeronautical and Space Sciences
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• 제17권1호
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• pp.8-19
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• 2016

This paper investigates the effects of inlet turbulence conditions and near-wall treatment methods on the heat transfer prediction of gas turbine vanes within the range of engine relevant turbulence conditions. The two near-wall treatment methods, the wall-function and low-Reynolds number method, were combined with the SST and ${\omega}RSM$ turbulence model. Additionally, the RNG $k-{\varepsilon}$, SSG RSM, and $SST_+{\gamma}-Re_{\theta}$ transition model were adopted for the purpose of comparison. All computations were conducted using a commercial CFD code, CFX, considering a three-dimensional, steady, compressible flow. The conjugate heat transfer method was applied to all simulation cases with internally cooled NASA turbine vanes. The CFD results at mid-span were compared with the measured data under different inlet turbulence conditions. In the SST solutions, on the pressure side, both the wall-function and low-Reynolds number method exhibited a reasonable agreement with the measured data. On the suction side, however, both wall-function and low-Reynolds number method failed to predict the variations of heat transfer coefficient and temperature caused by boundary layer flow transition. In the ${\omega}RSM$ results, the wall-function showed reasonable predictions for both the heat transfer coefficient and temperature variations including flow transition onset on suction side, but, low-Reynolds methods did not properly capture the variation of the heat transfer coefficient. The $SST_+{\gamma}-Re_{\theta}$ transition model showed variation of the heat transfer coefficient on the transition regions, but did not capture the proper transition onset location, and was found to be much more sensitive to the inlet turbulence length scale. Overall, the Reynolds stress model and wall function configuration showed the reasonable predictions in presented cases.

• 한국지반공학회논문집
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• 제22권7호
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• pp.23-35
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• 2006

본 연구에서는 암반에 근입된 현장타설말뚝의 주면하중전이특성을 분석하기 위하여, 주요 영향요소(일축압축강도, 거칠기, 수직강성, 초기구속응력, 재료성질)에 따라 일정수직강성(Constant Normal Stiffness, CNS)조건의 직접전단시험을 수행하였다. 그 결과 암반에 근입된 현장타설말뚝의 주변하중전이특성을 3구간으로 이상화할 수 있었으며, 각 구간에서의 거동을 지배하는 주요 요소의 영향 및 그에 따른 거동을 파악할 수 있었다. 이를 토대로 암반의 절리 및 풍화상태를 나타내는 GSI(Geological Strength Index)를 이용한 Hoek-Brown 파괴기준(1997)을 적용하여, 암반에 근입된 현장타설말뚝의 굴착면 거칠기를 고려한 새로운 주면 하중전이함수를 제안하였다. 제안된 하중전이함수는 기존 7본의 말뚝 재하시험 결과와 비교분석을 수행하였으며, 그 결과 본 제안식이 암반 굴착면의 거칠기 및 암반특성을 적절히 반영함을 알 수 있었다.

• International Journal of Fluid Machinery and Systems
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• 제9권3호
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• pp.229-236
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• 2016

Exergetic analysis was introduced in optimization of a rotating equilateral triangular internal cooling channel with staggered square ribs to maximize the net exergy gain. The objective function was defined as the net exergy gain considering the exergy gain by heat transfer and exergy losses by friction and heat transfer process. The flow field and heat transfer in the channel were analysed using three-dimensional Reynolds-averaged Navier-Stokes equations under the uniform temperature condition. Shear stress transport turbulence model has been selected as a turbulence closure through the turbulence model test. Computational results for the area-averaged Nusselt number were validated compared to the experimental data. Three design variables, i.e., the angle of rib, the rib pitch-to-hydraulic diameter ratio and the rib width-to-hydraulic diameter ratio, were selected for the optimization. The optimization was performed at Reynolds number, 20,000. Twenty-two design points were selected by Latin hypercube sampling, and the values of the objective function were evaluated by the RANS analysis at these points. Through optimization, the objective function value was improved by 22.6% compared to that of the reference geometry. Effects of the Reynolds number, rotation number, and buoyancy parameter on the heat transfer performance of the optimum design were also discussed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.136-139
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• 2004

The domestic concrete standard specification(l999) reports roughly about heat transfer analysis and thermal stress analysis for mass concrete. Engineers cannot but choice after all numerical method such FEM, FDM to escape review. It seems to us that the specification is room for reconsideration because above methods are vary expensive and without popularity. This study suggests thermal distributed function in mass concrete. The function consists of two independent variables, curing time and depth. It's results have been tested a sensitivity for unit cement content, form condition, curing condition, and shape(depth, width). Results of the function are made a comparison with analytical values of MIDAS/CIVIL and a few measurement values. The researchers could meet with coherent and good results for variable cases.