• 대한조선학회지
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• 제12권1호
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• pp.9-22
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• 1975

As a second step of a thermal stress analysis in a watertight bulkhead plate during welding of a spool type penetration piece, is idealized as a thin circular disk with a clamped boundary. The exact solution for the transient temperature distribution and associated quasi-static thermal stresses which arise in a circular disk subjected to an instantaneous point source of heat acting in its interior has been obtained. And the solutions have been extended to the case of moving source of heat with the aid of the Duhamel's superposition integral and the results finally derived have been compared with the other results from the typical cases. The solutions can be applied to the problem such as a welding of a penetration piece on the watertight bulkhead and also applicable to the problems which occur in cutting or welding.

• 대한조선학회지
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• 제12권1호
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• pp.1-8
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• 1975

As a first step of a thermal stress analysis in a watertight bulkhead plate during welding of a spool type penetration piece, the bulkhead plate has been idealized as infinite plate with a circular hole. The exact solution for the transient temperature distribution and the associated quasi-static thermal stress which arise in a infinite plate subjected to an instantaneous point source of heat acting on the periphery of the circular hole. And the solutions have been extended to the case of a moving heat source with the aid of the Duhamel's superposition integral. The solutions can be applied to the problems such as a circular cutting or welding of a plate.

• Journal of Welding and Joining
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• 제13권2호
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• pp.68-81
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• 1995

This paper presents an analytical solution to predict the transient temperature distribution in fillet arc welding. The analytical solution is obtained by solving a transient three -dimensional heat conduction equation with convection boundary conditions on the surfaces of an infinite plate with finite thicknesses, and mapping an infinite plate onto the fillet weld geometry with energy equation. The electric arc heat input on fillet weld and on infinite plate is assumed to have a traveling bivariate Gaussian distribution. To check the validity of the solution, GTA and FCA welding experiments were performed under various welding conditions. The actual isotherms of the weldment cross - sections at various distances from the arc start point are compared with those of simulation result. As the result shows a satisfactory accuracy, this analytical solution can be used to predict the transient temperature distribution in the fiIIet weld of finite thickness under a moving bivariate Gaussian distributed heat source. The simplicity and short calculation time of the analytical solution provides rationales to use the analytical solution for modeling the welding control systems or for an optimization tool of welding process parameters.

• 대한기계학회논문집A
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• 제27권9호
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• pp.1499-1507
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• 2003

Physical importance of cutting temperatures has long been recognized. Cutting temperatures have strongly influenced both the tool life and the metallurgical state of machined surfaces. Temperatures in drilling processes are particularly important, because chips remain in contact with the tool for a relatively long time in a hole. Tool temperatures tend to be higher in drilling processes than in other in machining processes. This paper concerns with modeling of thermal behaviors in drilling processes as well as estimation of the cutting temperature distribution based on remote temperature measurements. One- and two-dimensional estimation problems are proposed to analyze drilling temperatures. The proposed thermal models are compared with solutions of finite element methods. Observer algorithms are developed to solve inverse heat conduction problems. In order to apply the estimation of cutting temperatures, approximation methods are proposed by using the solution of the finite element method. In two-dimensional analysis, a moving heat source according to feedrate of the drilling process is regarded as a fixed heat source with respect to the drilling location. Simulation results confirm the application of the proposed methods.

• Tribology and Lubricants
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• 제18권6호
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• pp.389-395
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• 2002

The surface temperature at the interface of bodies in a sliding contact is one of the most important factors influencing the behavior of machine components. The calculation of the surface temperature at a sliding contact interface has been an interesting and important subject for tribologist. Temperature analyses were usually performed under the consideration contacted two bodies as semi-infinite. But the analysis was difficulty in being applied to finite body and considering the boundary condition. In this study, contact temperature rise of two finite bodies and surfaces due to frictional heating under the rectangular and the circular sliding contact is calculated. Heat partition factor is calculated using semi-infinite solid analysis and the temperature of the finite bodies is calculated using FVM. It will be shown that Most frictional heat in the fore part of contact region for sliding direction is conducted into body that has a moving heat source and the site of the maximum temperature rise moves to the opposite direction of sliding during sliding.

• 한국철도학회논문집
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• 제12권1호
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• pp.25-30
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• 2009

본 연구에서는 철도 화재 시 구난역에서의 화재 연기의 거동을 파악하기 위하여 상용코드를 사용하여 수치해석 하였다. 화원의 모사와 화재로 인한 생성물의 거동을 예측하기 위해 stoichiometric상태에서 연료 소모량에 따른 연소생성물의 생성률과 산소 소모율을 VHS 모델에 적용하고 종의 보존 방정식을 해석하는 HVHS 모델을 이용하였다. 해석결과 화재 연기는 온도에 따른 밀도 차에 의해 터널의 천장을 따라 이동 하였으며 열원으로부터 멀어지면서 하강하는 형태를 확인 할 수 있었다. 또한 터널 내 공기는 화원으로 집중되었으며 비사고 터널과 사고 터널의 압력 차에 의해 화재연기는 별다른 환기 시스템 없이도 비사고 터널로 유입되지 않았다.

• Journal of Advanced Marine Engineering and Technology
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• 제39권10호
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• pp.1062-1067
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• 2015

Floating architecture is a type of building that is geographically located on a sea or a river. It floats under the influence of buoyancy, and does not have an engine for moving it. Korea is a peninsula surrounded by sea except on the north side, so floating architectures have been mainly focused on two points: solving the issue of small territory and providing various leisure & cultural spaces. Floating architectures are expected to save energy effectively, if they use sea water heat, which is known to be clean energy with infinite reserves. To use sea water heat as the heat source and/or heat sink, this study proposes a model in which a sea water heat exchanger is embedded in the concrete structure in the lower part of the floating architecture that is submerged under the sea. Based on the results of performance evaluations of the sea water heat exchanger using CFD (computational fluid dynamics) analysis and mock-up experiments under various conditions, it is found out that the temperature difference between the inlet and outlet of the heat exchanger is in the range of $3.06{\sim}9.57^{\circ}C$, and that the quantity of heat transfer measured is in the range of 3,812~7,180 W. The CFD evaluation results shows a difference of 5% with respect to the results of mock-up experiment.

• Journal of Welding and Joining
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• 제31권5호
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• pp.15-19
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• 2013

In order to reduce a grand compute time in prediction of welding distortion and residual stress by 3D thermal elastic plastic analysis, idealization of welding that is methods to heat input simultaneously in all weld metal on the same welding direction is carried out on two weld joints(butt welding and fillet welding). Then, the accuracy of acquired results is investigated through the comparison of the high accuracy prediction results. The thermal conduction analysis results by idealization of welding, the temperature is raised accompany with beginning of heat input because all of weld metal is heated input at the same time. On the other side, the temperature witch predicted with high accuracy is raised at the moment heating source passes the measuring points. So, there is difference of time between idealization of welding and considering of moving heat source faithfully. However, temperature history by idealization of welding is well simulated a high accuracy prediction results.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.339-343
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• 2000

Rapid prototyping for welding and milling is a hybrid approach that makes use of welding as additive and conventional milling as subtractive technique. For two years this concept has been used to verify manufacturing mold and mechanical parts successfully. In latest new fabrication methods. For example, manufacturing mold for two sort of materials and shell fabrication, have been applied to the concept in KIST. This methods will be an alternative proposal in rapid prototyping. Metal deposition for welding causes the part to deform. It is a handicap in our proceeding. To overcome this problem, in this paper, we represent an optimal welding path for FEM analysis. Eight paths are tried to this and the value of deformation is average and standard deviation in four points'. Then we can compare with eight cases and select the optimal path.

• 한국음향학회지
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• 제22권3호
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• pp.217-223
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• 2003

30 ㎑의 초음파 (ultrasonic wave)의 미세 진동에 의해서 유도된 음향유동 (acoustic streaming)에 의한 공기대류를 이용한 새로운 냉각방법을 소개한다. 초음파 진동은 압전소자 (piezoelectric device)에 의해서 얻어지며 50 m 정도의 진동진폭을 얻기 위해 기계적 진동 증폭자인 혼 (horn)을 추가하여 전체 진동 시스템이 공진하도록 구성된다. 음향유동에 의한 열전달 효과의 상승을 측정하기 위해 열원 (heat source) 및 열원 주위의 대기의 온도변화를 실시간으로 측정하였다. 초음파 진동 시작 후 시간지연 없이 음향유동이 유도되어 진동자 주위의 대량의 공기유동으로 인한 급격한 온도감소가 관찰되었다. 또한 열원과 진동자와의 거리가 방사 (radiation)되는 음파 (sound wave)의 반파장 (half wave length)의 정배수가 될 때 열원의 냉각효과가 극대화됨을 실험적으로 관찰하였다. 이는 음파의 공진현상에 기인한 것으로 이론적 고찰을 통한 검증 또한 수행되었다. 음향유동을 이용한 냉각법의 장점은 초음파 진동을 이용하기 때문에 무소음이며 이동 형태의 부품이 없기 때문에 반영구적으로 사용할 수 있다. 또한 기존의 전기모터를 이용한 냉각팬 (cooling fan)으로는 냉각이 어려운 초소형 기전시스템 (MEMS)의 냉각법으로 사용될 수 있는 첨단 냉각방법이다.