• Journal of Mechanical Science and Technology
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• 제14권7호
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• pp.715-721
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• 2000

Residual stress is one of the causes which makes defects in engineering components and materials. These residual stresses can occur in many engineering structures and can sometimes lead to premature failures. There are commonly used methods by which residual stresses are currently measured. But these methods have a little damage and other problems; therefore, a new experimental technique has been devised to measure residual stress in materials with a combination of electronic laser interferometry, laser heating and finite element method. The electronic laser interferometer measures in-plane deformations while the laser heating and cooling provides for very localized stress relief. FEM is used for determining the heat temperature and other parameters. The residual stresses are determined by the amount of strain that is measured subsequent to the heat-up and cool-down of the region being interrogated. A simple model is presented to provide a description of the method. In this paper, the ambiguity problem for the fringe patterns has solved by a phase shifting method.

• 한국표면공학회지
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• 제51권1호
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• pp.40-46
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• 2018

The light-weight of the research and development materials is actively carried out by overseas automobile companies and technology development continues in Korea. For the sake of fuel efficiency, the development of lightweight technology by improving the manufacturing method has been very effective. Recently, to maximize the effects of light weight, automotive interior parts have been applied by the micro-cellular injection molding using supercritical fluids and we call the Mucell manufacturing. This technique causes a problem in the quality of the surface of the products, because the shooting cells are revealed as the surface layer of the products by forming micro cells at the center of the products during injection molding. To overcome these phenomenon, we increased the temperature of injection molding using joule heating until critical value. In this study, we have predicted the problem of Mucell injection molding through the finite element analysis as changed the temperature by joule heating. From the result of finite element analysis, we have determined the optimized process and made the injection mold included electric current heating system with Mucell manufacturing analyzed the surface characteristics of the injection product according to changing mold temperature.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권5호
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• pp.327-337
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• 2000

In this paper, the design sensitivity formula for the control of the transient temperature distribution is developed using the direct differentiation method, and used for the optimal design of induction heating coil position. The temperature distribution is calculated using the heat source of the induced eddy current and heat diffusion equation. The physical property variations of the workpiece depending on the temperature are considered. The eddy current distribution and the temperature distribution are calculated with the 2D finite element procedure. The adjoint variable technique is employed in expressing the design sensitivity. The goal of the design is to have the desired distribution of the temperature on a specific region of the sensitivity. The goal of the design is to have the desired distribution of the temperature on a specific region sensitivity. The goal of the design is to have the desired distribution of the temperature on a specific region of the workpiece. The numerical example shows that the proposed design sensitivity analysis for the control of the transient temperature distribution is very useful and practical in the optimal design of induction heating coils.

• 한국산업융합학회 논문집
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• 제22권3호
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• pp.353-364
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• 2019

The walk-way means a passage installed on the deck of a ship so that a person can safely move under any circumstances. So, the walk-way has to maintain a temperature of $5^{\circ}C$ or more for anti/de-icing even at an ambient temperature of $-62^{\circ}C$, a temperature in polar region. At present, the walk-way with heating cable is used, but the anti/de-icing effect is insufficient due to low heat transfer efficiency. Also, it has a construction problem due to heavy weight. In this study, an walk-way with a CNT surface heating element is proposed for the high anti/de-icing effect and the heating value per unit volume. The international standard survey, conceptual design, and simulation for the structural safety and the heat transfer are performed for the development of the proposed walk-way. To enhance the performance, the case studies based on the simulation analysis are conducted. Finally, the final prototype, applying the optimum material and thickness (3.2t of SS400) based on the case study results, is fabricated and experimented.

• 설비공학논문집
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• 제2권1호
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• pp.74-83
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• 1990

The temperature distributions inside molds with heating or cooling tubes were calculated using special boundary element method. This special boundary element method was employed in order to reduce the error for small diameter tubes. Calculated temperature was compared with results using finite element method. It was found that the current method becomes more accurate as tubes' diameter gets smaller. Optimal arrangement of tubes for uniform temperature distribution along specific surface was found. CONMIN program was employed for the optimization.

• 소성∙가공
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• 제32권3호
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• pp.153-159
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• 2023

This paper presents the optimal design of a heating system using radiant heating elements for application in smart farms. Smart farming, an advanced agricultural technology, is based on artificial intelligence and the internet of things and promotes crop production. Temperature and humidity regulation is critical in smart farms, and thus, a heating system is essential. Radiant heating elements are devices that generate heat using electrical energy. Among other applications, radiant heating elements are used for environmental control and heating in smart farm greenhouses. The performance of these elements is directly related to their electrical energy consumption. Therefore, achieving a balance between efficient electrical energy consumption and maximum heating performance in smart farms is crucial for the optimal design of radiant heating elements. In this study, the size, electrical energy supply, heat generation efficiency, and heating performance of radiant heating elements used in these heating systems were investigated. The effects of the size and electrical energy supply of radiant heating elements on the heating performance were experimentally analyzed. As the radiant heating element size increased, the heat generation efficiency improved, but the electrical energy consumption also increased. In addition, increasing the electrical energy supply improved both the heat generation efficiency and heating performance of the radiant heating elements. Based on these results, a method for determining the optimal size and electrical energy supply of radiant heating elements was proposed, and it reduced the electrical energy consumption while maintaining an appropriate heating performance in smart farms. These research findings are expected to contribute to energy conservation and performance improvement in smart farming.

• KIEAE Journal
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• 제7권5호
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• pp.65-71
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• 2007

The purpose of this study was to analyze the difference of thermal sensation by radiant floor heating as ecological design element. The experimental investigations were carried out in climate chamber, and subjects were 34 college-age females in good health. The experimental variable was radiant heat by floor heating, and experimental controlled conditions were indoor temperature, relative humidity, and air velocity in climate chamber and clothing value and activity of subjects. The results are as follows. (1) Indoor temperature($21{\pm}0.5^{\circ}C$) in climate chamber were maintained as controlling. Clothing values of the subjects were controlled as average 0.73 clo. In the floor heating-off, globe temperature was average $23.2^{\circ}C$(22.4~24.1), but in the floor heating-on, globe temperature was average $24.8^{\circ}C$(23.0~25.5). (2) In the floor heating-off, thermal sensation rating was average -1.03(slightly cool), in the floor heating-on, thermal sensation rating was average +1.03(slightly warm). (3) There were the differences of thermal sensation by radiant floor heating although indoor temperatures were maintained in an equal state. (4) The thermal sensation rating was tending upward according as the globe temperature was getting higher.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
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• pp.60-60
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• 2010

Since the curved hull plate was made by a series of manufacturing process including cold bending, manual local heating and correction work, the accuracy of curved plate strongly depends on the proficiency of worker. So the demands on the automatic local heating system for curved hull plate have continuously increased and the various researches relevant to it have been performed. Generally, the heat sources used for local heating were flame and induction heat. In terms of initial cost, flame heating is in a better favorable position than induction heating. However, from the viewpoint of the control of heat, induction heating has more advantage. So the various researches related to apply the induction heating to the automatic forming system has been performed. The purpose of this study is to establish the proper capacity of high frequency induction heating system for forming the curved hull plate. In order to do it, the proper coil shape for local heating was designed and the efficiency of induction heating system was determined by comparing of temperature results obtained by FEA and experiment. With the results, the extensive FEA was performed to identify the effect of heated plate dimension, cooling method and the capacity of induction heating system on the amount of heat loss introduced by induction heating. Based on the results, the proper capacity of high frequency induction heating system was proposed.

• 마이크로전자및패키징학회지
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• 제31권1호
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• pp.29-34
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• 2024

전류가 전도체를 통과할 때 발생하는 줄 열을 이용한 발열체는 자동차 창유리, 고속열차 창유리 및 태양전지와 같은 다양한 산업 분야에서 수분 제거 등을 위해 널리 연구되고 개발되고 있고, 최근에는 기계적 변형 조건 하에서도 안정적인 가열을 유지할 수 있는 유연 발열체를 개발하기 위하여 여러 나노 구조의 발열체를 이용한 연구가 활발하게 진행중이다. 본 연구에서는 유연성이 우수한 폴리우레탄을 기판으로 선정하고 마그네트론 스퍼터링을 이용하여 낮은 전기비저항(1.6 μΩ-cm)을 가지는 은 (Ag) 박막을 형성하여 발열층으로 이용한 연구를 진행하였다. 2D 박막구조에서의 전면발열에 의하여 열응답속도가 매우 높아 목표 온도의 95%까지 20초 이내에 도달하였으며 우수한 발열재현성을 보여주었다. 또한 기계적 변형이 가해지는 환경에서도 우수한 발열특성이 유지되었으며 반복적인 굽힘 테스트 (10,000회, 곡률반경 5 mm 기준)에서도 3% 이내의 전기저항 증가만이 발생할 정도로 우수한 유연성을 보유하여, 폴리우레탄/은 구조의 면상발열체는 굴곡진 형태를 가진 다양한 기기에서부터 인체분위와 같이 다양한 응력이 가해지는 환경에서 사용할 수 있는 플렉서블/웨어러블 면상발열체로의 적용이 매우 유망하다는 것을 보여준다. 또한 증착된 은 박막 발열 층 구조는 다양한 목적을 위한 기능을 추가하여 다양한 분야에서 사용할 수 있는 플렉서블/웨어러블 발열체로서의 적용 가능성을 보여줍니다.

• Composites Research
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• 제31권6호
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• pp.412-420
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• 2018

본 연구에서는 면상발열체 특성을 향상시키기 위해 피치계 탄소종이에 전도성 탄소필러로 석유계 코크스, 카본블랙, 흑연을 페놀수지와 함께 함침시켰으며, 탄소종이에 함침된 탄소필러가 물리화학적 성질에 미치는 영향을 전기적, 열적 특성 분석을 통해 고찰하였다. 그 결과, 면저항과 계면접촉저항이 선형적으로 감소하였으며, 탄소필러의 함량이 증가함으로써 전기전도도와 열전도도가 향상하였다. 또한, 탄소종이에 1~5 V 전압을 인가하였을 경우 탄소종이의 면상발열 특성을 관찰하였을 때 5 V 전압에서 최대 $125.01^{\circ}C$로 발열 특성을 나타내었다. 이러한 결과는 탄소섬유 사이에 존재하는 미세공극이 채워짐으로써, 전기적 네트워크가 형성되어 전기적 및 열적 특성이 향상되었기 때문이다.