• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2006년도 춘계학술대회 논문집
• /
• pp.145-148
• /
• 2006

Cold gas dynamic spray is a relatively new coating process by which coatings can be produced without significant heating during the process. Cold gas dynamic spray is conducted by powder sprayed by supersonic gas jet, and generally called the kinetic spray or cold-spray. Cold-spray was developed in Russia in the early 1980s to overcome the defect of thermal spray method. Its low process temperature can minimize thermal stress and also reduce the deformation of the substrate. Most researches on cold-spray have focused on micro scale coating, but our research team tried to apply this method to macro scale deposition. The macro scale deposition causes deformation of a thin substrate which is usually convex to the deposited side. In this research, the main cause of the deformation was investigated using 6061-T6 aluminum alloy and properties of deposited aluminum layer such as coefficient of thermal expansion, Elastic modulus, hardness, electric conductivity were measured. From the result of the analysis, it was concluded that compressive residual stress was the main reason of substrate deformation while CTE had little effect.

• 대한기계학회논문집
• /
• 제17권10호
• /
• pp.2574-2581
• /
• 1993

A Shadow mask in C. R. T. (Cathod Ray Tube) undergoes a temperature increase due to impinging electron beams emitted from guns, and thermal deformation from such temperature rise may cause the electron beams to island on the panel, and thus give rise to depolarization. Hence the analysis of temperature distribution for a shadow mask is an important procedure for designing the shadow mask. In this paper, we are concerned with nonlinear finite element analysis of the temperature distribution on a shadow mask. First of all, we replace shadow mask, containing numerous apertures of a slit type, by an orthotropic shell without apertures, and calculate the apparent thermal conductivities. Because of thermal radiation, which is one of the major heat transfer mechanism for shadow masks, the resulting finite element equation is nonlinear and solved by the Newton method. Finally numerical examples are illustrated for a 21" FST(Full Square Tube) shadow mask, and followed by discussion.sion.

• 에너지공학
• /
• 제24권4호
• /
• pp.48-54
• /
• 2015

본 연구에서는 야외용 가스보일러 형상에 따른 연소판을 열응력 결과를 통해 분석하였다. 정상상태 모드로 계산한 결과, 최대 응력 및 변형은 A형상과 B형상에서 각각 666.8MPa, 0.20476mm로 분석되었다. 변형은 연소판 중심에서 바깥쪽으로 갈수록 증가하는 경향을 보였다. 또한, 8가지 형상 중에서 최대 응력과 변형은 F와 C형상이 가장 안전함을 각각 보였다. 따라서, 8가지 형상 중에서 F형상이 강도 및 안전성 측면에서 가장 우수하다고 판단되었으며, 가스보일러의 연소판 형상에 따른 계산된 결과를 분석함으로서 보일러 시스템에 대한 안전한 구성요소 변수를 실질적으로 적용할 수 있는 모델을 설계할 수 있게 되었다.

• 한국융합학회논문지
• /
• 제11권5호
• /
• pp.139-144
• /
• 2020

본 연구에서는 드럼자체와 브레이크에 대한 시뮬레이션 해석을 하였으며 열해석 결과와 구조 해석을 통한 내구성을 고찰하여 그 해석 결과를 얻었다. 브레이크 실린더로 인하여 힘을 받는 라이닝,라이닝의 확장으로 인하여 힘을 받는 드럼 내부, 축의 회전으로 인하여 힘을 받는 드럼에 대한 열응력 및 구조 해석을 통하여 어느 부분에 등가응력과 변형량이 큰지를 확인하였다. 본 연구 결과를 종합하여 브레이크 디스크설계에 응용한다면 열변형 방지 및 그 내구성을 증대시키는데 활용성이 클 것으로 사료된다. 본 연구 결과는 실제적으로 드럼 브레이크에서의 열응력에 견딜 수 있는 내구성 있는 설계에 유용하게 적용할 수 있다. 계절별 기차선로 이음새에서의 내구성 해석을 적용함으로서 본 연구 결과가 미적인 설계에 응용되는 융합 연구에 유리하다고 보여진다.

• 한국생산제조학회지
• /
• 제22권2호
• /
• pp.228-234
• /
• 2013

This study focuses on development of a finite element model for analysis of thermal characteristics of a direct-connection spindle of a machining center by joint simulation of heat transfer and thermal deformation. Two finite element analyses were carried out procedurally for heat transfer, first, to identify temperature distribution of components of the spindle and then for thermal deformation to identify their structural behavior based on the temperature distribution. It was assumed that the heat transfer between a component revolving and the surrounding air is identical to that between a flat plate and the running air on it and the heat transfer is based on a uniform surface heat flux for turbulent flow. The results from the analyses were compared with those from experiments to validate the finite element model.

• Journal of Mechanical Science and Technology
• /
• 제18권10호
• /
• pp.1712-1721
• /
• 2004

A method of measuring the thermal diffusivity of semi-infinite solid material at room temperature using photothermal displacement is proposed. In previous works, within the constant thickness of material, the thermal diffusivity was determined by the magnitude and phase of deformation gradient as the relative position between the pump and probe beams. In this study, however, a complete theoretical treatment of the photothermal displacement technique has been performed for thermal diffusivity measurement in semi-infinite solid materials. The influence of parameters, such as, radius and modulation frequency of the pump beam and the thermal diffusivity, was studied. We propose a simple analysis method based on the zero -crossing position of real part of deformation gradient and the minimum position of phase as the relative position between two beams. It is independent of parameters such as power of pump beam, absorption coefficient, reflectivity, Poisson's ratio, and thermal expansion coefficient.

• Tribology and Lubricants
• /
• 제40권1호
• /
• pp.17-23
• /
• 2024

This study analyzes the thermal effects on the performance of an air foil thrust bearing (AFTB) using COMSOL Multiphysics to approximate actual bearing behavior under real conditions. An AFTB is a sliding-thrust bearing that uses air as a lubricant to support the axial load. The AFTB consists of top and bump foils and supports the rotating disk through the hydrodynamic pressure generated by the wedge effect from the inclined surface of the top foil and the elastic deformation of the bump foils, similar to a spring. The use of air as a lubricant has some advantages such as low friction loss and less heat generation, enabling air bearings to be widely used in high-speed rotating systems. However, even in AFTB, the effects of energy loss due to viscosity at high speeds, interface frictional heat, and thermal deformation of the foil caused by temperature increase cannot be ignored. Foil deformation derived from the thermal effect influences the minimum decay in film thickness and enhances the film pressure. For these reasons, performance analyses of isothermal AFTBs have shown few discrepancies with real bearing behavior. To account for this phenomenon, a thermal-fluid-structure analysis is conducted to describe the combined mechanics. Results show that the load capacity under the thermal effect is slightly higher than that obtained from isothermal analysis. In addition, the push and pull effects on the top foil and bump foil-free edges can be simulated. The differences between the isothermal and thermal behaviors are discussed.

• Journal of Ship and Ocean Technology
• /
• 제8권3호
• /
• pp.40-49
• /
• 2004

Welding deformations injure the beauty of appearance of a structure, decrease its buckling strength and prevent increase of productivity. Welding deformations of real structures are complicated and the accurate prediction of welding deformations has been a difficult problem. This study proposes a method to predict the welding deformations of large structures accurately and practically based on the simplified thermal elasto-plastic analysis method. The proposed method combines the inherent strain theory with the numerical or theoretical analysis method and the experimental results. The weld joint is assumed to be divided into 3 regions such as inherent strain region, material softening region and base metal region. Characteristic material properties are used in structural modeling and analysis for reasonable simplification. Calculated results by this method show good agreement with the experimental results. It was proven that this method gives an accurate and efficient solution for the problem of welding deformation calculation of large structures.

• 한국CDE학회논문집
• /
• 제21권2호
• /
• pp.143-150
• /
• 2016

In shipbuilding, hull assemblies are manufactured by welding. The thermal deformation caused by the welding produces shape deformation. Counter-deformed design methods have been used in shipyards to cope with the weld-induced deformation of ship assembles. Finite element methods (FEMs) are frequently used to estimate welding distortion in the counter-deformed design. For the estimation of welding distortion, producing uniform rectangular elements is required to enter thermal loads on the welding line and obtain accurate analysis results. In this paper, a new automatic mesh generation method is proposed for prediction of welding deformation in FEM. Meshes are constructed for test cases to demonstrate the feasibility of the proposed mesh generation method.

• 한국결정성장학회지
• /
• 제30권5호
• /
• pp.208-213
• /
• 2020

본 연구에서는 유한요소 해석과 PQRSM 알고리즘 기반의 최적설계 기법을 활용하여 IGZO 산화물 타겟과 구리백플레이트가 서로 접합되어 있는 타겟 모듈에서 IGZO 산화물의 열변형을 최소화할 수 있는 방법에 대해 고찰했다. 3차원 유한요소 해석 결과 고온에서 IGZO와 구리 백플레이트의 접합 이후 냉각될 때 IGZO 산화물의 열변형은 최대 0.161 mm로 예측되었다. 유한요소 해석을 연동한 최적설계기법을 적용하기 위해 타겟 모듈을 냉각할 때 사용하는 하부받침대와 상부고정대의 위치를 설계변수화하여 목적함수인 IGZO의 열변형이 최소화되도록 최적설계를 수행했고, 그 결과 IGZO 산화물의 열변형을 최대 42 % 감소시킬 수 있었다. 이는 타겟을 구성하는 주재료와 구조 변경 없이 공정 중에 사용되는 부재료의 위치 변경만으로도 산화물의 열변형을 감소시킬 수 있어 산업계에 유용할 것으로 사료된다.