• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.95-100
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• 1999

A FEA(finite element analysis model) was proposed to study stress and strain distributions in thick composites with fiber waviness and initial curvature under flexural loading. Three types of model with initial curvature were considered in this study: flat, concave and concave models. In the analysis, both material and geometrical nonlinearities were incorporated. Four point flexural tests were conducted on the flat specimens to obtain the flexural behavior of thick composites experimentally. It was concluded that the predictions from the models were in good agreement with the experimental results. It was shown that the stress and strain distributions as well as nonlinear flexural behaviors of thick composites were significantly affected by the fiber waviness and initial curvature.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 춘계학술대회논문집
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• pp.171-178
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• 2000

In order to evaluate the tensile behaviors of hoop direction for the nuclear fuel cladding tubes the shapes of specimen and jig fixtures for the ring test are decided with various conditions under the elastic-large plastic deformations. The axial displacement of the jig cylinders is converted to the circumferential direction elongations of specimen. The stress distributions on specimen are depended on the radii and locations of specimen and jig size and central angle. Therefore we calculated the stress distributions and decided the optimum shapes to get the uniform stress in the area of specimen gage length. Form the analysis the stress distributions in gate area are reviewed with the radii and location of specimen notch and the central angle of jig cylinder,. The optimum shapes of specimen and jig are proposed to the clad tube having 10.62 mm in diameter and 0.63mm in thickness for 16x16 PWR nuclear fuel assembly.

• Tribology and Lubricants
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• 제13권3호
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• pp.93-101
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• 1997

The numerical results on the stress distributions of rail-wheel contact problems are presented for three models in a high-speed rail system. These models which have straight and tapered (1:40 and 1:20) contact geometries between the wheelset and rail are analyzed using the finite element approach. From the simulation results we found that the tapered geometry (1:20) of railwheel contact base line showed very stable contact stress distributions for a whole contact position between the wheel and rail in a curved rail section. The FEM computed results may present an optimized slope geometry of rail-wheel contact in a high-speed railway system.

• Structural Engineering and Mechanics
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• 제57권5호
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• pp.823-835
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• 2016

Using the Complementary Functions Method (CFM), a general solution for the one-dimensional steady-state thermal and mechanical stresses in a hollow thick sphere made of functionally graded material (FGM) is presented. The mechanical properties are assumed to obey the exponential variations in the radial direction, and the Poisson's ratio is assumed to be constant, with general thermal and mechanical boundary conditions on the inside and outside surfaces of the sphere. In the present paper, a semi-analytical iterative technique, one of the most efficient unified method, is employed to solve the heat conduction equation and the Navier equation. For different values of inhomogeneity constant, distributions of radial displacement, radial stress, circumferential stress, and effective stress, as a function of radial direction, are obtained. Various material models from the literature are used and corresponding temperature distributions and stress distributions are computed. Verification of the proposed method is done using benchmark solutions available in the literature for some special cases and virtually exact results are obtained.

• Structural Monitoring and Maintenance
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• 제5권1호
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• pp.1-13
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• 2018

The Zhuhai Opera House has an external structure consisting of a type of spatial steel, where the stress of steel elements varies with the ambient temperature. A structural health monitoring system was implemented at Zhuhai Opera House, and the temperatures and stresses of the structures were monitored in real time. The relationship between the stress distribution and temperature variations was analysed by measuring the temperature and stresses of the steel elements. In addition to measurements of the structure stresses and temperatures, further simulation analysis was carried out to provide the detailed relationship between the stress distributions and temperature variations. The limited temperature measurements were used to simulate the structure temperature distribution, and the stress distributions of all steel elements of the structure were analysed by building a finite element model of the Zhuhai Opera House spatial steel structure. This study aims to reveal the stress distributions of steel elements in a real-world project based on temperature variations, and to supply a basic database for the optimal construction time of a spatial steel structure. This will not only provide convenient, rapid and safe early warnings and decision-making for the spatial steel structure construction and operation processes, but also improve the structural safety and construction accuracy of steel space structures.

• 한국결정성장학회지
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• 제10권6호
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• pp.412-417
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• 2000

High electric field stressed trap distributions were investigated in the thin silicon oxide of polycrystalline silicon gate metal oxide semiconductor capacitors. The transient currents associated with the off time of stressed voltage were used to measure the density and distribution of high voltage stress induced traps. The transient currents were due to the discharging of traps generated by high stress voltage in the silicon oxides. The trap distributions were relatively uniform near both cathode and anode interface in polycrystalline silicon gate metal oxide semiconductor devices. The stress generated trap distributions were relatively uniform the order of $10^{11}$~$10^{12}$ [states/eV/$\textrm{cm}^2$] after a stress. The trap densities at the oxide silicon interface after high stress voltages were in the $10^{10}$~$10^{13}$ [states/eV/$\textrm{cm}^2$]. It was appeared that the transient current that flowed when the stress voltages were applied to the oxide was caused by carriers tunneling through the silicon oxide by the high voltage stress generated traps.

• 대한조선학회지
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• 제9권2호
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• pp.21-32
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• 1972

The problems of thermal stress and residual stress in resistance spot welding are studied from two standpoint namely, effect of temperature distributions and effect of the radius of free boundary. The radius of the region where the temperature distributions are occured is taken as a function of time after welding and as a finite size, 6 times of heated zone. The region of the radial stress distribution is treated as a function of time under Saint-Venant's principle and 6 or 12 times of originally heated zone. Thermal stresses and strains are obtained by analytic solution under constant mechanical properties and by the finite difference method for varing properties under temperature variation. From the computed results following conclusions are derived (1) For the engineering purpose, the region of temperature distribution and stress distribution can be treated as a finite region, $R=r_o=6r_e$ (2) If the maximum temperature of the aluminum alloy plate is less than $500^{\circ}F$, thermal stresses and strains can be obtained with constant mechanical properties. (3) The residual stresses and strains will be remained in welds and its vicinity.

• 한국기계가공학회지
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• 제19권7호
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• pp.81-88
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• 2020

The geometry and the defect of the groove of the part provoke a sudden change of stress in a local region. The objective of this paper is to investigate the effects of the geometry and the imperfection of a small groove on stress distributions in the vicinity of the joined region for the ABS part with a thin wall using a three-dimensional finite element analysis (FEA). Several types of groove are designed to improve joining characteristics in the vicinity joined region. The imperfection model of the small-sized groove is obtained from observation of deposition characteristics of a fused deposition modeling process. Local stress distributions in the vicinity of the joined region are predicted by the FE model with refined meshes. The influence of the angle and the imperfection of the groove on appearance regions of the maximum stress and distributions of the defined principal stress for different loading conditions is examined using the results of FEAs. Finally, a proper design of the groove is proposed to improve joining characteristics between the substrate and the ABS part.

• 한국산학기술학회논문지
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• 제15권9호
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• pp.5474-5479
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• 2014

본 연구는 중형 유도전동기 신제품 개발 단계에서 브라켓 주조품 제작시 발생하는 품질문제를 미리 평가하기 위하여 수행한 것으로, 브라켓 주조품의 제작과정인 주조 및 기계가공시 용탕 충진 양상, 결함 발생, 잔류응력 및 변형 등 제품의 품질상태를 수치해석적인 방법을 사용하여 평가하였다. 평가 결과 최종 기계가공 후 브라켓 주조품에 발생하는 잔류응력은 -53~54MPa, 변형량은 최대 1.8mm로 크지 않으며 내부 품질관리 기준에 부합함을 알 수 있었다.

• 대한기계학회논문집A
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• 제34권4호
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• pp.413-421
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• 2010

본 연구에서는 실제 용접 과정을 모사하는 유한요소 해석을 이용하여 강도 불일치를 가지는 매설 천연가스 배관 용접부의 잔류응력 분포를 계산한다. 유한요소 해석 절차의 타당성을 검증하기 위해 온도 및 잔류응력 해석 결과들은 실제 용융부 형상과 API 579 적용 결과와 비교된다. 기계적 강도 차이, 용접 금속의 강도, 덧살 및 입열량 등과 같은 용접 및 재료 변수들이 잔류응력 분포에 미치는 영향을 평가하기 위해 Parametric Study가 수행된다. 최종적으로 Parametric Study 결과에 근거하여 용접 및 재료 변수들의 영향이 고찰된다. 특히, 모재들 사이의 강도 불일치는 잔류응력 분포에 미미한 영향을 미침을 확인하였다.