• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.4
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• pp.1178-1185
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• 2010

Recently, high speed of container freight cars is causing fatigue damage of wheel. Sudden failure accidents cause a lot of physical and human damages. Therefore, damage analysis for wheel prevents failure accident of container freight car. Wheel receives mechanical and thermal loads at the same time while rolling stocks are run. The mechanical loads applied to wheel are classified by the horizontal load from contact of wheel and rail in curve line section and by the vertical force from rolling stocks weight. Also, braking and deceleration of rolling stocks cause repeated thermal load by wheel tread braking. Specially, braking of rolling stocks is frictional braking method that brake shoe is contacted in wheel tread by high breaking pressure. Frictional heat energy occurs on the contact surface between wheel tread and brake shoe. This braking converts kinetic energy of rolling stocks into heat energy by friction. This raises temperature rapidly and generates thermal loads in wheel and brake shoe. There mechanical and thermal loads generate crack and residual stress in wheel. Wetenkamp estimated temperature distribution of brake shoe experimentally. Donzella proposed fatigue life using thermal stress and residual stress. However, the load applied to wheel in aforementioned most researches considered thermal load and mechanical vertical load. Exact horizontal load is not considered as the load applied to wheel. Therefore, above-mentioned loading methods could not be applied to estimate actual stress applied to wheel. Therefore, this study proposed safety estimation on wheel of freight car using heat-structural coupled analysis on the basis of loading condition and stress intensity factor.

• Journal of Navigation and Port Research
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• v.29 no.10 s.106
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• pp.871-876
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• 2005

Application of semiconductor sensors has been widely spreaded into various industries because those have several merits like easy miniaturization and batch production comparison with previous mechanical sensors. But external conditions such as thermal and repetitive load have a bad effect on sensors's lifetime. Especially, this paper was focused on fatigue life of a interconnect made by various materials. Firstly we implemented the stress analysis for interconnect under thermal load and wording pressure. And the fatigue lifetime of each material was induced by Manson & Coffin Equation using the plastic stress-strain curve obtained by the plastic-elastic Finite Element Analysis. The Fatigue lifetime in its bottom is smaller than others and bending load have not an effect on the fatigue lifetime of the interconnect but the stress distribution.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.5
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• pp.599-605
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• 2009

Changes of atmospheric pressures cause short- and long-term crustal deformations and thus become error sources in the site positions estimated from space geodesy equipments. In this study, we computed daily displacements due to the atmospheric pressure loading (ATML) at the 14 permanent GPS sites operated by National Geographic Information Institute. And the 10-year GPS data collected at those stations were processed to create a continuous time series of the height estimate. Then, we corrected for the ATML from the GPS height time series to see if the correction changes the site velocity and improves the precision of the time series. While the precision improved by about 4% on average, the velocity change was not significant at all. We also investigated the overall characteristics of the ATML in the southern Korean peninsula by computing the ATML effects at the inland grid points with a $0.5^{\circ}{\times}0.5^{\circ}$ spatial resolution. We found that ATML displacements show annual signals and those signals can be fitted with sinusoidal functions. The amplitudes were in the range of 3-4 mm, and they were higher at higher latitudes and lower at the costal area.

• Nuclear Engineering and Technology
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• v.27 no.3
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• pp.393-402
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• 1995

The structural analysis of the reactor coolant system mainly consist of too fields. The one is the static analysis considering the impact of pressure and temperature built up during normal operation. The other is the dynamic analysis to estimate the impact of postulated events such as the seismic loads or postulated branch line pipe breaks event. Since the most important goal of the RCS structural analysis is to prove the safety of the RCS during normal operation or postulated events, a widely proven theory having enough conservatism is adopted. The load occurring on the RCS during normal operation is considered as the basic design loading condition throughout whole plant life time. The most typical characteristic of the RCS during normal operation is the thermal expansion of the RCS caused by reactor coolant with high temperature and pressure. Therefore, the exact estimation on the thermal movement of the RCS is needed to get more clear understanding on the thermal movement behavior of the RCS. In this study, the general structural analysis concept and modeling method to evaluate the thermal movement of the RCS under the normal plant operation condition are presented. To discuss the validation of the suggested analysis, analysis results are compared with the measured data which ore referred from the standardized 1000 MWe PWR plant under construction.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2000.11a
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• pp.444-447
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• 2000

본 논문에서는 종래의 정적인 디지털 패턴 매칭을 행하는 연상메모리와는 달리 아놀로그의 시계열정보를 직접 처리하여 시간축 방향으로 설정하는 것으로 강인성이 뛰어난 연상기억시스템을 제안하였다. 시스템의 기본적인 능력을 조사하기 위하여 기억패턴을 주기계열로 그리고 하중은 전부 고정하는 조건으로 단순화하여 시뮬레이션을 행하여 오류 정정능력을 갖는 것을 확인하였다. 시간축 방향의 하중을 적절하게 설정하면 기억용량의 증대나 상기 오류의 저감 등의 효과가 기대된다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.3
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• pp.319-326
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• 1985

본 연구에서는 준 3차원 유한요소법(quasi 3-D finite element method)을 사 용하여 균일한 변위하중뿐 아니라 적층판의 제작 공정상 필연적인 열하중(thermal loading)의 영향을 동시에 고려하여 층간균열의 발생 및 성장에 대한 특성을 밝히고자 한다. 끝으로 층간 균열이 인장강도에 미치는 영향을 혼합법칙(rule of mixtures)의 개념을 사용하여 평가하고자 한다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.5
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• pp.511-521
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• 2015

The thermal bridge occurring in a building influences its thermal performance and durability. The domestic typical multi-unit residential buildings suffer thermal losses resulting from thermal bridges of the balcony slab. To minimize the thermal loss between inside and outside of the balcony slab, thermal bridge breaker(TBB) systems have been developed and applied in building construction. Although thermal bridge breaker systems for reinforced concrete(RC) wall-slab joints can improve the thermal performance of a building, it is necessary to verify the structural performance of TBB systems whether they provide proper resistance for cyclic loading. In order to investigate the structural characteristics of TBB systems embedded in RC slabs, cyclic tests of wall-slab joints were performed by applying two reversed cycles at each up to 30 cycles. The test results show that the RC slabs embedding TBBS systems can present excellent structural performance and the maximum moment capacity, energy dissipation capacity and ductility of TBBs systems are enhanced compared to those of the typical RC slabs.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.4
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• pp.313-319
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• 2017

Fiber optics sensors that have been mainly applied to aerospace areas are now finding applicability in other areas, such as transportation, including railways. Among the sensors, the fiber Bragg grating (FBG) sensors have led to a steep increase due to their properties of absolute measurement and multiplexing capability. Generally, the FBG sensors adhere to structures and sensing modules using adhesives such as an epoxy. However, the measurement errors that occurred when the FBG sensors were used in a long-term application, where they were exposed to environmental thermal load, required calibration. For this reason, the thermal curing of adhesives needs to be investigated to enhance the reliability of the FBG sensor system. This can be done at room temperature through cyclic thermal load tests using four types of specimens. From the test results, it is confirmed that residual compressive strain occurs to the FBG sensors due to an initial cyclic thermal load. In conclusion, signals of the FBG sensors need to be stabilized for applying them to a long-term SHM.

• Proceedings of the KAIS Fall Conference
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• 2004.11a
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• pp.90-92
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• 2004

본 연구에서는 절삭 가공시 공구가 받는 절삭력과 칩-공구 사이에서 발생하는 절삭 열에 의한 공구의 변형을 예측하였다. 3D CAD를 이용하여 공구를 모델링 하였으며 절삭력과 절삭 열을 하중조건으로 부여하여 유한요소해석을 수행하였다. 하중조건으로 사용한 절삭력과 절삭 열은 절삭이론을 이용한 절삭력 모델을 사용하여 예측하였으며 실험을 통해 모델의 타당성을 검증한 결과이다. 그러므로 본 연구는 어떠한 사전 실험도 없이 절삭조건과 재료 물성치 그리고 공구 형상만을 알면 이에 따른 절삭력성분 및 절삭열 등을 얻을 수 있고, 이를 이용하여 절삭 가공시 공구의 변형을 예측할 수 있다.

• Journal of the Korea Institute of Military Science and Technology
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• v.25 no.4
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• pp.355-363
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• 2022

Development of supersonic flying vehicle is one of the most latest issue in modern military technology. Specifically, structural integrity of supersonic flying vehicle can be verified by high temperature structural test. High temperature structural test is required to consider thermal load caused by aerodynamic heating while applying structural load simultaneously. Tubular quartz lamps are generally used to generate thermal load by emitting infrared radiation. In this study, modified heat flux model of tubular quartz lamp is proposed based on existing model. Parameters of the proposed model are optimized upon measured heat flux in three dimensions. Finally, thermal load of plate specimen is designed by the heat flux model. In conclusion, it is possible to predict heat flux applied on plate specimen and desired thermal load of high temperature structural test can be obtained.