• 제목/요약/키워드: 손상 메커니즘

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The Lightning Effects on Aircraft and Certification (항공기에 대한 낙뢰의 영향과 감항성 인증)

  • Han,Sang-Ho;Lee,Jong-Hui
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.31 no.9
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    • pp.110-120
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    • 2003
  • As the wooden aircraft in the early times has no way to let lightning flow when lighting flash attaches during flight, the aircraft got damage, or caught fire. Though all metal airplane was developed with an advent of aluminum, a lightning accident still occurred including a fire of a fuel tanks. Eventually, NACA declared problems in 1938, and an artificial lightning test began. III succession, FAA established Airworthiness Requirements for certification. The FAA committed test measures study for the protection of an airplane from lightning to SAE. SAE presented the test current and voltage waveforms that simulating natural lightning, and it is utilized on lightning protection certification of an airplane by public. A lightning effects of an airplane through an analysis of lightning mechanism was made in this technical note. Especially, lightning direct effects on aircraft are analyzed and lightning strike zones are described.

Structural Behavior of Reinforced Concrete Short Columns by Pseudo-Dynamic Test (유사동적실험을 이용한 철근콘크리트 단주실험에 관한 연구)

  • Min, Kyung-Min;Kim, Yong-In;Lee, Kang-Seok
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.73-76
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    • 2008
  • According to the survey of earthquake disaster, low-rise reinforced concrete building larger by the extent of damage and because of the underlying distribution of reinforced concrete structures more, it is very likely to be disasters. The purpose of this study is to discuss how strength and stiffness of each system in low-rise reinforced concrete buildings consisted of extremely brittle, shear and flexural failure lateral-load resisting systems have influence on seismic capacities of the overall system. Generally, if shear failure members including extremely brittle failure members are failed during an earthquake, the lateral-load resisting seismic capacities of RC buildings are lower rapidly, and if the seismic capacities of shear failure members were higher than that of flexural failure members, failures of shear failure members have influence on failures of the overall system. The result of this paper will provide pseudo-dynamic test of carried out to estimate the possibility of proposals.

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Analytical Investigation on the Deflection Characteristics of Steel Piles in Bridge Abutment for Aspect Ratio and Ground Properties (형상비 및 지반특성에 따른 교대 강관파일의 변위특성에 대한 해석적 연구)

  • Jang, Gab-Chul;Chang, Kyong-Ho;Han, Jung-Geun;Lee, Yang-Koo;Kim, Jong-Ryeol
    • Journal of Korean Association for Spatial Structures
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    • v.7 no.4
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    • pp.73-78
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    • 2007
  • The surrounding ground was much transformed by the lateral movement on the soft ground, and consequently the stake basis was damaged. In this case the installed stake is ratted the passive stake, and is actively being researched. When the unevenly distributed load was applied on the stake, and thus the lateral ground pressure was operated, and then the lateral movement was occurred, and consequently the structure is influenced. However, prediction and mechanism for the relationship of piles and abutment deformation is not sufficient. In this paper, coupled three-dimensional finite element analysis, which can be described solid, plate and frame elements at the same time, is developed by the authors. The lateral movement of bridge abutment for the aspect ratio of steel piles on soft clay is clarified by using developed numerical analysis.

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ITO, PR, 격벽 재료의 레이저 직접 미세가공

  • Lee, Cheon;Lee, Gyung-Chul;Ahn, Min-Young;Lee, Hong-Gyu
    • Proceedings of the Korean Vacuum Society Conference
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    • 1999.07a
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    • pp.80-80
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    • 1999
  • 플라즈마 디스플레이 패널(PDP)의 공정을 간단히 하기 위하여 포토레지스트, ITO, 격벽재료를 Ar+ laser(λ-514 nm, CW)와 Nd:YAG laser(λ=532, 266nm, pulse)로 직접 패터닝 하였다. 레이저에 의한 포토레지스트의 패턴결과, 아르곤 이온 레이저의 포토레지스트 가공의 반응 메카니즘은 레이저 빔의 열에 의한 시료 표면의 국부적인 온도상승에 의한 용융작용이며, 그 결과 식각 후 형성된 패턴의 단면 모양도 레이저빔의 profile과 같은 가우시안 형태를 나타낸다. Nd:YAG 레이저의 4고조파(532nm)를 이용한 경우 200$\mu\textrm{m}$/sce의 주사속도에서 포토레지스트를 패턴하기 위한 임계에너지(threshold energy fluence) 값은 25J/cm2이며, 약 40J/cm2의 에너지 밀도에서 하부기판의 손상이 발생하기 시작하였다. 글미 1은 Nd:YAG 레이저 4고조파를 이용하여 포토레지스트를 식각한 경우 SEM 표면사진(위)과 단차특정기에 의한 단면형상(아래)이다. ITO 막의 레이저에 의한 직접 패턴 결과, ITO 막은 레이저 펄스에 의한 급속 가열 및 증발에 의한 메커니즘으로 식각이 이루어지며, 레이저 파장에 따른 광흡수 정도의 차이에 의해 2고조파 (532nm)에서 ITO 막의 가공 품질이 4고조파(266nm)에 비해 우수하며 패턴의 폭도 출력에 따라 제어가 용이하였다. 그림 2는 Nd:YAG 레이저 2고조파를 이용하여 ITO를 식각한 경우 SEM표면 사진(위)과 단차측정기에 의한 단면형상(아래)이다. 격벽 재료의 레이저에 의한 직접 패턴 결과, Ar+ 레이저(514nm)는 출력 밀도 32NW/cm2에서 격벽을 유리 기판의 경계면까지 식각하였다. Nd:YAG 레이저(532nm)는 laser fluence가 6.5mJ/cm2에서 격벽을 식각하기 시작하였으며, 19.5J/cm2에서 유리기판의 rudraus(격벽 두께 130$\mu\textrm{m}$)까지 식각하였다.

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Effect of sliding velocity on the wear and friction characteristics of a carbon fiber composites (탄소 섬유 복합재의 마찰 및 마모 특성에 미치는 속도 효과)

  • Koh, Sung-Wi;Yang, Byeong-Chun
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.40 no.4
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    • pp.337-343
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    • 2004
  • This paper presents an experimental study of friction and wear properties of a unidirectional oriented continuous crbon-fiber reinforced epoxy composite at the ambient temperature. Friction and wear experiments were conducted in the three principal sliding direction of the fiber orientation in the composite were selected against the stainless steel counterpart specularly processed were using a pin -on-disc apparatus. Friction coefficient and specific wear rate at various normal loads and sliding velocities wear determined. When sliding took place against smooth and hard counterpart, the hightest were resistance and the lowest friction coefficient were observed in the anti-parallel direction. The wear track of the worn specimens was examined with a scanning electron microscope(SEM) to observe the damaged fibers on the surface. In addition, SEM observations of the worn surfaces allowed to identify the involved different wear mechanisms.

An Experimental Study for Supposed Heating Temperature of Deteriorated Concrete Structure by fire Accident (화재피해를 입은 콘크리트구조물의 수열온도 추정을 위한 실험적 연구)

  • 권영진
    • Fire Science and Engineering
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    • v.18 no.3
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    • pp.51-56
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    • 2004
  • A fire outbreak in a reinforcement concrete structure looses the organism by the different contraction and expansion of hardened cement pastes and aggregate, and causes cracks by thermal stress, leading to the deterioration of the durability. So concrete reinforcement structure is damaged partial or whole structure system. Therefore diagnosis of deterioration is needed based on mechanism of fire deterioration in general concrete structures. Fundamental information and data on the properties of concrete exposed to high temperature are necessary for accurate diagnosis of deterioration. In this study, it was presented data for the accurate diagnosis and selection of repair and reinforcement system for the deteriorated concrete heated highly, various concrete such as standard design compressive strength, fine aggregate and admixture were exposed to a high temperature environment. And fundamental data were measured engineering properties such as explosive spatting, ultrasonic pulse velocity and compressive strength.

Development of Acoustic Emission Training Technique and Localization Method using Q-switched Laser and Multiple Sensors/Single Channel Acquisition (Q-switched 레이저와 다중센서/단일채널 신호수집을 이용한 복합재 구조 음향방출 트레이닝 및 위치탐지 기법 개발)

  • Choi, Yunshil;Lee, Jung-Ryul
    • Composites Research
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    • v.31 no.4
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    • pp.145-150
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    • 2018
  • Various structural health monitoring (SHM) systems have been suggested for aerospace industry in order to increase its life-cycle and economic efficiency. In the case of aircraft structure madden with metal, a major concern was hot spots, such as notches, bolts holes, and where corrosion or stress concentration occurs due to moisture or salinity. However, with the increasing use of composites in the aerospace industry, further advanced SHM systems have been being required to be applied to composite structures, which have much complex damage mechanism. In this paper, a method of acoustic emission localization for composite structures using Q-switched laser and multiple Amplifier-integrated PZTs have been proposed. The presented technique aims at localization of the AE with an error in distance of less than 10 mm. Acoustic emission simulation and the localization attempt were conducted in the composite structure to validate the suggested method. Localization results, which are coordinates of detected regions, grid plots and color intensity map have been presented together to show reliability of the method.

Modeling of Non-Equilibrium Kinetics of Fuel Rich Combustion in Gas Generator (농후 연소 가스발생기의 비평형 연소 화학반응 모델링)

  • 유정민;이창진
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.34 no.7
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    • pp.89-96
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    • 2006
  • The combustion temperature in gas generator should be kept below around 1,000K to avoid any possible thermal damages to turbine blade by adopting either fuel rich or oxidizer rich combustion. Thus, non-equilibrium chemical reaction dominates in the gas generator. Meanwhile, Kerosene is a compounded fuel mixed with various types of hydrocarbon elements and difficult to model the chemical kinetics. This study focus to model the non-equilibrium chemical reaction of kerosene/LOX with detailed kinetics developed by Dagaut using PSR(Perfectly stirred reactor) assumption. Also, droplet evaporation time is taken into account by calculating for the residence time of droplet and by decoupling reaction temperature from the reactor temperature. In Dagaut’s surrogate model for kerosene, chemical kinetics of kerosene consists of 1592 reaction steps with 207 chemical species. The comparison of calculation results with experimental data could provide very reliable and accurate numbers in the prediction of combustion gas temperature, species fraction and other gas properties.

Study on Safety Design of Vertical-Type Heat Recovery Steam Generator Based on Large-Scale Analysis (대규모해석을 활용한 수직형 배열회수 증기발생기의 안전설계에 관한 연구)

  • Ryu, Tae-Young;Yang, Sang-Mo;Jang, Hyun-Min;Choi, Jae-Boong;Myung, Ki-Chul;Lee, Dong-Yun;Choi, Shin-Beom
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.12
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    • pp.1535-1542
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    • 2012
  • A Heat Recovery Steam Generator(HRSG) is the main component of a Combined Cycle Power Plant(CCPP). It is a very large structure that is made from relatively thin metal sheets. Therefore, the structural integrity of an HRSG is very important to ensure safe operation during plant lifetime. In particular, thermal deformation and thermal fatigue have been revealed as the main causes of the mechanical degradation of an HRSG. In order to prevent unexpected damage, safety evaluation based on a large-scale analysis is necessary. Therefore, this study aims to improve the safety of HRSG by using Finite Element Analysis(FEA) results derived from large-scale analysis. Furthermore, the modified design is verified by comparing it with the original one. This result will be used as basic data for improving the safety of a vertical-type HRSG.

Numerical Simulation of Failure Mechanism of PELE Perforating Thin Target Plates (얇은 표적체판에 천공하는 PELE 의 파괴 메커니즘 수치시뮬레이션)

  • Jo, Jong Hyun;Lee, Young Shin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.12
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    • pp.1577-1583
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    • 2012
  • Penetrator with enhanced lateral effect (PELE) is a novel projectile that does not require dynamite and a fuse. It comprises a high-density jacket that is closed at its rear end and filled with a low-density filling material. To study the explosion characteristics of PELE using AUTODYN-3D code, the calculation models of the projectile body and the bullet target were developed and the process of penetrating an aluminum-2024 alloy target using PELE was simulated. The scattering characteristics after PELE penetrated the aluminum-2024 alloy target were studied for different filling materials. The explicit finite element analysis of PELE fragmentation was implemented with the stochastic failure criterion in AUTODYN-3D code. As the filling expanded, the fragments gained velocity and dispersed laterally, increasing the damage area considerably. The number and shape of PELE fragments differed depending on the impact pressure of the filling that fragmented during the penetration and lateral dispersion processes.