• Title, Summary, Keyword: Bending Resistance

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Experimental Studies on PSC Airpit-Slab with Fire Resistance Panel under Static and Dynamic Loads (내화패널이 부착된 프리캐스트 PSC 풍도슬래브의 정적/동적하중에 관한 실험연구)

  • Kim, Tae Kyun;Bae, Jeong;Choi, Heon;Min, In Gi
    • Journal of The Korean Society of Civil Engineers
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    • v.32 no.4A
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    • pp.245-253
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    • 2012
  • In the longway tunnel and underground traffic road, the structure of transverse ventilation system is constructed by the airpit slab. In this study, the full scale specimens of the PSC airpit slab that attached fire resistance panel are performed the static and dynamic loading tests for evaluation of bending capacity. The first of all, it confirmed the evaluations about the fundamental efficiency of the fire resistance panel and PSC slab by the 3-point bending test and pull-off test. The tests are performed for evaluation of the bending resistance under ultimate static load and the bonded capacity under dynamic fatigue load. A fatigue test is performed for an investigation of the effect on wind pressure that is developed by transit of traffic. The damage or debonding on surface between fire resistance panel and PSC slab was not developed in dynamic fatigue load test, also the behavior of the specimens is very stable and the debonding of the fire resistance panel attached at the bottom surface of PSC slab was not developed in static load test, too. Therefore, the crack or debonding of the fire resistance panel will be not developed by external loads during the construction or completion of the precast fire resistance system.

Development of a Gable-roofed Prefabricated Pipe-house for Improvement of Snow Endurance (내설성 향상을 위한 지붕형 조립식 파이프하우스의 개발)

  • Yang, In-Kyoo;Nam, Sang-Woon
    • Journal of The Korean Society of Agricultural Engineers
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    • v.51 no.3
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    • pp.71-78
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    • 2009
  • Pipe section of bending part at the arch type pipe-house showed an ellipse with oblateness of 0.076 on the average. Flexural rigidity of bending part decreased by average 6.3% than that of an original round shape section. The deflection of arch type pipe-house measured by model experiments showed much bigger than the result of structural analysis. In case of arch type pipe-house, we supposed that the decrease of flexural rigidity for the bending part of pipes had an effect on deflection of roof under the working load. This effect should be considered in the structural analysis. Bending resistance of gable type pipe-house used a prefabricated connector which developed in this study showed about $1.5{\sim}1.8$ times stronger than that of the existing arch type or gable type processed bending. Therefore, we supposed that the gable-roofed prefabricated pipe-house is safer than arch type or bent gable type in case of heavy snowfall. According to house scales and section properties of steel pipe in use, safe snow depths and rafter intervals were presented for design of gable-roofed prefabricated pipe-house. Their standards were established in the range of the durable models recommended by RDA, and the comparative examinations were conducted by means of structural analysis. It was evaluated that the developed greenhouse model had a high applicability in the field.

Influence of Residual Bending Fatigue Strength on Impact Damage of CFRP Composites (CFRP 적층판의 충격손상이 잔류 굽힘 피로강도에 미치는 영향)

  • Yang, Yong Jun;Yang, In Young
    • Journal of the Korean Society of Safety
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    • v.30 no.3
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    • pp.7-12
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    • 2015
  • CFRP composites are used as primary structural members in various industrial fields because their specific strength and specific stiffness are excellent in comparison to conventional metals. Their usage is expanding to high added-value industrial fields because they are more than 50% lighter than metals, and have excellent heat resistance and wear resistance. However, when CFRP composites suffer impact damage, destruction of fiber and interface delamination occur. This causes an unexpected deterioration of strength, and for this reason it is very difficult to ensure the reliability of the excellent mechanical properties. Therefore, for the destruction mechanism in bending with impact damage, this study investigated the reinforcement data regarding various external loads by identifying the consequential strength deterioration. Specimens were damaged by impact with a steel ball propelled by air pressure. Decrease in bending strength caused by the tension and compression of the impact side, and depending on the lamination direction of fiber and interface inside the specimen. From the bending test it was found that the bending strength reduced when the impact energy increased. Especially in the case of compression on the impact side, as tensile stress occurred at the damage starting point, causing rapid failure and a substantially reduced failure strength.

Fire Resistance Test of Steel Fiber Reinforced Concrete (강섬유보강콘크리트의 내화성에 관한일실험)

  • 윤재환
    • Fire Science and Engineering
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    • v.1 no.1
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    • pp.19-26
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    • 1987
  • In this study, fire resistance of steel fiber reinforced concrete was investigated Cylindrical and prismatic specimens made of Ordinary Portland Cement plain concrete and steel fiber reinforced concrete were exposed to heating in accordance with a standard time-temperature curve as specified in KS·F22 57, method of fire resistance test for structural parts of buildings, the period of heating was 1 hour and 2 hours. After the fire resistance test, mechanical properties of specimens such as compressive and bending strength, stress-strain curve, static and dynamic modulus of elasticity and bending toughness were investigated. Also the cracks and spallings of the specimens were observed. From the test results, it was confirmed that steel fiber reinforced concrete has a excellent fire resistance than plain concrete in the view of higher residual strength of concrete and smaller crackings because of steel fibers in concrete.

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Electrical Reliability of ITO Film on Flexible Substrate During bending Deformations and Bending Fatigue (유연 기판상 ITO 전극의 굽힘변형 및 굽힘피로에 따른 전기적 신뢰성 연구)

  • Seol, Jea-Geun;Kim, Byoung-Joon
    • Journal of the Microelectronics and Packaging Society
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    • v.24 no.4
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    • pp.47-52
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    • 2017
  • Recently, a great attention has been paid to the mechanical behavior of ITO (Indium Tin Oxide) film, which is widely used in current smart devices due to its excellent electrical properties and transparency. In this study, the reliability of ITO thin films on flexible substrates was investigated using bending test and bending fatigue test. According to the relative position of ITO and substrate, the experiment was conducted on both outer and inner bending conditions. Inner bending condition exhibited superior electrical stability compared to outer bending test. The electrical resistance during outer bending fatigue test significantly increased compared to that in the inner bending fatigue. The crack nucleation and propagation differs according to the stress state and they have a great influence on the electrical resistance. The crack morphologies were observed by scanning electron microscopy.

Influences of Casting Conditions and Constituent Materials on the Production of Duo-castings (이중복합 주조체의 제조에 미치는 구성 재질과 주조 조건의 영향)

  • Jung, Jae-Young
    • Journal of Korea Foundry Society
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    • v.38 no.1
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    • pp.16-26
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    • 2018
  • In this study, the effects of the pouring temperature, preheating temperature, surface condition and fraction of the wear resistant part on the production of duo-castings were investigated using a high Cr white cast iron with excellent abrasion resistance and a low Cr alloy steel with good toughness. The constituent materials of the duo-castings were designed to have high hardness, fracture toughness and abrasive wear resistance for the replacement of high Mn alloy steels with low abrasive wear resistance. In particular, the amount of abrasive wear of 17% Cr white cast iron was about 1/20 of that of high Mn alloy steel. There was an intermediate area of about 3mm due to local melting at the bonding interface of the duo-castings. These intermediate regions were different from those of the constituent materials in chemical composition and microstructure. This region led to fracture within the wear resistant part rather than at the bonding interface in the bending strength test. The bending fracture strengths were 516-824 MPa, which were equivalent to the bending proof strength of high Mn steel. The effects of various casting conditions on the duo-cast behavior were studied by simple pouring of low Cr alloy steel melt, but the results proved practically impossible to manufacture duo-castings with a sound bonding interface. However, the external heating method was suitable for the production of duo-castings with a sound bonding interface.

Long-term Loads based on Evaluation of Resistance and Seakeeping Performances for a Desalination Plant Ship (해상 이동형 해수담수화 플랜트 선박의 저항 및 내항 성능 평가에 따른 장기 하중 추정)

  • Lee, Jae-bin;Paik, Kwang-Jun;Choung, Joonmo
    • Journal of Ocean Engineering and Technology
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    • v.33 no.6
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    • pp.632-640
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    • 2019
  • Desalination plant ships have been recently regarded as one of the probable solutions for drought seasons in many countries. Because desalination plants should be mounted on the desalination ships and special purpose storages such as salty waste water tanks are necessary, onboard and compartment arrangements would be distinguished from those of other conventional commercial ships. This paper introduces some basic design procedure including resistance/propulsion and seakeeping performances. The ship lines were improved step by step after modification of the ship lines and verification of resistance/propulsion performances using computational fluid dynamics (CFD). After finalization of the ship lines, the seakeeping performance was also evaluated to check motion behaviors and drive wave-induced loads such as the wave shear force and bending moment. It was proved that the predicted long-term vertical wave shear force and bending moment were significantly less than the rule-based ones, thus it is expected that the deliverables of this study will reduce the construction cost of desalination plant ships.

Roof Crush Analysis Technique Using Simple Model with Plastic Hinge Concepts (소성 힌지를 갖는 단순 보 모델을 이용한 루프 붕괴 해석 기술)

  • 강성종
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.6
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    • pp.216-222
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    • 1996
  • This paper presents a computational technique to predict roof crush resistance in early design stage of passenger car development. This technique use a simple F.E. model with nonlinear spring elements which represent plastic hinge behavior at weak areas. By assuming actual sections as equivalent simple sections, maximum bending moments which weak areas in major members can stand are theoretically calculated. Results from prediction of roof crush resistance are correlated well with test results.

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Bending Behaviors of Stainless Steel Tube Filled with Al5Si4Cu4Mg Closed Cell Aluminum Alloy Foam (발포 Al5Si4Cu4Mg 알루미늄 합금이 충진된 304 스테인리스강 원통의 굽힘저항 특성)

  • Kim, Am-Kee;Lee, Hyo-Jin;Cho, Seong-Seock
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.10
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    • pp.1686-1694
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    • 2003
  • The foam-filled tube beams can be used for the front rail and firewall structures to absorb impact energy during frontal or side collision of vehicles. In the case of side collision where bending is involved in the crushing mechanism, the foam filler would be effective in maintaining progressive crushing of the thin-walled structures so that much impact energy could be absorbed. In this study, bending behaviors of the closed-cell-aluminum-alloy-foam-filled stainless steel tube were investigated. The various foam-filled specimens including piecewise fillers were prepared and tested. The aluminum-alloy-foam filling offered the significant increase of bending resistance. Their suppression of the inward fold formation at the compression flange as well as the multiple propagating folds led to the increase of load carrying capacity of specimens. Moreover, the piecewise foams would provide the easier way to fill the thin-walled shell structures without the drawback of strength.

Mechanical Characteristics when Wire Electrical Discharge Machining and Surface Grinding for Titanium Alloy (티타늄합금의 와이어 방전가공과 연삭가공시 기계적 특성)

  • 김종업;왕덕현;김원일;이윤경
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • pp.172-178
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    • 2001
  • Titanium alloys have lightness, high strength and good corrosion resistant characteristics, and broadly used in manufacturing parts for military and aerospace industries. And these alloys also are recognized for organism materials comparatively and used as fixing ones in the human body. Nevertheless thess alloys have excellent properties such as corrosion resistance, heat resistance, and good tensile strength, it is difficult to machine by traditional methods because of high hardness and chemically activated property. So higher tool wear is expected when cutting by tools. Therefore, it is required nontraditional machining process. And the mechanical characteristics such as surface structure and shape, hardness and bending strength are studied for wire electrical discharge machined and surface ground titanium alloys for various heat-treated conditions.

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