• Title, Summary, Keyword: 굽힘 저항

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A study on application of KS C IEC 62561-2 standard of lightning protection earth electrodes (피뢰용 접지극에 대한 KS C IEC 62561-2 표준의 적용성 검토)

  • Kim, Dong-kyu;Eom, Ju-Hong;Lee, Tae-Hyung
    • Proceedings of the KIEE Conference
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    • pp.1619-1620
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    • 2015
  • KS C IEC 62561-2 표준은 피뢰시스템 구성요소로서의 도체 및 접지극에 관한 요구사항 및 시험에 대하여 규정되어 있다. 외부 피뢰 구성자재는 대기 중 혹은 대지에 직접 노출되어 있기 때문에 전기적 성능과 기계적 성능을 모두 만족해야 한다. 또한 피뢰도체와 접지극은 재질과 크기, 형태가 모두 다르기 때문에 각각의 요구사항에 부합할 수 있는 성능을 지녀야 한다. 본 논문에서는 일반적으로 많이 쓰이는 재질과 단면적을 가지는 접지봉으로 성능시험을 진행하였으며, 접지봉의 재료는 스테인레스강에 구리를 코팅한 동복강선으로 구성된다. 시험 결과 점착 시험 및 굽힘 시험에서 모두 크랙 및 코팅이 벗겨지는 것을 확인할 수 있었다. 코팅에 크랙 혹은 벗겨짐이 발생하면 지중에서 접지극의 부식이 진행되고, 접지저항이 높아져 전기적 성능을 저하시키는 결과를 야기한다. 때문에 스테인레스강에 구리 혹은 아연 등을 코팅하는 과정에서 벗겨짐이 없도록 점착 성능이 개선되어야 한다고 판단된다.

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A Study on the Ultimate Strength Analysis of Damaged Tubular Members (손상원통부재(損傷圓筒部材)의 최종강도(最終强度) 해석(解析)에 관한 연구(硏究))

  • Jeom-K.,Paik;Byung-C.,Shin
    • Bulletin of the Society of Naval Architects of Korea
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    • v.27 no.1
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    • pp.24-34
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    • 1990
  • In this paper, the formulation of a new simplified finite element is made to analyze the ultimate strength of damaged tubular members subjected to combined axial force and end moment. A damaged tubular member that has the bending deformation and the local dent is modeled by beam elements. Tangent elastic stiffness matrix of a beam element which contains the effect of the geometric nonlinearity is derived by using the updated Lagrangian approach. Here the contribution of the stiffness in the dented area is neglected since its resistance against the external loads is considered to be small. A fully plastic interaction curve of the element under combined loads taking account of the local dent effect is selected as a yielding criterion at each nodal point. Also tangent elasto-plastic stiffness matrix of the element is formulated by plastic node method. Comparison with the present solution and the existing experimental results is made showing that the present method gives quite an accurate solution.

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A study on bio-signal process for prosthesis arm control (인공의수의 능동 제어를 위한 생체 신호 처리에 관한 연구)

  • Ahn, Young-Myung;Yoo, Jae-Myung
    • 전자공학회논문지 IE
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    • v.43 no.4
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    • pp.28-36
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    • 2006
  • In this paper, an algorithm to classify the 4 motions of arm and a control system to position control the prosthesis are studied. To classify the 4 motions, we use flex sensors which is electrical resistance type sensor that can measure warp of muscle. The flex sensors are attached to the biceps brchii muscle and coracobrachialis muscle and the sensor signals are passed the sensing system. 4 motion of the forearm - flexion and extension, the pronation and supination are classified from this. Also position of forearm is measured from the classified signals. Finally, A two D.O.F prosthesis arm with RC servo-motor is designed to verify the validity of the algorithm. At this time, fuzzy controller is used to reduce the position error by rotary inertia and noise. From the experiment, the position error had occurred within about 5 degree.

Influence of Implant Fixture-Abutment Connection and Abutment Design on Mechanical Strength (임플란트 고정체-지대주 연결부 및 지대주 디자인이 기계적 강도에 미치는 영향)

  • Chun, Mi-Hyun;Jeong, Chang-Mo;Jeon, Young-Chan;Eom, Tae-Gwan;Yoon, Ji-Hoon
    • Journal of Dental Rehabilitation and Applied Science
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    • v.24 no.3
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    • pp.269-281
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    • 2008
  • Fatigue or overload can result in mechanical problems of implant components. The mechanical strength in the implant system is dependent on several factors, such as screw and fixture diameters, material, and design of the fixture-abutment connection and abutment. In these factors, the last rules the strength and stability of the fixture-abutment assembly. There have been some previous reports on the mechanical strength of the fixture-abutment assembly with the compressive bending test or short-term cyclic loading test. However, it is restrictive to predict the long-term stability of the implant system with them. The purpose of this study was to evaluate the influence of the design of the fixture-abutment connection and abutment on the mechanical strength and failure mode by conducting the endurance limit test as well as the compressive bending strength test. Tests were performed according to a specified test(ISO/FDIS 14801) in 4 fixture-abutment assemblies of the Osstem implant system: an external butt joint with Cemented abutment (group BJT), an external butt joint with Safe abutment (group BJS), an internal conical joint with Solid abutment (group CJO), and an internal conical joint with ComOcta abutment (group CJT). The following conclusions were drawn within the limitation of this study. Compressive bending strengths were decreased in order of group BJS(1392.0N), group CJO(1261.8N), group BJT(1153.2N), and group CJT(1110.2N). There were no significant differences in compressive bending strengths between group BJT and group CJT(P>.05). Endurance limits were decreased in order of group CJO(600N), group CJT(453N), group BJS(360N), and group BJT(300N). 3. Compressive bending strengths were influenced by the connection and abutment design of the implant system, however endurance limits were affected more considerably by the connection design.

Characteristics of Flexible Transparent Capacitive Pressure Sensor Using Silver Nanowire/PEDOT:PSS Hybrid Film (은나노와이어·전도성고분자 하이브리드 필름을 이용한 유연 투명 정전용량형 압력 센서의 특성)

  • Ahn, Young Seok;Kim, Wonhyo;Oh, Haekwan;Park, Kwangbum;Kim, Kunnyun;Choa, Sung-Hoon
    • Journal of the Microelectronics and Packaging Society
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    • v.23 no.3
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    • pp.21-29
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    • 2016
  • In this paper, we developed a flexible transparent capacitive pressure sensor which can recognize X and Y coordinates and the size of force simultaneously by sensing a change in electrical capacitance. The flexible transparent capacitive pressure sensor was composed of 3 layers which were top electrode, pressure sensing layer, and bottom electrode. Silver nanowire(Ag NW)/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) hybrid film was used for top and bottom flexible transparent electrode. The fabricated capacitive pressure sensor had a total size of 5 inch, and was composed of 11 driving line and 19 sensing line channels. The electrical, optical properties of the Ag NW/PEDOT:PSS and capacitive pressure sensor were investigated respectively. The mechanical flexibility was also investigated by bending tests. Ag NW/PEDOT:PSS exhibited the sheet resistance of $44.1{\Omega}/square$, transmittance of 91.1%, and haze of 1.35%. Notably, the Ag NW/PEDOT:PSS hybrid electrode had a constant resistance change within a bending radius of 3 mm. The bending fatigue tests showed that the Ag NW/PEDOT:PSS could withstand 200,000 bending cycles which indicated the superior flexibility and durability of the hybrid electrode. The flexible transparent capacitive pressure sensor showed the transmittance of 84.1%, and haze of 3.56%. When the capacitive pressure sensor was pressed with the multiple 2 mm-diameter tips, it can well detect the force depending on the applied pressure. This indicated that the capacitive pressure sensor is a promising scheme for next generation flexible transparent touch screens which can provide multi-tasking capabilities through simultaneous multi-touch and multi-force sensing.

Relationship between Tensile Characteristics and Fatigue Failure by Folding or Bending in Cu Foil on Flexible Substrate (유연성 기판에 사용되는 전해 동박의 절곡 및 굴곡 피로 파괴와 인장 특성과의 관계)

  • Kim, Byoung-Joon;Jeong, Myeong-Hyeok;Hwang, Sung-Hwan;Lee, Ho-Young;Lee, Sung-Won;Cbun, Ki-Do;Park, Young-Bae;Joo, Young-Cbang
    • Journal of the Microelectronics and Packaging Society
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    • v.18 no.1
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    • pp.55-59
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    • 2011
  • Folding endurance, bending fatigue and monotonic tensile tests of 4 kinds of Cu foil on flexible substrate was performed to investigate the relationship between folding or bending endurances and tensile characteristics. The repeated 5.3 or 2.0% strain was applied to Cu foil in folding endurance test or bending fatigue test while monitoring the electrical resistance. Elastic modulus, yield strength, ultimate tensile strength, ductility, and toughness were obtained by monotonic tensile test on the same samples. The Cu foil with higher toughness and ductility showed higher reliabilities in folding or bending fatigue. However, elastic modulus and yield strength did not show any relationship with folding and bending reliability. This is because the failures of Cu foil by folding or bending fatigue were closely related to the fracture energy of metal.

Dispersion and property evaluation of nanocomposites by aspect ratio of MWCNT (다중벽 탄소나노튜브 형상비에 따른 나노복합재료 분산 및 물성 평가)

  • Jang, Jung-Hoon;Yi, Jin-Woo;Lee, Won-Oh;Lee, Hak-Gu;Um, Moon-Kwang;Kim, Jin-Bong;Byun, Joon-Hyung
    • Composites Research
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    • v.23 no.3
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    • pp.58-63
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    • 2010
  • Tensile and flexural properties and electrical conductivity of MWCNT/epoxy composites with different aspect ratios of MWCNTs were compared. The MWCNT/epoxy mixtures were prepared by mechanical dispersion methods using a homomixer and a three-roll mill, and then composite samples were fabricated by compression molding process. The fractured surfaces of the samples were observed by SEM in order to evaluate the degree of dispersion of MWCNTs. The addition of MWCNTs into epoxy resin improved its tensile strength by 7.0% while its flexural strength increased slightly as compared with the one without MWCNTs. In the case of MWCNTs having highest aspect ratio, the mechanical properties of the composites were decreased. When the contents of CM-95 MWCNTs were varied, maximum of tensile and flexural strengths occurred at 1wt% and 0.5wt%, respectively. From the higher contents than these, tensile and flexural strengths of the composites decreased. Electrical conductivities of in-plane and thought-the-thickness directions of MWCNT/epoxy composites were measured using a two-point probe method. They increased with the increase of the aspect ratios and concentrations of MWCNTs in the epoxy matrix.

Control of Position of Neutral Line in Flexible Microelectronic System Under Bending Stress (굽힘응력을 받는 유연전자소자에서 중립축 위치의 제어)

  • Seo, Seung-Ho;Lee, Jae-Hak;Song, Jun-Yeob;Lee, Won-Jun
    • Journal of the Microelectronics and Packaging Society
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    • v.23 no.2
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    • pp.79-84
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    • 2016
  • A flexible electronic device deformed by external force causes the failure of a semiconductor die. Even without failure, the repeated elastic deformation changes carrier mobility in the channel and increases resistivity in the interconnection, which causes malfunction of the integrated circuits. Therefore it is desirable that a semiconductor die be placed on a neutral line where the mechanical stress is zero. In the present study, we investigated the effects of design factors on the position of neutral line by finite element analysis (FEA), and expected the possible failure behavior in a flexible face-down packaging system assuming flip-chip bonding of a silicon die. The thickness and material of the flexible substrate and the thickness of a silicon die were considered as design factors. The thickness of a flexible substrate was the most important factor for controlling the position of the neutral line. A three-dimensional FEA result showed that the von Mises stress higher than yield stress would be applied to copper bumps between a silicon die and a flexible substrate. Finally, we suggested a designing strategy for reducing the stress of a silicon die and copper bumps of a flexible face-down packaging system.

Study on the Characteristics of the Corrosion Fatigue Crack Propagation of Al-Alloy used for the Shipbuilding (선박용 알루미늄 합금재의 부식피로구열 진전특성에 관한 연구)

  • Im, U-Jo;Lee, Jong-Rak;Lee, Jin-Yeol
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.24 no.2
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    • pp.94-100
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    • 1988
  • Recently with the rapid development in marine and shipbuilding industries such as marine structures, ship, and chemical plants, there occurs much interest in the study of corrosion fatigue characteristics was closed up an important role in mechanical design. In this study, the 5086 Al-Alloy was tested by used of a rotary bending fatigue tester and was investigated under the environments of various specific resistance and air. The specific resistance, as a corrosion environment, was changed 15, 20, 25 and 5000$\Omega$.cm. The corrosion fatigue crack initiation sensitivity was quantitatively inspected for 5086 Al-Alloy in the various specific resistance. The experimental constants of Paris rule were examined in the various specific resistances, and the influences of load and corrosion with affect the crack growth rate were compared with. Main results obtained are as follows: (1) Number of stress cycles to corrosion fatigue crack initiation delaies and corrosion fatigue crack initiation sensitivity decreases with the increasing for the specific resistance. (2) The experimental constant m of Paris rule decreases with the decreasing for specific resistance. Hence the effect of corrosion is more susceptible than that of stress intensity factor. (3) The corrosion fatigue crack of 5086 Aluminium Alloy appears intergranular fracture. (4) Corrosion sensitivity is decreased with the increasing stress intensity factor and is nearly uniform when stress intensity factor is over 40kg.mm super(-3/2)

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Development of Thin-Film Thermo-Electrochemical Cell for Harvesting Waste Thermal Energy (폐열 에너지 수집을 위한 박막형 열-전기화학전지 개발)

  • Im, Hyeongwook;Kang, Tae June;Kim, Dae Weon;Kim, Yong Hyup
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.40 no.11
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    • pp.1010-1015
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    • 2012
  • In this study, a thin-film thermo-electrochemical cell that directly converts waste thermal energy into electrical energy was fabricated. Electrical conductivity of conducting carbon fiber, which was used as flexible electrode, was increased through coating of carbon nanotube, and resistance of the CNT-coated fiber electrode was not changed even after bending test with various curvatures. Maximum output power of the thermocell was increased quadratically with the temperature difference, and showed a value of about 2.5 mW/kg at temperature difference of $3.4^{\circ}C$. As a result of discharge test for 12 hours, it is confirmed that the cell can operates continuously. And thin-film thermocell wrapped around a pipe with hot liquid flowing within was demonstrated. Internal resistance of the cell was decreased with various curvature of heat pipe, and maximum output power was increased by 30 %. Therefore, the cell can be applied to various heat source.