• Title, Summary, Keyword: 파괴메카니즘

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Plastic Hinge Length of Reinforced Concrete Columns with Low Height-to-Width Ratio (전단경간비가 작은 철근콘크리트 기둥의 소성힌지 길이)

  • Park, Jong-Wook;Woo, Jae-Hyun;Kim, Byung-Il;Lee, Jung-Yoon
    • Journal of the Korea Concrete Institute
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    • v.22 no.5
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    • pp.675-684
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    • 2010
  • The reinforced concrete members are designed to fail in flexural to lead ductile fracture. In the building structures, the failure is typically imposed on beams to prevent damages in columns. However, progression of plastic collapse mechanism may ultimately develop, a plastic hinge at the bottem end of the first floor column, which then can be subjected to shear or bond finally due to large axial force and small shear span-to-depth ratio. In this study, 10 RC column specimens failed in shear after flexural yielding was investigated to determine the factors affecting the plastic hinge length. The findings of this study showed that the most effective factor affecting the plastic hinge length was an axial force. As an axial force increase, an axial strain and a ductility ratio were decreased obviously. The test also shows the observed plastic hinge length was about 0.8~1.2d and the this result has difference compared with forward research.

DGEBA-MDA-SN-Hydroxyl Group System and Composites : 2. Fracture Energy of Fiber Reinforced Composites (DGEBA-MDA-SN-Hydroxyl Group System의 합성 및 복합재료 제조 : 2. 섬유강화 복합재료의 파괴에너지)

  • Lee, Jae-Young;Shim, Mi-Ja;Kim, Sang-Wook
    • Applied Chemistry for Engineering
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    • v.5 no.4
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    • pp.737-742
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    • 1994
  • The fracture energy of glass fiber/carbon fiber/epoxy resin hybrid composite system was investigated in the aspect of fracture mechanism. Epoxy resin matrix was DGEBA-MDA-SN-HQ system. On the interface of glass fiber and matrix, post debone friction energy provided a major contribution to the fracture energy, and debonding energy and pull-out energy were of the similar value. In the case of fracture on the interface of carbon fiber and matrix, pull-out energy was the major contributor.

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Centrifuge Model Experiments on Failure of Reinforced Earth Retaining Walls due to Breakage of Reinforcements (보강재 절단에 의한 보강토옹벽의 파괴에 관한 원심모형실험)

  • Yoo, Nam Jae;Kim, Young Gil
    • Journal of The Korean Society of Civil Engineers
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    • v.12 no.2
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    • pp.161-167
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    • 1992
  • Centrifuge model tests were performed to find the capacity and the failure mechanism of reinforced earth retaining wall subjected to the failure due to breakage of reinforcements. Parametric model tests were carried out to figure out effects of factors on the capacity of wall by changing materials of reinforcing strip, strip length, strip arrangement. Tests were analyzed and were compared with the various design methods currently in use to verify feasibility of them. As a result of it, a proper design method was recommended.

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Self Healing Characteristics of Polypropylene Films Capacitor (폴리프로필렌 필름 커패시터의 자기회복과 절연 특성)

  • Lee, Seong-Jae;Lee, Seung;Kim, Pil-Su;Yang, Chang-Hoon;Park, Ha-Young;Min, Nam-Ki
    • Proceedings of the KIEE Conference
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    • pp.2049-2051
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    • 2005
  • 디지털 산업을 주도해 나아가고 있는 오늘날 아날로그 능동 소자의 대표라고 할 수 있는 커패시터는 모든 전기 전자 부품 소재에서 매우 중요하게 적용되고 있다. 커패시터는 절연재료의 종류와 구조 그리고 사용목적에 따라서 많은 종류를 가지고 있다. 최근 들어서는 용도에 적합하도록 선택사양을 가지고 있으며 소형화, 대용량화, 그리고 사용 온도범위를 넓게 하기 위한 온도특성 연구가 활발하게 진행되고 있다. 동시에 고분자 필름 내부에서 결함이 존재하여 커패시터 자체가 파괴되기 전에 기본사양을 만족하면서 신속하게 회복할 수 있는 메카니즘이 발표되고 있다. 따라서 본 연구에서는 결함에 따른 유전 재료의 절연 파괴시 파괴 지점 주위에 급격하게 발생하는 열과 압력으로 패턴 또는 국부적인 자기 증발 현상을 발생시켜서 신속하게 전기적으로 절연시키는 방식에 대해서 언급하고자 한다.

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Pinholes on Oxide under Polysilicon Layer after Plasma Etching (플라즈마 에칭 후 게이트 산화막의 파괴)

  • 최영식
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.6 no.1
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    • pp.99-102
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    • 2002
  • Pinholes on the thermally grown oxide, which is called gate oxide, on silicon substrate under polysilicon layer are found and its mechanism is analyzed in this paper. The oxide under a polysilicon layer is broken during the plasma etching process of other polysilicon layer. Both polysilicon layers are separated with 0.8${\mu}{\textrm}{m}$ thick oxide deposited by CVD (Chemical Vapor Deposition). Since broken oxide points are found scattered around an arc occurrence point, it is assumed that an extremely high electric field generated near the arc occurrence point makes the gate oxide broken. 1'he arc occurrence point has been observed on the alignment key and is the mark of low yield. It is found that any arc occurrence can cause chips to fail by breaking the gate oxide, even if are occurrence points are found on scribeline.

An Experimental Study on the Failure Mechanism of Foundation with Depth (근입깊이에 따른 기초지반의 파괴형태에 관한 실험적 연구)

  • Bong, Hyoun Gyu;Lee, Sang Duk;Koo, Ja Kap;Jeon, Mong Gag
    • Journal of The Korean Society of Civil Engineers
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    • v.14 no.4
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    • pp.923-932
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    • 1994
  • The studies on the bearing capacity of shallow and deep foundations have been made in various fields and formulas for various failure mechanisms have been presented. But, for these models, the method of classification with foundation depth has been obscure and bearing capacity factors have not been uniformly applied. An experiment was performed, in plane strain conditions, with ground model made of carbon rods. The failure mechanism of foundation and ultimate bearing capacity with foundation depth were observed. Based on experimental results the classification between shallow and deep foundations by failure shape was tried. Various present failure mechanisms of foundation were verified through the experiment.

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Microfailure Degradation Mechanisms and Interfacial Properties of Bioabsorbable Composites for Implant Materials using Micromechanical Technique and Acoustic Emission (Micromechanical 시험법과 음향방출을 이용한 Implant용 Bioabsorbable 복합재료의 미세파괴 분해메커니즘과 계면물성)

  • 박종만;김대식
    • Composites Research
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    • v.14 no.4
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    • pp.15-26
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    • 2001
  • Interfacial properties and microfailure degradation mechanisms of the bioabsorbable composites fur implant materials were investigated using micromechanical technique and nondestructive acoustic emission (AE). As hydrolysis time increased, the tensile strength, the modulus and the elongation of poly(ester-amide) (PEA) and bioactive glass fibers decreased, whereas these of chitosan fiber almost did not change. Interfacial shear strength (IFSS) between bioactive glass fiber and poly-L-lactide (PLLA) was much higher than PEA or chitosan fiber/PLLA systems using dual matrix composite (DMC) specimen. The decreasing rate of IFSS was the fastest in bioactive glass fiber/PLLA composites whereas that of chitosan fiber/PLLA composites was the slowest. AE amplitude and AE energy of PEA fiber decreased gradually, and their distributions became narrower than those in the initial state with hydrolysis time. In case of bioactive glass fiber, AE amplitude and AE energy in tensile failure were much higher than in compression. In addition, AE parameters at the initial state were much higher than those after degradation under both tensile and compressive tests. In this work, interfacial properties and microfailure degradation mechanisms can be important factors to control bioabsorbable composite performance.

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Strength Model for Eccentric Shear of Flat Plate-Column Connections under Unbalanced Moment (불균형 휨모멘트를 받는 플랫플레이트-기둥 접합부의 편심전단강도)

  • Choi Kyoung-Kyu;Park Hong-Gun
    • Journal of the Korea Concrete Institute
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    • v.16 no.2
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    • pp.229-240
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    • 2004
  • Many experiments have been performed to investigate eccentric shear strength and unbalanced moment-carrying capacity of flat plate-column connections under combined gravity and lateral load. However, each existing experiment used different test setup, and the shear strength of the connection was different depending on the test setup. Current design methods which were based on the experimental results might not accurately explain the shear strength of the flat plate. In a companion study, based on results of nonlinear finite element analyses, an alternative design method for the plate-column connection was developed. However, in this method, eccentric shear strength of the connection which was required for assessing unbalanced moment-carrying capacity was evaluated by an empirical formula. In the present study, a theoratical approach using Rankine's failure criterion was attemped to investigate failure mechanism of the eccentric shear. Based on the results, an improved strength model of the eccentric shear was developed, and it was verified by comparison with the existing experimental results. By means of the strength model, the design method developed in the companion study was re-verified.

Finite Element Analysis of the Direct Shear Test (직접 전단시험의 유한 요소 해석)

  • 이장덕
    • Geotechnical Engineering
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    • v.12 no.6
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    • pp.21-36
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    • 1996
  • The stress transfer mechanism between soil and grid reinforcements involves two basic mechanism : frictional soil resistance and passive soil resistance. However the mechanism of the passive soil resistance is very complex to understand. To study the failure mechanism of ribbed reinforcement, the direct shear tests which are dominated by passive soil resistance are analyzed by using the finite element method. The finite element method is used to examine the effects of ribs on this passive soil resistance development and the met hanism of failure. The calculated behavior of the ribbed reinforcement is compared with the measured behavi or. Comparisons between the measured and the simulated strain pat terns, failure modes and load displacement relationship are presented. The behavior of the ribbed reinforcements in a cohesive soil is predicted on the basis of a good agreement between the measured and the Predicted behavior of the Ottawa sand.

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Numerical Investigation on Load Supporting Mechanism of a Pile Constructed above Underground Cavity (공동이 존재하는 암반에 시공된 말뚝기초의 하중지지 메카니즘에 관한 수치해석 연구)

  • Choi, Go-Ny;Yoo, Chung-Sik
    • Journal of the Korean Geotechnical Society
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    • v.27 no.1
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    • pp.5-16
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    • 2011
  • This paper presents the results of a three-dimensional finite element analysis on load supporting mechanism of pile constructed above underground cavity in limestone rock formation. Considering a wide range of cavity conditions, the behavior of pile was studied using the bearing capacity, rock yielding pattern, stress distribution and deformation of pile head and the cavity. The results indicate that the load transfer mechanism of pile, rock yielding pattern and the reduction of bearing capacity of pile significantly vary with the location, size and length of cavity. Based on the results, graphical solutions defining the reduction of the bearing capacity with specific cavity conditions were suggested.