• Title/Summary/Keyword: 파손기구

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Evaluation of AR Characteristics on Microscopic Fracture Mechanism of A17075/CERP Hybrid Composite (Al 7075/CFRP 하이브리드 복합재료의 미시적 파괴특성에 대한 AE특성평가)

  • 이진경;이준현;윤한기
    • Composites Research
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    • v.15 no.5
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    • pp.1-6
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    • 2002
  • When compared to other composite materials such as FRP and MMC, hybrid composite material is more attractive one due to the high specific strength and the resistance to fatigue. However, the fracture mechanism of hybrid composite material is extremely complicated because of the bonding structure of metals and FRP. Recently, nondestructive technique has been used to evaluate the fracture mechanism of these composite materials. In this study. AE technique has been used to clarify the fracture mechanism and the degree of damage for Al 7075/CFRP hybrid composite material. It was found that AE event, energy and amplitude among AE parameters were effective to evaluate fracture process of Al 7075/CFRP composite material. In addition, the relationship between the AE signal and the characteristics of failure surface using optical microscope was discussed.

On-Line Monitoring of Microscopic Fracture Behavior of Concrete Using Acoustic Emission (음향방출을 이용한 콘크리트 부재의 미시적 파괴특성의 온라인 모니터링)

  • Lee, Joon-Hyun;Lee, Jin-Kyung;Yoon, Dong-Jin
    • Journal of the Korean Society for Nondestructive Testing
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    • v.19 no.1
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    • pp.25-33
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    • 1999
  • Since concrete is an inhomogeneous material consisting of larger aggregates and sand embedded in a cement paste matrix, it relatively shows a complex failure mechanism. In order to assure the reliability of concrete structure. microscopic fracture behavior and internal damage progress of concrete under the loading should be fully understood. In this study, an acoustic emission(AE) technique has been used to clarify microscopic failure mechanism and their corresponding AE signal characteristics of concrete under three-point bending test. In addition 2-dimensional AE source location has been performed to monitor the progress of an internal damage and the successive crack growth behavior during the loading. The relationship between AE signal characteristics and microscopic fracture mechanism is discussed.

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재료파손과 신뢰성

  • 김태원
    • Journal of the KSME
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    • v.43 no.6
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    • pp.66-69
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    • 2003
  • 이 글에서는 제품의 고장 및 신뢰성과 밀접한 관계가 있는 재료의 역할과 기능에 대해 알아보고 특히 파손의 원인 및 유형, 기구, 분석방법 등을 통하여 제품의 신뢰성 설계를 위한 재료파손과 재료거동분석의 중요성을 소개하고자 한다.

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Evaluation of Microscopic Deformation Behaviors of Metal Matrix Composite due to Heat Treatment by means of SFC Test and Acoustic Emission (음향방출과 SFC 시험법에 의한 금속복합재료의 기지재 열처리 효과에 따른 미시적 변형기구 특성 평가)

  • Kang, Moon-Phil;Lee, Joon-Hyun
    • Journal of the Korean Society for Nondestructive Testing
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    • v.20 no.5
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    • pp.381-389
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    • 2000
  • Metal matrix composite(MMCs) have been rapidly becoming one of the strongest candidates for structural materials for high temperature application. It is well recognized that MMCs always experience at least one large cool-down from processing temperature before my significant applied service loading. Due to the large difference in thermal expansion coefficient between the fiber and matrix, large thermal residual stresses generally develop in composites. It was reported from many previous studies that the effects of thermal residual stress on mechanical properties and fracture behavior were much more complex and dramatic than conventional engineering materials. Therefore it is crucial to evaluate the effect of heat treatment which changes the characteristic of distribution of thermal residual stress in MMCs. Single fiber composite(SFC) test based on the balance in a micromechanical model is a quite convenient method to evaluate interfacial shear strength(IFSS) and the failure mode of composite. In this study the effect of heat treatment on IFSS and the microscopic failure mechanism of MMC is investigated by combining acoustic emission(AE) technique with SFC test. The characteristic of AE signal, IFSS and microscopic failure mechanism due to heat treatment condition is discussed.

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A Study on Microscopic Damage Behavior of Carbon Fiber Sheet Reinforced Concrete using Acoustic Emission Technique (음향방출 기법을 이용한 탄소섬유시트강화 콘크리트의 미시적 손상 거동에 관한 연구)

  • 이진경;이준현;정성륜
    • Composites Research
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    • v.12 no.4
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    • pp.62-70
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    • 1999
  • It was well recognized that damages associated mainly with the aging of civil infrastructrues were one of very serious problems for assurance of safety and reliability. In recent, carbon fiber sheet(CFS) has been widely used for reinforcement and rehabitation of damaged concrete beam. However, the fundamental mechanism of load transfer and its load-resistant for carbon fiber sheet reinforced concrete are not fully understood. In this study, three point bend test has been carried out to understand the damage progress and micro-failure mechanism of CFS reinforced concretes. For these purposes, four kinds of specimens are used, that is, concrete, respectively. Acoustic Emission(AE) technique was used to evaluate the characteristics of damage progress and failure mechanism of specimens. In addititon, two-dimensional AE source location was also performed to monitor crack initiation and propagation processes for four types of these specimens.

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A Study on Fatigue Damage Accumulation of MMC using Ultrasonic Wave and Acoustic Emission (초음파와 AE기법을 이용한 금속복합재료의 피로손상진전 평가)

  • 이진경;이준현
    • Composites Research
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    • v.13 no.4
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    • pp.1-10
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    • 2000
  • SiC particulate reinforced metal matrix composites(MMCs) are emerging as candidate materials for the automobile and aerospace industries due to their significant increase in elastic modulus and strength compared to conventional metallic materials. However, in order to make successful application of MMCs, it is very important to understand micro-failure mechanism under cyclic loading because failure mechanism of MMC is dominated by accumulation of micro-failure due to applied loading. In this study, ultrasonic Lamb wave and acoustic emission(AE) have been used to monitor microscopic damage accumulation under cyclic loading for SiC particulate reinforced metal matrix composite(SiCp/A356). It was found that the change in velocity and attenuation of ultrasonic Lamb wave due to the increase of loading cycles could be characterized by three different stages corresponding to the microscopic fracture processes. The characteristic of AE signal at each stage was analyzed and discussed by comparing with the change of ultrasonic characteristic in MMCs.

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복사전열 가열로 튜브의 파손방지에 대한 연구

  • 윤기봉;심상훈;유흥선;오현환
    • Proceedings of the Korean Institute of Industrial Safety Conference
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    • 1997.11a
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    • pp.217-222
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    • 1997
  • 본 연구에서는 국내에서 원심주조로 제작되어 소둔로내에서 사용되는 복사전열 튜브의 손상 및 균열발생 기구(mechanism)를 조사한 후, 파손된 튜브 샘플의 균열주위를 금속학적으로 관찰하고, 관찰결과 및 재료의 성분분석 결과를 분석하여, 튜브의 파손원인을 분석함으로써, 향후 균열발생을 방지할 수 있는 대책에 대해 연구하였다. 우선 복사전열 튜브의 내면 균열발생 부위에 대해 현미경 관찰을 실시하였으며, 균열부의 산화물 및 균열부근 튜브모재에 대해서 성분분석을 실시하고, 전자현미경(SEM, Scanning Electron Microscope)으로 균열을 상세히 관찰하여 그 결과로부터 파손원인을 규명하였다. (중략)

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A Study on Failure Assessment Diagrams for a Solid Propellant (고체추진제의 파손평가선도 작성에 관한 연구)

  • Ha, Jae-Seok;Kim, Jae-Hoon;Yang, Ho-Young
    • Journal of the Korean Society of Propulsion Engineers
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    • v.16 no.5
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    • pp.67-73
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    • 2012
  • Failure mechanisms for a solid propellant were discussed, and the stip-yield and the inherent flaw models were applied to them. Then, failure assessment diagram methods were investigated by means of modified two models. Fracture toughness tests using CCT(center-cracked tension) specimens made of a solid propellant were conducted to generate the failure assessment diagrams. The failure assessment diagram of the inherent flaw model was normalized in order to compare with that of the modified strip-yield model. From the comparison of two failure assessment diagrams, it was found that the failure assessment diagram of the modified inherent flaw model more conservatively assesses the failure than that of the modified strip-yield model.

A Study on Failure Assessment Diagrams for a Highly Filled Elastomer (고충전 탄성중합체의 파손평가선도 작성에 관한 연구)

  • Ha, Jae-Seok;Kim, Jae-Hoon;Yang, Ho-Young
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2012.05a
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    • pp.532-538
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    • 2012
  • Failure mechanisms for a highly filled elastomer were discussed, and the stip-yield and the inherent flaw models were applied to them. Then, failure assessment diagram methods were investigated by means of modified two models. Fracture toughness tests using CCT(center-cracked tension) specimens made of a highly filled elastomer were conducted to generate the failure assessment diagrams. The failure assessment diagram of the inherent flaw model was normalized in order to compare with that of the modified strip-yield model. From the comparison of two failure assessment diagrams, it was found that the failure assessment diagram of the modified inherent flaw model more conservatively assesses the failure than that of the modified strip-yield model.

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The Interpretation of Separation Mechanism of Ridge-Cut Explosive Bolt Using Simulation Programs (해석프로시져를 이용한 리치컷형 폭발볼트 분리기구 해석)

  • Lee, Yeung-Jo
    • Journal of the Korean Society of Propulsion Engineers
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    • v.8 no.2
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    • pp.102-114
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    • 2004
  • The present work has been developed the interpretation processor including the behavior of material failure and the separation phenomena under transient dynamic loading (the operation of explosive bolt) using AUTODYN V4.3, SoildWork 2003 and TrueGrid V2.1 programs. It has been demonstrated that the interpretation in ridge-cut explosive bolt under dynamic loading condition should be necessary to the appropriate failure model and the basic stress of bolt failure is the principal stress. The use of this interpretation processor developing the present work could be extensively helped to design the shape and the amount of explosives in the explosive bolt having a complex geometry. It is also proved that the interpretation processor approach is an accurate and effective analysis technique to evaluate the separation mechanism in explosive bolts.