• Title/Summary/Keyword: 계면손상 진전

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A Micromechanics based Elastic Constitutive Model for Particle-Reinforced Composites Containing Weakened Interfaces and Microcracks (계면손상과 미세균열을 고려한 입자강화 복합재료의 미세역학 탄성구성모델)

  • Lee, Haeng-Ki;Pyo, Suk-Hoon;Kim, Hyeong-Ki
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.21 no.1
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    • pp.51-58
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    • 2008
  • A constitutive model based on a combination of a micromechanics-based weakened interface elastic model (Lee and Pyo, 2007) and a crack nucleation model (Karihaloo and Fu, 1989) is proposed to predict the effective elastic behavior of particle-reinforced composites. The model specifically considers imperfect interfaces in particles and microcracks in the matrix. To exercise the proposed constitutive model and to investigate the influence of model parameters on the behavior of the composites, numerical simulations on uniaxial tension tests were conducted. Furthermore, the present prediction is compared with available experimental data in the literature to verify the accuracy of the proposed constitutive model.

Development of On-line Monitoring System for Shape Memory Alloy Composite (형상기억복합재료에 대한 온라인 모니터링 시스템 개발)

  • Lee, Jin-Kyung;Park, Young-Chul;Lee, Min-Rae;Lee, Dong-Hwa;Lee, Kyu-Chang
    • Journal of the Korean Society for Nondestructive Testing
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    • v.23 no.1
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    • pp.7-13
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    • 2003
  • A hot press method was use for the optimal manufacturing condition for a shape memory alloy(SMA) composite. The bonding between the matrix and the reinforcement within the SMA composite by the hot press method was strengthened by cold rolling. In this study, the objective was to develop an on-line monitoring system for the prevention of the crack initiation and propagation by shape memory effort of SMA composite. Shape memory effect was used to prevent the SMA composite from cracking. For the system to be developed, an optimal hE parameter should be determined based on the degree of damage and crack initiation. When the SHA composite was heated by the plate heater attached at the composite, the propagating cracks appeared to be controlled by the compressive force of SMA.

Evaluation of SHCC on Direct Tensile Load using Acoustic Emission Technique (음향방출기법을 이용한 혼입되는 섬유의 종류에 따른 SHCC의 직접인장거동특성 평가)

  • Kim, Yun-Su;Yun, Hyun-Do;Jeon, Esther;Park, Wan-Shin
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.177-180
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    • 2008
  • SHCC shows the high energy tolerance capacity due to the interfacial bonding of the fibers to the cement matrix. For effective material design and application of SHCC, it is needed to investigate the damage process and micro-fracture mechanism of cement matrix reinforced with different types of fibers. The objective of this paper is to investigate the direct tensile response of cement composites reinforced with single and hybrid fibers using acoustic emission(AE) technique. In this study, the correlations between AE signal and result of the direct tensile response of SHCC. For these purposes, three kinds of fibers were used: PET1.5%, PET1.0+PE0.5%, PET1.0%+PVA0.5%. The result of the direct tensile response of SHCC, for the same volume fraction of fibers, ultimate strength of PET-PE specimen was 2.7 times higher than specimens with PET fibers. And from AE signal value, AE event numbers and cumulative energy were different according to kind of fiber because of the different material properties of reinforced fiber.

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Durability Test and Micro-Damage Formation of Rubber Hose for Automotive Hydraulic Brake (자동차 유압브레이크용 고무호스의 내구성 시험 및 미세손상에 관한 연구)

  • Kwak, Seung-Bum;Choi, Nak-Sam;Lim, Young-Han
    • Composites Research
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    • v.21 no.1
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    • pp.40-45
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    • 2008
  • Rubber hose assembly for automotive hydraulic brake during operation is subject to combined stresses of cyclic pressure, cyclic bending and torsion as well as thermal load. The rubber hose is composed of ethylene-propylene diene monomer(EPDM) rubber layers reinforced by polyvinyl acetate(PVA) braided fabrics. A durability tester with loading rigs for inducing the above cyclic stresses was used to investigate failure mechanisms in the rubber hose assembly. Failure examination was performed at every 100 thousands cycles of bending and torsion. Hose samples were sectioned with a diamond-wheel cutter and then polished. The polished surface was observed by optical microscope and scanning electron microscope (SEM). Some interfacial delamination with a length of about 1mm along the interface between EPDM rubber and PVA fabrics was shown at the test cycles of 400,000. The delamination induced some cracking into the outer rubber skin layer to leading the final rupture of the hose.

Assessment of the Damage in High Performance Fiber-Reinforced Cement Composite under Compressive Loading Using Acoustic Emission (AE기법에 의한 압축력을 받는 고인성 섬유보강 시멘트 복합체의 손상 평가)

  • Kim, Sun-Woo;Yun, Hyun-Do
    • Journal of the Korea Concrete Institute
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    • v.21 no.5
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    • pp.589-597
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    • 2009
  • High Performance Fiber-reinforced Cement Composite (HPFRCC) shows the multiple crack and damage tolerance capacity due to the interfacial bonding of the fibers to the cement matrix. For practical application, it is needed to investigate the fractural behavior of HPFRCC and understand the micro-mechanism of cement matrix with reinforcing fiber. This study is devoted to the investigation of the AE signals in HPFRCC under monotonic and cyclic uniaxial compressive loading, and total four series were tested. The major experimental parameters include the type and volume fraction of fiber (PE, PVA, SC), the hybrid type and loading pattern. The test results showed that the damage progress by compressive behavior of the HPFRCC is a characteristic for the hybrid fiber type and volume fraction. It is found from acoustic emission (AE) parameter value, that the second and third compressive load cycles resulted in successive decrease of the amplitude as compared with the first compressive load cycle. Also, the AE Kaiser effect existed in HPFRCC specimens up to 80% of its ultimate strength. These observations suggested that the AE Kaiser effect has good potential to be used as a new tool to monitor the loading history of HPFRCC.

A Review of the Deterioration and Damage of the Top Flange of the Highway PSC Box Girder Bridge based on the Condition Assessment Results (상태평가 결과 기반 고속도로 PSC Box 거더교 상부플랜지 열화·손상 실태 고찰)

  • Ku, Young-Ho;Han, Sang-Mook
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.26 no.6
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    • pp.23-32
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    • 2022
  • Although PSCB girder bridges account for 4% of the bridges in use on highways, they do not account for much, but 98% of PSCB girder bridges are 1st type and 2nd type of bridge. Also, the total length of the PSCB girder bridge is 16% (192km) of the total length of the highway bridge. Thus, the PSCB girder bridge can be one of the bridge types where maintenance is important. In order to analyze the damage types of PSCB girder bridges, a detailed analysis was conducted by selecting 62 places (477 spans) precision safety diagnosis reports considering ratio of the construction method and snow removal environment exposure class. Analysis of report and a field investigation was conducted, and as a result, most of the causes of deterioration damage were caused by rainwater (salt water) flowing into the bridge pavement soaking in between the top flange and the interface. After concrete slab deteriorate occurred then bridge pavement cracking and breaking increased and exfoliation of concrete occurred by corrosion and expansion of the reinforcing bars occurred. In addition, the cause of cracks in the longitudinal direction on the bottom of the top flange is considered to be cracks caused by restrained drying shrinkage. In conclusion, for reasonable maintenance considering the characteristics of PSCB girder bridges, it should be suggested in the design aspect that restrained drying shrinkage crack on top flange. Also, it is believed that differentiated maintenance method should be proposed according to snow removal environment exposure class.

Evaluation of Seismic Response of Masonry Walls Strengthened with Steel-bar Truss Systems by Non-linear Finite Element Analysis (비선형 유한요소 해석에 의한 강봉 트러스 시스템으로 보강된 조적벽체의 내진거동 평가)

  • Hwang, Seung-Hyeon;Yang, Keun-Hyeok;Kim, Sang-Hee;Lim, Jin-Sun;Im, Chae-Rim
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.4
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    • pp.20-27
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    • 2021
  • The present study presents a nonlinear finite element analysis (FEA) approach using the general program of Abaqus to evaluate the seismic response of unreinforced masonry walls strengthened with the steel bar truss system developed in the previous investigation. For finite element models of masonry walls, the concrete damaged plasticity (CDP) and meso-scale methods were considered on the basis of the stress-strain relationships under compression and tension and shear friction-slip relationship of masonry prisms proposed by Yang et al. in order to formulate the interface characteristics between brick elements and mortars. The predictions obtained from the FEA approach were compared with test results under different design parameters; as a result, a good agreement could be observed with respect to the crack propagation, failure mode, rocking strength, peak strength, and lateral load-displacement relationship of masonry walls. Thus, it can be stated that the proposed FEA approach shows a good potential for designing the seismic strengthening of masonry walls.