• 한국전산구조공학회논문집
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• 제22권6호
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• pp.579-585
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• 2009

본 연구에서는 분사식 섬유보강 코팅층(sprayed fiber reinforced polymer, SFRP)으로 보강된 RC보의 성능평가를 위하여 유한요소해석을 수행하였다. 이를 위하여 미세역학을 기반으로 한 구성모델(micromechanical constitutive model)(Lee, 2001)과 손상모델(Damage models)(Lee 등, 2000; 2005)을 결합시킨 손상구성모델(damage constitutive model)을 유한요소 프로그램인 ABAQUS에 적용하였다. 유한요소해석 결과를 실험값(Ha, 2007; Ha 등, 2009)과 비교하여 손상구성모델의 정확성을 증명하고자 하였다. 비교분석 결과, 손상구성모델을 유한요소 프로그램에 적용한 해석은 실험결과(Ha, 2007; Ha 등, 2009)를 비교적 잘 예측하고 있음을 보여주었다.

• 비파괴검사학회지
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• 제32권3호
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• pp.269-275
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• 2012

Carbon-fiber reinforced plastic(CFRP) laminates made of nano-particle-coated carbon fibers and damaged by a simulated lightning strike were tested under compression-after-impact(CAI) mode, during which the damage progress due to compressive loading has been monitored by acoustic emission(AE). The impact damage was induced not by mechanical loading but by a simulated lightning strike. Conductive nano-particles were coated directly on the fibers, from which CFRP coupons were made. The coupon were subjected to the strikes with a high voltage/current impulse of 10~40 kA within a few ${\mu}s$. The effects of nano-particle coating and the degree of damage induced by the simulated lightning strikes on AE activities were examined, and the relationship between the compressive residual strength and AE behavior has been evaluated in terms of AE event counts and the onset of AE activity with the compressive loading. The degree of impact damage was also measured in terms of damage area by using ultrasonic C-scan images. The assessment during the CAI tests of damaged CFRP showed that AE monitoring appeared to be useful to differentiate the degree of damage hence the mechanical integrity of composite structures damaged by lightning strikes.

• 콘크리트학회논문집
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• 제12권3호
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• pp.67-75
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• 2000

It was well recognized that the damages associated mainly with the aging of civil infrastructures were one of very serious problems for assurance of safety and reliability. Recently carbon fiber sheet(CFS) has been widely used for reinforcement and rehabilitation 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 bending test has been carried out to understand the damage progress and the micro-failure mechanism of CFS reinforced mortars. For this purpose, four different types of specimens are used, that is, mortar, steel bar reinforced mortar, CFS reinforced mortar, and steel bar and CFS reinforced morter. Acoustic Emission(AE) technique was used to evaluate the characteristics of damage progress and the failure mechanism of specimens. in addition, two-dimensional AE source location was also performed to monitor crack initiation and propagation processes for these specimens.

• Structural Engineering and Mechanics
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• 제55권1호
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• pp.79-92
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• 2015

In this study, free vibration analyses of symmetric laminated cantilever and simply supported damaged composite beams are investigated by using finite element method (FEM). Free vibration responses of damaged beams are examined using Euler Bernoulli beam and classical lamination theories. A computer code is developed by using MATLAB software to determine the natural frequencies of a damaged beam. The local damage zone is assumed to be on the surface lamina of the beam by broken fibers after impact. The damaged zone is modeled as a unidirectional discontinuous lamina with $0^{\circ}$ orientations in this study. Fiber volume fraction ($v_f$), fiber aspect ratio ($L_f/d_f$), damage length ($L_D$) and its location (${\lambda}/L$), fiber orientation and stacking sequence parameters effects on natural frequencies are investigated. These parameters are affected the natural frequency values significantly.

• Current Optics and Photonics
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• 제7권5호
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• pp.511-517
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• 2023

Pipelines play an important role in urban water supply and drainage, oil and gas transmission, etc. This paper presents a technique for pattern recognition of fiber optic vibration signals collected by a distributed vibration sensing (DVS) system using a deep learning residual network (ResNet). The optical fiber is laid on the pipeline, and the signal is collected by the DVS system and converted into a 64 × 64 single-channel grayscale image. The grayscale image is input into the ResNet to extract features, and finally the K-nearest-neighbors (KNN) algorithm is used to achieve the classification and recognition of pipeline damage.

• 한국안전학회지
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• 제17권1호
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• pp.1-5
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• 2002

An approach for the damage of delamination which is the major concern during mechanical working for composite laminate material is proposed based on linear elastic fracture mechanics. This paper presents method evaluating of damage crack length using by average thrust force with AE characteristics. Also, the relations of AE characteristics are obtained from delamination damages. We found the onset ply of the delamination and a critical energy release rate and expressed a stress intensity factor by AEcount equation.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 추계학술발표대회 논문집
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• pp.171-174
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• 2004

In order to improve the damage tolerance of the conventional laminated composites, three­dimensional fiber structures incorporated with stitching yams have been utilized in this study. From the newly developed process termed as TAPIS(TApe Placement Incorporated with Stitching), carbon/epoxy composites have been fabricated. Two-dimensional composites with the same stacking sequence as 3D counterparts have also been fabricated for the property comparison. To examine the damage resistance performance the low speed drop weight impact test has been adopted. For the assessment of damage after the impact loading, specimens were subjected to C-scan nondestructive inspection compression after impact(CAI) were also conducted to evaluate residual compressive strength. Although the damage area of 3D composites was greatly reduced$(30-40\%)$ compared with that of 2D composites, the CAI strength did not show drastic improvement.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.307-312
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• 2003

The object of this study is to investigate a damage estimation of single edge cracked tensile specimens ($2_a$/W) as a function of acoustic emission (AE) according to the unidirectionally oriented carbon/epoxy composites, CFRP AE signals were analyzed and classified 3 regions by event counts, energy and amplitude for coressponding applied load. On tensile loading and using the results of the AE analysis, it was found that the event counts, cumulative counts or energy, and amplitude distributions useful for the prediction of damage failure.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.675-676
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• 2012

• 산업융합연구
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• 제21권2호
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• pp.93-101
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• 2023

본 연구에서는 칼과 가위 및 화학약품에 의한 물리·화학적 섬유 손상을 분석하여 손상의 원인 파악을 위한 기술 데이터 자료로써 활용하고자 하였다. 칼 4종류 및 가위 5종류와 4종류의 화학약품(황산, 염산, 수산화나트륨, 수산화칼륨)을 이용하여 면(Cotton), 울(Wool), 폴리에스터(Polyester), 레이온(Rayon), T/C(Polyester 50%, Cotton 50%), T/W(Polyester 50%, Wool 50%)에 물리·화학적 손상을 생성하여 공구와 화학약품에 따른 손상을 분석하였다. 칼과 가위에 의한 관통 손상은 칼의 날 부분이 관통한 경우 공통으로 "V" 유형의 손상이 나타났으며, 칼의 등 부분이 관통한 칼의 경우 "T", "ㅁ", 갈고리, "ㄷ" 유형의 손상이 나타났다. 또한, 가위의 경우 모두 "Y" 유형의 손상이 공통으로 나타났다. 화학약품에 의한 섬유 손상은 유류 흔적, 부식, 분해, 수축, 변색 등 다양한 손상이 나타났으며, 화학약품과 섬유의 종류에 따라 나타나는 손상에 차이를 보였다. 섬유의 물리적 손상은 공구의 형태적 특성에 따라 나타나는 특징에 차이를 보였으며, 화학적 손상은 화학약품과 섬유의 종류에 따른 특징 차이를 보임을 확인하였다.