• Title/Summary/Keyword: 손상감지

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Manufacturing Method for Sensor-Structure Integrated Composite Structure (센서-구조 일체형 복합재료 구조물 제작 방법)

  • Han, Dae-Hyun;Kang, Lae-Hyong;Thayer, Jordan;Farrar, Charles
    • Composites Research
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    • v.28 no.4
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    • pp.155-161
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    • 2015
  • A composite structure was fabricated with embedded impact detection capabilities for applications in Structural Health Monitoring (SHM). By embedding sensor functionality in the composite, the structure can successfully perform impact localization in real time. Smart resin, composed of $Pb(Ni_{1/3}Nb_{2/3})O_3-Pb(Zr,\;Ti)O_2$ (PNN-PZT) powder and epoxy resin with 1:30 wt%, was used instead of conventional epoxy resin in order to activate the sensor function in the composite structure. The embedded impact sensor in the composite was fabricated using Hand Lay-up and Vacuum Assisted Resin Transfer Molding(VARTM) methods to inject the smart resin into the glass-fiber fabric. The electrodes were fabricated using silver paste on both the upper and bottom sides of the specimen, then poling treatment was conducted to activate the sensor function using a high voltage amplifier at 4 kV/mm for 30 min at room temperature. The composite's piezoelectric sensitivity was measured to be 35.13 mV/N by comparing the impact force signals from an impact hammer with the corresponding output voltage from the sensor. Because impact sensor functionality was successfully embedded in the composite structure, various applications of this technique in the SHM industry are anticipated. In particular, impact localization on large-scale composite structures with complex geometries is feasible using this composite embedded impact sensor.

An Analysis on the Deployment Methods for Smart Monitoring Systems (스마트 모니터링 시스템의 배치 방식 분석)

  • Heo, No-Jeong
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.10 no.6
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    • pp.55-62
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    • 2010
  • Monitoring systems are able to report certain events at region of interest(ROI) and to take an appropriate action. From industrial product line full of robots to fire detection, intrusion detection, smart grid application, environmental pollution alarm system, monitoring system has widely used in diverse industry sector. Recently, due to advance of wireless communication technology and availability of low cost sensors, intelligent and/or smart monitoring systems such as sensor networks has been developed. Several deployment methods are introduced to meet various monitoring needs and deployment performance criteria are also summarized to be used to identify weak point and be useful at designing monitoring systems. Both efficiency during deployment and usefulness after the deployment should be assessed. Efficiency factors during deployment are elapsed time, energy required, deployment cost, safety, sensor node failure rate, scalability. Usefulness factors after deployment are ROI coverage, connectivity, uniformity, target density similarity, energy consumption rate per unit time and so on.

Feasibility Check of Textile Sensor Made of P(VDF-TrFE) for Structural Health Monitoring of Composite Structures (복합재료 구조물의 건전성 모니터링을 위한 P(VDF-TrFE) 직물센서의 가능성 평가)

  • Bae, Ji-Hun;Chang, Seung-Hwan
    • Composites Research
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    • v.30 no.2
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    • pp.126-131
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    • 2017
  • For structural health monitoring of a complex shaped structure a new sensor that can compensate for the drawbacks of the current sensors such as brittleness is needed and the sensor should be highly flexible and durable. In this study a textile sensor made of polyvinylidene fluoride trifluoroethylene (PVDF-TrFE) which is a type of electroactive polymer was fabricated. And the textile sensors were applied to a complex shaped structure (an egg-box panel made of carbon/epoxy composite) for checking their feasibility of structural health monitoring. To correlate the collapse response with failure mechanisms of the structure the multiply-interrupted compressive test was carried out. During the test, the textile sensors succeeded to prove their applicability for damage detection (crack initiation) by generating electric voltages (0.05 V-0.25 V) in the real time.

Defect Detection of Impacted Composite Tubes by Lock-in Photo-Infrared Thermography Technique (위상잠금 열화상기법을 이용한 복합재 튜브 충격 손상 결함 측정)

  • Kim, Kyoung-Suk;Jeon, So-Young;Jung, Hyun-Chul
    • Journal of the Korean Society for Nondestructive Testing
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    • v.31 no.2
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    • pp.139-143
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    • 2011
  • The problem of delamination of composite tubes by impact has been acknowledged in aerospace and automobile industry. Non-destructive testing(NDT) methods in composite material structure are important to evaluate reliability of composite structure. There are many kinds of NDT methods which can detect the inside defect of the composite material such as Infrared Thermography(IRT). Infrared thermal imaging of object is different from that of a defect, in heated composite tubes with an internal defect, and then location and size of a defect can be measured by the analysis of thermal imaging pattern. In this study, Lock-in Infrared thermography detect internal defects of Impacted composite tubes by the inspection of infrared lay radiated from the surface of composite tubes.

Low Velocity Impact Monitoring for a Composite Sandwich Beam Using Piezo Thin Film Sensors (압전필름센서를 이용한 복합재 샌드위치 보의 저속충격 모니터링)

  • Park, Chan Ik;Lee, Gwan Ho;Kim, In Geol;Lee, Yeong Sin
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.31 no.2
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    • pp.51-56
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    • 2003
  • The piezoelectric thin film(PVDF: polyvinylidene fluoride) sensors having good dynamic sensing charachteristics can be used to monitor low vwlocit impact on composite structures. The impact response function for composite sandwich beam was derved. The impact tests at low energy without inducing damage were performed on the instrumented drop weight impact tester. The measured signals of PVDF sensors attached on the surface of the beam agreed well with the simulated signals. And the inverse technique was applied to reconstruct the impact forces from the PVDF sensor signals. Most of reconstructed impact forces showed good agreement with the measured forces. The comparison results showed that the piezoelectric thin film sensor can be used to monitor the low velocity impact on composite sandwich structures.

Estimation of Modal Parameters for Plastic Film-Covered Greenhouse Arches (비닐하우스 아치구조의 모달계수 산정)

  • Cho, Soon-Ho
    • Journal of the Earthquake Engineering Society of Korea
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    • v.14 no.2
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    • pp.67-74
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    • 2010
  • To a series of vibration records obtained from experimental modal testing using a fixed hammer and roving accelerometers for greenhouse arch structures, modal parameters such as natural frequencies, damping ratios and mode shapes are extracted by applying the two most advanced system identification methods in the frequency-domain up to now, so-called PolyMAX and FDD. The former involves both input and output data, while the latter utilizes only the output data. The possibility of determining the static buckling load, detecting damages, etc., for very slender steel-pipe arches by means of a non-destructive testing method based on vibration measurements is primarily investigated. The extracted modal parameters generally correlated well with those obtained using finite element analysis, demonstrating promising results for further on-going research.

Interfacial Evaluation and Damage Sensing of Carbon Fiber/Epoxy-AT-PEI Composite using Electro-Micromechanical Techniques (Electro-micromechanical 시험법을 이용한 탄소섬유 강화 Epoxy-AT PEI 복합재료의 손상 감지능 및 계면물성 평가)

  • Kim, Dae-Sik;Kong, Jin-Woo;Park, Joung-Man;Kim, Minyoung;Kim, Wonho;Ahn, Byung-Hyun;Park, Jin-Ho
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2002.10a
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    • pp.212-215
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    • 2002
  • Interfacial evaluation and damage sensing of the carbon fiber/epoxy-amine terminated (AT)-polyetherimide (PEI) composites were performed using micromechanical test and electrical resistance measurement. As AT-PEI content increased, the fracture toughness of epoxy-AT-PEI matrix increased, and thus their interfacial shear strength (IFSS) was improved due to the improved toughness. After curing process, the changes in electrical resistance (ΔR) with increasing AT-PEI contents increased gradually because of the changes in thermal expansion coefficient (TEC) and thermal shrinkage of matrix. Matrix fracture toughness was correlated to the IFSS, residual stress and electrical resistance. The results obtained from the electrical resistance measurement during curing process, reversible stress/strain, and durability test were consistent with modified matrix toughness properties.

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An Integrated Mach-Zehnder Interferometric Sensor based on Rib Waveguides (Rib 도파로 기반 집적 마흐젠더 간섭계 센서)

  • Choo, Sung-Joong;Park, Jung-Ho;Shin, Hyun-Joon
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.47 no.4
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    • pp.20-25
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    • 2010
  • An integrated Mach-Zehnder interferometric sensor operating at 632.8 nm was designed and fabricated by the technology of planar rib waveguides. Rib waveguide based on silica system ($SiO_2-SiO_xN_y-SiO_2$) was geometrically designed to have single mode operation and high sensitivity. It was structured by semiconductor fabrication processes such as thin film deposition, photolithography, and RIE (Reactive Ion Etching). With the power observation, propagation loss measurement by cut-back method showed about 4.82 dB/cm for rib waveguides. Additionally the chromium mask process for an etch stop was employed to solve the core damaging problem in patterning the sensing zone on the chip. Refractive index measurement of water/ethanol mixture with this device finally showed a sensitivity of about $\pi$/($4.04{\times}10^{-3}$).

The Study for Establishing the Criteria of Measurement Items in the Monitoring System for the Steel-Box Girder Bridge by FEM Analysis (구조해석에 의한 강상자형교 상시계측시스템 계측항목별 관리기준치 설정 연구)

  • Joo, Bong-Chul;Park, Ki-Tae;You, Young-Jun;Lee, Chin-Hyung;Hwang, Yoon-Koog
    • Journal of Korean Society of societal Security
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    • v.2 no.4
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    • pp.35-41
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    • 2009
  • If any bridge has the monitoring system, the bridge manager can check the history of bridge behavior and the progress of the damage more exactly. When the unexpected event (ex: earthquake and flood) happens, the manager can check the safety condition of the bridge and make the pertinent action for bridge management which is reduction of vehicle speed or traffic control through the system. Additionary the manager can make the well-timed repair or reinforcement through the system, so he can save the management cost or the life cycle cost. This study presents the method of setting the criteria by FEM analysis in bridge monitoring system, and the standard progress for setting the criteria about measurement items of monitoring system for the steel box type bridge.

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Improvement of Steganalysis Using Multiplication Noise Addition (곱셉 잡음 첨가를 이용한 스테그분석의 성능 개선)

  • Park, Tae-Hee;Eom, Il-Kyu
    • Journal of the Institute of Electronics Engineers of Korea CI
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    • v.49 no.4
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    • pp.23-30
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    • 2012
  • This paper proposes an improved steganalysis method to detect the existence of secret message. Firstly, we magnify the small stego noise by multiplying the speckle noise to a given image and then we estimate the denoised image by using the soft thresholding method. Because the noises are not perfectly eliminated, some noises exist in the estimated cover image. If the given image is the cover image, then the remained noise will be very small, but if it is the stego image, the remained noise will be relatively large. The parent-child relationship in the wavelet domain will be slighty broken in the stego image. From this characteristic, we extract the joint statistical moments from the difference image between the given image and the denoised image. Additionally, four statistical moments are extracted from the denoised image for the proposed steganalysis method. All extracted features are used as the input of MLP(multilayer perceptron) classifier. Experimental results show that the proposed scheme outperforms previous methods in terms of detection rates and accuracy.