• 제목/요약/키워드: Damage Measurement

검색결과 1,055건 처리시간 0.029초

기계적 후면 손상이 레이저/극초단파 광전도 기법에 의한 소수 반송자 재결합 수명 측정에 미치는 영향 (Effect of mechanical backside damage upon minority carrier recombination lifetime measurement by laser/microwave photoconductance technique)

  • 조상희;최치영;조기현
    • 한국결정성장학회지
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    • 제5권4호
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    • pp.408-413
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    • 1995
  • 초크랄스키 실리콘 기판의 뒷면에 형성된 기계적 손상이 레이저 여기/극초단파 반사 광전도 감쇠법에 의한 소수반송자 재결합 수명 측정에 미치는 영향을 고찰하였다. 기계적손상의 정도는 X-선 이중결정 회절법과 X-선 단면 측정법 및 습식산화/선택적 식각 방법으로 평가하였다. 그 결과, 웨이퍼 뒷면에 가해지는 기계적 손상의 세기가 강할수록 소수반송자 재결합 수명은 짧아지고, 소수반송자 재결합 수명 측정에 영향을 미치는 반치전폭의 임계값은 약13초임을 알 수 있다.

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Generalization of the statistical moment-based damage detection method

  • Zhang, J.;Xu, Y.L.;Xia, Y.;Li, J.
    • Structural Engineering and Mechanics
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    • 제38권6호
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    • pp.715-732
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    • 2011
  • A novel structural damage detection method with a new damage index has been recently proposed by the authors based on the statistical moments of dynamic responses of shear building structures subject to white noise ground motion. The statistical moment-based damage detection (SMBDD) method is theoretically extended in this paper with general application. The generalized SMBDD method is more versatile and can identify damage locations and damage severities of many types of building structures under various external excitations. In particular, the incomplete measurements can be considered by the proposed method without mode shape expansion or model reduction. Various damage scenarios of two general forms of building structures with incomplete measurements are investigated in consideration of different excitations. The effects of measurement noise are also investigated. The damage locations and damage severities are correctly identified even when a high noise level of 15% and incomplete measurements are considered. The effectiveness and versatility of the generalized SMBDD method are demonstrated.

Modified Tikhonov regularization in model updating for damage identification

  • Wang, J.;Yang, Q.S.
    • Structural Engineering and Mechanics
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    • 제44권5호
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    • pp.585-600
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    • 2012
  • This paper presents a Modified Tikhonov Regularization (MTR) method in model updating for damage identification with model errors and measurement noise influences consideration. The identification equation based on sensitivity approach from the dynamic responses is ill-conditioned and is usually solved with regularization method. When the structural system contains model errors and measurement noise, the identified results from Tikhonov Regularization (TR) method often diverge after several iterations. In the MTR method, new side conditions with limits on the identification of physical parameters allow for the presence of model errors and ensure the physical meanings of the identified parameters. Chebyshev polynomial is applied to approximate the acceleration response for moderation of measurement noise. The identified physical parameter can converge to a relative correct direction. A three-dimensional unsymmetrical frame structure with different scenarios is studied to illustrate the proposed method. Results revealed show that the proposed method has superior performance than TR Method when there are both model errors and measurement noise in the structure system.

유연도 변화를 이용한 연속교의 손상부위 추정 및 민감도 해석 (Damage Location Detection by Using Variation of Flexibility and its Sensitivity to Measurement Errors)

  • 최형진;백영인;이학은
    • 한국전산구조공학회:학술대회논문집
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    • 한국전산구조공학회 1996년도 가을 학술발표회 논문집
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    • pp.138-146
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    • 1996
  • The presence of a damage, such as a crack, in a structure increases the flexibility and damping in the structure. Most of methods to detect damage or damage location uses stiffness matrix of the structural system. The modification of stiffness matrix, however, has complicated procedures to identify structural. system in the basis of finite element model and has too many degree of freedom to calculate. Identification of changes of flexibility of structure can offer damage information immediately and simple procedure can employ real time continuous monitoring system. To identify changes of the flexibility, vibration mode shapes and natural frequencies are usually used. In this paper, a procedure for damage location in continuous girder bridges using vibration data is described. The effectiveness and sensitivity of the presented method to measurement errors in mode shapes and natural frequencies are investigated using analytical results from finite element models. It is shown that the errors in the first mode shape and first natural frequency demonstrate much larger influence than those in the higher mode shapes and modal frequencies.

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구조물의 손상탐지를 위한 센서위치 연구 (A Study on the Sensor Placement for Structural Damage Detection)

  • 최영재;이우식
    • 대한기계학회논문집A
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    • 제27권6호
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    • pp.938-945
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    • 2003
  • In the present study, the inverse perturbation method is applied to the structural damage detection in conjunction with a system condensation technique. The system condensation technique is adopted to r esolve the problem due to the incomplete measurement of the degrees-of-freedom (DOFs) in a natural mode. However, the numerical difficulty may arise in the system condensation when the DOFs to be measured are not properly selected. Thus, the issue of sensor placement for structural damage detection, in the framework of the condensation technique-based inverse perturbation method, is considered in this study. Also, a methodology to measure the number of sensors required to obtain reliable damage detection is proposed and then verified through some illustrative example problem.

초음파에 의한 발전소 고온배관재료의 크리프손상 평가 (Creep Damage Evaluation of High-Temperature Pipeline Material for Fossil Power Plant by Ultrasonic Test Method)

  • 이상국;정민화
    • 한국해양공학회지
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    • 제13권2호통권32호
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    • pp.99-107
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    • 1999
  • Boiler high-temperature pipelines such as main steam pipe, header and steam drum in fossil power plants are degraded by creep damage due to severe operationg conditions which are high temperature and high pressure for an extended period time. Such material degradation leads to various component failures causing serious accidents at the plants. Conventional measurement techniques such as replica method, electric resistance method, and hardness test method have such disadvantages as complex preparation and measurement procedures, too many control parameters, and therefore, low practicality and they were applied only to component surfaces with good accessibility. In this paper, artificial creep degradation test and ultrasonic measurement for their creep degraded specimens have been carried out for the purpose of evaluation for creep damage which can occur in high-temperature pipeline of fossil power plant. Absolute measuring method of quantitative ultrasonic measurement for material degradation was established, and long term creep degradationtests using life prediction formula were carried out. As a result of ultrasonic tests for crept specimens, we confirmed that the sound velocity decreased and the attenuation coefficient linearly increased in proportion to the increase of creep fractiin(${\phi}$c).

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효과적인 구조물 진단 시스템을 위한 MULTI MODE 계측법의 연구 (Study about MULTI MODE Measurement Algorithm For Effective Structural Monitoring System)

  • 홍용;왕고평;황승호;박현우;홍동표
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2007년도 추계학술대회논문집
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    • pp.1382-1385
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    • 2007
  • In this paper, we study about the measuring algorithm that can implement Structural Health Monitoring (SHM) more efficiently by two measurement methods using smart sensor. Through the impedance measurement method, the damage condition of structures on wide area is monitored first, and then it changes the mode to guided wave measurement mode by mode switching algorithm when impedance measurement mode detects abnormal signals. Efficient handling of the real-time data would be available by analyzing location and shape of damage through guided wave measurement.

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A novel computer vision-based vibration measurement and coarse-to-fine damage assessment method for truss bridges

  • Wen-Qiang Liu;En-Ze Rui;Lei Yuan;Si-Yi Chen;You-Liang Zheng;Yi-Qing Ni
    • Smart Structures and Systems
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    • 제31권4호
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    • pp.393-407
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    • 2023
  • To assess structural condition in a non-destructive manner, computer vision-based structural health monitoring (SHM) has become a focus. Compared to traditional contact-type sensors, the advantages of computer vision-based measurement systems include lower installation costs and broader measurement areas. In this study, we propose a novel computer vision-based vibration measurement and coarse-to-fine damage assessment method for truss bridges. First, a deep learning model FairMOT is introduced to track the regions of interest (ROIs) that include joints to enhance the automation performance compared with traditional target tracking algorithms. To calculate the displacement of the tracked ROIs accurately, a normalized cross-correlation method is adopted to fine-tune the offset, while the Harris corner matching is utilized to correct the vibration displacement errors caused by the non-parallel between the truss plane and the image plane. Then, based on the advantages of the stochastic damage locating vector (SDLV) and Bayesian inference-based stochastic model updating (BI-SMU), they are combined to achieve the coarse-to-fine localization of the truss bridge's damaged elements. Finally, the severity quantification of the damaged components is performed by the BI-SMU. The experiment results show that the proposed method can accurately recognize the vibration displacement and evaluate the structural damage.

초음파 감쇠 및 전기저항 측정법에 의한 발전소 고온배관의 크리프손상 평가 (Nondestructive Creep Damage Evaluation of High-Temperature Pipelines by Ultrasonic Attenuation Measurement and Electric Resistance Methods)

  • 이인철;길두송;정계조;조용상;이상국
    • 한국해양공학회지
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    • 제13권3호통권33호
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    • pp.100-107
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    • 1999
  • Due to the high temperature and pressure, the materials of pipeline in power plant are degraded by creep damage. So far, many conventional measurement techniques such as replica method, electric resistance method, adn hardness test method for creep damage have been used. Among them, the replica method has mainly been used for the inspection of components. But this technique is restricted to the applications at the surface of the objects and cannot be used to material inside. In this paper, the measuring methods of evaluation by using ultrasonic attenuation and electric resistance for the creep detection of creep damage in the form of cavities on grain boundaries or intergranular microcracks were carried out. Absolute measuring method of quantitave ultrasonic attenuation technique for 1Cr0.5Mo material degradation was analyzed for determining the creep degradation steps using life prediction formula. As a result of measurement for creep specimens, we founded that the coefficient of utrasonic attenuation was increased as the increase of creep life fracton(${phi}c$) and the decreasing rate of wlwctric resistance was also increased.

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Damage assessment of a bridge based on mode shapes estimated by responses of passing vehicles

  • Oshima, Yoshinobu;Yamamoto, Kyosuke;Sugiura, Kunitomo
    • Smart Structures and Systems
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    • 제13권5호
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    • pp.731-753
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    • 2014
  • In this study, an indirect approach is developed for assessing the state of a bridge on the basis of mode shapes estimated by the responses of passing vehicles. Two types of damages, i.e., immobilization of a support and decrease in beam stiffness at the center, are evaluated with varying degrees of road roughness and measurement noise. The assessment theory's feasibility is verified through numerical simulations of interactive vibration between a two-dimensional beam and passing vehicles modeled simply as sprung mass. It is determined that the damage state can be recognized by the estimated mode shapes when the beam incurs severe damage, such as immobilization of rotational support, and the responses contain no noise. However, the developed theory has low robustness against noise. Therefore, numerous measurements are needed for damage identification when the measurement is contaminated with noise.