• 제목/요약/키워드: damage process

검색결과 2,741건 처리시간 0.032초

Seismic risk assessment of deficient reinforced concrete frames in near-fault regions

  • Cao, Vui Van;Ronagh, Hamid Reza;Baji, Hassan
    • Advances in concrete construction
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    • 제2권4호
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    • pp.261-280
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    • 2014
  • In many parts of the world, reinforced concrete (RC) buildings, designed and built in accordance with older codes, have suffered severe damage or even collapse as a result of recent near-fault earthquakes. This is particularly due to the deficiencies of most of the older (and even some of the recent) codes in dealing with near fault events. In this study, a tested three-storey frame designed for gravity loads only was selected to represent those deficient buildings. Nonlinear time history analyses were performed, followed by damage assessment procedures. The results were compared with experimental observation of the same frame showing a good match. Damage and fragility analyses of the frame subjected to 204 pulse-type motions were then performed using a selected damage model and inter-storey drifts. The results showed that the frame located in near-fault regions is extremely vulnerable to ground motions. The results also showed that the damage model better captures the damage distribution in the frame than inter-storey drifts. The first storey was identified as the most fragile and the inner columns of the first storey suffered most damage as indicated by the damage index. The findings would be helpful in the decision making process prior to the strengthening of buildings in near-fault regions.

광대역 정규 프로세스에 대한 주파수 영역 기반 피로해석법의 적용성에 관한 연구 II : 광대역 피로예측 모델 (Study on Applicability of Frequency Domain-Based Fatigue Analysis for Wide Band Gaussian Process II : Wide Band Prediction Models)

  • 정준모;김경수;남지명;구정본;김민수;심용래;엄항섭
    • 대한조선학회논문집
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    • 제49권4호
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    • pp.359-366
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    • 2012
  • This is the final one of the two companion papers dealing with accuracy of accumulated fatigue damage estimation under wide band process. It is stated that four kinds of wide band models exist: typed of equivalent stress, combined PDF, correction factor, and damage combination. For the idealized ESDs from full scale measurement data on an 8100TEU container vessel, fatigue damages are compared for a narrow band prediction model based on Rayleigh PDF and five wide band fatigue prediction models of Dirlik, Wirsching-Light, Jiao-Moan, Benasciutti and DNV. DNV model consistently overestimates fatigue damages regardless of variation of ESDs. Predictions by Jiao-Moan model, which is understood as standard method for design of offshore platforms, are also in conservative side. Best accuracy is found from the results by Dirlik and Benasciutti models, but Benasciutti model is preferred since it can easily combined with narrow band fatigue damage based on Rayleigh PDF.

Speedy Two-Step Thermal Evaporation Process for Gold Electrode in a Perovskite Solar Cell

  • Kim, Kwangbae;Park, Taeyeul;Song, Ohsung
    • 한국재료학회지
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    • 제28권4호
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    • pp.235-240
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    • 2018
  • We propose a speedy two-step deposit process to form an Au electrode on hole transport layer(HTL) without any damage using a general thermal evaporator in a perovskite solar cell(PSC). An Au electrode with a thickness of 70 nm was prepared with one-step and two-step processes using a general thermal evaporator with a 30 cm source-substrate distance and $6.0{\times}10^{-6}$ torr vacuum. The one-step process deposits the Au film with the desirable thickness through a source power of 60 and 100 W at a time. The two-step process deposits a 7 nm-thick buffer layer with source power of 60, 70, and 80 W, and then deposits the remaining film thickness at higher source power of 80, 90, and 100 W. The photovoltaic properties and microstructure of these PSC devices with a glass/FTO/$TiO_2$/perovskite/HTL/Au electrode were measured by a solar simulator and field emission scanning electron microscope. The one-step process showed a low depo-temperature of $88.5^{\circ}C$ with a long deposition time of 90 minutes at 60 W. It showed a high depo-temperature of $135.4^{\circ}C$ with a short deposition time of 8 minutes at 100 W. All the samples showed an ECE lower than 2.8 % due to damage on the HTL. The two-step process offered an ECE higher than 6.25 % without HTL damage through a deposition temperature lower than $88^{\circ}C$ and a short deposition time within 20 minutes in general. Therefore, the proposed two-step process is favorable to produce an Au electrode layer for the PSC device with a general thermal evaporator.

Assessment of modal parameters considering measurement and modeling errors

  • Huang, Qindan;Gardoni, Paolo;Hurlebaus, Stefan
    • Smart Structures and Systems
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    • 제15권3호
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    • pp.717-733
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    • 2015
  • Modal parameters of a structure are commonly used quantities for system identification and damage detection. With a limited number of studies on the statistics assessment of modal parameters, this paper presents procedures to properly account for the uncertainties present in the process of extracting modal parameters. Particularly, this paper focuses on how to deal with the measurement error in an ambient vibration test and the modeling error resulting from a modal parameter extraction process. A bootstrap approach is adopted, when an ensemble of a limited number of noised time-history response recordings is available. To estimate the modeling error associated with the extraction process, a model prediction expansion approach is adopted where the modeling error is considered as an "adjustment" to the prediction obtained from the extraction process. The proposed procedures can be further incorporated into the probabilistic analysis of applications where the modal parameters are used. This study considers the effects of the measurement and modeling errors and can provide guidance in allocating resources to improve the estimation accuracy of the modal data. As an illustration, the proposed procedures are applied to extract the modal data of a damaged beam, and the extracted modal data are used to detect potential damage locations using a damage detection method. It is shown that the variability in the modal parameters can be considered to be quite low due to the measurement and modeling errors; however, this low variability has a significant impact on the damage detection results for the studied beam.

자동차 트랜스미션 기어의 손상과정 평가 (Damage Process Appraisal of Gears in Automobile Transmission)

  • 배효준;조연상;이충엽;서영백;박흥식
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 1999년도 제29회 춘계학술대회
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    • pp.272-278
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    • 1999
  • It is the effective method to diagnosis damage process of gear system such as automobile transmission to observe wear particle in gear oil. We tested with new transmission and took out gear oil according to drive distance. 4 shape parameters of wear particles in gear oil were calculated and wear volume were presumed with the image processing system. To be applied to damage diagnosis of gear system in transmission of automobile, we discuss number of wear particles, shape characteristics and total wear volume according to driving distance.

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결함을 고려한 결정 재료의 밀리 성형에 관한 연구 (A Study on the Milli-Forming of Crystalline Materials with Damage)

  • 김용일;심경섭;이용신
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2003년도 춘계학술대회논문집
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    • pp.120-126
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    • 2003
  • Finite element analysis model is suggested for analysis of milli-forming process, which forms milli-size products. Since the size of workpiece in a milli-forming process ranges from a few hundred micrometers to a few millimeters, microstructural changes such as the growth of micro-voids and the development of preferred orientation in a grain become crucial factors for the success of milli-forming. This analysis model incorporates anisotropy from deformation torture and deterioration of mechanical properties due to the growth of micro-voids. Applications of the proposed modeling to milli-forming are given and the results are carefully examined to understand the deformation characteristics such as texture development and damage evolution during extrusion/drawing of a milli-bar.

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저장매체용 스크류의 냉간 헤딩 공정 설계에 대한 연구 (Design of Cold Heading Process of a Screw for Storage Parts)

  • 서원상;민병욱;박근;나승우;이상훈;김종호;김종봉
    • 소성∙가공
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    • 제20권1호
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    • pp.48-53
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    • 2011
  • Fasteners are used to join the various electronic products and machines. So, the quality and reliability of the fastener are strongly requested. In this study, the analyses of the multi-stage cold forging of TORX screws for storage parts are carried out. In manufacturing of TORX screws, crack and folding defects are observed. Therefore, the analysis is focused on the prediction of the defects. Based on the analysis results, the upper die and process conditions are redesigned to reduce the defects. The upper die shape for preform forming is redesigned to prevent folding and sharp shape change. The Cockroft-Latham damage criterion is introduced to predict the crack initiation. Analysis results shows that the maximum Cockroft-Latham damage value is decreased by 40% in the forming using the modified upper die.

불규칙 피로하중을 받는 2인승용 자전거의 차대에 관한 내구성 연구 (Durability Study on Two-passenger Bicycle Frame under Non-uniform Fatigue Load)

  • 한문식;조재웅
    • 한국기계가공학회지
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    • 제14권3호
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    • pp.92-98
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    • 2015
  • This study investigates the durability of a two-passenger bicycle frame under non-uniform fatigue load. The bicycle frame of Model 1 installed with reinforcement support has a 20% lower maximum equivalent stress than the existing Model 2. Model 1 has a maximum total deformation that is less than half that of Model 2. Model 1 has a higher maximum fatigue life than Model 2. In addition, Model 1 has lower fatigue damage than Model 2. Thus, the bicycle frame of Model 1 installed with reinforcement support can be described as safer, as it offers more strength than Model 2. Applying this result to the design of a real two-passenger bicycle frame under non-uniform fatigue load can effectively prevent fatigue damage and improve durability.

누적 손상 이론을 이용한 가속 등가 하중 분석 프로그램의 개발 (Development of Accelerated Equivalent Load Analysis Program using Cumulative Damage Theory)

  • 권종호;공현식;이강용;오철성;정순배;설인환;김태진
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2000년도 추계학술대회논문집A
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    • pp.206-211
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    • 2000
  • The accelerated testing technique using the equivalent load condition plays an important part in development process. However, in the industrial field, the theoretical background and advantages of this accelerated testing technique have been lack of understanding. Because the environmental durability condition forms the foundation of the accelerated testing technique, it is important to analyze the loading components and damage in service environment. In this work, we present the theoretical background and process for accelerated testing, and introduce our accelerated equivalent load analysis program. We developed the GUI program, and the user can easily obtain the result by selecting the program module.

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정면밀링에서 공구마멸 패턴과 메커니즘 분석에 관한 연구 (A Study on the Analysis of Tool-wear Patterns and Mechanisms in Face Milling)

  • 장성민;백승엽
    • 한국기계가공학회지
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    • 제16권4호
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    • pp.24-29
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    • 2017
  • This paper provides an experimental analysis on the breakage of the coated tool using the face-milling cutter of the machining center due to changes in the cutting speed and the feed rate. The experimental studies were conducted using STS 304 materials and the damage to the tool was analyzed according to the change in machining time. The experiments confirmed that the cutting speed and feed rate affected the tool damage and the mechanical impact and thermal shock were determined to severely damage the tool. From the production engineering point of view, it has been experimentally investigated that the increased feed rate significantly influences the material removal rate more than the increased cutting speed.