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  • Title/Summary/Keyword: Tool Failure

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Effect of joining methods on the failure of aluminum honeycomb sandwich joints under shear loading (전단하중을 받는 알루미늄 하니콤 샌드위치의 체결방식이 체결부의 파손에 미치는 영향 연구)

  • Park, Yong-Bin;Kweon, Jin-Hwe;Choi, Jin-Ho;Cho, Hyun-Il
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.39 no.7
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    • pp.643-651
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    • 2011
  • An experimental study on the failure of aluminum sandwich joints under shear loading was conducted. A total of 60 specimens including three different insert types and two different potting types were fabricated and tested. The test results showed that the through-clearance type of joint fails at the highest load among insert type joints. The failure load of the potted joints with the dimple washer increased by 10% compared to the simple potted joints. As expected, the shear failure load became higher in accordance with the face thickness increase. It was also found that the upper face in contact with the loading tool is more dominant over the failure load.

Acoustic emission monitoring of damage progression in CFRP retrofitted RC beams

  • Nair, Archana;Cai, C.S.;Pan, Fang;Kong, Xuan
    • Structural Monitoring and Maintenance
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    • v.1 no.1
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    • pp.111-130
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    • 2014
  • The increased use of carbon fiber reinforced polymer (CFRP) in retrofitting reinforced concrete (RC) members has led to the need to develop non-destructive techniques that can monitor and characterize the unique damage mechanisms exhibited by such structural systems. This paper presented the damage characterization results of six CFRP retrofitted RC beam specimens tested in the laboratory and monitored using acoustic emission (AE). The focus of this study was to continuously monitor the change in AE parameters and analyze them both qualitatively and quantitatively, when brittle failure modes such as debonding occur in these beams. Although deterioration of structural integrity was traceable and can be quantified by monitoring the AE data, individual failure mode characteristics could not be identified due to the complexity of the system failure modes. In all, AE was an effective non-destructive monitoring tool that can trace the failure progression in RC beams retrofitted with CFRP. It would be advantageous to isolate signals originating from the CFRP and concrete, leading to a more clear understanding of the progression of the brittle damage mechanism involved in such a structural system. For practical applications, future studies should focus on spectral analysis of AE data from broadband sensors and automated pattern recognition tools to classify and better correlate AE parameters to failure modes observed.

Parallel computation for debonding process of externally FRP plated concrete

  • Xu, Tao;Zhang, Yongbin;Liang, Z.Z.;Tang, Chun-An;Zhao, Jian
    • Structural Engineering and Mechanics
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    • v.38 no.6
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    • pp.803-823
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    • 2011
  • In this paper, the three dimensional Parallel Realistic Failure Process Analysis (RFPA3D-Parallel) code based on micromechanical model is employed to investigate the bonding behavior in FRP sheet bonded to concrete in single shear test. In the model, the heterogeneity of brittle disordered material at a meso-scale was taken into consideration in order to realistically demonstrate the mechanical characteristics of FRP-to-concrete. Modified Mohr-coulomb strength criterion with tension cut-off, where a stressed element can damage in shear or in tension, was adopted and a stiffness degradation approach was used to simulate the initiation, propagation and growth of microcracks in the model. In addition, a Master-Slave parallel operation control technique was adopted to implement the parallel computation of a large numerical model. Parallel computational results of debonding of FRP-concrete visually reproduce the spatial and temporal debonding failure progression of microcracks in FRP sheet bonded to concrete, which agrees well with the existing testing results in laboratory. The numerical approach in this study provides a useful tool for enhancing our understanding of cracking and debonding failure process and mechanism of FRP-concrete and our ability to predict mechanical performance and reliability of these FRP sheet bonded to concrete structures.

Slope Failure Index System Based on the Behavior Characteristics : SFi-system (거동 특성에 따른 사면 파괴 지수 시스템 : SFi-system)

  • 윤운상;정의진;최재원;김정환;김원영;김춘식
    • Journal of the Korean Geotechnical Society
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    • v.18 no.2
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    • pp.23-37
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    • 2002
  • Failure of the cut slope is triggered by combination of internal and extemal failure factors. Internal failure factors are related to geological and geometrical conditions of slope itself, and natural and/or artificial loadings on slope can be the external failure factors. Influences of these failure factors show different intensity according to the ground condition and are controlled by behavior characters of the slope. In this study, the soil depth ratio(SR), block size ratio(BR) and rock strength are used as the criteria to divide ground condition based on behavior characteristics. Ground condition of the slope is divided into discontinuous jointed rock mass and continuos soil-like mass, highly fractured rock mass and massive rock mass by the criteria(SR and BR). The SFi-system is a rating system to determine the slope failure index(SFi) by analyzing internal and external factors based on classification of the ground condition. The results of the SFi-system application to the real cut slopes show close relationship between the SFi value and potential or dimension of the failure. Therefore, the SFi-system can be used as a useful tool to predict and analyze the characteristic of the slope failure.

Intensive management of acute right heart failure (급성 우심 부전의 집중 치료)

  • Kim, Gi Beom;Noh, Chung Il
    • Clinical and Experimental Pediatrics
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    • v.50 no.11
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    • pp.1041-1048
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    • 2007
  • Not a few patients in children and adolescents are suffering from right ventricular (RV) dysfunction resulting from various conditions such as chronic lung disease, left ventricular dysfunction, pulmonary hypertension, or congenital heart defect. The RV is different from the left ventricle in terms of ventricular morphology, myocardial contractile pattern and special vulnerability to the pressure overload. Right ventricular failure (RVF) can be evaluated in terms of decreased RV contractility, RV volume overload, and/or RV pressure overload. The management for RVF starts from clear understanding of the pathophysiology of RVF. In addition to correction of the underlying disease, management of RVF per se is very important. Meticulous control of volume status, inotropic agents, vasopressors, and pulmonary selective vasodilators are the main tools in the management of RVF. The relative importance of each tool depends on the individual clinical status. Medical assist device and surgery can be considered selectively in case of refractory RVF to optimal medical treatment.

Studies on Morphologies and Mechanical Properties of Multi-walled Carbon Nanotubes/Epoxy Matrix Composites

  • Seo, Min-Kang;Byun, Joon-Hyung;Park, Soo-Jin
    • Bulletin of the Korean Chemical Society
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    • v.31 no.5
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    • pp.1237-1240
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    • 2010
  • The mechanical properties of multiwalled carbon nanotubes (MWNTs)-reinforced epoxy matrix composites with different weight percentages of MWNTs have been investigated. Also, the morphologies and failure behaviors of the composites after mechanical tests are studied by SEM and TEM analyses. As a result, the addition of MWNTs into the epoxy matrix has a remarkable effect on the mechanical properties. And the fracture surfaces of MWNTs/epoxy composites after flexural strength tests show different failure mechanisms for the composites under different nanotube contents. Also, a chemical functionalization of MWNTs can be a useful tool to improve the dispersion of the nanotubes in an epoxy system, resulting in increasing the mechanical properties of the composite materials studied.

A Study on the Advanced Reliability Assessment Method about Hot-Standby Sparing System for Railway Signaling (철도신호 대기이중중계구조 제어기의 향상된 신뢰도평가방법에 관한 연구)

  • Min, Geun-Hong;Lee, Jong-Woo
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.9
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    • pp.1589-1595
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    • 2007
  • This paper suggests the advanced reliability assessment tool for railway signaling Hot-Standby sparing system. Existing reliability assessment for Hot-Standby sparing system controller is done by using single module mean failure rate based on approximated Hot standby sparing system function. Although approximated Hot standby sparing system function can be applied to various Hot standby sparing system, however, it is not able to reflect the exact system structure. In this paper, we suggest the advanced reliability function by identifying changeover-related failure factors and common failure mode which is not considered in existing approximated Hot standby sparing system reliability function via developing Hot standby sparing system model for railway signaling and applying FMECA to this model. Also. we compare reliability assessment results for model system to reliability assessment for existing system.

Numerical Analysis of Interfacial Fracture Behavior in Repaired Structures. (구조 보강재와 피보강재 접합경계면의 역학적 특성에 관한 해석적 연구)

  • 박진완;신승교;임윤묵;김문겸
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.10a
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    • pp.471-474
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    • 1999
  • An interface always appears when a repair is applied to an aged infrastructure system for repair. These repaired structures have the high chance to fail along the interface because of the stress concentration/discontinuity along the interface. So, mechanical properties of the interface have much influence on the behavior of repaired structure systems. In this paper, numerical tool that can predict effectively the interfacial fracture behavior is developed using axial deformation link elements, and this numerical technique is applied to the interfacial failure behavior. The results coincide with the ultimate strength and failure profile on the interfacial behavior of carbon fiber sheets for strengthening with epoxy adhesion. Thus, the mechanical behavior of the interface up to failure can be predicted using numerical technique with the proposed axial deformation link elements.

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Shape Optimization of Three-Dimensional Cutouts in Laminated Composite Plates (삼차원 적층복합재 구멍의 형상 최적화)

  • 한석영;마영준
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2004.04a
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    • pp.275-280
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    • 2004
  • Shape optimization was performed to obtain the precise shape of cutouts including the internal shape of cutouts in laminated composite plates by three dimensional modeling using solid element. The volume control of the growth-strain method was implemented and the distributed parameter chosen as Tsai-Hill fracture index for shape optimization. The volume control of the growth-strain method makes Tsai-Hill failure index at each element uniform in laminated composites under the initial volume. Then shapes optimized by Tsai-Hill failure index were compared with those of the initial shapes for the various load conditions and cutouts. The following conclusions were obtained in this study. (1) It was found that growth-strain method was applied efficiently to shape optimization of three dimensional cutouts in a laminate composite, (2) The optimal shapes of the various load conditions and cutouts were obtained, (3) The maximum Tsal-Hill failure index was reduced up to 67% when shape optimization was peformed under the initial volume by volume control of growth-strain method.

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The Failure Mode Analysis of Machine Tools using Performance Tests (공작기계의 성능시험을 통한 고장모드해석)

  • 이수훈;김종수;박연우;이승우;송준엽;박화영
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.05a
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    • pp.90-93
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    • 2002
  • In view of reliability assessment, the failure mode analysis by performance tests for machine totals is researched in this study. First, the error analysis with circular movement test data is studied. The various errors and their origins are analyzed by error equations and related parts are investigated. Second, This paper deals with analysis of vibration testing fur machine tools spindle. The various frequency components are classified by FFT and order analysis. The simple measuring devices and error evaluation programs for tests are also developed.

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