• Title, Summary, Keyword: failure mechanism

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Failure Mechanism of Cu/PET Flexible Composite Film with Anisotropic Interface Nanostructure

  • Park, Sang Jin;Han, Jun Hyun
    • Korean Journal of Materials Research
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    • v.30 no.3
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    • pp.105-110
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    • 2020
  • Cu/PET composite films are widely used in a variety of wearable electronics. Lifetime of the electronics is determined by adhesion between the Cu film and the PET substrate. The formation of an anisotropic nanostructure on the PET surface by surface modification can enhance Cu/PET interfacial adhesion. The shape and size of the anisotropic nanostructures of the PET surface can be controlled by varying the surface modification conditions. In this work, the effect of Cu/PET interface nanostructures on the failure mechanism of a Cu/PET flexible composite film is studied. From observation of the morphologies of the anisotropic nanostructures on plasma-treated PET surfaces, and cross-sections and surfaces of the fractured specimens, the Cu/PET interface area and nanostructure width are analyzed and the failure mechanism of the Cu/PET film is investigated. It is found that the failure mechanism of the Cu/PET flexible composite film depends on the shape and size of the plasmatreated PET surface nanostructures. Cu/PET interface nanostructures with maximal peel strength exhibit multiple craze-crack propagation behavior, while smaller or larger interface nanostructures exhibit single-path craze-crack propagation behavior.

Strength Evaluation of Inverted T-shaped Composite Basement Wall Based on Failure Mechanisms (파괴기구에 근거한 역 T형 합성지하벽의 강도평가)

  • 박지환;서수연;이리형
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.415-420
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    • 2003
  • This Study is performed to analyze the behavior of inverted T-shaped Composite Basement Wall(CBW). For this, it is purposed to analyze the failure mechanisms of inverted T-shaped composite basement wall and propose the method of evaluating strength for design. The failure mechanisms would be devided into 4 type mechanisms from previous experimental results, that is hanger failure, punching shear failure, flexural failure and the buckling of H-pile. A strength evaluation procedure for CBW is induced by analyzing respective failure mechanism. Then, the strength for actual structure consisted of inverted T-shaped composite basement wall was evaluated and the expected failure mechanism was determined.

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Model Test and Numerical Analysis for Failure Behaviour of Shallow Tunnel Considering Unsupported Tunnel Length (굴진장을 고려한 얕은 터널파괴거동에 대한 모형실험 및 수치해석)

  • Kim, Young-Min
    • Tunnel and Underground Space
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    • v.15 no.6
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    • pp.400-410
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    • 2005
  • During excavation of shallow tunnels in soft ground, failure mechanism around the tunnel face have major influence on the stability of tunnels. In this paper, a series of laboratory tests under plane strain condition on the small scale of a shallow tunnel considering unsupported tunnel length has been performed. The results have shown that tunnel failure mechanism changes from failure mode 1 to failure mode 2 as unsupported tunnel length increases. By comparing the experimental and the numerical results, the loosening pressure for the shallow tunnel and progressive failure have been investigated.

A Study on the Characteristic of Acoutic Emission with Concrete Compressive Strength Level (콘크리트 강도수준별 음향방출(Acoustic Emission)의 특성에 관한 연구)

  • 이웅종;이종열;정연식;양승규;한상훈
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.789-794
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    • 2001
  • The acoustic emission(AE) signal from concrete cylinder specimen during failure process under cycling compressive loads were recorded and analyzed. Different filters were set on the AE signal duration based on the characteristic of amplitude distribution. From the value of AE signal amplitude, which corresponds to the occurrence of the peak for AE hits, the AE signals from concrete compressive specimen were divided into five sections. The relationship between the AE signal section and the failure mechanism of these materials, analyzed on the meso-structure level was determined. Based on the experiments, the AE characteristics of each failure mechanism are given. The results show that the AE technique is a valuable tool to study the failure mechanism of concrete.

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The Mechanical Properties Evaluation on Lay-up Orientation Effect of CFRP Laminate Composite with the Hole Notch (원공노치를 가진 CFRP의 적층방향에 따른 기계적 특성 평가)

  • Tae, Young-Il;Yun, Yu-Seong;Kwon, Oh-Heon
    • Journal of the Korean Society of Safety
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    • v.17 no.1
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    • pp.25-32
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    • 2002
  • The tensile tests for [0/90]s, [90/0]s, and $[0/{\pm}45/90]s$ laminate composite were accomplished with acoustic sensor and failure processes were recorded by a video camera in real time. Also SEM examinations for fracture and side surface were carried out. The purpose of study is estimation of the failure mechanism and the mechanical properties effected by lay-up orientation for CFRP laminate composite with the hole notch. From the results, mechanical properties were obtained and they are similar between two kinds of cross-ply orientation in CFRP laminate composites, but not on $[0/{\pm}45/90]s$. And accordings to increasing the load, accumulate AE count was increased, regardless of lay-up orientation. Futhermore, failure mechanism was described by a video monitoring and SEM.

Reliability Analysis of Exhaust Bellows Based on ALT (가속 수명 시험을 이용한 자동차용 배기 벨로우즈의 수명 해석)

  • Kim, Hyung-Min;Wee, Shin-Hwan;Kim, Tae-Soo;Kim, Sung-Hyun
    • Proceedings of the KSME Conference
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    • pp.1667-1672
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    • 2007
  • In order to assess the reliability of the exhaust bellows for automobiles, accelerated life test model and procedure are developed. By using this method, failure mechanism and life distribution are analyzed. The main results are as follows; i) the main failure mechanism is crack or breakage of inner flexible tube by shaken displacement at shear direction. ii) temperature is a second factor to affect a failure. iii) the life distribution of exhaust bellows is fitted well to Weibull life distribution and the shape parameter is 13.3 on condition of shaken displacement and $600^{\circ}C$

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Development of Robot Mechanism for Cleaning and Inspection of Live Line Insulator (송전선로 활선 애자 청소 및 점검용 로봇 기구부의 개발)

  • Park, Joon-Young;Cho, Byung-Hak;Byun, Seung-Hyun
    • Proceedings of the KIEE Conference
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    • pp.421-423
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    • 2005
  • Power transmission lines have been playing a key role as the mainstay of national industry. When a power failure occurs, it can have severe effects on national security as well as national industry and economy. In this paper, we consider an insulator failure, which is one of the main causes of such a power failure. In spite of its importance, however, a shortage of manpower in the insulator maintenance field is getting more serious due to working environments with a high voltage and a high place. For this reason, a new active maintenance technique using a robot system is required to prevent such an insulator failure. In this paper, a new robot mechanism for insulator cleaning and inspection was developed. We confirmed its effectiveness through experiments.

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Direct shear testing of brittle material samples with non-persistent cracks

  • Haeri, Hadi;Sarfarazi, Vahab;Shemirani, Alireza Bagher;Zhu, Zheming
    • Geomechanics and Engineering
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    • v.15 no.4
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    • pp.927-935
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    • 2018
  • The mechanical behavior of the brittle material samples containing the internal and edge cracks are studied under direct shear tests. It is tried to investigate the effects of stress interactions and stress intensity factors at the tips of the pre-existing cracks on the failure mechanism of the bridge areas within these cracks. The direct shear tests are carried out on more than 30 various modeled samples each containing the internal cracks (S models) and edge cracks (E models). The visual inspection and a low power microscope are used to monitor the failure mechanisms of the tested samples. The cracks initiation, propagation and coalescences are being visualized in each test and the detected failure surfaces are used to study and measure the characteristics of each surface. These investigations show that as the ratio of the crack area to the total shear surface increases the shear failure mode changes to that of the tensile. When the bridge areas are fixed, the bridge areas in between the edge cracks have less strength than those of internal cracks. However, the results of this study show that for the case of internal cracks as the bridge area is increased, the strength of the material within the bridge area is decreased. It has been shown that the failure mechanism and fracture pattern of the samples depend on the bridge areas because as the bridge area decreases the interactions between the crack tip stress fields increases.

Degradation characteristics of pumps in nuclear power plants (원전 펌프의 성능저하 특성)

  • Lee, D.H.;Park, S.G.;Hong, S.D.;Lee, B.H.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.593-598
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    • 2008
  • In the present study, degradation characteristics of pumps in nuclear power plants were investigated to provide the information of degradation mechanism and stressors. The failure records of pumps for the periods 2000 to 2006 on INPO(Institute of Nuclear Power Operations) EPIX(Equipment Performance and Information Exchange System) DB were reviewed. The 1,834 failure records reveal that the critical areas of pump failures are bearing, mechanical seal, gasket/o-ring, shaft, impeller, coupling and packing. Based on the failure rate of critical areas, the important degradation mechanism and stressors were determined. Additionally, the relationship between degradation mechanism and stressors such as wear was examined. Finally, the monitoring parameters related to degradation and stressors were discussed for the future development of degradation evaluation and prognosis technology of pumps.

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Analysis of the failure mechanism and support technology for the Dongtan deep coal roadway

  • Chen, Miao;Yang, Sheng-Qi;Zhang, Yuan-Chao;Zang, Chuan-Wei
    • Geomechanics and Engineering
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    • v.11 no.3
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    • pp.401-420
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    • 2016
  • The stability of deep coal roadways with large sections and thick top coal is a typical challenge in many coal mines in China. The innovative Universal Discrete Element Code (UDEC) trigon block is adopted to create a numerical model based on a case study at the Dongtan coal mine in China to better understand the failure mechanism and stability control mechanism of this kind of roadway. The failure process of an unsupported roadway is simulated, and the results suggest that the deformation of the roof is more serious than that of the sides and floor, especially in the center of the roof. The radial stress that is released is more intense than the tangential stress, while a large zone of relaxation appears around the roadway. The failure process begins from partial failure at roadway corners, and then propagates deeper into the roof and sides, finally resulting in large deformation in the roadway. A combined support system is proposed to support roadways based on an analysis of the simulation results. The numerical simulation and field monitoring suggest that the availability of this support method is feasible both in theory and practice, which can provide helpful references for research on the failure mechanisms and scientific support designing of engineering in deep coal mines.