• Title, Summary, Keyword: failure mode

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Progressive Failure Analysis and Strength Prediction based on Hashin Failure Criterion of Bolted Composite Joint (Hashin 파손이론을 이용한 복합재 볼트체결부의 점진적 파손 해석 및 강도 예측)

  • Kim, Seongmin;Kim, Pyunghwa;Doh, Sungchul;Kim, Hyounggun;Park, Jungsun
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.936-938
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    • 2017
  • In this paper, the progressive failure analysis of a bolted composite joint which is used in combustion tubes of projectiles and weapon systems is performed. Hashin's failure criterion is considered as fiber tensile failure mode, fiber compressive failure mode, matrix tensile failure mode, and matrix compressive failure mode for this analysis. And this criterion is used to make user subroutine, UMAT. Through the progressive failure analysis we predicted failure strength and compared failure strength with specimen test result.

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Strength failure behavior of granite containing two holes under Brazilian test

  • Huang, Yan-Hua;Yang, Sheng-Qi;Zhang, Chun-Shun
    • Geomechanics and Engineering
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    • v.12 no.6
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    • pp.919-933
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    • 2017
  • A series of Brazilian tests under diameter compression for disc specimens was carried out to investigate the strength and failure behavior by using acoustic emission (AE) and photography monitoring technique. On the basis of experimental results, load-displacement curves, AE counts, real-time crack evolution process, failure modes and strength property of granite specimens containing two pre-existing holes were analyzed in detail. Two typical types of load-displacement curves are identified, i.e., sudden instability (type I) and progressive failure (type II). In accordance with the two types of load-displacement curves, the AE events also have different responses. The present experiments on disc specimens containing two pre-existing holes under Brazilian test reveal four distinct failure modes, including diametrical splitting failure mode (mode I), one crack coalescence failure mode (mode II), two crack coalescences failure mode (mode III) and no crack coalescence failure mode (mode IV). Compared with intact granite specimen, the disc specimen containing two holes fails with lower strength, which is closely related to the bridge angle. The failure strength of pre-holed specimen first decreases and then increases with the bridge angle. Finally, a preliminary interpretation was proposed to explain the strength evolution law of granite specimen containing two holes based on the microscopic observation of fracture plane.

Failure analysis about deterioration of Source voltage in Power MOSFET (Power MOSFET에서 Source voltage 저하에 관한 Failure analysis)

  • 정재성;김종문;이재혁;하종신;박상득
    • Proceedings of the IEEK Conference
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    • pp.1109-1112
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    • 2003
  • 본 연구는 switching mode 의 Power NMOSFET failure mode 에 관하여 분석하고 원인을 규명하였다. 분석된 power NMOSFET은 30V급이며, vender A의 상용화 제품이다. 발생한 failure mode는 power switch 회로에서 특정 ID 를 detect 하지 못하는 mode 였다. 측정결과 source voltage 가 저하되었으며, power NMOSFET DC 동작특성 분석 결과 Vgs 변화에 따라 Id 가 저하되었다. Fail 된 power MOSFET 특성값 reference는 동일 LOT의 양품을 선정하였다. De-cap후 Inversion 과 Accumulation mode 별로 Photoemission spectrum analyzer(PSA) 분석 방법을 적용하였다. 결과 accumulation mode 에서 intensity가 감소하였으며, forward diode mode에서 국소적으로 변화하는 영역이 검출되었다. SEM 분석결과 gate metal 과 source metal 의 micro-contact 이 이루어져 있었다. 이 경우 gate metal 과 source metal 사이 close loop 를 형성하여 gate charge량을 변화시켜 power NMOSFET의 출력을 저하하는 failure mode가 발생됨을 분석할 수 있었다.

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Risk Evaluation Based on the Time Dependent Expected Loss Model in FMEA (FMEA에서 시간을 고려한 기대손실모형에 기초한 위험 평가)

  • Kwon, Hyuck-Moo;Hong, Sung-Hoon;Lee, Min-Koo;Sutrisno, Agung
    • Journal of the Korean Society of Safety
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    • v.26 no.6
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    • pp.104-110
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    • 2011
  • In FMEA, the risk priority number(RPN) is used for risk evaluation on each failure mode. It is obtained by multiplying three components, i.e., severity, occurrence, and detectability of the corresponding failure mode. Each of the three components are usually determined on the basis of the past experience and technical knowledge. But this approach is not strictly objective in evaluating risk of a given failure mode and thus provide somewhat less scientific measure of risk. Assuming a homogeneous Poisson process for occurrence of the failures and causes, we propose a more scientific approach to evaluation of risk in FMEA. To quantify severity of each failure mode, the mission period is taken into consideration for the system. If the system faces no failure during its mission period, there are no losses. If any failure occurs during its mission period, the losses corresponding to the failure mode incurs. A longer remaining mission period is assumed to incur a larger loss. Detectability of each failure mode is then incorporated into the model assuming an exponential probability law for detection time of each failure cause. Based on the proposed model, an illustrative example and numerical analyses are provided.

Effects of Thinning Length on Failure Mode of Local Wall Thinned Pipe (감육 배관의 손상모드에 미치는 감육부 길이의 영향)

  • Kim, Jin-Weon;Park, Chi-Yong;Lee, Sung-Ho;Kang, Tai-Kyung
    • Proceedings of the KSME Conference
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    • pp.357-362
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    • 2001
  • The pipe fracture tests were performed on 102mm-Sch.80 carbon steel pipe with various local wall thinning shapes, in order to understand failure behavior of thinned pipe. Pipe specimens were subjected to monotonic bending moment, using 4-points loading system, under internally pressurized condition. From the results of experiment, the failure mode, load carrying capacity, and deformability of local wall thinning pipe were investigated. Failure mode of thinned pipe depended on magnitude of internal pressure and thinning length as well as loading direction and thinning depth and angle. The variation in load carrying capacity and deformability of thinned pipe with length of thinned area was determined by stress type appled to thinning region and circumferential thinning angle. Also, the effect of internal pressure on failure behavior was dependent on failure mode of thinned pipe, and it promoted crack occurrence and mitigated local buckling at thinned area.

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Reliability Assessment of Machine Tools Using Failure Mode Analysis Programs (고장모드 분석 프로그램을 통한 공작기계의 신뢰성 평가)

  • Kim Bong-Suk;Lee Soo-Hun;Song Jun-Yeob;Lee Seung-Woo
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.14 no.1
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    • pp.15-23
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    • 2005
  • For reliability assessment for machine tools, failure mode analyses by two viewpoints were studied in this paper. First, this study developed the reliability data analysis program, which searches f3r optimal failure distribution like failure rate or MTBF(Mean Time Between Failure) using failure data and reliability test data of mechanical parts in the web. Moreover, this data analysis program saves both failure data or reliability data and their failure rate or MTBF for database establishment. Second, this paper conducted failure mode analysis through such performance tests as circular movement test and vibration testing for machine tools when reliability data is not available. A developed web-based analysis program shows correlations between failure mode and performance test result and also accumulates all the data. These kinds of data analysis programs and stored data furnish valuable information for improving the reliability of mechanical system.

An Optimal Block Replacement Policy Using Items with Different Reliability

  • Lie, Chang-Hoon;Bae, Moon-Sik;Chun, Young-Ho
    • Journal of the military operations research society of Korea
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    • v.10 no.2
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    • pp.61-73
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    • 1984
  • A block replacement policy using items with different reliability is discussed. We divide system unit failure modes into two modes and use less reliable unit when operating unit fails near the planned preventive replacement time. In this policy, item A has two failure modes. Mode-1 failure is removed by minimal repair, mode-2 failure by replacement. If mode-2 failure of item A happens in (0, $T-{\delta}$), failure item A is replaced by new item A. If mode-2 failure of item A happens in ($T-{\delta}$, T), failure item A is replaced by new item B. Item B should be cheaper and less durable than item A. Under this policy, we determine the preventive replacement interval $T^{*}$ and the interval ${\delta}^{*}$ of item B replacement which minimize the cost rate per unit time.

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Block 대체정책에 관한 연구

  • Bae, Mun-Sik
    • ETRI Journal
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    • v.6 no.3
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    • pp.17-20
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    • 1984
  • A block replacement policy using items with different reliability is discussed. We devide system unit failure modes into two modes and use less reliable unit when operating unit fails near the planned preventive replacement time. In this policy, item A has two failure modes. Mode-1 failure is removed by minimal repair, mode-2 failure by replacement. If mode-2 failure of item A happens in (0,T- $\delta$). failure item A is replaced by new item A. If mode-2 failure of item A happens in(T-$\delta$,T), failure item A is replaced by new item B. Item B should be cheaper and less durable than item A. Under this policy, we determine the preventive replacement interval T and the interval $\delta$ of item B replacement which minimize the cost rate per unit time.

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A Study on the Failure Mode Identification of Railway Signaling Embedded System (철도신호용 임베디드시스템의 고장모드도출에 관한 연구)

  • Shin, Duck-O;Lee, Jae-Ho;Lee, Kang-Me;Kim, Young-Kye
    • Proceedings of the KSR Conference
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    • pp.262-265
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    • 2007
  • This paper is about the study on the failure mode identification of railway signaling embedded system thru which quantitative reliability and safety can be compared reciprocally. Frequency of each failure mode makes possible to compare the reliability of each system and frequency of dangerous failure is used as the measurement standards for system safety. Therefore, this paper provides both reliability-related failure mode and safety-related failure mode by modeling the railway signaling embedded system.

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Analytical study of the failure mode and pullout capacity of suction anchors in sand

  • Liu, Haixiao;Peng, Jinsong;Zhao, Yanbing
    • Ocean Systems Engineering
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    • v.5 no.4
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    • pp.279-299
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    • 2015
  • Suction anchors are widely adopted and play an important role in mooring systems. However, how to reliably predict the failure mode and ultimate pullout capacity of the anchor in sand, especially by an easy-to-use theoretical method, is still a great challenge. Existing methods for predicting the inclined pullout capacity of suction anchors in sand are mainly based on experiments or finite element analysis. In the present work, based on a rational mechanical model for suction anchors and the failure mechanism of the anchor in the seabed, an analytical model is developed which can predict the failure mode and ultimate pullout capacity of suction anchors in sand under inclined loading. Detailed parametric analysis is performed to explore the effects of different parameters on the failure mode and ultimate pullout capacity of the anchor. To examine the present model, the results from experiments and finite element analysis are employed to compare with the theoretical predictions, and a general agreement is obtained. An analytical method that can evaluate the optimal position of the attachment point is also proposed in the present study. The present work demonstrates that the failure mode and pullout capacity of suction anchors in sand can be easily and reasonably predicted by the theoretical model, which might be a useful supplement to the experimental and numerical methods in analyzing the behavior of suction anchors.