• 제목/요약/키워드: failure pressure

검색결과 1,651건 처리시간 0.024초

수격현상에 대한 수치적 고찰 (A Computational Analysis of Water-Hammer)

  • 전광민
    • 대한설비공학회지:설비저널
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    • 제11권1호
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    • pp.1-10
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    • 1982
  • The water-hammer phenomena caused by pump power failure are analysed by digital computer. Asan cool ins water pipe system has been chosen as a model. It is Shown that after power failure the pressure at the pump outlet drops sharply, and to prevent reverse flow, either butterfly valve or check valve can be used. After the valve closure, pressure oscillates behind the valve. To weaken the pressure wave, it is recommended to install a servo-operated valve in a bypass Line around the pamp and the check valve.

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충격파압에 의한 콘크리트 방파제의 거동 예측 (Response Prediction of Concrete Breakwater In Wave Impact Pressure)

  • 양종석;김성훈;김동완;경민수;김장호
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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    • pp.197-202
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    • 2002
  • The most common failure of breakwater comes from impact wave pressure generated by intense storms. This impact pressure is 10 folds greater than the pressure generated by normal waves. Therefore, the precise knowledge of magnitude of impact wave pressure applied on breakwater and its structural response is crucial for the economical and safe design. However, presently, a precise analysis of breakwater is restricted by insufficient and incorrect consideration of the effect of soil-structure Interaction. 3 major research areas included in this study are (1) theoretical analysis of impact wave pressure, (2) selection of breakwater structure model (3) soil-structure interaction analysis using limit analysis computer program. Based on this analysis, predicted response of concrete breakwater and probable failure location under wave impact pressure are determined.

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Effect of the support pressure modes on face stability during shield tunneling

  • Dalong Jin;Yinzun Yang;Rui Zhang;Dajun Yuan;Kang Zhang
    • Geomechanics and Engineering
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    • 제36권5호
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    • pp.417-426
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    • 2024
  • Shield tunneling method is widely used to build tunnels in complex geological environment. Stability control of tunnel face is the key to the safety of projects. To improve the excavation efficiency or perform equipment maintenance, the excavation chamber sometimes is not fully filled with support medium, which can reduce the load and increase tunneling speed while easily lead to ground collapse. Due to the high risk of the face failure under non-fully support mode, the tunnel face stability should be carefully evaluated. Whether compressive air is required for compensation and how much air pressure should be provided need to be determined accurately. Based on the upper bound theorem of limit analysis, a non-fully support rotational failure model is developed in this study. The failure mechanism of the model is verified by numerical simulation. It shows that increasing the density of supporting medium could significantly improve the stability of tunnel face while the increase of tunnel diameter would be unfavorable for the face stability. The critical support ratio is used to evaluate the face failure under the nonfully support mode, which could be an important index to determine whether the specific unsupported height could be allowed during shield tunneling. To avoid of face failure under the non-fully support mode, several charts are provided for the assessment of compressed air pressure, which could help engineers to determine the required air pressure for face stability.

측방변형지반속 줄말뚝에 작용하는 토압의 산정법 (Estimation Method of Earth Pressures Acting on a Row of Piles due to Lateral Soil Movements)

  • 홍원표;송영석
    • 한국지반공학회논문집
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    • 제20권3호
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    • pp.13-22
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    • 2004
  • 줄말뚝이 설치된 지반에서 지반의 측방변형에 의한 지반아칭발생시 말뚝주변지반의 파괴는 지반아칭영역중 외부아 치의 정상부에서 정상파괴가 발생될 때부터 시작하여 말뚝전면의 패기부에서 캡파괴가 발생될 때까지 진행된다. 따라서, 측방변형지반속 줄말뚝에 작용하는 측방토압은 정상파괴와 캡파괴 모두의 경우를 검토할 필요가 있다. 정상파괴시의 측방토압 산정식은 원주공동확장이론을 적용하여 제안할 수 있다. 이 제안식을 검토한 결과 말뚝에 작용하는 측방토압은 주변지반의 내부마찰각, 점착력 및 수평토압과 말뚝직경 및 말뚝설치간격에 큰 영향을 받고 있음을 알 수 있다. 그리고, 캡파괴에 의한 측방토압과 정상파괴에 의한 측방토압의 이론식을 이용하여 줄말뚝에 작용하는 측방토압 범위를 정의할 수 있다. 또한, 본 논문에서는 캡파괴와 정상파괴시 측방토압의 이론치과 모형실험으로부터 구한 실험치를 비교 검토하였다. 모형실험에서 얻은 캡파괴와 정상파괴의 실험치는 제안된 각 이론의 이론치와 잘 일치하고 있으므로, 제안된 이론식의 합리성을 확인할 수 있다.

AAKR을 이용한 원자력 발전소 고장 패턴 추출에 관한 연구 (Study on the Extraction of Nuclear Power Plant Failure Patterns using AAKR)

  • 박기범;안홍민;강성기;채장범
    • 한국압력기기공학회 논문집
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    • 제13권1호
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    • pp.40-47
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    • 2017
  • In this paper, we investigate the feasibility of a strategy of failure detection and identification. The point of proposed strategy includes a pattern extraction approach for failure identification using Auto-Associative Kernel Regression (AAKR). We consider a simulation data concerning 605 signals of a Generic Pressurized Water Reactor(GPWR). In the application, the reconstructions are provided by a set of AAKR models, whose input signals have been selected by Correlation Analysis(CA) for the identification of the groups. The failure pattern is extracted by analyzing the residuals of observations and reconstructions. We present the possibility of extraction of patterns for six failure.

원자력터빈의 LTAM 전략개발을 위한 미래고장률 결정 및 적용 (A Determination and application of a future failure rate for LTAM strategies Development on Nuclear Turbines)

  • 신혜영;윤은섭
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2008년도 추계학술대회B
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    • pp.2845-2849
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    • 2008
  • Long Term Asset Management(LTAM) means a plan developed by using LCM(Life Cycle Management) process for optimum life cycle management of significant plant assets at each plant across the fleet. As a part of development of LTAM Strategies on nuclear turbines, a method so as to determine the future failure rates for low pressure turbine facilities at a nuclear plant was studied and developed by using both plant specific and industry-wide performance data. INPO's EPIX data were analyzed and some failure rate evaluation values considering preventive maintenance practices were calculated by using EPRI's PM Basis software. As the result, failure rate functions applicable to a priori and a posteriori replacement of low pressure turbines at a nuclear plant were developed and utilized in an assessment of economics of LCM alternatives on the nuclear turbine facilities in the respects of 40-year and 60-year operation bases.

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심실의 부하감소 측면에서 좌심실 보조장치의 최적 치료시기 예측을 위한 시뮬레이션 연구 (Prediction of Pumping Efficacy of Left Ventricular Assist Device according to the Severity of Heart Failure: Simulation Study)

  • 김은혜;임기무
    • 한국기계가공학회지
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    • 제12권4호
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    • pp.22-28
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    • 2013
  • It is important to begin left ventricular assist device (LVAD) treatment at appropriate time for heart failure patients who expect cardiac recovery after the therapy. In order to predict the optimal timing of LVAD implantation, we predicted pumping efficacy of LVAD according to the severity of heart failure theoretically. We used LVAD-implanted cardiovascular system model which consist of 8 Windkessel compartments for the simulation study. The time-varying compliance theory was used to simulate ventricular pumping function in the model. The ventricular systolic dysfunction was implemented by increasing the end-systolic ventricular compliance. Using the mathematical model, we predicted cardiac responses such as left ventricular peak pressure, cardiac output, ejection fraction, and stroke work according to the severity of ventricular systolic dysfunction under the treatments of continuous and pulsatile LVAD. Left ventricular peak pressure, which indicates the ventricular loading condition, decreased maximally at the 1st level heart-failure under pulsatile LVAD therapy and 2nd level heart-failure under continuous LVAD therapy. We conclude that optimal timing for pulsatile LVAD treatment is 1st level heart-failure and for continuous LVAD treatment is 2nd level heart-failure when considering LVAD treatment as "bridge to recovery".

Elastic-Plastic Stress Analysis and Fatigue Lifetime Prediction of Cross-Bores in Autofrettaged Pressure Vessels

  • Koh, Seung-Kee
    • Journal of Mechanical Science and Technology
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    • 제14권9호
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    • pp.935-946
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    • 2000
  • Elastic-plastic stress analysis has been performed to evaluate the fatigue life of an autofrettaged pressure vessel containing cross-bores subjected to pulsating internal pressure of 200 MPa. Finite element analyses were used to calculate the residual and operating stress distributions of the pressure vessel due to the autofrettage process and pulsating internal pressure, respectively. Theoretical stress concentration factors of 3.06, 2.58, and 2.64 were obtained at the cross-bore of the pressure vessel due to internal pressure, 50%, and 100% autofrettage loadings, respectively. Local stresses and local strains determined from the elastic-plastic finite element analysis were employed to calculate the failure location and fatigue life of the pressure vessel with radial cross-bores, incorporating the low-cycle fatigue properties of the pressure vessel steel and fatigue damage parameters. Increase in the amount of overstrain by autofrettage process moved the crack initiation location from the inner radius toward a mid-wall, and extended the crack initiation life. Predicted fatigue life of the fully autofrettaged pressure vessel with cross-bores increased about 50%, compared to the unautofrettaged pressure vessel. At the autofrettage level higher than 50%, the failure location and fatigue life of the pressure vessel were not significantly influenced by the autofrettage level.

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복합재료 수소 압력용기의 탄소성 해석 (Elasto-plastic Analysis of a hydrogen pressure vessel of Composite materials)

  • 도기원;한훈희;하성규
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2008년도 추계학술대회A
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    • pp.275-280
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    • 2008
  • To improve the durability of a hydrogen pressure vessel which is applied high-pressure, it needs the autofrettage process which induces compressive residual stress in the Aluminum liner. This study presents the elasto-plastic analysis to predict the behavior of structure accurately, and the Tsai-Wu failure criterion is applied to predict failure of pressure vessel of Aluminum liner and composite materials. Generally, plastic analysis is more complex than elastic analysis and has much time to predict. To complement its weakness, the AxicomPro(EXCEL program), applied radial return algorithm and nonlinear classical laminate theory (CLT), is developed for predicting results with more simple and accurate than the existing finite element analysis programs.

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소형 잠수함 압력선체의 구조설계 (Structural Design of Small Submarine Pressure Hull)

  • 김흥열;신용구;김수영;신성철;정보영;조정화;김현수
    • 대한조선학회논문집
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    • 제49권2호
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    • pp.116-123
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    • 2012
  • This study aims to analyze the strength of pressure hull of a small submarine. The pressure hull of a submarine has to withstand very large differential pressure between hydrostatic pressure in submarine operating depth and atmospheric pressure in inner space of a submarine. To do that, the pressure hull is generally ring-stiffened cylindrical shell under external pressure. In this situation, there are some foreseeable failure modes of the pressure hull such as shell yielding, axisymmetric shell buckling, asymmetric shell buckling, overall buckling and buckling of end closure. We calculated collapse pressures of these failure modes with approximation and empirical formulas. And, to analyze critical buckling pressure, we performed eigenvalue analysis with finite element method tools.