• Title/Summary/Keyword: 탄성관

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Limit Loads for Circular Wall-Thinned Feeder Pipes Subjected to Bending and Internal Pressure. (원형 감육이 발생한 중수로 피더관의 한계하중 평가)

  • Je, Jin-Ho;Lee, Kuk-Hee;Chung, Ha-Joo;Kim, Jong-Sung;Kim, Yun-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.11
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    • pp.1675-1680
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    • 2010
  • Flow Accelerated Corrosion (FAC) occurring during in-service conditions results in localized wall-thinning in the feeder pipes of CANDU. The wall-thinning of the feeder pipes is the main degradation mechanisms affecting the integrity of piping systems. In this paper, we assess the integrity of wall-thinned feeder pipes by limit load analysis. The limit loads for wall-thinning feeder pipes subjected to in-plane bending and internal pressure were determined on the basis of finte element limit analyses. The limit loads are determined from the results of limit analyses of elasticperfectly-plastic materials using the large geometry change. Closed-form approximations of limit load solutions for wall-thinning feeder pipes subjected to in-plane bending and pressure are proposed.

Flow-induced Vibration Time Response Analysis of Loosely Supported Multi-Span Tube using Commercial FEA Code (지지점 간극을 갖는 다점지지 유연관의 유동하중에 의한 시간응답 이력해석과 상용유한요소 해석코드의 적용)

  • Lee, Kang Hee;Kang, Heung Seok;Shin, Chang Hwan
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.11 no.2
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    • pp.68-74
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    • 2015
  • Time domain response analysis for vibro-impact nonlinear behavior of multi-span tube with loose supports was performed using commercial FEA code and user subroutine. Support geometry of multi-span tube with a finite gap is realistically modeled by analytical rigid surface. Model of hydrodynamic force is based on the Qusai-steady model which accounts for the inclined angle of relative flow velocity and time delay between flow force and resulting tube motion. During tube vibration from flow loading, impact and friction at the support location is simulated using commercial FEA code with master slave contact algorithm. Analysis results has reasonable agreement with those of references and test experience. Plan of further refinement of analysis model and future test verification is briefly introduced.

A Study on the Strength and Fracture Toughness of High Strength Hardened Cement Paste (고강도 시멘트 경화체의 강도 및 파괴인성에 관한 연구)

  • 김정환
    • Magazine of the Korea Concrete Institute
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    • v.6 no.6
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    • pp.151-158
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    • 1994
  • In this work, in order to inrprove the flexural strength of hardened portlarid cerncrit paste, mix ing water was reduced to water ccrnent ratio of 0.1 aid water soluble polymer such as hydroxy propyl methyl cellulose was adclelri to the paste to obtain a better dispersion. The paste was kneaded by the twin roll mill for cornpact and homogeneous mixing. The high strength mechanism of the hardened cement paste may be due to the removal of macropores larger than 100${\mu}m$, the reduction of capillary pores acting as the passage of crack propagation, the increase of Young's moculus with iticrease of unhytlratcci cenxxnt ard the incicasc of fracture toughnevs with the crack toughening mechanism (grain bridging, polymer fibril bridging and fritional inter-locking).

A Theoretical Analysis of the Weak Shock Waves Propagating through a Bubbly Flow (기액 이상류를 전파하는 약한 충격파에 관한 이론해석적 연구)

  • Jun, Gu-Sik;Baek, Seung-Cheol;Kim, Heuy-Dong
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.1617-1622
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    • 2004
  • Two-phase flow of liquid and gas through pipe lines are frequently encountered in nuclear power plant or industrial facility. Pressure waves which can be generated by a valve operation or any other cause in pipe lines propagate through the two-phase flow, often leading to severe noise and vibration problems or fatigue failure of pipe line system. It is of practical importance to predict the propagation characteristics of the pressure waves for the safety design for the pipe line. In the present study, a theoretical analysis is performed to understand the propagation characteristics of a weak shock wave in a bubbly flow. A wave equation is developed using a small perturbation method to analyze the weak shock wave through a bubbly flow with comparably low void fractions. It is known that the elasticity of pipe and void fraction significantly affect the propagation speed of shock wave, but the frequency of relaxation oscillation which is generated behind the shock wave is not strongly influenced by the elasticity of pipe. The present analytical results are in close agreement with existing experimental data.

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Analysis of Fluid-elastic Instability In the CE-type Steam Generator Tube (CE형 증기발생기 전열관에 대한 유체탄성 불안정성 해석)

  • 박치용;유기완
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.12 no.4
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    • pp.261-271
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    • 2002
  • The fluid-elastic instability analysis of the U-tube bundle inside the steam generator is very important not only for detailed design stage of the SG but also for the change of operating condition of the nuclear powerplant. However the calculation procedure for the fluid-elastic instability was so complicated that the consolidated computer program has not been developed until now. In this study, the numerical calculation procedure and the computer program to obtain the stability ratio were developed. The thermal-hydraulic data in the region of secondary side of steam generator was obtained from executing the ATHOS3 code. The distribution of the fluid density can be calculated by using the void fraction, enthalpy, and operating pressure. The effective mass distribution along the U-tube was required to calculate natural frequency and dynamic mode shape using the ANSYS ver. 5.6 code. Finally, stability ratios for selected tubes of the CE type steam generator were computed. We considered the YGN 3.4 nuclear powerplant as the model plant, and stability ratios were investigated at the flow exit region of the U-tube. From our results, stability ratios at the central and the outside region of the tube bundle are much higher than those of other region.

Buckling Behavior of Corrugated Steel Pipe under External Uniform Pressure (등분포하중을 받는 파형강관의 좌굴거동)

  • Ahn, Woo Cheul;Han, Taek Hee;Lim, Nam Hyoung;Kang, Young Jong
    • Journal of Korean Society of Steel Construction
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    • v.15 no.1
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    • pp.33-40
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    • 2003
  • There are two basic concepts about concerning the buckling analysis of a buried pipe. One concept considers the soil around the pipe asn elastic continuum mediaum. The other concept holds that the pipe is sup ported by an elastic spring, which replaces the effects of the surrounding soil (the Winkler model). Theise buckling analysis is based on plane analysis, without considering the corrugation effect and the length effect. This paper thus presents a parametric study using the Finite Element Method (FEM) for the Winker model and proposes a buckling strength formula after examining a 3D analysis considering the corrugation effect and the length effect, thatwhichhelp in estimating the critical buckling strength of such CSP

Detection of Elastic Waves Using Stabilized Michelson Interferometer (광로차 보상회로가 부착된 마이켈슨 간섭계에 의한 탄성파 신호검출)

  • Kim, Y.H.;So, C.H.;Kwon, O.Y.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.13 no.4
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    • pp.32-41
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    • 1994
  • The stabilized Michelson interferometer was developed in order to measure micro dynamic displacement at the surface of solids due to elastic wave propagation. The stabilizer was designed to compensate light path disturbances using a reference mirror driven by piezoelectric actuator. Using stabilizer, the effect of external vibration was reduced and the quadrature condition was satisifed. As the results, the output of photodetector had maximum sensitivity and linearity. The minimum detectable displacement was 0.3nm at the band width of 10 MHz. The epicentral displacements due to the glass capillary breaks and the steel ball drop impact were measured using the developed interferometer and the results were compared with the calculated one.

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Elastic Behavior Characteristics of GFRP Pipes Reinforced Ribs (리브로 보강된 GFRP 관로의 탄성 좌굴거동 특성)

  • Han, Taek Hee;Seo, Joo Hyung;Youm, Eung Jun;Kang, Young Jong
    • Journal of Korean Society of Steel Construction
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    • v.18 no.6
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    • pp.737-746
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    • 2006
  • The elastic buckling strength of a Glass Fiber Reinforced Plastic (GFRP) pipe reinforced with ribs was evaluated. The height and thickness of a rib and the spacing between two adjacent ribs were considered as factors affecting the buckling strength of the pipe. And also, the ratio of the longitudinal stiffness and transverse stiffness was considered as the parameter affecting the buckling strength as the GFRP is orthotropic material. Buckling strengths of various GFRP pipe models with different shapes and stiffness ratios were evaluated by FE analyses and a formula to estimate the elastic buckling strength of a rib-reinforced pipe made of orthotropic material was suggested from the regression with the results from the FE analysis. Analytical results show that a rib-reinforced pipe has a buckling strength superior to a general flat pipe and the suggested formula estimates accurate buckling strength of the rib-reinforced pipe.

Pressure Analysis of Sterntube after Bush Bearing Considering Elastic Deflection of Misaligned Journal and Partial Slope of Bearing Bush (탄성 변형된 저어널의 편심과 베어링 부시의 부분경사를 고려한 선미관 후부 베어링의 압력분포 해석)

  • Choung, Joon-Mo;Choe, Ick-Heung
    • Journal of the Society of Naval Architects of Korea
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    • v.44 no.6
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    • pp.666-674
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    • 2007
  • It is very important to estimate static squeezing pressure distributions for lining material of sterntube after bearing at dry dock stage since the maximum squeezing pressure value can be one of the significant characteristics representing coming navigation performances of the propulsion system. Moderate oil film pressure between lining material and propulsion shaft is also essential for safe ship service. In this paper, Hertz contact theory is explained to derive static squeezing pressure. Reynolds equation simplified from Navier-Stokes equation is centrally differentiated to numerically obtain dynamic oil film pressures. New shaft alignment technology of nonlinear elastic multi-support bearing elements is also used in order to obtain external forces acting on lining material of bearing. For 300K DWT class VLCC with synthetic bush of sterntube after bearing, static squeezing pressures are calculated using derived external forces and Hertz contact theory. Optimum partial slope of the after bush is presented by parametric shaft alignment analyses. Dynamic oil film pressures are comparatively evaluated for partially bored and unbored after bush. Finally it is proved that the partial slope can drastically reduce oil film pressure during engine running.

Characterization of Tensile Strength of Anisotropic Rock Using the Indirect Tensile Strength Test (간접인장강도시험을 통한 이방성 암석의 인장강도 특성)

  • 김영수;정성관;최정호
    • Journal of the Korean Geotechnical Society
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    • v.18 no.5
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    • pp.133-141
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    • 2002
  • Isotropic rock and anisotropic rock have different tensile strength which has the greatest influence on rock failure. In this study, elastic modulus of anisotropic rock is obtained through uniaxial compression test, and tensile strength and tension failure behavior are analyzed through indirect tensile strength test. Stress concentration factor of a specimen at the center is obtained from anisotropic elastic modulus and strain by indirect tensile strength test. Theoretical solutions for tensile strength of isotropic and anisotropic rock are compared. Stress concentration factor of anisotropic rock is either higher or lower than isotropic rock depending on the inclination angle of bedding plane. The use of stress concentration factor of isotropic rock resulted in overestimation or underestimation of tensile strength.