• Title/Summary/Keyword: 마스터 커브

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Evaluation of Fracture Toughness for SA508 Gr. 3 Reactor Pressure Vessel Steel Using Bimodal Master Curve Approach (이봉분포 마스터커브를 이용한 SA508 Gr. 3 원자로용기강의 파괴인성 평가)

  • Kim, Jong Min;Kim, Min Chul;Lee, Bong Sang
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.13 no.2
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    • pp.60-66
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    • 2017
  • The standard master curve (MC) approach has the major limitation because it is only applicable to homogeneous datasets. In nature, materials are macroscopically inhomogeneous and involve scatter of fracture toughness data due to various deterministic material inhomogeneity and random inhomogeneity. RPV(reactor pressure vessel) steel has different fracture toughness with varying distance from the inner surface of the wall due to cooling rate in manufacturing process; deterministic inhomogeneity. On the other hand, reference temperature, $T_0$, used in the evaluation of fracture toughness is acting as a random parameter in the evaluation of welding region; random inhomogeneity. In the present paper, four regions, the surface, 1/8T, 1/4T and 1/2T, were considered for fracture toughness specimens of KSNP (Korean Standard Nuclear Plant) SA508 Gr. 3 steel to investigate deterministic material inhomogeneity and random inhomogeneity. Fracture toughness tests were carried out for four regions and three test temperatures in the transition region. Fracture toughness evaluation was performed using the bimodal master curve (BMC) approach which is applicable to the inhomogeneous material. The results of the bimodal master curve analyses were compared with that of conventional master curve analyses. As a result, the bimodal master approach considering inhomogeneous materials provides better description of scatter in fracture toughness data than conventional master curve analysis. However, the difference in the $T_0$ determined by two master curve approaches was insignificant.

TGA열분석을 이용한 개질된 NR고무의 열화반응

  • An, Won-Sul;Park, Gi-Ho
    • Proceedings of the Korean Environmental Sciences Society Conference
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    • 2008.11a
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    • pp.488-490
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    • 2008
  • 등온 및 비등온 TGA 열분석을 이용하여 TTSP를 이용하여 실험적으로 Shift factor(Acceleration factor) ${\alpha}_T$를 구하고 이로부터 마스터 커브 (master curve)를 도출할 수 있었고, 실험에 사용된 개질된 NR고무재료는 Arrhenius식을 잘 따르는 것이 확인되었으며, 이로부터 TTSP에 의한 촉진시험 결과의 신빙성을 확인할 수 있었다. 한편, 등온 TGA 실험으로부터 얻은 활성화에너지는 37.70 kJ/mol인 반면, 비등온 TGA로부터 Kissinger plot에 의해 얻은 활성화에너지는 166.20 kJ/mol이었는데, 이는 저온과 고온에서 서로 다른 분해기구에 의해 중량 감소가 일어나기 때문인 것으로 생각 되었다.

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A Study on Life Assessment for In-Service High-Temperature Components Using Image Processing Technique (컴퓨터 화상처리 기법을 이용한 고온 구조물의 수명평가 연구)

  • 김효진;정재진
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.4
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    • pp.44-50
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    • 1998
  • The creep life fraction can be evaluated by the degree of grain deformation since the grain of Cr-Mo base metal deforms in the direction of stress. The grain deformation method using image processing technique is developed for life assessment of in-service high-temperature components. The new assessment model of grain deformation method is presented to apply to in-service components and is verified by interrupted creep test for ex-serviced material of 1Cr-0.5Mo steel. The proposed model, which is irrespective of stress direction, is to evaluate mean of the absolute deviation for the measured ratios which are diametrical maximum to minimum dimensions for grains.

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Fracture Toughness Evaluation for Main Feed Water Valves of Korean Standard Nuclear Power Plant (한국표준원전 주급수 밸브의 파괴인성 평가)

  • Yoon, Ji-Hyun;Hong, Seokmin;Lee, Bong-Sang
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.11 no.1
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    • pp.39-44
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    • 2015
  • The fracture toughness of 2.25Cr-1Mo cast steel (SA217-WC9) samples which were taken from the check valves of feed water piping of Korean Standard Nuclear Power Plant(KSNPP) was measured by Master Curve method. The measured $T_0$ reference temperature of SA217-WC9 steel was $-30^{\circ}C$. The obtained $T_0$ was compared to the derived value from Charpy impact test data following to SINTEP procedure. The heat-to-heat variation in fracture toughness of SA217-WC9 steel was observed. It was found that the low toughness of a heat of SA217-WC9 steel was attributed to the coarse MnS inclusion originated by high sulfur content as the results of microanalyses.

Evaluation of Creep Behaviors of Alloy 690 Steam Generator Tubing Material (Alloy 690 증기발생기 전열관 재료의 크리프 거동 평가)

  • Kim, Jong Min;Kim, Woo Gon;Kim, Min Chul
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.15 no.2
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    • pp.64-70
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    • 2019
  • In recent years, attention has been paid to the integrity of steam generator (SG) tubes due to severe accident and beyond design basis accident conditions. In these transient conditions, steam generator tubes may be damaged by high temperature and pressure, which might result in a risk of fission products being released to the environment due to the failure. Alloy 690 which has increased the Cr content has been replaced for the SG tube due to its high corrosion resistance against stress corrosion cracking (SCC). However, there is lack of research on the high temperature creep rupture and life prediction model of Alloy 690. In this study, creep test was performed to estimate the high temperature creep rupture life of Alloy 690 using tube specimens. Based on manufacturer's creep data and creep test results performed in this study, creep life prediction was carried out using the Larson-Miller (LM) Parameter, Orr-Sherby-Dorn (OSD) parameter, Manson-Haford (MH) parameter, and Wilshire's approach. And a hyperbolic sine (sinh) function to determine master curves in LM, OSD and MH parameter methods was used for improving the creep life estimation of Alloy 690 material.

A Viscoelastic Study of Glass Transition and Degradation Processes of Phenolic Resin/Carbon Fiber Composites (페놀수지/탄소섬유 열경화성 복합재료의 유리전이와 고온 분해과정에서 관찰되는 점탄성 특성 연구)

  • ;J. C. Seferis
    • The Korean Journal of Rheology
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    • v.11 no.1
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    • pp.9-17
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    • 1999
  • Viscoelastic characteristics of cured phenolic resin/carbon fiber composite materials were investigated through glass transition and degradation reaction processes in the high temperature region up to $400^{\circ}C$. A typical glass transition of the cross-linked thermoset polymer was followed by irreversible degradation reactions, which were exhibited by the increasing storage modulus and loss modulus peak. A degradation master curve was constructed by using the vertical and horizontal shift factors, both of which complied well with the Arrhenius equation in light of the kinetic expression of degradation rate constants. Using an analogy to the Havriliak-Negami equation in dielectric relaxation phenomena, a viscoelastic modeling methodology was developed to characterize the frequency- and temperature-dependent complex moduli of the degrading thermoset polymer composite systems. The temperature-dependent relaxation time of the degrading composites was determined in a continuous fashion and showed a minimum relaxation time between the glass transition and degradation reaction regions. The capability of the developed modeling methodology was demonstrated by describing the complex behavior of the viscoelastic complex moduli of reacting phenolic resin composite systems.

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Sliding Friction of Elastomer Composites in Contact with Rough Self-affine Surfaces: Theory and Application (자기-아핀 표면 특성을 고려한 유기탄성체 복합재료 마찰 이론 및 타이어 트레드/노면 마찰 응용)

  • Bumyong Yoon;Yoon Jin Chang;Baekhwan Kim;Jonghwan Suhr
    • Composites Research
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    • v.36 no.3
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    • pp.141-153
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    • 2023
  • This review paper presents an introduction of contact mechanics and rubber friction theory for sliding friction of elastomer composites in contact with rough surfaces. Particularly, Klüppel & Heinrich theory considers the self-affine (or fractal) characteristic for rough surfaces to predict adhesion and hysteresis frictions of elastomers based on the contact mechanics of Greenwood & Williamson. Due to dynamic excitation process of elastomer composites while sliding in contact with multiscale surface roughness (or asperity), viscoelastic properties in a wide frequency range becomes major contributor to friction behaviors. A brief description and examples are provided to construct a viscoelastic master curve considering nonlinear viscoelasticity of elastomer composites. Finally, application of rubber friction theory to tire tread compounds in traction with road surfaces is discussed with several experimental and theoretical results.