• 대한기계학회논문집
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• 제19권5호
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• pp.1182-1189
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• 1995

Several methods have been developed to predict the creep rupture time of the steam pipes in thermal power plant. However, existing creep life prediction methods give very conservative value at operating stress of power plant and creep rupture strain cannot be well estimated. Therefore, in this study, creep rupture time and strain prediction method accounting for material damage and grain boundary sliding is newly proposed and compared with the existing experimental data. The creep damage evolves by continuous cavity nucleation and constrained cavity growth. The results showed good correlation between the theoretically predicted creep rupture time and the experimental data. And creep rupture strain may be well estimated by using the proposed method.

• 대한기계학회논문집A
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• 제24권11호
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• pp.2812-2822
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• 2000

Several methods have been developed to predict the rupture time of the boiler tubes in thermal power plant. However, existing life prediction methods give very conservative value at operating stress of power plant and rupture strain cannot be well estimated. Therefore, in this study, rupture time and strain prediction method accounting for creep, corrosion and heat transfer is newly proposed and compared with the current research results. The creep damage evolves by continuous cavity nucleation and constrained cavity growth. The corrosion damage evolves by steam side and fire side corrosion. The results showed good correlation between the theoretically predicted rupture time and the current research results. And rupture strain may be well estimated by using the proposed method.

• 한국구조물진단유지관리공학회 논문집
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• 제7권3호
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• pp.157-165
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• 2003

섬유시트들로 보강된 철근 콘크리트보에서 섬유시트들의 정당한 파단변형률을 평가하기 위해 적층수를 달리한 120개의 섬유시트 인장시험편과 72개의 섬유보강 콘크리트보들에 대한 실험적 연구를 수행하였다. 철근콘크리트보는 세 종류의 인장철근비를 선택하였다. 인장시험에 의한 섬유시트 파단변형률은 섬유시트 적층수에 관계없이 기술자료에서 주어진 값보다 다소 낮게 나타났으며, 보에 부착된 섬유시트들의 파단변형률은 적층수가 증가할 때 감소하는 경향을 보여주었다. 본 연구에서는 이들 결과를 바탕으로 섬유시트들의 파단변형률을 평가하였다.

• 소성∙가공
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• 제17권8호
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• pp.558-563
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• 2008

The initial strain, the applied stress exponent, the activation energy, and rupture time in AZ31 magnesium alloy have been measured in order to predict the deformation mechanism and rupture life of creep over the temperature range of 423-443K. Creep tests were carried out under constant applied stress and temperature, and the lever type tester and automatic temperature controller was used for it, respectively. The experimental results showed that the applied stress exponent was about 9.74, and the activation energy for creep, 113.6KJ/mol was less than that of the self diffusion of Mg alloy including aluminum. From the results, the mechanism for creep deformation seems to be controlled by cross slip at the temperature range of 423-443K. Also the higher the applied stress and temperature, the higher the initial strain. And the rupture time for creep decreased as quadratic function with increasing the initial strain in double logarithmic axis.

• 한국지반공학회지:지반
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• 제9권4호
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• pp.55-64
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• 1993

이방압밀이 비배수크리프파괴거동에 미치는 영향을 연구하기 위하여 4가지의 압밀응력비(a:In'/clc': 1.0, 0.7, 0.5, 0.4)로서 정규압밀시킨 점토시료에 대해서 비배수크리프시험을 수행하였다. 어떤 최소변형률속도에 이르는 경과시간은 압밀응력비의 감소에 따라 줄어들고 이 최소변형률속도에 대한 파괴시간도 감소된다. Finn and Shead(1.1의 제안식에 의해서 구한 상한항복강도는 압밀응력비의 크기에 관계없이 크리프강도와 잘 일치하며 평균구속응력으로서 정규화한 상한항복 강도는 압밀응력비가 증가할수록 감소한다.

• 한국해양공학회지
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• 제10권1호
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• pp.47-52
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• 1996

This paper deals with a study on improvement of long-time creep life prediction of steam turbine rotor steels by using initial strain method as a new approach at high temperatures of 500 to 70$0^{\circ}C$ . The main result shows that the inital strain method could be reliably utilized to predict and evaluate the long-time creep life as creep rupture strength and that the predicting equation for long-time creep life under a certain creep stress at a certain high temperature could be empirically derived out from each initial instantaneous strain measured.

• 한국추진공학회지
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• 제16권3호
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• pp.49-56
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• 2012

파열판은 고압장치에서 안전장치로써 사용하고 있으며, 추진기관에서는 파열을 임의로 제어하기 위한 장치로써 사용한다. 본 논문은 파열판의 파열압력 시험결과와 유한요소해석 결과를 비교하기 위한 것이다. 본 논문에서는 AISI 316L을 이용하여 제작한 파열판의 파열시험을 수행하였으며, 탄소성 물성치와 진 응력-변형률 관계의 다양한 가정을 이용하여 파열판의 파열압력을 계산하였다. 파열시험과 탄소성해석 결과를 통하여 파열판의 크기에 대한 파열압력의 변화를 확인하였다. 시험과 유한요소해석을 통해 파열압력은 파열판의 크기에 의존하며, 탄소성해석을 수행한 결과 다중 선형 응력-변형률 선도만이 의미있는 예측치를 계산할 수 있었다. 파열시험을 통하여 파열판의 크기에 따라 파열위치가 다르다는 것을 확인할 수 있었다. 시험과 해석 결과는 파열판의 크기 변화를 통하여 파열판의 파열압력을 제어하기 위해 사용할 수 있다.

• 대한기계학회논문집A
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• 제33권10호
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• pp.1119-1124
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• 2009

This paper deals with the variability analysis of short term creep rupture test data based on the previous creep rupture tests and the possibility of the creep life prediction. From creep tests performed by constant uniaxial stresses at 600, 650 and $700^{\circ}C$ elevated temperature, in order to investigate the variability of short-term creep rupture data, the creep curves were analyzed for normalized creep strain divided by initial strain. There are some variability in the creep rupture data. And, the difference between general creep curves and normalized creep curves were obtained. The effects of the creep rupture time (RT) and steady state creep rate (SSCR) on the Weibull distribution parameters were investigated. There were good relation between normal Weibull parameters and normalized Weibull parameters. Finally, the predicted creep life were compared with the Monkman-Grant model.

• 한국해양공학회지
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• 제22권6호
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• pp.52-57
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• 2008

The short-term high temperature creep rupture behavior of Ni-based Alloy718 steel was investigated at the elevated temperatures range of 550 to $700^{\circ}C$ under constant stress conditions. The creep rupture characteristics such as creep stress, rupture time, steady state creep rate, and initial strain were evaluated. Creep stress has a quantitative correlation between creep rupture tim and steady state creep rate. The stress exponents (n, m) of the experimental data at 550, 600, 650 and $700^{\circ}C$ were derived as 33.5, -24.9, 26.1, -21.2, 16.8, -12.8 and 10, -8.2, respectively. The stress exponent decreased with increasing creep temperature. The creep lift prediction was derived by the Larson-Miller parameter (LMP) method and the resultant equation was obtained as follows: T($logt_r$+20)=-0.00252 ${\sigma}^2$-1.377${\sigma}$+-22718.

• Nuclear Engineering and Technology
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• 제54권1호
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• pp.138-151
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• 2022

Cladding ballooning and rupture are the important phenomena at the early stage of a severe accident. Most severe accident analysis codes determine the cladding rupture based on simple parameter models. In this paper, a FRTMB module was developed using the thermal-mechanical model to analyze the fuel mechanical behavior. The purpose is to judge the cladding rupture with the severe accident analysis code. The FRTMB module was integrated into the self-developed severe accident analysis code ISAA to simulate the PHEBUS FPT3 experiment. The predicted rupture time and temperature of the cladding were basically consistent with the measured values, which verified the correctness and effectiveness of the FRTMB module. The results showed that the rising of gas pressure in the fuel rod and high temperature led to cladding ballooning. Consequently, the cladding hoop strain exceeded the strain limit, and the cladding burst. The developed FRTMB module can be applied not only to rod-type fuel, but also to plate-type fuel and other types of reactor fuel rods. Moreover, the FRTMB module can improve the channel blockage model of ISAA code and make contributions to analyzing the effect of clad ballooning on transient and subsequent parts of core degradation.