• 한국안전학회지
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• 제15권4호
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• pp.35-40
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• 2000

The influence of cyclic loading history on the creep behavior of the 30 vol% hot-pressed $SiC_f/Si_3N_4copmposite was experimentally investigated at $1200^{\circ}C$. The duration of loading/unloading had great effects on the creep behaviors. The short term duration cyclic loading history test results showed significant reduction in the primary and steady-state creep rates. For example, 300sec loading/300sec unloading history resulted in 70% lower steady-state creep rate than that of the continuous loading. However the long term duration cyclic loading history test results showed little change in creep rates compared to those of the continuous one. The reason for the significant change in the short term duration cycles was estimated due to the change in the stress redistribution between the fiber and matrix during the creep recovery in the primary stage.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 춘계학술대회
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• pp.164-166
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• 1996

Human aorta has viscoelastic behavior. The test of tissues such as aorta, skin, muscle, and ok. is required to consider visco effect on deformation behavior. Creep and slow recovery are main aspects of viscoelasticity of tissue engineering. Volumatric strain plays a important role in determine slow recovery of human arota. This study is to suggest the method avoiding viscous effect in tissue experiment The results shows the time scale when the specimen can be fully recovered from slow deformation. Also, this study observes the qualitative creep-effect on elastic strain in 1 minute at the same loading.

• 한국구조물진단유지관리공학회 논문집
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• 제14권1호
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• pp.125-132
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• 2010

최근 건설 사업에서 FRP를 단순 부착하여 구조물을 보강하는 공법은 현재 가장 널리 사용되고 있는 보수보강법이다. 본 논문에서는 FRP로 보강된 철근콘크리트 구조물은 지속하중을 받고 있기 때문에 크리프와 건조수축의 영향을 받는다. 이로 인하여 FRP의 보강효과도 달라지며, 처짐 및 변형의 회복성능, 잔존 내력 역시 크게 달라진다. 따라서 CFRP, GFRP가 휨성능에 영향을 미치는 보강 성능을 파악하고, 일정 시간이 흐른 후 하중을 제거하여 장기 변형 및 처짐의 회복성능을 파악하고, 잔존하는 내력을 알아보고자 정적 재하 실험을 수행하였다. 실험한 결과, FRP 보강 실험체는 즉시 처짐을 제어하는 측면은 매우 효율적이고, 즉시변형 회복량 또한 즉시 변형량보다 큰 결과를 보였다. 잔존강도 실험을 통하여 CFRP로 보강된 실험체가 가장 큰 내력을 가지는 것으로 나타났다. FRP로 보강된 보는 지속하중에 의한 부착성능 및 잔존내력에는 영향이 없었던 것으로 판단된다.

• Journal of Biosystems Engineering
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• 제16권1호
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• pp.37-48
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• 1991

Rice plants are subjected to various forces such as natural force of wind and mechanical force of cultivating machines. Rheological behavior of the rice stem can be expressed in terms of three variables : stress, relaxation and time. The objectives of this study are to examine stress relaxation, creep and recovery characteristics on the rice stem in case of axial and radial loading. Stress relaxation with time was studied on three levels of loading rate and on four levels of applied stress. The results were summarized as follows : 1. The hysterisis losses of the rice stem distinctly observed at the radial compression in comparison with axial compression. The hysterisis loss implied that the stem to absorbed energy without being deformed beyond the yield point. 2. Ageneralized Maxwell model consisting of three elements gave a good description of the relaxation behavior of the rice stem. Rate of loading was more significant on the observed relaxation behavior within the short relaxation time, but there were little influences of rate of loading on the relaxation time. 3. The stress relaxation intensity and the residual stress increased in magnitude as the applied stress increased, but the relaxation time was little affected by the applied stress. 4. The coefficients of the stress relaxation model showed much differences in the radial compression and the axial compression, especially the higher relaxation stress of the third element was observed in the radial compression. 5. The behaviors of rice stem in creep and recovery test also might be represented by a four element Burger's model. But the coefficients of the creep model were different from those of the recovery model. 6. The steady-state phenomena of creep appeared at the stress larger than 20 MPa in Samkang and 1.8 MPa in Whajin. 7. The elastic modulus of the stem showed the range from 40 to 60 MPa. It could be considered, as a result, the rice stems had viscoelastic properties.

• 한국재난정보학회 논문집
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• 제14권1호
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• pp.79-88
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• 2018

본 연구에서는 긴급복구용 팽창재료의 온도에 따른 팽창량 및 강도의 변화를 컵발포 실험과 일축압축강도 실험을 통하여 물리적 특성을 확인하였고, 장기안전성을 확인하기 위하여 가속 압축 크리프 시험을 진행하였다. 크리프 성능을 평가하기 위하여 단기 크리프 시험과 가속 압축 크리프 실험을 실시하였으며, 단기크리프 실험은 팽창재료의 초기 크리프 변형률을 결정하고 시간-온도 중첩정리가 적용된 단계 등온법은 가속시험방법으로 장기 압축 크리프 성능을 평가하였다.

• 한국주조공학회지
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• 제33권1호
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• pp.1-7
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• 2013

The effect of the Mo addition on the high temperature creep properties of the 9Cr-3W steel was also evaluated. Two experimental steels, (9Cr-3W and 9Cr-3W-0.5Mo), were prepared using a vacuum induction melting process, followed by hot rolling and heat treatment processes. Three types of precipitates, ($M_{23}C_6$, Nb-rich MX and V-rich MX) were observed in a typical tempered martensitic matrix. Significant effects of the Mo addition on the tensile properties were not observed. However, the creep properties at $650^{\circ}C$ under applied stresses of 140 and 150 MPa were considerably enhanced by the Mo addition. The microstructural observation after the creep test indicated that the addition of Mo could function to retain the recovery of the martensitic matrix, thus resulting in the enhanced creep properties of the 9Cr-3W-0.5Mo steel. Furthermore coarsening of the $M_{23}C_6$ carbides and formation of Laves phases were observed in both samples after the creep tests.

• 대한금속재료학회지
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• 제48권11호
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• pp.965-973
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• 2010

The small punch creep (SPC) test has recently received much attention as a new alternative to the conventional uniaxial creep test because it needs only a miniature-sized specimen directly detached from an operating system or component without any serious sampling damages. However, it is difficult to obtain the equivalent uniaxial creep data directly from the SPC data. As a specimen is deformed by a punch in the SPC test, the test result is sensitive to the friction between them. Finite element analyses with various friction coefficients was performed and showed a tendency of increased SPC life with an increased friction coefficient. The necking position predicted by the SPC simulation with a proper friction coefficient showed good agreement with that observed from the real SPC test. Finally, a noble method to convert the SPC load and displacement rate into the equivalent uniaxial creep stress and strain rate, respectively, was established in this study.

• 대한기계학회논문집
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• 제10권3호
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• pp.292-297
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• 1986

본 연구에서는 2024 Al 합금에 대하여 260-380.deg. C의 온도 범위 및 2~5kgf/ m $m^{2}$의 부과응력 범위에서 실시한 고온 정상 크리이프 변형 중의 내부응력 .sigma. $_{i}$,의탄성 변형 .epsilon.$_{A}$ 및 회복율 r의 측정 실험을 통하여 이들 상호간의 관계 를 살펴 보고자 한다.다.다.

• 전산구조공학
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• 제1권2호
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• pp.131-142
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• 1988

유동화 콘크리트의 건조수축 및 크리프 특성을 검토하기 위하여 유동화제 2종류와 일반감수제 1종류를 사용하여 재하 하중조건(압축강도의 15% 및 30%)별, 양생조건별로 압축강도 및 건조수축을 측정하고 기건상태하의 크리프 및 크리프변형을 측정하여 유동화 콘크리트의 장기 변형특성을 검토하였다. 그 결과, 유동화 콘크리트는 보통 콘크리트에 비하여 재령 28일의 압축강도는 약 22% 증가하였고, 건조수축은 15% 감소하였으며, 크리프변형은 약 11% 감소하였고 28일간의 크리프회복은 보통 콘크리트에 비하여 작음을 알 수 있었다. 따라서 사용목적에 따른 적절한 유동화제의 선택과 적정량의 유동화제 사용은 건조수축 및 크리프변형에 효과적인 것으로 판단된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.103-104
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• 2009

본 연구는 지속하중을 받은 철근콘크리트보의 처짐 특성을 파악하고 하중이 제거된 후의 변형 회복특성을 파악하였다. 또한 잔존강도를 파악하기위해 정적 재하실험을 실시하였으며 지속하중을 받지 않은 RC보와 비교를 하였다.