• 한국지반공학회논문집
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• 제15권1호
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• pp.151-160
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• 1999

광양만의 해저에서 채취한 점성토시료의 물리적 성질과 역학적 특성을 규명하기 위한 일련의 실내시험을 수행하였다. 주요 시험내용은 제반 물리적 성질시험, 표준압밀시험, 비배수 및 배수 삼축시험(CIU, CID) 등이다. 통일분류에 의하면 CL, CH로 구분되는 광양만 점토는 자연함수비, 38.3~84.6%, 액성지수, 0.71~0.98 이고 과압밀비가 1.06~l.60인 실질적인 정규압밀상태라고 볼 수 있다. 비배수 삼축시험에서의 유효응력경로는 (q, p)공간에서 등방압밀응력($p_0$) 으로 규준화되고, 등 전단변형률선은 원점을 통과하며 선형적이다. 비배수 전단변형률($\varepsilon$)은 응력비($\eta$) 만의 함수이고, ($\varepsilon/\eta, \eta$) 공간에서 절편값을 갖는 직선으로 나타났다. 또한, 등방압밀응력으로 규준화된 간극수압도 응력비에 대하여 직선이고, 그 구배, C는 간극수압 매개변수로 정의될 수 있다. 이상에서 기술된 경향을 근거로 하여 비배수 응력경로 및 전단변형률을 예측할 수 있는 계산식을 제안하였고, 제안식에 의하여 계산된 응력경로와 전단변형률은 기존의 Cam-clay이론 보다 실측치에 더 가까운 값을 주는 것으로 나타났다. 배수시험 결과에서 얻어진 응력경로 상의 파괴점은 비배수 응력경로의 한계상태선과 동일 선상에 위치하며, 이 사실은 한계상태이론의 기본 개념과 일치한다.

• 한국산학기술학회논문지
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• 제10권10호
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• pp.2551-2556
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• 2009

링 레이저 자이로스콥의 주 동작은 폐경로 내의 상대 전파에 대한 위상 차에 의존한다. 공명 블록위에 설치 된 반사경들이 순항 파를 형성한다. 따라서, 공명 블록의 차원 정확도가 빔의 순항 경로에 영향을 미친다. 링의 공진 내에서 안정된 광학 빔 경로를 유지하기 위해서 피에조로 구동되는 이동거울이 공명 블록의 열팽창이나 기계적 변형하에서 경로치 제어를 하고자 선택되었다. 이 논문에서는 피에조 구동 거울의 탄성거동에 대한 수학적 설명을 제시하였다. 이 설명은 피에조 구동 거울의 개념 설계에도 적용될 수 있다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.209-216
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• 2000

When subjected to earthquake shaking, saturated sandy soil may generate excess pore pressure. And a time may come when initial confining pressure will equal to excess pore pressure. Depending on the characteristics of the soil and the length of the drainage path, excess pore pressure was dissipated after earthquake. For this reason, it was induced settlement in grounds and fatal damage of various structures. In this study, settlement in silty sand grounds induced earthquake was evaluated using post-liquefaction constitutive equation between volumetric strain and shear strain from previous study. Using that, it was proposed that simplified estimation of settlement in silty sand grounds induced liquefaction.

• Computers and Concrete
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• 제20권1호
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• pp.85-97
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• 2017

With a special attention to the different stages of a typical loading path travelled in a fluid confined concrete test, this paper introduces a physically consistent model for the stress-strain curve of actively confined normal-strength concrete in the axial direction. The model comprises of the five elements of: (1) a criterion for the peak or failure strength, (2) an equation for the peak strain, (3) a backbone hydrostatic curve, (4) a transient hardening curve linking the point of departure from the hydrostatic curve to the failure point, and finally (5) a set of formulas for the post-peak region. Alongside, relevant details and shortcomings of existing models will be discussed in each part. Finally, the accuracy and efficiency of the proposed model have been verified in a set of simulations which compare well with the experimental results from the literature.

• Geomechanics and Engineering
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• 제13권6호
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• pp.963-975
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• 2017

Improvement of soft clay deposit by preloading with vertical drains is one of the most popular techniques followed worldwide. These drains accelerate the rate of consolidation by shortening the drainage path. Although the analytical and numerical solutions available are mostly based on equal strain hypothesis, the adoption of free strain analysis is more realistic because of the flexible nature of the imposed surcharge loading, especially for the embankment loading used for transport infrastructure. In this paper, a numerical model has been developed based on free strain hypothesis for understanding the behaviour of soft ground improvement by vertical drain with preloading. The unit cell analogy is used and the effect of smear has been incorporated. The model has been validated by comparing with available field test results and thereafter, a hypothetical case study is done using the available field data for soft clay deposit existing in the eastern part of Australia and important conclusions are drawn therefrom.

• 한국농공학회지
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• 제30권4호
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• pp.134-153
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• 1988

This paper was carried out to investigate the existence of a unique stress- strain behavior by obtaining some factors influencing the time dependent stress- strain behavior of clay. The results obtained from this study were summarized as follows ; 1. The relationship between stress ratro and strain in normally consolidated clay was in- dependent on pre-shear consolidation pressure. Therefore, shear strain could be expressed as a function with stress ratio. 2. The constitutive equation of shear strain on Modified Carn Clay Model coincided better with the observed value than Cam Clay Model. 3. The relationships between deviator stress and shear strain, between pore water pressure and shear strain were unified by the mean equivalent pressure. 4. The shear strain contour in norrnally consolidated clay was increased linearly through origin, but that in overconsolidated clay was not in accordance with the result of the former. 5. Because the effective stress path of normally consolidated clay was unified by the mean equivalent pressure, state boundary surface in (e,p,q) space was transformed into two dimensional surface. But it was considered to be suitable that the unified stress- strain in overconsolidated clay be expressed by a function with overconsolidation ratio. 6. The deviator for constant strain was increased linearly with increment of strain rate ($\varepsilon$) on semi-log scale, but pore water pressure was decreased. 7. The behavior of stress relaxation was transformed from linear to curvilinear with inc - rement of strain rate before stress relaxation test, and pore water pressure was increased in total range. 8. The strain of creep was increased linearly with increment of time on semi-log scale. The greater the strain rate before creep test became, the greater the increment of strain of creep became. And the pore water pressure during creep test was increased generally with increment of time on semi-log scale.

• 방사성폐기물학회지
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• 제18권2_spc호
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• pp.275-289
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• 2020

2017년 미국 DOE 주도하에 수행된 국제공동 복합모드운반시험 중 도로트럭운반시험, 연안항해시험, 대서양항해시험에서 측정된 가속도 및 변형률 데이터를 분석하였다. 먼저 각 운반모드 별로 발생한 하중이 전달경로에 따라 하중이 증폭되는지 감쇄되는지가 조사되었다. 그 결과 운반모드 및 하중경로 내 어떤 부분이냐에 따라 발생한 하중이 모의핵연료집합체에 전달되는 특성이 다름을 확인하였다. 그리고 변형률 데이터를 분석하여 육상 및 해상운반동안 발생한 변형률이 사용후핵연료에 건전성에 미치는 영향을 파악하였다. 그 결과 측정된 변형률은 사용후핵연료의 건전성에는 영향을 미치지 못하는 정도로 작은 크기임을 확인하였다. 본 연구에서 분석된 가속도와 피로평가 결과는 예정된 국내 정상운반시험조건에서의 운반시험에 유용한 기초자료로 활용될 것이다.

• Nuclear Engineering and Technology
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• 제54권11호
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• pp.4030-4048
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• 2022

In this study, road transportation tests were conducted with surrogate fuel assemblies under normal conditions of transport to evaluate the vibration and shock load characteristics of spent nuclear fuel (SNF). The overall test data analysis was conducted based on the measured acceleration and strain data obtained from the speed bump, lane-change, deceleration, obstacle avoidance, and circular tests. Furthermore, representative shock response spectrums and power spectral densities of each test mode were acquired. Amplification or attenuation characteristics were investigated according to the load transfer path. The load attenuated significantly as it transferred from the trailer to the cask. By contrast, the load amplified as it transferred from the cask to the surrogate SNF assembly. The fuel loading location on the cask disk assembly did not exhibit a significant influence on the strain measured from the fuel rods. The principal strain was in the vertical direction, and relatively large strain values were obtained in spans with large spacing between spacer grids. The influence of the lateral location of fuel rods was also investigated. The fuel rods located at the side exhibited relatively large strain values than those located at the center. Based on the strain data obtained from the test results, a hypothetical road transportation scenario was established. A fatigue evaluation of the SNF rod was performed based on this scenario. The evaluation results indicate that no fatigue damage occurred on the fuel rods.

• 한국지반공학회논문집
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• 제22권1호
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• pp.5-14
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• 2006

본 연구에서는 평면변형률조건하에서 발생 가능한 다양한 응력조건을 보다 자유롭게 구현할 수 있는 간편한 형태의 평면변형률 시험장비를 새롭게 개발하였다. 개발된 시험장비의 적용성은 먼저 이상화된 가정조건하에서 이론적으로 검토되었으며, 실제 점성토시료에 대한. 일련의 평면변형률시험을 통해 실험적으로 확인 검증되었다. 그 결과 개발된 시험장비는 기존의 평면변형률 시험장비들에 비해 광범위한 적용성을 가지고 있음을 확인할 수 있었다. 또한 개발된 시험장비는 일반적인 삼축시험용 재하장치만으로도 다양한 응력조건에 대한 평면변형률시험이 가능하므로, 향후 관련분야에서 그 활용도가 매우 높을 것으로 기대된다.

• 소성∙가공
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• 제32권1호
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• pp.35-40
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• 2023

In the case of a wire with a very fine diameter during the multi-stage drawing process, the heterogeneity of the deformation in the radial direction tends to develop strongly as the amount of deformation is accumulated. It is known that the heterogeneity of deformation in the radial direction of the wire is closely related to the process parameters during the multi-stage drawing process. In this study, finite element analysis (FEA) was used to theoretically examine the effect of friction between the surface of the wire and the drawing die during the multi-stage drawing process of Cu-0.2wt%Mg alloy on the deformation heterogeneity developed in the radial direction of the wire. The distribution of effective strain, radial strain, circumferential strain, and shear strain developed in the radial direction of the wire during the multi-stage drawing process was analyzed while changing the friction coefficient, and the results were analyzed and compared for each path and position. The FEA results revealed that the shear strain developed in the radial direction of the wire during the multi-stage drawing process of Cu-0.2wt%Mg alloy showed the most non-uniform distribution and was also severely affected by the friction coefficient.