• 한국기계연구소 소보
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• s.18
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• pp.169-175
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• 1988

The influence of mean strain on the behavior of early stage stress amplitude was investigated quantitatively in low cycle fatigue. It was obtained that the exponent of cyclic strain(n') and the coefficient of cyclic strain(C') decreased with increasing cycle numbers in compressive mean strain level. But it was the opposite in 0% mean strain and tensile mean strain level. And the cyclic yield strength ($\delta_(yc)$) was constant irrespective of mean strain or cyclic strain

• Tunnel and Underground Space
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• v.18 no.2
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• pp.134-148
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• 2008

The state of in situ stress is an important factor in considering the suitability of a site as a geological repository for nuclear waste. In this study, three-dimensional distinct numerical analysis was conducted to investigate the effect of deformation zones on the state of stress in the Oskarshamn area, which is one of two candidate sites in Sweden. A discontinuum numerical model was constructed by explicitly representing the numerous deformation zones identified from site investigation and far-field tectonic stress was applied in the constructed model. The numerical model successfully captured the variation of measured stress often observed in the rock mass containing large-scale fractures, which shows that numerical analysis can be an effective tool in improving the understanding of the state of stresses. Discrepancies between measured and modelled stress are attributed to the inconsistent quality of measured stress, uncertainty in geological geometry. and input data for fractures.

• Journal of Korean Society of Steel Construction
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• v.14 no.4
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• pp.539-547
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• 2002

The study proposed the initial equilibrium state analysis method that considers axial deformation, in order to accurately determine the initial shape of a cable-stayed bridge. Sepecifically, the proposed method adopted the successive iteration method. In order to evaluate appropriate initial cable force introduced in the initial equilibrium state analysis, parametric studies were performed and a useful linear analysis method proposed. The geometrically nonlinear static behaviors of cable-stayed bridges were considered, using three-dimensional frame element and elastic catenary cable element. The usefulness and applicability of the analytic method proposed in this study were demonstrated using numerical examples, including a real cable-stayed bridge. The algorithm, is applicable in cases wherein axial deformation is not adopted in the fabrication camber, or final cable force is adjusted to eliminate construction and fabrication errors occurring during construction.

• Journal of the Korean Society for Railway
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• v.20 no.5
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• pp.637-648
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• 2017

In this paper, the effects of initial built-in deformation and temperature deformation on the stress distribution of discontinuous precast concrete track slab under train load were examined. According to the results, when train load is put on a precast concrete slab with initial built-in deformation and deformation due to temperature gradient, the maximum tensile stresses develop at the upper side of slab in the slab center, edge center and corner of shear pocket; the stress distribution is different from that of the case under train load only. Therefore, to accurately predict the actual weak points and failure modes, one should calculate the stress under train load considering the initial built-in and temperature deformation of the slab.

• The Korean Journal of Rheology
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• v.7 no.2
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• pp.128-138
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• 1995

본 논문에서는 전단띠형성에 있어서 전단변형의 집중화 현상을 이방성 탄소성 재료 에 대해서 해석하였고 소성스핀과 비등방성이 전단띠 형성에 미치는 영향을 연구하였다. 평 면응력 상태에서 소성스핀을 갖고있는 이방성 탄-소성 재료에 대해서 재료 분랑ㄴ정 해서 을 수행하여 변형률 집중화의 시작에 미치는 소성스핀과 비등방성의 효과를 연구하였다. 해 석 결과 이방성 재료에서의 전단띠 형성은 압축 또는 인장의 하중 형태나 이방성 축의 초기 각도 그리고 소성스핀의크기에 따라 그 시작이 촉진되거나 지연되었고 전단띠 생성의 방향 도 달라졌다.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.6
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• pp.35-45
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• 2008

To investigate the effects of residual displacement, the structural responses of buckling-restrained braced frames (BRBF) and special moment-resisting frames (SMRF) were evaluated for design-based excitations following an application of initial residual drift. The initial residual drift was applied to the structure in two ways. The first way was to simply apply the same earthquake record to the structure twice, with an appropriate pause between applications to allow the structural response from the first record to return to zero. The second way to apply the initial residual drift was to apply a pushover to the structure until it arrives at the desired residual drift value. According to the analysis results, the initial residual drifts had a significant effect on the responses of steel BRBF and SMRF. The responses of BRBF were more highly dependent on the initial residual deformation than the responses of SMRF. Therefore, in order to minimize the post-event repair cost, a reduction of residual drift is required.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.5
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• pp.522-526
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• 1997

잔류 응력이 존재하는 부품의 가공 시에는 잔류 응력 상태가 새로운 평형 상태를 이루기 위해 재 분포되며 이는 가공 자체에 따른 변형 이와의 부가적 변형을 초래한다. 고도의 정밀도를 요하는 가공에는 이러한 잔류 응력에 의한 부가적 변형을 고려하여야 하며, 가공 후의 잔류 응력의 재 분포 상태는 가공 후 부품의 물질적 성능을 결정하는데 중요한 요소이므로 이를 예측할 수 있어야 한다. 본 연구에서는 잔류 응력에 의한 부가적 치수 변화를 고려한 가공 후의 부품의 내경 및 두께와 잔류 응력의 재 분포를 예측할 수 있는 이론적 수식을 제시하고 유한요소법에 의한 시뮬레이션의 결과와 비교하였다. 초기 잔류 응력의 분포는 autofrettage process에 의해 유도되었다.

• Geotechnical Engineering
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• v.14 no.5
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• pp.219-234
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• 1998

Modulus measurements in vertical boreholes under simulated horizontal in-situ stress conditions were performed on laboratory rock specimens. The experimental program was focused on the examination of modulus change with the variation of the orientation, magnitude and ratios of horizontal biaxial stresses. The experiment results show that the modulus increases when the magnitude of the horizontal stresses increases. The modulus measured in the minimum principal direction increased when the ratio between the horizontal principal stresses increased, while the modulus measured in the maximum principal direction decreased when the ratio of the horizontal principal stresses increased. These were caused by the tangential stresses that vary depending upon the magnitude of horizontal stresses, the applied pressure and the orientation of measurement. Also, the measured moduli were determined under tensile stress, compressive stress, or both stresses. Thus, the stress effect on deformation modulus should be considered, not only for the interpretation of the results of borehole deformability measurement, but also for the design of underground gas storage and pressure tunnel, and for the interpretation of tunnel monitoring.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.4
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• pp.301-305
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• 2012

In this work the mechanical behaviors of GaN nanowires are analyzed during tension, compression, and unloading deformations. The thermal conductivity of the nanowires at each deformed state is evaluated using an equilibrium Green-Kubo approach. Under tensile loading, the [0001]-oriented nanowires with hexagonal cross-sections undergo a phase transformation from wurtzite to a tetragonal structure. The phase transformation is not observed under compressive loading. The thermal conductivity decreases on going from compressive strains to tensile strains. The strain dependence of the thermal conductivity results from the relaxation time of phonon. A reverse transformation from the tetragonal structure to the wurtzite structure is observed during unloading. The thermal conductivities in the intermediate states are lower than the conductivity in the wurtzite structure at same strain. Such differences in the thermal conductivity between different atomic structures are mainly due to changes in the group velocity of phonon.

• The Korean Journal of Rheology
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• v.7 no.3
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• pp.203-210
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• 1995

전기장 하에서 폴리아닐린/미네랄 오일 현탁액의 유변학적 특성에 관한 실험적인 연 구를 큐엣 셀 형태의 레오미터를 사용하여수행하였다. 폴리아닐린 현탁액은 전기장을 가해 줄 때 점도가 크게 상승하는 현상을 보였고 부피분율과 전기장의 3/2승에 비례하는 동적 항 복응력을 나타내었다. 작은 변형 진폭의 동적 상태 실험을 통하여 저장계수와 손실계수를 변형진폭, 변형의 구동 주파수 및 전기장의 함수로 나타내었다. 저장계수는 전기장을 증가시 킬 때 증가하나 손실계수(5wt%)는 약한 전기장 의존성을 보였다. 낮은 응력을 가해줄때의 크립과 회복곡선은 초기의 순간적인 변형 증가와 지연되는 변형 그리고 회복 불가능한 영구 적 변형으로 구성되어진다. 탄성 한계 항복응력은 전기장의 세기가 증가함에 따라 증가하였 다. 매우 작은 변형에서는 응력과 변형사이의 선형적 관계를 보여 고체와 유사한 거동을 나 타내었다.