• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.1243-1251
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• 2013

The purpose of this study is to investigate the influence of initial clamping force of tension clamp on the performance of an elastic rail fastening system used in sharp curve track. In this study, the initial clamping force and the increasing lateral wheel loads were conducted in the analytical and experimental study, i.e., finite element analysis, laboratory and field test. Using the analytical and experimental results, the performance of the tension clamp was investigated. It was found that the stress of tension clamp depends on the initial clamping force. Therefore the initial clamping force appeared to directly affect the compression stress of the tension clamp. It was found that the compression stress of tension clamp was transferred to the tensile stress by applied the lateral wheel load in service sharp curve track. Further, it was concluded that the initial clamping force was applied on the strengthening force for the tension clamp and then the appropriate initial clamping force was important to ensure a stable performance and long term endurance of tension clamp.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.89-90
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• 2010

최근 우리는 InGaAs 위에 성장한 InAs 양자점에 GaAs를 얇게 덮음으로써 양자고리를 성장하고, 그 광학적 특성을 분석하였다. [1] 이번 연구에서는 이 양자고리 구조의 전자 구조 및 광학적 특성을 전산모사를 통해 계산하였고, GaAs가 구조의 응력, 압전 포텐셜 및 light-hole 분율에 미치는 영향을 분석하였다. 이론적인 분석을 위해, valence force field 방법을 이용하여 이종 물질간의 격자상수 차이에 의한 격자 변형 및 압전 포텐셜의 변화를 계산하였고, 양자고리 내 전자의 양자화 에너지 및 파동함수를 k p 방법을 통해 얻을 수 있었다. 또한 광학적인 특성 등의 다체 효과를 예측하기 위해 configuration interaction 방법을 사용하였다. 이 연구에서 우리는, GaAs가 InAs에 강한 압축 응력을 가할 것이라는 일반적인 예측과 달리, InGaAs 매트릭스 안에서는 격자상수가 작은 GaAs가 InAs 양자고리에 효과적인 압축 응력을 가할 수 없음을 보였다. 특히 GaAs 층의 두께가 얇을 경우, InGaAs 매트릭스에 의해 인장 응력을 받는 GaAs가 InAs의 응력을 해소하기 충분한 공간을 제공하여, 오히려 InAs의 압축 응력을 약화시키는 것을 알 수 있었다. 이 연구 결과는 응력 분포가 단순한 양자우물 등의 2차원 구조와 달리, 응력 분포가 복잡한 3차원 나노 구조에서는 단순히 격자상수만으로 파장 변화 경향을 예측할 수 없음을 나타낸다. 또한 우리는, GaAs의 큰 negative 이방 응력과 InAs의 작은 positive 이방 응력에 의해 전자와 heavy-hole은 InAs에, light-hole은 GaAs에 구속됨을 보였다. 즉, InAs보다 밴드갭이 큰 GaAs가 전자와 heavy-hole에 대해서는 강한 포텐셜 배리어로 작용하지만 light-hole에 대해서는 포텐셜 우물로 작용하는, 반 우물-반 배리어 특성을 가짐을 알 수 있었다. 이로 인해 GaAs가 있는 양자고리의 light-hole 분율이 GaAs가 없을 경우에 비해 2배에서 8배가량 증가함을 보일 수 있었다. 비슷한 특성이 hole에 대해서는 InP나 InGaAsP 위에 성장한 GaAs 층에서 보고된 바가 있으나, 전자는 InAs로, hole은 GaAs로 분리할 수 있는 3차원 나노 구조에 대한 연구는 이 연구가 처음이다. [2]

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.5
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• pp.428-431
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• 2005

In this paper, the displacement and stress of pile foundation constructed in the soft cohesive soils were measured and investigated at each construction phase. The piles belongs to compressive stress then extension due to lateral flow of soft soils. Battered piles showed different stress state according to construction direction. The lateral displacements of piles radically occurred at the embankment phase.

• Elastomers and Composites
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• v.40 no.4
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• pp.258-265
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• 2005

To study the compressive stress, recovery force and permanent strain of foams for footwear midsole, polyurethane(PU), phylon(PH) and injection phylon(IP) foams were repetitively compressed with constant compressive stress. Maximum compressive stress of PU did not decrease with repetitive compression on the constant compressive stress, but that of IP largely decreased. Engineering strain of foams were formed by repetitively compressing the three types of foam. The engineering strain of PU was smaller than that of IP and PH. Compressive stress and recovery force of IP and PH at certain strain were decreased with repetitive compression, but that of PU was not noticeably changed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5C
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• pp.183-190
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• 2009

It is necessary to predict the deformation and stresses on soils to establish the nonlinear stress-strain relationship of geomaterials at various strain levels. Especially, a need exists to establish the pre-failure nonlinear characteristic of cemented granular geomaterials used in road constructions. In this paper, therefore, conventional granular soils were mixed with various cementing materials, such as cement and fly ash from coal combustion by-products. Then, the normalized nonlinear behavior of cemented geomaterials was assessed using unconfined compression test. In addition, various constitutive models of soils were evaluated for estimating pre-failure non-linear behavior of cemented geomaterials from the test results.

• 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 Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.458-466
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• 2020

The purpose of this experimental research is to evaluate the compressive and tensile behaviors of high performance hybrid fiber reinforced concrete(HPHFRC) using amorphous steel fiber(ASF) and polyamide fiber(PAF). For this purpose, the HPHFRCs using ASF and PAF were made according to their total volume fraction of 1.0% for target compressive strength of 40MPa and 60MPa, respectively. And then the compressive and tensile behaviors such as the compressive strength, compressive toughness, direct tensile strength, and stress-strain characteristics under compressive and tensile tests were estimated. It was observed from the test results that the compressive strength of HPHFRC was slightly decreased than that of plain concrete, but the compressive toughness, compressive toughness ratio, and direct tensile strength of HPHFRC increased significantly. Also, it was revealed that the plain concrete showed brittle fracture after the maximum stress from the stress-strain curves, but HPHFRC showed strain softening.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.10
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• pp.113-120
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• 1995

여러가지 두꺼운 복합재료 구조물은 3차원 압축 부하 상태에 노출되는 경우가 발생한다. 이런 경우에 있어 서의 복합재료 압축 강도는 압축 평균 응력을 이용하면 예측이 가능할지도 모른다. 이번 연구 에서는 압축 평균 응력을 이용하여 탄소섬유 강화 복합재료들의 압축 강도를 예측하는 모델을 개발 하고자 한다. 이 모델은 압축강도에 영향을 주는 요소, 초기 misalignment를 고려하였고, 탄소섬유와 수지사이에 접합강도가 임계값을 초과할때 복합재료의 파괴가 일어난다고 가정한다. 또 여라가지 문헌들을 통하여 유압이 접합강도에 미치는 점들을 보여준다. 본 모델을 이용한 예측값들은 가해지는 유압에 따라 증가되며, 실험값들과 비교 분석될 것이다.

• Journal of the Korean Geotechnical Society
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• v.16 no.5
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• pp.213-226
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• 2000

지반 앵커(이하에서는 "앵커"로 칭한다)는 앵커두부, 자유부, 정착부로 나누어져 있다. 현재 주로 사용되고 있는 앵커는 지반과 앵커체 표면의 마찰저항력에 의해 지지하는 마찰방식이며, 앵커체에 발생하는 응력에 따라 크게 인장형과 압축형 앵커로 나누어진다. 그런데, 현재까지 이들 앵커의 설계 및 극한하중의 결정은 대부분이 인장형 앵커에 대한 것으로서, 긴장시 압축형 앵커의 선단정착부의 응력집중으로 이한 그라우트 압축저항에 대해서는 명확히 연구되어져 있지 않다. 본 연구에서는, 현장과 비슷한 조건에서 실내시험을 실시하여 선잔 장착부 그라우트의 보강형식에 따른 압축거동특성과 보강효과, 지반의 구속(정지와 포아송 구속)을 고려한 압축형 앵커의 선단 정착부 그라우트 압축저항력 산정식을 제안하였다.정식을 제안하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.333-338
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• 2013

The compressive residual stress and fatigue behavior of shot peened alloy 600 under a high-temperature environment is investigated in this study. Alloy 600 is used in the main parts of nuclear power plants, and the compressive residual stress induced by the shot peening process is considered to prevent SCC (stress corrosion cracking). To obtain practical results, the fatigue characteristics and compressive residual stress are evaluated under the actual operating temperature of a domestic nuclear power plant, as well as a high-temperature environment. The experimental results show that the peening effects are valid at a high temperature lower than approximately $538^{\circ}C$, which is the threshold temperature. The fatigue life was maintained at temperatures lower than $538^{\circ}C$, and the compressive residual stress at $538^{\circ}C$ was 68.2% of that at room temperature. The present results are expected to be used to obtain basic safety and reliability data.