• Journal of Ginseng Research
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• 제15권3호
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• pp.183-187
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• 1991

Effect of ginseng hairy and native roots on body absorption, fecal and urinary excretion of Ingested radiostrontium were investigated in the mouse(NIH-strain, male) treated with or without pre-feeding of each ginseng soluble fraction. The test groups were fed with basic diet supplemented with 1% each ginseng soluble fraction for 7 darts before the radiostrontium were administered by intragastric intubation. In the groups of treated with soluble fraction from ginseng hairy roots, the radioactivities of fecal and urinary excretion increased about 15% over than that of control groups and the whole body retention were about 38%. In the groups of treated with soluble fraction from native ginseng roots, the radioactivities of fecal and urinary excretion increased about 25% over than that of control groups and the whole body retention were about 28%. Also, the levels of radiostrontium accumulation retained significantly the higher percent in skeletons than in other organs.

• 한국구조물진단유지관리공학회 논문집
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• 제22권3호
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• pp.103-110
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• 2018

표면매립공법으로 매립한 철계-형상기억합금으로 보강한 보의 휨 거동을 장기 하중 재하실험을 통해 평가하였다. 철계-형상기억합금 길이대비 2%와 4%의 사전변형 및 형상기억효과 활성화에 의한 프리스트레스 하중 도입을 실험변수로 설정하였다. 1 tonf의 콘크리트 추를 보 중앙에 거치한 후 6개월간의 보 중앙부의 장기 처짐을 측정하였다. 실험결과, 철계-형상기억합금으로 보강한 보의 휨 강성이 증대되었으며, 사전변형이 증가할수록 보강재의 강성감소로 인한 처짐이 증가하는 것으로 나타났다. 프리스트레스 하중 도입에 따른 처짐을 비교했을 때, 프리스트레스 하중을 도입하지 않은 실험체에 비해, 프리스트레스 하중을 도입한 실험체는 약 30%의 처짐 감소 효과를 보이는 것으로 나타났다.

• 한국구조물진단유지관리공학회 논문집
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• 제14권3호
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• pp.186-195
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• 2010

본 논문은 SC합성보에 정착구의 높이, 새들의 형태, 가력시점을 변수로 하여 비부착 포스트텐션 보강을 하고 휨실험을 통해 보강방법을 평가하여 적절한 보강방법을 제시하고자 하엿다. 실험결과 보강 전 SC합성보의 최대내력은 실험값/이론값이 0.97로 나타났으나 보강 후는 1.00~1.21로 나타나 보강효과를 확인할 수 있었다. 변위 및 변형률 분석결과 정착구의 높이 및 가력시점에 상관없이 보강 후 중립축에 정착구를 설치한 D120계열 실험체가 최대하중이후 급격한 하중저하 없이 변위가 지속적으로 증가하며 각 부분의 변형률도 비교적 적게 나타나는 안정적인 거동을 했다. 보강효과면에서 선 가력 후 보강한 SCR-UD120실험체가 보강 전 SC합성보에 비해 최대내력이 1.72배 증가하여 가장 우수한 것으로 나타났다.

• 비파괴검사학회지
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• 제24권3호
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• pp.233-239
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• 2004

지능재료는 안경테, 치아 교정과 같은 의료용 재료, 각종 센서 및 밸브 등의 광범위한 분야에서 적용되고 있다. 이와 같은 지적재료의 형상기억효과를 이용한 지적복합재료는 항공기의 부품, 산업구조물 및 항공산업에서도 그들 시스템의 모니터링을 위하여 사용되어 질 수 있다. 그러나 지능복합재료의 형상기억효과에 대한 분석과 시뮬레이션은 대단히 어렵다. 본 연구에서는 유한요소법을 이용하여 기지재와 하나의 강화섬유에 대한 2차원의 축 대칭 모델에 대하여 분석하였다. 상온(293K)과 고온(363K)에서 각각 해석되었으며 해석결과와 실험결과와의 강도 값을 비교 검토하였다. 더불어 음향방출 기법을 이용하여 지능복합재료(TiNi/A16061)의 예변형률과 고온에서의 미시적 손상거동을 평가하였다.

• 대한기계학회논문집A
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• 제29권10호
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• pp.1315-1320
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• 2005

TiNi alloy fiber was used to recover the original shape of materials using its shape memory effect. The shape memory alloy plays an important role within the metal matrix composite. The shape memory alloy can control the crack propagation in metal matrix composite, and improve the tensile strength of the composite. In this study, TiNi/A16061 shape memory alloy(SMA) composite was fabricated by hot press method, and pressed by a roller for its strength improvement. The four kinds of specimens were fabricated with $0\%,\;3.2\%,\;5.2\%\;and\;7\%$ and volume fraction of TiNi alloy fiber, respectively. A fatigue test has performed to evaluate the crack initiation and propagation for the TiNi/A16061 SMA composite fabricated by かis method. In order to study the shape memory effect of the TiNi alloy fiber, the test has also done under both conditions of the room temperature and high temperature. The relationship between the crack growth rate and the stress intensity factor was clarified for the composite, and the cold rolling effect was also studied.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 센서 박막재료 반도체 세라믹
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• pp.253-256
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• 2003

This study presents the combined effect of electric field application and mechanical compressive stress loading on deformation in a multilayer ceramic actuator, designed with stacking alternatively $0.2(PbMn_{1/3}Nb_{2/3}O_3)-0.8(PbZr_{0.475}Ti_{0.525}O_3)$ ceramics and Ag-Pd electrode. The deformation behaviors were thought to be attributed to relative $180^{\circ}$domain quantities which is determined by pre-loaded stress and electric field. The non-linearity of piezoelectricity and strain are dependent upon the young's modulus resulting from the domain reorientation.

• 소성∙가공
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• 제33권3호
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• pp.185-192
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• 2024

This study examined how varying tempering temperatures affect the susceptibility of Cr-Mo low alloy steels to hydrogen embrittlement. A slow strain-rate test (SSRT) was carried out on the steels electrochemically pre-charged with hydrogen in order to examine the hydrogen embrittlement behavior. The results showed that the hydrogen embrittlement resistance of the Cr-Mo low alloy steels improved with increasing tempering temperature. Thermal desorption analysis (TDA) revealed that diffusible hydrogen content decreased with increasing tempering temperature, accompanied by a slight increase in the peak temperature. This decrease in hydrogen content was likely due to a reduction in dislocation density which served as reversible hydrogen trap sites. These findings underline the significant role of tempering temperature in enhancing the hydrogen embrittlement resistance of Cr-Mo low alloy steels.

• 열처리공학회지
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• 제13권2호
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• pp.91-97
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• 2000

The structure and mechanical properties of TiN and TiCN thin films deposited on STD61 steel substrates by the RF-sputtering methods has been studied by using XPS, XRD, micro-hardness tester, scratch tester, and wear-resistance tester. XPS results showed that the TiCN thin film formed with chemical bonding state. The TiN thin films grew with (111) orientation having the lowest strain energy by compressive stress, whereas the TiCN thin films grew with both (111) and (200) orientation, but (200) orientation having the lowest surface energy becomes dominant as carbon contents increase. The pre-etching treatment of substrate did not affect on the preferred orientation of thin films, but it played an important role in improving mechanical properties of thin films such as the hardness, adhesion and wear- resistance. Especially, the TiCN thin films showed the superior wear resistances due to high hardness and low friction coefficient compared with TiN thin films.

• 열처리공학회지
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• 제4권4호
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• pp.24-33
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• 1991

The effects of thermomechanical treatments on microstructure and fatigue properties of 7050 Al alloy were investigated. The precipitation kinetics changed to a faster rate due to cold deformation employed in this special TAHA thermomechanical treatments including pre-aging, plastic deformation and two step final-aging. The G.P. zones in the under-aged condition were cut by dislocations and dissolved during the plastic deformation. During the low cycle fatigue, the T6' condition showed cyclic hardening behavior whereas the TMT5, TMT27 and T76 conditions showed cyclic softening at above 0.7% total strain amplitudes. The ${\Delta}K_{th}$ value of TMT27 was improved more than two times, compared with that of T76 condition. The T6' with small shearable precipitates resulted in the markedly high ${\Delta}K_{th}$ value. This is thought to be resulted from dislocation reversibility and roughness-induced crack closure due to planarity of slip.

• Structural Engineering and Mechanics
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• 제23권6호
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• pp.713-737
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• 2006

This paper presents the results of an experimental investigation on the behaviour of 56 reinforced concrete beams subjected to pure torsion. The reported results include the behaviour curves, the failure modes and the values of the pre-cracking torsional stiffness, the cracking and ultimate torsional moments and the corresponding twists. The influence of the volume of stirrups, the height to width ratios and the arrangement of longitudinal bars on the torsional behaviour is discussed. In order to describe the entire torsional behaviour of the tested beams, the combination of two different analytical models is used. The prediction of the elastic till the first cracking part is achieved using a smeared crack analysis for plain concrete in torsion, whereas for the description of the post-cracking response the softened truss model is used. A simple modification to the softened truss model to include the effect of confinement is also attempted. Calculated torsional behaviour of the tested beams and 21 beams available in the literature are compared with the experimental ones and a very good agreement is observed.