• 지구물리와물리탐사
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• 제7권1호
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• pp.25-32
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• 2004

We have carried out laboratory measurements of P-wave velocity and deformation strain during $CO_2$ injection into a porous sandstone sample, in dry and water-saturated conditions. The rock sample was cylindrical, with the axis normal to the bedding plane, and fluid injection was performed from one end. Using a piezoelectric transducer array system, we mapped fluid movement during injection of distilled water into dry sandstone, and of gaseous, liquid, and supercritical $CO_2$ into a water-saturated sample. The velocity changes caused by water injection ranged from $5.61\;to\;7.52\%$. The velocity changes caused by $CO_2$ injection are typically about $-6\%$, and about $-10\%$ for injection of supercritical $CO_2$, Such changes in velocity show that the seismic method may be useful in mapping $CO_2$ movement in the subsurface. Strain normal to the bedding plane was greater than strain parallel to the bedding plane during $CO_2$ injection; injection of supercritical $CO_2$ showed a particularly strong effect. Strain changes suggest the possibility of monitoring rock mass deformation by using borehole tiltmeters at geological sequestration sites. We also found differences associated with $CO_2$ phases in velocity and strain changes during injection.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 추계학술대회 논문집
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• pp.645-646
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• 2012

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권1호
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• pp.157-173
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• 2015

In the present study, the existing equivalent stain method is improved to make up for its weaknesses. The improved inherent strain model is built considering more sophisticated three dimensional constraints which are embodied by six cubic elements attached on three sides of a core cubic element. From a few case studies, it is found that the inherent strain is mainly affected by the changes in restraints induced by changes of temperature-dependent material properties of the restraining elements. On the other hand, the degree of restraints is identified to be little influential to the inherent strain. Thus, the effect of temperature gradients over plate thickness and plate transverse direction normal to welding is reflected in the calculation of the inherent strain chart. The welding deformation can be calculated by an elastic FE analysis using the inherent strain values taken from the inherent strain chart.

• 한국정밀공학회지
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• 제6권4호
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• pp.94-102
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• 1989

The effect of plastic strain on the surface integrity of mild steel (SS 41) was studied. This paper shows that the recrystallization technique is adequate to evaluate the plastic strain in a machined surface experimentally. The relations between the plastic strain and the machining conditions are quantitatively evaluated by using the recrystallization technique. The obtained results are summarized as follows. 1. The surface integrity of steel is considerably influenced by the amount of surface region deformation produced by changes in cutting conditions. 2. The plastic strain in machined surface produced by changes of the cutting conditions is evaluated by the recyrstallization technique. 3. The plastic strain increases with the increase of depth of cut and the decrease of rake angle. 4. When the cutting force is high and the rake angle is small, the value of maximum true strain reaches to high. 5. The maximum true strain is related to the cutting energy, and the values increase with the increase of the unit shear and total engergy in constant depth with the increase of the energy values.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
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• pp.33-39
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• 2002

Unsteady behaviors of counterflow flame were studied experimentally in opposing jet counterflow burner using diluted methane. To generate the unsteadiness on the flame, the counterflow diffusion flame was perturbed by velocity changes made by the pistons installed on both sides of the air and fuel stream. The velocity changes were measured by Hot wire and Laser Doppler Velocimetry, and the flame behaviors were observed by High speed ICCD and ICCD. In this investigation, the spatial irregularity of the strain rate caused the flame to extinguish from the outside to the axis during the extinction, and we found the following unsteady phenomena. First, the extinction strain rates of unsteady cases are much larger than those of the steady ones. Second, the extinction strain rates become larger as the slope of the change of the strain rate increases. Third, the unsteady extinction strain rates become smaller with the increase of the initial strain rate.

• 대한소아치과학회지
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• 제35권1호
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• pp.18-29
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• 2008

본 연구는 복합레진 적층방법에 따른 복합레진의 수축양상을 스트레인 게이지를 이용하여 비교 평가하고자 하였다. 사용된 광중합기의 광원은 light-emitting diode(LED)와 plasma arc lamp(PAL)이었으며, 복합레진은 Filtek $Z350^{TM}$를 사용하였다. 교정 치료를 목적으로 발거된 60개의 소구치를 대상으로 하여, 교합면에 와동을 형성하고 일회충전법, 수평적층법, 사면적층법으로 나누어 복합레진을 충전하여 치면에 발생된 strain과 응력을 측정하였고, 법랑질 표면에 시편을 부착하여 동일한 적층방법으로 충전한 후 전단결합강도를 측정한 결과 다음과 같은 결론을 얻었다. 1. Strain의 변화를 살펴보면, LED와 PAL 조사군 모두 와동의 협설면에서는 주로 팽창이 일어났다가 시간이 지남에 따라 서서히 수축하는 양상을 보여주었다. 2. 와동의 근원심면에서는 팽창과 수축이 반복적으로 나타나면서 서서히 수축량이 증가하였다. 3. LED와 PAL 조사군 모두 적층방법 간의 응력 차이는 없었다(p>0.05). 4. LED 및 PAL 조사군 간의 응력 차이는 협면에서만 존재하였다(p<0.05). 5. 전단결합강도 측정 결과 LED 군에서는 사면적층법이 일회충전법, 수평적층법 보다 유의하게 낮게 나타났으나(p<0.05), PAL 광조사군에서는 유의차가 없었다(p>0.05). 6. 각 치면에 발생된 응력은 전단결합강도보다 낮았다(p<0.05).

• Geomechanics and Engineering
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• 제37권4호
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• pp.419-429
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• 2024

The primary goal was to assess how the addition of cement dust, a byproduct known to be harmful, could be used to stabilize clay. Various percentages of cement dust were added to soil samples, which were then subjected to triaxial testing at different rates of strain using an unconsolidated undrained triaxial machine. Six different rates of strain were applied to analyze the response of the clay under different conditions, resulting in 216 triaxial sample tests. As the percentage of cement dust in the clay samples increased, there was a noticeable increase in the strength properties of the clay, indicating a positive effect of cement dust on the clay's strength characteristics. Higher rates of strain during testing led to increased strength properties of the clay. Varying cement dust content influenced the impact of increasing the rate of strain on the clay's strength properties. Higher cement dust content reduced the sensitivity of the clay to changes in strain rate, indicating that the clay became less responsive to changes in strain rate as cement dust content increased. Potential for Clay Stabilization Cement dust proved the potential to enhance the strength properties of clay, indicating its potential utility in clay stabilization applications. Both higher percentages of cement dust and higher rates of strain were found to increase the clay's strength. It's essential to consider both the percentage of cement dust and the rate of strain when assessing the strength properties of clay in practical applications.

• 한국결정성장학회지
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• 제9권1호
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• pp.64-69
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• 1999

PANrP 탄소섬유의 고온연신에서의 변형 거동을 검토하기 위해서, 일정 하중하에서 내부저항 가열법에 의해 $1200^{\circ}C$부터 $2200^{\circ}C$까지 열처리 온도를 변화시키며 섬유의 strain 변화를 측정하였다. 부하된 응력이 증가함에 따라서 strain 변화가 크게 발생하며 또한 열처리 온도 약 $1700^{\circ}C$를 경계로 해서 그 온도 이상과 이하 사이에는 큰 차이를 보였다. 각 응력에 있어서의 strain 속도 변화로부터 얻어진 활성화 에너지는 70 MPa 및 322 MPa에 대하여 각각 67.46 및 52.27 kJ/mol로써, 큰 응력의 경우가 작은 응력을 부하하는 것 보다 섬유구조 발달에 있어서 더욱 효과적이라는 것을 알았다.

• International Journal of Safety
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• 제2권1호
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• pp.12-16
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• 2003

In Part 1, the flame structure of the counterflow nonpremixed flames computed by using Fire Dynamics Simulator was compared with that of OPPDIF for different concentrations of methane in the fuel stream. In this study, comparisons were made for the global strain rate that is an important parameter for diffusion flames for further evaluation of FDS. At each of the three fuel concentrations, $20% CH_4＋ 80% N_2, 50% CH_4 ＋ 50% N_2, 90% CH_4 ＋ 10% N_2$ in the fuel stream, the temperature and axial velocity profiles were investigated for the global strain rate in the range from 20 to $100s^{-1}$. Changes in flame thickness and radius were also compared with OPPDIF. There was good agreement in the temperature and axial velocity profiles between the axisymmetric simulations and the one-dimensional computations except for the regions where the flame temperature reach its peak and the axial velocity rapidly changes. The simulations of the axisymmetric flames with FDS showed that the flame thickness decreases and the flame radius increases with increasing global strain rate.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 제2회 박판성형심포지엄 논문집 박판성형기술의 현재와 미래
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• pp.156-163
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• 1998

During an actual forming operation, a material may undergo considrably large changes in strain path, and these changes can significantly alter the forming limits. So, in this study, modified forming limit curves(FLCs) in complex strain path are determined with specially designed jig to give test specimens with desired prestrains in uniaxial or biaxial deformation mode. In another part of present study, theoretical prediction of FLCs is attempted with MK's theory and Hosford's yield criterion to give forming limit curves in positive minor strain region and with Hill's local necking theory in negative minor strain region. Comparison of these theoretical results with experimental ones will be mentioned for both linear and complex strain path.