• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집B
• /
• pp.410-415
• /
• 2001

Hydraulic mounts have been used as an alternative to the conventional rubber mounts for they can provide more desirable stiffness and damping properties which may vary with frequency and excitation amplitude. Although a lumped-parameter non-linear model of the hydraulic mount developed by a simple fluid dynamic analysis can be successfully used for representing the inertia track dynamics, a linear model is still preferred. In this paper, an analytic technique for making a linear model of the hydraulic mount is proposed.

• Nuclear Engineering and Technology
• /
• 제47권5호
• /
• pp.633-645
• /
• 2015

In order to analyze the mechanical properties of two-way different configurations of prestressed concrete members subjected to axial loading, a finite element model based on the nuclear power plant containments is demonstrated. This model takes into account the influences of different principal stress directions, the uniaxial or biaxial loading, and biaxial loading ratio. The displacement-controlled load is applied to obtain the stress estrain response. The simulated results indicate that the differences of principal stress axes have great effects on the stress-strain response under uniaxial loading. When the specimens are subjected to biaxial loading, the change trend of stress with the increase of loading ratio is obviously different along different layout directions. In addition, correlation experiments and finite element analyses were conducted to verify the validity and reliability of the analysis in this study.

• 한국토양비료학회지
• /
• 제47권1호
• /
• pp.66-70
• /
• 2014

Bed-soils can be used to help plants to overcome unfavorable conditions of soils, especially hydraulic properties of soils. This study was conducted to evaluate the effect of organic and inorganic raw materials on saturated hydraulic conductivity ($K_s$) of bed-soils. Perlite and bottom ash, which are inorganic materials, increased more $K_s$ of bed-soils than coco peat, an organic material. However, vermiculite, an inorganic material, increased less than coco peat. Saturated hydraulic conductivity of bed-soil mixed with fine vermiculite ($0.14{\pm}0.02mh^{-1}$) was much lower than one containing coarse vermiculite ($0.85{\pm}0.21mh^{-1}$). Such effect was more apparent when pressure was added on bed-soils containing fine vermiculite ($0.07{\pm}0.01mh^{-1}$), probably reflecting the decrease in pore size with the expansion of vermiculite wetted. Compacting decreased more $K_s$ in the bed-soils containing coco peat or vermiculite than other mixtures. Those results suggest that perlite and bottom ash in bed-soils play an important role in improving saturated hydraulic conductivity but vermiculite in bed-soils may suppress the improvement of saturated hydraulic conductivity with the decrease of its size and with the increase of compacting pressure.

• Geomechanics and Engineering
• /
• 제9권1호
• /
• pp.101-113
• /
• 2015

Saturated soil hydraulic conductivity is a very important soil parameter in numerous practical engineering applications, especially rainfall infiltration and slope stability problems. This parameter is difficult to measure since it is very highly sensitive to various soil conditions. There have been many analytical and empirical formulas to predict saturated soil hydraulic conductivity based on experimental data. However, there have been few studies to investigate in-situ hydraulic conductivity of weathered granite soils, which constitute the majority of soil slopes in Korea. This paper introduces an estimation method to derive saturated hydraulic conductivity of Korean weathered granite soils using in-situ experimental data which were obtained from a variety of slope areas of South Korea. A robust regression analysis was performed using different physical soil properties and an empirical solution with an $R^2$ value of 0.9193 was suggested. Besides that this research validated the proposed model by conducting in-situ saturated soil hydraulic conductivity tests in two slope areas.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2005년도 지반공학 공동 학술발표회
• /
• pp.649-654
• /
• 2005

Shallow slope failures in residual soil during periods of prolonged infiltration are common over the world. One of the key factors that dominate slope stability is hydrological response associated with infiltration. Hence, the soil-water profile during rainfall infiltration into unsaturated soil must me examined to evaluate slope stability. However, the hydraulic response of unsaturated soil is complicated by inherent uncertainties of the soil hydraulic properties. This study presents a methodology for assessing the effects of parameter uncertainty of hydraulic properties on the response of a analytical infiltration model using first-order reliability method. The unsaturated soil properties are considered as uncertain variables with means, standard deviations, and marginal probability distributions. Sensitivities of the probabilistic outcome to the basic uncertainties in the input random variables are provided through importance factors.

• 한국주조공학회지
• /
• 제3권1호
• /
• pp.28-36
• /
• 1983

본 실험에서는 고정수압하에서 응고한 Al-l0% Mg합금의 조직 및 기계적 성질에 미치는 가압력의 영향을 조사하기 위하여 압력을 $0㎏f/cm^2$, 500$kgf/cm^2$, $1500㎏f/cm^2$ 및 $2000㎏f/cm^2$로 변화시키면서 냉각곡선, 조직검사, 기계적시험 및 비중 측정을 하여 얻은 결론은 다음과 같다. 1. 가압력이 증가할수록 합금의 냉각속도는 증가하였다. 2. 기공 및 수축공의 발생은 가압에 의해 억제되었다. 3. 가압력이 증가할수록 dendrite arm spacing은 감소하였다. 4. 기계적 성질 및 비중은 가압력이 증가함에 따라 증가하였다.

• International Journal of Fluid Machinery and Systems
• /
• 제8권4호
• /
• pp.254-263
• /
• 2015

The failure of hydraulic turbine runners is a rare event. So in order to assess the reliability of these components one cannot rely solely on the number of observed failures in a given population. However, as there is a limited number of degradation mechanisms involved, it is possible to use physically-based reliability models. Such models are often more complicated but are able to account for physical parameters in the degradation process. They can therefore help provide solutions to improve reliability. With such models, the effect of materials properties on runner reliability can be highlighted. This paper presents a brief review of the Kitagawa-Takahashi diagram which links the damage tolerance approach, based on fracture mechanics, to the stress or strain-life approaches. Using simplified response spectra based on runner stress measurements, we will show how fatigue reliability is sensitive to materials fatigue properties, namely fatigue crack propagation behaviour and fatigue limit obtained on S-N curves. Furthermore, we will review the influence of the main microstructural features observed in 13%Cr-4%Ni stainless steels commonly used for runner manufacturing. The goal is ultimately to identify the most influential microstructural features and to quantify their effect on fatigue reliability of runners.

• 한국지반신소재학회논문집
• /
• 제1권1호
• /
• pp.43-51
• /
• 2002

본 연구에서는 차수재의 차수성를 결정짓는 벤토나이트 팽윤재를 이용하여 증류수, 침출수, 바닷물 및 3% NaCl 용액등의 반응물에 대한 자유팽윤도를 측정하였으며 Poly(acrylic acid)와 PVA(polyvinyl Alcohol), SCMC(Sodium Carboxymethyl Cellulose)를 각각 첨가한 벤토나이트의 자유팽윤도의 변화를 비교 평가하였다. 또한 바닷물에서의 토목섬유점토차수재의 투수계수를 측정하였으며 바닷물이 차수성에 어떤 영향을 미치는지 확인하였다. 벤토나이트의 평균 자유팽윤도는 증류수>침출수>바닷물 순으로 감소하였다. 바닷물에서와 3% NaCl 용액에서의 자유팽윤도 값은 근소한 차이를 보였다. Poly(acrylic acid)가 첨가된 벤토나이트는 모든 반응물에서 팽윤성 향상을 나타내었고 PYA가 첨가된 벤토나이트는 증류수를 제외한 반응물에서는 팽윤성 향상을 보이지 않았다. SCMC가 첨가된 벤토나이트의 팽윤성은 3% NaCl 용액에서 다소 자유팽윤도가 떨어지나 전반적으로 팽윤성이 향상되었다.

• 한국환경농학회지
• /
• 제41권2호
• /
• pp.101-107
• /
• 2022

BACKGROUND: Soil amendment was necessary applied for the sand that had been used to root zone of green ground in golf course because of its low water retention power and cation exchangeable capacity. This study was conducted to evaluate the effect of the mixed ratio of peat moss and coconut coir as soil amendment materials on the soil physicochemical properties applied to rootzone based on sand. METHODS AND RESULTS: The soil amendments were blended at 0, 3, 5, 7 and 10% by soil volume. The pH in the peat moss treatment was lower than that of control (0% soil amendment), and pH and electrical conductivity (EC) in the coconut coir were higher. The blending ratio of peat moss was negatively correlated with pH of rootzone soil (p<0.01), and that of coconut coir positively with EC (p<0.01). As compared with control, capillary porosity, the physical factors such as air-filled porosity, total porosity, and hydraulic conductivity of rootzone soil were increased by applying peat moss and coconut coir. For correlation coefficients between percentage of soil amendments and soil physical factors, peat moss and coconut coir were positively correlated with porosity and hydraulic conductivity (p<0.01). CONCLUSION(S): These results indicated that the application of peat moss and coconut coir affected on the change of physicochemical properties of rootzone soil, and improved soil porosity and hydraulic conductivity.

• 한국정밀공학회지
• /
• 제18권6호
• /
• pp.127-132
• /
• 2001

An automatic design system for a hydraulic gate has been developed to cut down the time for the design calculation and to optimize its design. It is oriented to the radial gate which is the simplest, most reliable, least expensive and most widely used hydraulic gate. This system is composed of data input, strength computation and result display modules with databases of the properties of components and materials. In this development, the existing intricate design procedure has been changed to the straightforward procedure without assumption of weight. With this code, the design time of the radial gate could be reduced below one thirtieth in comparison with manual work and the optimum design could be accomplished easily.