• Title/Summary/Keyword: Shear Stress

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Experimental Study on Physical Characteristics of MR Fluid along Temperature Conditions (온도조건에 따른 MR 유체의 물리 특성에 대한 실험 연구)

  • Lee, Seok-Hyun;Son, June;Baek, Dae-Sung;Kwon, Young-Chul
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.15 no.3
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    • pp.1247-1252
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    • 2014
  • In the present study, sedimentation and shear stress of MR fluid are investigated to physical characteristics of MR fluid along temperature conditions. MR fluid is a suspension of micrometer-sized magnetic particles in a base liquid. Therefore, dispersion of MR fluid is important in the case of the design and optimization of the system using MR fluid. Due to sedimentation characteristics of MR fluid by magnetic particles, the sedimentation and shear stress of commercial MR fluid are investigated at $25^{\circ}C$ and $80^{\circ}C$ temperatures by using a forced convection oven and a viscometer. From experimental results, the sedimentation and shear stress are more affected by the temperatures of $80^{\circ}C$ than $25^{\circ}C$ and the mixing time of 5min than 10min. Shear stress by the applied current increases the shape of a quadratic equation and are lower 6-18% at $80^{\circ}C$ than $25^{\circ}C$.

Analysis for the Flow and Wall Shear Stress with the Diameter Ratios of an Abdominal Aortic Aneurysm in a Pulsatile Flow (맥동 유동에서 복부 대동맥류의 직경비에 따른 유동 및 벽면전단응력 해석)

  • 모정하
    • Journal of Biomedical Engineering Research
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    • v.23 no.3
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    • pp.181-187
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    • 2002
  • The objective of the present study was to two-dimensionally investigate the characteristics of flow and wall shear stress under pulsatile flow in the aneurysm which is a local dilatation of the blood vessel for pulsatile flow. The numerical simulation using the commercial software were carried out for the diameter ratios(ratio of maximum diameter of aneurysm to the diameter of blood vessel) ranging from 1.5 to 2.5 and Womersley number, 15.47. It was shown that a recirculating flow at the bulge was developed and disappeared for one Period and the strength of vortex increased with the diameter ratio Especially. at time of 3.19s. the very weak recirculating flow was developed at the left upper sites of the aneurysm. The maximum values of the wall shear stress increased in Proportion to the diameter ratio. However. the Position of a maximum wall shear stress was the distal end of the aneurysm(z = 35mm) regardless of the diameter ratios.

A Study of Pull-out strength increasement by root of grasses (식물뿌리에 의한 인발력 증가에 관한 연구)

  • Kim, Taegyun;Chae, Soo Kwon;Chun, Seung Hoon;Jeong, Jae Cheol
    • Journal of Wetlands Research
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    • v.14 no.2
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    • pp.199-210
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    • 2012
  • In this study, a pull-out strength increasement of grasses was tested in field and the relationship between a weight of root and pull-out strength was established. The tested grasses were commmon reed, reed and sedge which were cultivated by mat-type like turf and used for revegetation of bank. The shear stress of soil at a section can be discribed as a function of root area and pull-out strength, therefore the result of this study will be used as a foundational data for reinforcing the shear stress of the revegetated bank. The heavier weight of root increased, the stronger shear stress was for all grasses. But the relationship between the weight and the shear stress were different by a kind of grass. The difference between common reed, sedge and reed is due to difference of growth and propagation. A reed propagates by subterranean stem and a root weight and pull-out strength are linearly increased by root and growth of subterranean stem.

Wall Shear Stress and Flow Patterns in Unruptured and Ruptured Anterior Communicating Artery Aneurysms Using Computational Fluid Dynamics

  • Lee, Ui Yun;Jung, Jinmu;Kwak, Hyo Sung;Lee, Dong Hwan;Chung, Gyung Ho;Park, Jung Soo;Koh, Eun Jeong
    • Journal of Korean Neurosurgical Society
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    • v.61 no.6
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    • pp.689-699
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    • 2018
  • Objective : The goal of this study was to compare several parameters, including wall shear stress (WSS) and flow pattern, between unruptured and ruptured anterior communicating artery (ACoA) aneurysms using patient-specific aneurysm geometry. Methods : In total, 18 unruptured and 24 ruptured aneurysms were analyzed using computational fluid dynamics (CFD) models. Minimal, average, and maximal wall shear stress were calculated based on CFD simulations. Aneurysm height, ostium diameter, aspect ratio, and area of aneurysm were measured. Aneurysms were classified according to flow complexity (simple or complex) and inflow jet (concentrated or diffused). Statistical analyses were performed to ascertain differences between the aneurysm groups. Results : Average wall shear stress of the ruptured group was greater than that of the unruptured group (9.42% for aneurysm and 10.38% for ostium). The average area of ruptured aneurysms was 31.22% larger than unruptured aneurysms. Simple flow was observed in 14 of 18 (78%) unruptured aneurysms, while all ruptured aneurysms had complex flow (p<0.001). Ruptured aneurysms were more likely to have a concentrated inflow jet (63%), while unruptured aneurysms predominantly had a diffused inflow jet (83%, p=0.004). Conclusion : Ruptured aneurysms tended to have a larger geometric size and greater WSS compared to unruptured aneurysms, but the difference was not statistically significant. Flow complexity and inflow jet were significantly different between unruptured and ruptured ACoA aneurysms.

A Two Mobilized-Plane Model for Soil Liquefaction Analysis (액상화해석을 위한 두 개의 활성면을 가진 구성모델)

  • Park, Sung-Sik
    • Journal of the Korean Geotechnical Society
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    • v.22 no.10
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    • pp.173-181
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    • 2006
  • A Two Mobilized-Plane Model is proposed for monotonic and cyclic soil response including liquefaction. This model is based on two mobilized planes: a plane of maximum shear stress, which rotates, and a horizontal plane which is spatially fixed. By controlling two mobilized planes, the model can simulate the principal stress rotation effect associated with simple shear from different $K_0$ states. The proposed model gives a similar skeleton behaviour for soils having the same mean stress, regardless of $K_0$ conditions as observed in laboratory tests. The soil skeleton behaviour observed in cyclic drained simple shear tests, including compaction during unloading and dilation at large strain is captured in the model. Undrained monotonic and cyclic response is predicted by imposing the volumetric constraint of the water on the drained or skeleton behaviour. This constitutive model is incorporated into the dynamic coupled stress-flow finite difference program of FLAC (Fast Lagrangian Analysis of Continua). The model was first calibrated with drained simple shear tests on Fraser River sand, and verified by comparing predicted and measured undrained behaviour of Fraser River sand using the same input parameters.

Characteristics of Shear Strength for an Unsaturated Soil with the Matric Suction (흡인력에 따른 불포화토의 전단강도 특성)

  • Song, Chang-Seob;Choi, Dook-Ho
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.10 no.1
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    • pp.82-90
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    • 2007
  • In order to analyse the strength problems for an unsaturated soil, it is required to examine closely the characteristics of the parameters of shear strength which was changed with the metric suction and void ratio. To this ends, a triaxial compression test was conducted on the three samples-granular soil, cohesive soil and silty soil. The specimen was made by pressing the static pressure on the mold filled soil and was controled the void ratio with the different compaction ratio. And the test was performed by using the modified apparatus of the triaxial compression tester. The range of matric suction was 0-90 kPa.The measured results for the deviator stress and parameters of shear strength were analysed with the void ratio and the compaction ratio, and they were examined closely the characteristics of the strength for an unsaturated soil.

Shear Strength of Fine Sand -Curvature Characteristics of Failure Envelope and Stress Parameter- (가는 모래의 전단강도 -파괴포락선의 곡률특성과 상태정수에 관하여-)

  • Yoon, Yeo Won
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.14 no.1
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    • pp.195-202
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    • 1994
  • In this research, a lot of triaxial test results (CID) are analyzed to study the curvature characteristics of failure envelope of sand and parametric relationship between shear strength and state parameter by Been and Jefferies. In the conventional triaxial tests, correction for the change of sectional area of a sample and for membrane influence is essential especially in order to determine critical state (or steady state) condition more correctly. Based on the test results, a model to express the shear strength of fine sand as a function of density and stress level is presented and curvature characteristics of shear failure envelope and parametric relationship between state parameter and shear strength parameters are evaluated.

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Shear Angle Variation Depending on Chip-Tool Friction in Orthogonal Cutting (二次元 切削時 칩-工具 마찰상태에 따른 剪斷角 변화)

  • 이영문;송지복
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.2
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    • pp.252-261
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    • 1988
  • Through the careful interpretation of the results of the cutting tests carried out in this study, it is found that under the cutting conditions when the internal shear of the chips take place the cutting can be treated essentially as a steady state problem. A new shear angle equation has been developed employing the conditions of force and moment equilibrium about the tool edge and the stress distribution model suggested by Zorev.The equation contains the chip-tool contact length C and stress distribution index n as important parameters.

Variations in Ductility of Shear Wall with Length of Boundary Confinement (단부 횡보강영역에 따른 전단벽 연성도의 변화)

  • 강수민;오재은;박홍근
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.05a
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    • pp.853-858
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    • 2001
  • Experimental studies were peformed to investigate variations in ductility of shear wall with length of boundary confinement. Eight specimens containg different lengths of confinment zone, which model compressive zone in plastic regions of shear walls, were tested against eccentric vetical load. Stress-strain model for confined concrete was used to predict strength and ductility of the specimens, which was compared to the test results. The results obtained show that failure of the compressive zone occurs in a brittle manner when the stress of unconfined zone softened after the ultimate strength were reached. To enhance the ductility of shear walls with concentrated confinement zone such as barbell-type walls, the ultimate strength of the confinement zone needs to be increased, and for shear walls with distributed confinement zone the length of the confinement zone needs to be extended.

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Experimental Study for the Long-term Behavior of Shear Wall (전단벽의 장기거동 특성에 관한 실험적 연구)

  • 권승희;김진근
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.11a
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    • pp.197-202
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    • 2001
  • It is necessary to Investigate long-term behavior of vertical members such as column and shear wall because the long-term behavior induces the serviceability problem of reinforce-concrete structures. However, the long-term behavior on shear wall has not been fully studied. Experimental works are performed to understand the time dependent behavior of shear wall, especially the effect of loading area in this research. Three different types of cross sections are adopted, i.e., 10$\times$10 cm, 10$\times$30 cm, and 10$\times$50 cm with the same loading area of 10$\times$10 cm. The creep strains were different from point to point in the section of the shear wall specimen because of the nonlinear stress distribution. The effect of the nonlinear stress distribution was larger in the specimen with the larger width.

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