• Title, Summary, Keyword: dilatant

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Flow Mechanism of Dilatant Systems. (Ⅰ) Starch Suspension in Water

  • Bang, Jeong-Hwang;Kim, Eung-Ryul;Hahn Sang-Joon;Ree, Tai-kyue
    • Bulletin of the Korean Chemical Society
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    • v.4 no.5
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    • pp.212-217
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    • 1983
  • Depending on the range of shear rates, temperatures and concentrations, the potato starch suspension in water behaves as a typical dilatant system. The flow curves of the suspension at various concentrations and temperatures were obtained by using a Couette type rotational viscometer. The flow mechanism of the suspension is explained by a structure model of starch granules in the suspension. Based on the experimental results, a general flow equation for the dilatant system is proposed. By analyzing the temperature dependency of the relaxation time, the activation enthalpy and activation entropy for flow in the starch-water suspension were calculated, the former being about 10 kcal/mol.

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Undrained Behavior on Saemangeum Dredged Sands (새만금 준설모래의 비배수 거동)

  • Jeong, Sang-Guk;Kang, Kwon-Soo;Yang, Jae-Hyouk
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.6 no.1
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    • pp.193-203
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    • 2002
  • The results of an experimental study on Saemangeum dredged sands are presented. Undrained triaxial compression tests were performed with there different initial relative densities, namely 18, 34, and 50%, intend to evaluate undrained Behavior. All undrained triaxial compression tests were performed under static loading conditions. Undrained triaxial compression tests were exhibited complete static liquefaction, zero effective confining pressure and zero stress difference at lower confining pressures. As confining pressures were increased, the effective stress paths indicated increasing resistance to static liquefaction by showing increasing dilatant tendencies. The fines and larger particles create a particle structure with high compressibility at lower confining pressure. The effect of increasing relative density was to increase the resistance of the sand against static liquefaction by making the sand more dilatant.

FLUID-GRANULE MIXED FLOIW DOWNSTREAM OF SCOUR HOLE AT OUTLET OF HYDRAULIC STRUCTURE

  • Kim, Jin-Hong;Shim, Myung-Pil;Kim, Kyung-Sub
    • Water Engineering Research
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    • v.3 no.3
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    • pp.155-162
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    • 2002
  • This study presents the theoretical approach for volume concentration, velocity profile, and granular discharge on the fluid-granule mixed flow downstream of the scour hole at the outlet of the hydraulic structure. Concept of dilatant model was applied for the stress-strain relationships of fluid-granule mixed flow since the flow downstream of the scour hole corresponds to debris flow, where momentum transfers through particle collisions. Mathematical formulations were derived using momentum equation and stress-strain relation of the fluid-granule mixture. Velocity profile under the assumption of uniform concentration over flowing layer showed the downward convex type. Deposition angle of downstream hump was found to be a function of an upstream slope angle, a dynamic friction angle and a volume concentration irrespective of flow itself, Granular discharge and the overflow depth were obtained with given values of inflow rates. Experimental results showed relatively good agreements with theoretical ones.

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Rheological Properties of Gamma Irradiated Arrowroot (Pueraria thunbergina. B) Starch (감마선 조사 칡 전분 gel의 rheology 특성)

  • Kuhm, Herena;Lim, Jin-Hyuk;Lee, Eun-Ju;Chang, Kyu-Seob
    • Korean Journal of Food Science and Technology
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    • v.36 no.5
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    • pp.740-743
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    • 2004
  • Rheological properties of gamma-irradiated arrowroot starch was examined to utilize as fundamental research data far processing. Irradiated arrowroot starch solutions (3, 4, 5, 6%) were gelatinized at $95^{\circ}C$ for 40 min, and its flow properties measured using rheometer at $30^{\circ}C$ and 10 to 200 rpm rotation rate. Rheological parameters of irradiated arrowroot starch gelatinized solution were calculated using Herschel-Bulkley equation. Gelatinized arrowroot starch solutions irradiated at $0^{\circ}C$ and 5kGy showed pseudoplastic fluid behavior, while those irradiated at 10, 20, and 30kGy were the dilatant with ${\tau}_y=0$ (yield stress).

Rheological Properties of Cement Pastes Containing Metakaoline (메타카올린을 혼합한 시멘트 페이스트의 유동특성)

  • 송종택;최해영
    • Journal of the Korean Ceramic Society
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    • v.40 no.12
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    • pp.1229-1234
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    • 2003
  • The utilization of metakaoline as a mineral admixture for cement has received considerable attention in recent years. This paper investigates the rheological properties of cement pastes containing metakaoline in view of fluidity. The rheology of the paste is assessed by using a BROOKFIELD RVDV II + viscometer (SC4-21, 29) having cylindrical spindle. The results show the fluidity of cement pastes with metakaoline is increased by increasing W/S ratio and the dosage of superplastcizer. And also cement pastes with metakaoline as a partial replacement of cement show a dilatant behavior. Dilatancy is heavily influenced by W/S ratio and by the amount of metakaoline. However the thixotropy of the pastes is increased by silica fume.

A Study on Distinct Element Modelling of Dilatant Rock Joints (팽창성 암석절리의 개별요소 모델링에 관한 연구)

  • 장석부;문현구
    • Tunnel and Underground Space
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    • v.5 no.1
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    • pp.1-10
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    • 1995
  • The behavior of a jointed rock mass depends mainly on the geometrical and mechanical properties of joints. The failure mode of a rock mass and kinematics of rock blocks are governed by the orientation, spacing, and persistence of joints. The mechanical properties such as dilation angle, shear strength, maximum closure, strength of asperities and friction coeffiient play important roles on the stability and deformation of the rock mass. The normal and shear behaviour of a joint are coupled due to dilation, and the joint deformation depends also on the boundary conditions such as stiffness conditons. In this paper, the joint constitutive law including the dilatant behaviour of a joint is numerically modelled using the edge-to-edge contact logic in distinct element method. Also, presented is the method to quantify the input parameters used in the joint law. The results from uniaxial compression and direct shear tests using the numeical model of the single joint were compared to the analytic results from them. The boundary effect on the behaviour of a joint is verified by comparing the results of direct shear test under constant stress boundary condition with those under constant stiffness boundary condition. The numerical model developed is applied to a complex jointed rock mass to examine its performance and to evaluate the effect of joint dilation on tunnel stability.

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Quality Change of High Fructose Corn Syrups During Storage (과당시럽의 저장중 품질 변화)

  • Nahmgoong, Bae;Shin, Dong-Bin;Jeong, Mun-Cheol;Kim, Oui-Woung;Kim, Byeong-Sam
    • Applied Biological Chemistry
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    • v.38 no.3
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    • pp.232-238
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    • 1995
  • Quality changes of high fructose corn syrups (HFCS) were investigated during storage at $-5{\sim}60^{\circ}C$. Color properties such as spectrophotometric properties, HMF and Hunter color value increased continuously during storage period. And the change was most evident as storage temperature and fructose content were elevated. High fructose corn syrups all showed flow behaviors as dilatant fluid and their viscosities increased slightly during storage. Content of fructose decreased, while glucose, maltose and oligosaccharide contents increased during storage. Especially, crystallization of what was observed below $13^{\circ}C$ during storage.

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Effect of Phosphate on Rheological Properties of Rice Starch Suspension (인산염이 쌀전분 현탁액의 리올로지에 미치는 영향)

  • Kim, Il-Hwang;Kim, Sung-Kon;Lee, Shin-Young
    • Korean Journal of Food Science and Technology
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    • v.19 no.3
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    • pp.239-244
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    • 1987
  • Rheological properties of 5% starch suspension were investigated using a capillarity tube viscometer. Nonglutinous and glutinous rice starch suspensions at $30-60^{\circ}C$, and $30-55^{\circ}C$, respectively, had no yield stress and showed dilatant flow behavior in the absence or presence of phosphate. However, flow behavior of nonglutinuous starches at $65^{\circ}C$ and glutinous starch at $60^{\circ}C$ was pseudopalastic. Flow activation energies for rice starch suspensions were 0.88-1.45 kcal/mole at $30-50^{\circ}C$ and about 45-73 kcal/mole $60-65^{\circ}C$. Flow activation energy in the presence of phosphate was 90-182 kcal/mole at $60-65^{\circ}C$. Akibare starch had the highest activation energy, and glutinous starch the lowest.

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Non-Newtonian Flow Mechanism for Thixotropic and Dilatant Flow Units of Sodium bis-(2-ethylhexyl)sulfosuccinate-water Micelles (Sodium bis-(2-ethylhexyl)sulfosuccinate-water 미셀의 틱소트로 피와 다일레턴시 유동단위에 대한 비뉴톤 유동메카니즘)

  • Kim, Nam Jeong
    • Journal of the Korean Applied Science and Technology
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    • v.33 no.3
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    • pp.540-548
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    • 2016
  • The non-Newtonian flow curves of sodium bis-(2-ethylhexyl)sulfosuccinate-water lamellar liquid crystals were obtained in various concentrations and temperatures by using a cone-plate rheometer. By applying non-Newtonian flow equation to the flow curves for AOT-water lamellar liquid crystal samples, the rheological parameters were obtained. Particular attention is given to the hysteresis loop detected when the liquid crystal samples are shear under increasing-decreasing shear stress modes which result in thixotropic and dilatant behavior. Sodium bis-(2-ethylhexyl)sulfosuccinate-water lamellar liquid crystals behave as weak gels when they are subjected to shear flow, but when the applied stress surpasses the yield stress, they exhibit non-linear viscoelasticity. Upon decreasing shear rate, the dispersion still preserves much of its structure and consequently its shear stress remains higher than the values measured in the increasing shear rate mode.

Damage Evolution and Texture Development During Plate Rolling (판재 압연에서의 결함성장과 집합조직의 발전)

  • 이용신
    • Transactions of Materials Processing
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    • v.9 no.4
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    • pp.372-378
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    • 2000
  • A process model including the effects of both the texture development and ductile damage evolution In plane strain rolling is presented. In this process model, anisotropy from deformation texture and deterioration of mechanical properties due to growth of micro voids are directly coupled Into the virtual work expressions for the momentum and mass balances. Special treatments in obtaining the initial values of field variables in the nonlinear simultaneous equations for the anisotropic, dilatant viscoplastic deformation are also given. Mutual effects of the texture development and damage evolution during plate rolling are carefully examined in terms of the distribution of strain components, accumulated damage, R-value as well as yield surfaces.

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