• Title, Summary, Keyword: Rate dependent

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Application of Field test to the Rate-dependent relation in Constitutive model (변형률속도-의존 구성모델의 현장 시험 적용)

  • Song, Young-Sun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.9 no.2
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    • pp.470-474
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    • 2008
  • The rate-dependent constitutive model and the rate-independent model were analyzed for comparing with the piezocone penetration test and dissipation test. The mathematical expressions of the rate-dependent constitutive model were introduced, and the predictions using the both models were compared with the experimental results of in-situ field test. The rate-dependent model analysis gave better results than the rate-independent model analysis, that is appreciated since the process of the piezocone penetration and dissipation depends on the strain rate. Therefore, it is recommended the concept of the rate-dependent model for the prediction of soil behaviors using the field penetration test.

Measurement of the Shear Rate-Dependent Thermal Conductivity for Suspension with Microparticles (미립자를 포함한 현탁액의 전단율에 의존적인 열전도율 측정)

  • Lee, Sung-Hyuk;Shin, Sehyun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.8
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    • pp.1141-1151
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    • 1998
  • An effective thermal conductivity measurement for suspensions of microparticles in oil mixture is conducted in order to evaluate the shear rate-dependence of the thermal conductivity of suspensions. Measurements are made for rotating Couette flows between two concentric cylinders. The rotating outer cylinder is immersed into a constant temperature water bath while the stationary inner cylinder is subject to a uniform heat fluff. Test fluids are made to be homogeneous suspensions, in which neutrally buoyant microparticles ($d=25{\sim}300{\mu}m$) are uniformly dispersed. The present measurements show strong shear-rate dependent thermal conductivities for the suspensions, which are higher than those at zero shear rate. The shear rate dependent thermal conductivity increases with the particle size and volume concentration.4 new model for shear rate-dependent thermal conductivity of microparticle suspensions is proposed; the correlation covers from zero shear rate value to asymptotic plateau value at moderately high shear rates.

Strain Rate-dependent Model for Anisotropic Cohesive Soils (비등방성 점성토에 있어서 변형률속도 의존적 구성모델)

  • Kim, Dae-Kyu
    • Journal of the Korean Geotechnical Society
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    • v.19 no.3
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    • pp.15-22
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    • 2003
  • The appropriate description of the stress-anisotropy and time-dependent behavior of cohesive soils is very important in representing the real soil behavior. In this study, two constitutive relations have been incorporated based on the generalized viscous theory: one is the plastic constitutive relation adopted to capture the stress-anisotropy with a few model parameters; the other is the rate-dependent constitutive relation adopted to describe the strain rate-dependent behavior, an important time-dependent behavior in cohesive soils. The incorporated and proposed constitutive model has relatively a few model parameters and their values need not to be re-evaluated at different strain rates. The proposed model has been verified and investigated with the anisotropic triaxial test results obtained by using the artificial homogeneous specimens.

A Rate-Dependent Elastic Plastic Constitutive Equation in Finite Deformation Based on a Slip Model (슬립모델을 이용한 변형률의존 유한변형 탄소성재료의 구성방정식 개발)

  • 남용윤;김사수;이상갑
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.181-188
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    • 1994
  • Generally, the structural material shows rate dependent behaviors, which require to constitute different strain-stress relations according to strain rates. Conventional rate- independent constitutive equations used in general purpose finite analysis programs are inadequate for dynamic finite strain problems. In this paper, a rate dependent constitutive equation for elastic-plastic material was developed. The plastic stretch rate was modeled based on slip model with dislocation velocity and density so that there is no yielding condition, and no loading conditions. Non-linear hardening rule was also introduced for finite strain. Material constants of present constitutive equation were determined by experimental data of mild steel. The constitutive equation was applied to uniaxile tension. It was appeared that the present constitutive equation well simulates rate dependent behaviors of mild steel.

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Studies on the Dissolution of the Famotidine Matrix Tablets using Polymer (고분자를 이용한 파모티딘 매트릭스 정의 용출에 관한 연구)

  • Choi, G. H.;Han, S.S.;Sohn, D.H.;Kim, J.B.
    • Journal of Pharmaceutical Investigation
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    • v.24 no.3
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    • pp.139-144
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    • 1994
  • The effect of some formulation variables on the release rate of famotidine, a $H_2$ receptor antagonist, from cellulose matrices containing hydroxypropylcellulose (HPC) in different ratios and types was investigated. The effects of tablet shape and compression pressure on dissolution rate of famotidine were studied. And the effect of the pH of dissolution media was also studied. Increase in the ratio of polymer to drug decreased the release rate of famotidine. Increase of the polymer viscosity also decreased the release rate. The release rate of famotidine was dependent on the pH of dissolution media. The release rate of drug was not much dependent on the compression pressure but dependent on the tablet shape and/or surface area. Consequently, the release rate of famotidine can be modified by changing the HPC contents, types of polymers with different viscosity grades or using appropriate fillers.

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The Rate Dependent Deformation Behavior of AISI Type 304 Stainless Steel at Room Temperature (304 스테인리스강의 점소성 특성에 관한 연구)

  • Ho, Kwang-Soo
    • Transactions of Materials Processing
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    • v.16 no.2
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    • pp.101-106
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    • 2007
  • Uniaxial displacement controlled tests were performed on annealed Type 304 stainless steel at room temperature. A servo-controlled testing machine and strain measurement on the gage length were employed to measure the response to a given input. The test results exhibit that the flow stress increases nonlinearly with the strain rate and the relaxed stress at the end of the relaxation periods depends strongly on the strain rate preceding the relaxation test. The rate-dependent inelastic deformation behavior is simulated using a new unified viscoplasticity model that has the rate-dependent format of nonlinear kinematic hardening rule, which plays a key role in modeling the rate dependence of relaxation behavior. The model does not employ yield or loading/unloading criteria and consists of a flow law and the evolution laws of two tensor and one scalar-valued state variables.

Modified Integration Algorithm on the Strain-Space for Rate and Temperature Dependent Elasto-Plastic Constitutive model (변형률 공간에서 변형률속도 및 온도를 고려한 구성방정식의 개선된 적분방법)

  • Cho, S.S.;Huh, H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.272-275
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    • 2007
  • This paper is concerned with modified integration algorithm on the strain-space for rate and temperature dependent elasto-plastic constitutive relations in order to obtain more accurate results in numerical implementation. The proposed algorithm is integrated analytically using integration by part and chain rule and then is applied to the 2-stage Lobatto IIIA with second-order accuracy. It has advantage that is able to consider the convective stress rates on the yield surface of the strain-space. Also this paper is carried out the iteration procedure using the Newton-Raphson method to enforce consistency at the end of the step. And the performance of the proposed algorithm for rate and temperature dependent constitutive relation is illustrated by means of analysis of adiabatic shear bands.

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A Condition Based Maintenance Model for Systems with Weibull Distributed Deterioration (와이블 분포로 열화하는 시스템의 상태에 기초한 정비모형)

  • Kong, Myung Bock;Park, Il Gwang
    • Journal of Korean Institute of Industrial Engineers
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    • v.33 no.1
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    • pp.70-75
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    • 2007
  • This paper discusses condition based preventive replacement for deteriorating systems. The system continuouslydeteriorates in time and fails at any deterioration level which is always monitored, It is replaced at failure or atsome deteriorated level preventively before failure. The deterioration process is represented by a Weibulldistribution with a time-linear scale parameter. The cost rate function is formed considering replacement costand opportunity loss cost and deterioration dependent failure distribution, If the system has an increasingdeterioration dependent failure rate, the optimal deterioration level for preventive replacement can be determinedfrom minimizing the cost rate. An illustrative example is given for a Weibull deterioration dependent failuredistribution.

A Rate Dependent Plasticity Model under Cyclic Loading of Metals (주기하중을 받고 있는 금속의 시간의존적 소성 모델 비교)

  • Kim, Dongkeon;Dargush, Gary F.
    • Journal of the Korean Society for Advanced Composite Structures
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    • v.4 no.1
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    • pp.25-32
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    • 2013
  • In real world applications, the response of structures may be dependent on the rate of loading and thus can be affected by transient loading, especially when the rate of loading is significant. In such situations, the rate of loading may become a major issue to understand structures during earthquake excitation or under blast or high velocity impact. In some cases, the rate effect on structures under strong earthquake excitation cannot be ignored when attempting to understand inelastic behavior of structures. Many researchers developed the constitutive theories in cyclic plasticity and viscoplasticity. In this study, numerical simulation by cyclic visocoplasticity models is introduced and analyzed. Finally, the analytical results are compared with experimental results as a means to evaluate and verify the model.

A Study on the Long and Short Term Effect of Exchange Rate about the Import of Korea's Fisheries during Feely Flexible Exchange Rate System Period - Focus on Main Fisheries Imported from China - (자유변동환율체제하의 수산물 수입에 대한 환율의 장단기 영향분석 - 중국으로부터의 주요 수산물 수입품목을 중심으로 -)

  • Kim, Woo-Kyung;Kim, Ki-Soo
    • The Journal of Fisheries Business Administration
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    • v.40 no.3
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    • pp.169-187
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    • 2009
  • This study analyzes the long and short term effect of exchange rate on the import of Korea's fisheries focussed on main fisheries imported from China. The estimation models consist of the following contents. The first model consists of one dependent variable-import quantity of fisheries imported from China(${IMQ_t}^{CHO}$) and three independent variables-${RP_t}^{CHO}$, $EXC_t$ and $GDP_t$. The second one-one dependent variable-import quantity of fisheries imported from China(${JMQ_t}^{NAG})$ and three independent variables-${RP_t}^{NAG}$, $EX_t$ and $GDP_t$. the third one-one dependent variable-import quantity of fisheries imported from China(${IMQ_t}^{AH}$) and three independent variables-${RP_t}^{AH}$, $EX_t$ and $GDP_t$. the forth one-one dependent variable-import quantity of fisheries imported from China(${IMQ_t}^{KO}$) and three independent variables-${RP_t}^{KO)$, $EX_t$ and $GDP_t$. the last one is made up of one dependent variable-import quantity of fisheries imported from China(${IMQ_t}^{GAL}$) and three independent variables-, ${RP_t}^{GAL}$, $EX_t$ and $GDP_t$. and. The estimation results show that exchange rate of the independent variables are statistically significant in only the first model. The figure is elastic. Especially, the effect of exchange rate in first model is grater than that of the. However, the effect of exchange rate, one of independent variables in the ECM, is not statistically significant.

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