• Tunnel and Underground Space
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• v.10 no.2
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• pp.173-179
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• 2000

The influence of the plastic flow rules on the elasto-plastic behaviour of a discrete joint element was investigated by performing the numerical direct shear tests under both constant normal displacement and normal displacement conditions. The finite interface elements obeying Plesha’s joint constitutive law was used to allow the relative motion of the rock blocks on the joint surface. Realistic results were obtained in the tests adopting the non-associated flow rule, while the associated flow rule overestimated the joint dilation. To overcome the computational drawbacks coming from the non-symmetric element stiffness matrix in the conventional non-associated plasticity, the symmetric formulation of the tangential stiffness matrix for a non-associated joint element was proposed. The symmetric elasto-plastic matrix it derived by assuming an imaginary equivalent joint with associated flow rule which shows the same plastic response as that of original Joint with non-associated flow rule. The validity of the formulation was confirmed through the numerical direct shear tests under constant normal stress condition.

• Transactions of Materials Processing
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• v.10 no.5
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• pp.396-401
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• 2001

The concept of the mixtures can be used not only in the composites but also in the materials with precipitates and matrix. In this investigation, the finite element method of axisymmetric unit cell models and the rule of mixtures of the Voigt and the Reuss models are used to analyze the overall mechanical response of composites with homogeneously distributed particles. The calculations have been cameo out by taking the materials as i) hardening and ii) perfect plastic materials. The Plastic properties are predicted for various volume fractions of the soft and hard particles. The computational results are compared with the results of the rule of mixtures. It is found that the plastic flow curves agree well with the Voigt model when the volume fraction of the particles is high. On the other hand, the calculated flow curves exist between the Voigt model and the Reuss model when the volume fraction of the particles is low.

• Journal of Ocean Engineering and Technology
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• v.14 no.2
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• pp.70-75
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• 2000

In this paper a new constitutive model for ductile materials was proposed. This model can describe the material degradation due to the evolution of isotropic damage during elasto-platic deformation. The plastic flow rule was derived under the framework of thermodynamic approach of continuum damage mechanics(CDM) in which plastic strain hardening parameters and isotropic damage were taken as thermodynamic state variables. And the process to determine material constants for constitutive model using an experimental data was presented.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.2
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• pp.193-200
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• 2008

Cohesive and frictional materials such as concrete and soil are pressure dependent. In general, failure criterion for such materials inclined with respect to positive hydrostatic axis in Haigh-Westergaard stress space. Consequently, inelastic volumetric strain always positive with associated flow rule. In this study, to overcome this shortcoming, non-associated flow rule which controls volumetric component of plastic flow is adopted. Numerical analysis based on a constitutive model using nonuniform hardening plasticity with five parameter failure criterion and non-associated flow rule has conducted to predict concrete behavior under multi-axial stress state and verified with experimental result.

• Structural Engineering and Mechanics
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• v.58 no.4
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• pp.719-729
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• 2016

The main objective of the present paper is to study the effect of the yield criterion on the magnitude of the strain rate and plastic work rate intensity factors in axisymmetric flow of isotropic incompressible rigid perfectly plastic material by means of a problem permitting a closed-form solution. The boundary value problem consisting of the axisymmetric deformation of a plastic tube is solved. The outer surface of the tube contracts. The radius of the inner surface does not change. The material of the tube obeys quite a general yield criterion and its associated flow rule. The maximum friction law is assumed at the inner surface of the tube. Therefore, the velocity field is singular near this surface. In particular, the strain rate and plastic work rate intensity factors are derived from the solution. It is shown that the strain rate intensity factor does not depend on the yield criterion but the plastic work rate intensity factor does.

• Geotechnical Engineering
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• v.12 no.2
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• pp.95-106
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• 1996

In this study, a constitutive model which can describe the anisotropic and plastic behaviors of natural cohesive soils, was developed based on anisotropic bounding surface theory. The model was fomulated by the concepts of the improved anisotropic bounding surface function, nonassociated flow rule with new plastic potential function, anisotropic hardening rule, and new mapping rule governing the plastic behavior inside bounding sutraface. Comparing with the results of Ku consolidation and triaxial shearing tests, the predictions by the proposed model agree quite well with real soil responses.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.431-436
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• 2001

Lateral confining effect due to the existence of the shear reinforcements in R.C. beam is investigate in a numerical way. For the purpose, a three dimensional constitutive model of concrete is developed based on the elasto-plasticity using non-associated plastic flow rule to control the excessive inelastic dilatancy. The plastic flow direction is determined based on the associated plastic flow direction in a way to adjust the directional angle between the two normal vector components along the hydrostatic and deviatoric axis in a meridian plane in which the loading function prescribed. The current formulation is combined with the four parameter elasto-plastic triaxial concrete model recently developed. The resulting elasto-plastic triaxial concrete model predicts the fundamental behaviors of concrete under different confining levels and the 4-points flexural test of a beam with shear reinforcements, compares with the experimental results.

• Structural Engineering and Mechanics
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• v.4 no.1
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• pp.9-23
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• 1996

The behaviour of elasto-plastic planar arches subjected to dynamic loads in presented. The governing equations are formulated through the dynamic equations and compatibility conditions. The latter is established by applying the generalized conjugate segment analogy. Bending moments at the nodes and axial forces in the members are considered as primary variables in the elastic regime. They are supplemented by the rotations at the nodes and dislocations in the elements when plastic hinges occur. Newmark-${\beta}$ method is adopted in the time marching process. The interaction diagram of each element is treated as the yield surface for the element and the associated flow rule is enforced as plastic flow occurs. The method provides good prediction of dynamic response of elasto-plastic arches while requiring small core storage and short computer time.

• Magazine of the Korean Society of Agricultural Engineers
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• v.35 no.4
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• pp.106-118
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• 1993

The purpose of this study is to develop a multireservoir water balance model which may be used to evaluate rural water demands such as agricultural water, domestic water, industrial water and livestock water and to determine effective storage of reservoir. The model was verified to compare the observed reservoir release data with the simulated reservoir release data of the existing Munsan and Dongbu reservoirs located in the Gisan rural district for 3 years('87~'89). For model application, the effective storages of existing reservoirs(Munsan & Dongbu) were evaluated for 10-year frequency drought and that of newly planned reservoirs(Kumbok & Kudong) were determined for 10-year frequency drought. In addition, the behavior of effective storages for existing reservoirs were analyzed in the case of introducing new reservoirs in the existing system.

• Geomechanics and Engineering
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• v.17 no.4
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• pp.385-392
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• 2019

The present fractional-order plasticity models for granular soil are mainly established under the triaxial compression condition, due to its difficult in analytically solving the fractional differentiation of the third stress invariant, e.g., Lode's angle. To solve this problem, a three dimensional fractional-order elastoplastic model based on the transformed stress method, which does not rely on the analytical solution of the Lode's angle, is proposed. A nonassociated plastic flow rule is derived by conducting the fractional derivative of the yielding function with respect to the stress tensor in the transformed stress space. All the model parameters can be easily determined by using laboratory test. The performance of this 3D model is then verified by simulating multi series of true triaxial test results of rockfill.