• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.207-214
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• 2002

A constitutive model was implemented in ABAQUS code, The constitutive equation can model the behavior for overall range of strain level from small to large deformation, which is based on anisotropic hardening rule and total stress concept. The formulation includes (1) finite strain formulation on the basis of Jaumann rate, (2) implicit stress integration and (3) consistent tangent moduli. Therefore, the mathematical background was established in order that large deformation analysis can be performed accurately and efficiently with the anisotropic constitutive model. Companion paper(Jeon et al., 2002) will contain the large deformation analysis results of examples with the constitutive model using ABAQUS.

• Journal of the Korean Society for Advanced Composite Structures
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• v.5 no.4
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• pp.11-17
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• 2014

A progressive failure analysis procedure for composite laminates is completed in here. An anisotropic plastic constitutive model for fiber-reinforced composite material is implemented into computer program for a predictive analysis procedure of composite laminates. Also, in order to describe material behavior beyond the initial yield, the anisotropic work-hardening model and subsequent yield surface are implemented into a computer code, which is Predictive Analysis for Composite Structures (PACS). The accuracy and efficiency of the anisotropic plastic constitutive model and the computer program PACS are verified by solving a number of various fiber-reinforced composite laminates with and without geometric discontinuity. The comparisons of the numerical results to the experimental and other numerical results available in the literature indicate the validity and efficiency of the developed model.

• Fibers and Polymers
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• v.7 no.1
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• pp.42-50
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• 2006

In this paper, elasto-plastic constitutive equations for highly anisotropic and asymmetric materials are developed and their numerical implementation is presented. Some engineering materials such as fiber reinforced composites show different material behavior in the different material directions (anisotropy) as well as in tension and compression (asymmetry). Although these materials have mostly been analyzed using the anisotropic elastic constitutive equations, the necessity of consideration of plastic properties has been frequently reported in the previous works. In order to include both the anisotropic and asymmetric properties of composite materials, the Drucker-Prager yield criterion is modified by adding anisotropic parameters and initial components of translation. The implementation procedure for the developed theory and algorithms is presented based on the implicit finite element scheme. The measured data from the previous work are used to validate the present constitutive equations.

• Journal of the Korean Society for Advanced Composite Structures
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• v.5 no.4
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• pp.1-10
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• 2014

A progressive failure analysis procedure for composite laminates is developed in here and in the companion paper. An anisotropic plastic constitutive model for fiber-reinforced composite material, is developed, which is simple and efficient to be implemented into computer program for a predictive analysis procedure of composites. In current development of the constitutive model, an incremental elastic-plastic constitutive model is adopted to represent progressively the nonlinear material behavior of composite materials until a material failure is predicted. An anisotropic initial yield criterion is established that includes the effects of different yield strengths in each material direction, and between tension and compression. Anisotropic work-hardening model and subsequent yield surface are developed to describe material behavior beyond the initial yield under the general loading condition. The current model is implemented into a computer code, which is Predictive Analysis for Composite Structures (PACS), and is presented in the companion paper. The accuracy and efficiency of the anisotropic plastic constitutive model are verified by solving a number of various fiber-reinforced composite laminates with and without geometric discontinuity. The comparisons of the numerical results to the experimental and other numerical results available in the literature indicate the validity and efficiency of the developed model.

• Geomechanics and Engineering
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• v.25 no.4
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• pp.303-315
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• 2021

A rigorous and generic similarity solution is developed for assessment of the undrained expansion responses of a cylindrical cavity expansion in K₀-consolidated anisotropic soils. A K₀-consolidated anisotropic modified Cam-clay (K₀-AMCC) model that can represent the initial stress anisotropy and the effects of stress-induced anisotropy is used to model the soil behaviors during cavity expansion. All the seven basic unknowns, the three stress components, the pore water pressure, the particle velocity, the specific volume and the hardening parameter, are reduced to the functions of a dimensionless radial coordinate and are taken as coupled variables to formulate the problem. The governing equations are formulated by making use of the equilibrium equation, the constitutive equation, the consistency condition, the continuity condition and the undrained condition, which are then solved as an initial value problem. The proposed rigorous similarity solution is compared with some well-documented rigorous solutions to validate the solution and to highlight the special expansion responses in anisotropic soils. The results reveal that the present solution can yield more predictions for cavity expansion problems in soils with initial anisotropic stresses.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.58-61
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• 1998

Anisotropy is closely related to the formability of sheet metal and should be considered carefully for more realistic analysis of actual sheet metal forming operations. In order to better describe anisotropic plastic properties of aluminum alloy sheets, a planar anisotropic yield function which accounts for the anisotropy of uniaxial yield stresses and strain rate ratios simultaneously was proposed recently[1]. This yield function was used in the finite element simulations of cup drawing tests for an aluminum alloy 2008-T4. Isotropic hardening with a fixed initial back stress based on experimental tensile and compressive test results was assumed in the simulation. The computation results were in very good agreement with the experimental results. It was shown that the initial back stress as well as the yield surface shape have a large influence on the prediction of the cup height profile.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.254-257
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• 2007

In this paper, anisotropic tensile properties of the AZ31B Mg-alloy sheet are obtained with the tensile test at elevated temperatures. Change of microscopic structures and the hardness is inspected after the solution heat treatment process in order to confirm the micro-structural stability of the used sheet metal. Results obtained from tensile tests show that it is very difficult to apply the conventional modeling scheme with the assumption of strain hardening to the forming analysis of the magnesium alloy sheet which shows the strain-softening behavior at the elevated temperature.

• Geomechanics and Engineering
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• v.11 no.3
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• pp.325-343
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• 2016

A total stress-based bounding surface model is developed to predict the undrained behaviour of saturated soft clays under cyclic loads based on the anisotropic hardening modulus field and bounding-surface theories. A new hardening rule is developed based on a new interpolation function of the hardening modulus that has simple mathematic expression and fewer model parameters. The evolution of hardening modulus field is described in the deviatoric stress space. It is assumed that the stress reverse points are the mapping centre points and the mapping centre moves with the variation of loading and unloading paths to describe the cyclic stress-strain hysteresis curve. In addition, by introducing a model parameter that reflects the accumulation rate and level of shear strain to the interpolation function, the cyclic shakedown and failure behaviour of soil elements with different combinations of initial and cyclic stresses can be captured. The methods to determine the model parameters using cyclic triaxial compression tests are also studied. Finally, the cyclic triaxial extension and torsional shear tests are performed. By comparing the predictions with the test results, the model can be used to describe undrained cyclic stress-strain responses of elements with different stress states for the tested clays.

• Computers and Concrete
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• v.12 no.4
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• pp.565-583
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• 2013

Existing numerical models for strain-hardening cement-based composites (SHCC) are short of providing sufficiently accurate solutions to the failure patterns of coupling beams of different designs. The objective of this study is to develop an effective model that is capable of simulating the nonlinear behavior of SHCC coupling beams subjected to cyclic loading. The beam model proposed in this study is a macro-scale plane stress model. The effects of cracks on the macro-scale behavior of SHCC coupling beams are smeared in an anisotropic model. In particular, the influence of the defined crack orientations on the simulation accuracy is explored. Extensive experimental data from coupling beams with different failure patterns are employed to evaluate the validity of the proposed SHCC coupling beam models. The results show that the use of the suggested shear stiffness retention factor for damaged SHCC coupling beams is able to effectively enhance the simulation accuracy, especially for shear-critical SHCC coupling beams. In addition, the definition of crack orientation for damaged coupling beams is found to be a critical factor influencing the simulation accuracy.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.148-151
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• 2003

In order to achieve reliable but cost-effective crash simulations of stamped parts, sheet forming process effects were incorporated in simulations using the ideal forming theory mixed with the 3D hybrid membrane/shell method, while the subsequent crash simulations were carried out using a dynamic explicit finite element code. Example solutions performed for forming and crash simulations of I- and S-shaped rails verified that the proposed approach is cost-effective without sacrificing accuracy. The method required a significantly small amount of additional computation time, less than 3% for the specific examples, to incorporate sheet forming effects to crash simulations. As for the constitutive equation, the combined isotropic-kinematic hardening law and the non-quadratic anisotropic yield stress potential as well as its conjugate strain-rate potential were used to describe the anisotropy of AA6114-T4 aluminum alloy sheets.