• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.235-242
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• 2003

The solids and the fluids in porous media have a relative velocity to each other. Due to physically and chemically different material properties and their relative velocity, the behavior of saturated porous media is extremely complicated. Thus, in order to describe and clarify the deformation behavior of saturated porous media, constitutive models for deformation of porous media coupling several effects such as flow of the fluids or thermodynanical change need to be developed in frame of Arbitrary Lagrangian Eulerian (ALE) description. The aim of ALE formulations is to maximize the advantages of Lagrangian and Eulerian elements, and to minimize the disadvantages. Therefore, this method is appropriate for the analysis of porous media that are considered for the behavior of the solids and the fluids. In this work, governing equations of porous media based on ALE description are obtained from governing equations in frame of updated Lagrangian description. Then, weak forms of these equations are derived using arbitrary weighting functions.

• Computers and Concrete
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• v.5 no.3
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• pp.243-260
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• 2008

The present article summarises the fundamental characteristics of concrete behaviour which underlie the formulation of an engineering finite element model capable of realistically predicting the behaviour of (plain or reinforced) concrete structural forms in a wide range of problems ranging from static to impact loading without the need of any kind of re-calibration. The already published evidence supporting the proposed formulation is complemented by four additional typical case studies presented herein; for each case, a comparative study is carried out between numerical predictions and the experimental data which reveals good agreement. Such evidence validates the material characteristics upon which the FE model's formulation is based and provides an alternative explanation regarding the behaviour of structural concrete and how it should be modelled which contradicts the presently (widely) accepted assumptions adopted in the majority of FE models used to predict the behaviour of concrete.

• The Journal of Korean Medical History
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• v.22 no.2
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• pp.67-98
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• 2009

This paper initiates an effort to look at "South Korean" medicine as perhaps distinct from "Korean" medicine, focusing specifically on the possibility of offering a post-colonial history of medicine. As such, the paper looks at the formation of the NMC (National Medical Center) in Seoul in 1958 (1958-1963, 1963-1968, 1968-1971) by a consortium of European actors--Denmark, Sweden, and Norway--invested in developing new forms of international assistance after the Korean War. Rather than take a firm stance, the paper ultimately suggests that the role of these actors in formative South Korean institutions was constitutive, and perhaps requires much more examination in the future.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.375-382
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• 2003

Porous media consist of physically and chemically different materials and have an extremely complicated behavior due to the different material properties of each of its constituents. In addition, the internal structure of porous media has generally a complex geometry that makes the description of its mechanical behavior quite complex. Thus, in order to describe and clarify the deformation behavior of porous media, constitutive models for deformation of porous media coupling several effects such as flow of fluids of thermodynamical change need to be developed in frame of Arbitrary Lagrangian Eulerian (ALE) description. The aim of ALE formulations is to maximize the advantages of Lagrangian and Eulerian methods, and to minimize the disadvantages. Therefore, this method is appropriate for the analysis of porous media that are considered for the behavior of solids and fluids. First of all, governing equations for saturated porous media based on ALE description are derived. Then, weak forms of these equations are obtained in order to implement numerical method using finite element method. Finally, Petrov-Galerkin method Is applied to develop finite element formulation.

• Coupled systems mechanics
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• v.6 no.4
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• pp.465-485
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• 2017

In this paper, free vibration and static response of magneto-electro-elastic (MEE) beams has been investigated. To this end, a 3D finite element formulation has been derived by minimization the total potential energy and linear constitutive equation. The coupling between elastic, electric and magnetic fields can have a significant influence on the stiffness and in turn on the static behaviour of MEE beam. Further, different Barium Titanate ($BaTiO_3$) and Cobalt Ferric oxide ($CoFe_2O_4$) volume fractions results in indifferent coupled response. Therefore, through the numerical examples the influence of volume fractions and boundary conditions on the natural frequencies of MEE beam is illustrated. The study is extended to evaluate the static response of MEE beam under various forms of mechanical loading. It is seen from the numerical evaluation that the volume fractions, loading and boundary conditions have a significant effect on the structural behaviour of MEE structures. The observations made here may serve as benchmark solutions in the optimum design of MEE structures.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.264-265
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• 2006

The directions of further developments in the modeling of sintering are pointed out, including multi-scale modeling of sintering, on-line sintering damage criteria, particle agglomeration, sintering with phase transformations. A true multi-scale approach is applied for the development of a new meso-macro methodology for modeling of sintering. The developed macroscopic level computational framework envelopes the mesoscopic simulators. No closed forms of constitutive relationships are assumed for the parameters of the material. The model framework is able to predict the final dimensions of the sintered specimen on a global scale and identify the granular structure in any localized area for prediction of the material properties.

• Journal of the Korean Geotechnical Society
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• v.15 no.3
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• pp.71-81
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• 1999

A study on the undrained behavior of isotropically consolidated clay-sand mixtures was carried out using the automated triaxial testing apparatus. Overconsolidated ratio, effective mean pressure and clay content( up to 20% bentonite) were the factors varied in the experimental investigation. Undrained behavior(strength and pore water pressure generation during shear in triaxial loading) depends upon overconsolidation ratio, confining pressure and clay content. Significant changes in undrained compression characteristics occurred at around 20% of clay contents in the sand. The test results were analyzed and their behaviors were interpreted within the framework of plasticity constitutive model for clay-sand mixtures. Possible physical bases for the proposed forms are discussed. Validation of the applied model using the laboratory results is also given.

• Journal of Industrial Technology
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• v.24 no.B
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• pp.95-105
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• 2004

This paper is an experimental and numerical research works about the effects of the b earing capacity of sloped rubble mound on the density of rubble mound and the position of footing. Centrifuge model tests were performed to investigate the bearing capacity of rubble m ound by changing the density of rubble mound and the location of loading in forms of s trip loading to simulate the caisson. Materials of rubble mound used in the model tests were crushed rocks having similar value of uniformity coefficient to the value in field. Two different relative densities of 80% and 90% were prepared during tests. The dimens ions of centrifuge model were trapezoidal shape of model mound having the bottom wid th of mound, 30cm and height of mound, 10cm. Gravity level applied during the centrif uge test was 50G. Surcharge loading in the forms of strip loading was applied on the t op of the sloped model mound. Tests were carried out by changing the position of loadi ng. The rigid model footing was located in the center of top of the model rubble mound and the edge of model footing was at the crest of mound. Test results were analyzed by using the limit equilibrium methods proposed by Meyer hof(1957) and Bowles(1982) and the numerical approach with FLAC being available com mercially software. For the numerical estimations with FLAC, the rubble mound was si mulated with the constitutive relationship of Mohr-Coulomb elasto-plastic model.

• Interaction and multiscale mechanics
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• v.1 no.2
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• pp.279-301
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• 2008

This paper develops a 3D homogenization based continuum damage mechanics (HCDM) model for fiber reinforced composites undergoing micromechanical damage under monotonic and cyclic loading. Micromechanical damage in a representative volume element (RVE) of the material occurs by fiber-matrix interfacial debonding, which is incorporated in the model through a hysteretic bilinear cohesive zone model. The proposed model expresses a damage evolution surface in the strain space in the principal damage coordinate system or PDCS. PDCS enables the model to account for the effect of non-proportional load history. The loading/unloading criterion during cyclic loading is based on the scalar product of the strain increment and the normal to the damage surface in strain space. The material constitutive law involves a fourth order orthotropic tensor with stiffness characterized as a macroscopic internal variable. Three dimensional damage in composites is accounted for through functional forms of the fourth order damage tensor in terms of components of macroscopic strain and elastic stiffness tensors. The HCDM model parameters are calibrated from homogenization of micromechanical solutions of the RVE for a few representative strain histories. The proposed model is validated by comparing results of the HCDM model with pure micromechanical analysis results followed by homogenization. Finally, the potential of HCDM model as a design tool is demonstrated through macro-micro analysis of monotonic and cyclic damage progression in composite structures.

• Smart Structures and Systems
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• v.25 no.2
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• pp.219-228
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• 2020

This work presents a modified continuum model to explore and investigate static and vibration behaviors of perforated piezoelectric NEMS structure. The perforated nanostructure is modeled as a thin perforated nanobeam element with Euler-Bernoulli kinematic assumptions. A size scale effect is considered by included a nonlocal constitutive equation of Eringen in differential form. Modifications of geometrical parameters of perforated nanobeams are presented in simplified forms. To satisfy the Maxwell's equation, the distribution of electric potential for the piezoelectric nanobeam model is assumed to be varied as a combination of a cosine and linear functions. Hamilton's principle is exploited to develop mathematical governing equations. Modified numerical finite model is adopted to solve the equation of motion and equilibrium equation. The proposed model is validated with previous respectable work. Numerical investigations are presented to illustrate effects of the number of perforated holes, perforation size, nonlocal parameter, boundary conditions, and external electric voltage on the electro-mechanical behaviors of piezoelectric nanobeams.