• Structural Engineering and Mechanics
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• 제18권5호
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• pp.691-707
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• 2004

This paper presents the micro-mechanical modeling for predicting concrete behavior under compressive loading. The model is able to represent the heterogeneities in the microstructure up to three phases, i.e., aggregate particles, matrix and interfaces. The smeared crack concept based on non-linear fracture mechanics is implemented in order to formulate the constitutive relation for each component. The splitting tensile strength is considered as a fracture criterion for cracking in micro-level. The finite element method is employed to simulate the model based on plane stress condition by using quadratic triangular elements. The validation of the model is verified by comparing with the experimental results. The influence of tensile strength from both aggregate and matrix phases on the concrete compressive strength is demonstrated. In addition, a guideline on selecting appropriate tensile strength for each phase to obtain specified concrete compressive strength is also presented.

• Journal of applied mathematics & informatics
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• 제20권1_2호
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• pp.345-354
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• 2006

In this paper first, we find a canonical symmetrical trapezoidal(triangular) for the solution of the fuzzy linear system $A\tilde{x}=\tilde{b}$, where the elements in A and $\tilde{b}$ are crisp and arbitrary fuzzy numbers, respectively. Then, a model for fuzzy linear programming problem with fuzzy variables (FLPFV), in which, the right hand side of constraints are arbitrary numbers, and coefficients of the objective function and constraint matrix are regarded as crisp numbers, is discussed. A numerical procedure for calculating a canonical symmetrical trapezoidal representation for the solution of fuzzy linear system and the optimal solution of FLPFV, (if there exist) is proposed. Several examples illustrate these ideas.

• 한국전산유체공학회지
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• 제2권2호
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• pp.97-103
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• 1997

A modified Delaunay triangulation technique is tested for complicated computational domain. While a simple geometry. both in topology and geometry, has been well discretized into triangular elements, a complex geometry having difficulty in triangulation had to be divided into small sub-domains of simpler shape. The present study presents a modified Delaunay triangulation method based on the data structure of geometric modeller. This approach greatly enhances the reliability of triangulation, especially in complicated computational domain. We have shown that efficiency of Delaunay triangulation can be much improved by using both the GUI (Graphic User Interface) and OOP (Object-Oriented Programming).

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.289-294
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• 2010

Numerical stud of an oscillating body in incompressible fluid is performed. Stabilized finite element method comprising of Streamline-Upwind/Petrov-Galerkin (SUPG) and Pressure-Stabilizing/Petrov-Galerkin (PSPG) formulations of linear triangular elements was employed to solve 2D incompressible Navier-Stokes equations whereas the motion of the body was considered by incorporating the arbitrary Langrangian-Eulerian(ALE) formulation. An algebraic moving mesh strategy is utilized for obtaining body conforming mesh deformation at each time step. Two tests cases, namely motion of a circular cylinder and of an airfoil in incompressible flow were analyzed. The model is first validated against the stationary cases and then the capability to handle moving boundaries is demonstrated.

• 대한기계학회논문집
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• 제19권5호
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• pp.1211-1219
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• 1995

An upper bound elemental technique (UBET) program has been developed to analyze forging load, die-cavity filling and effective strain distribution for flash and flashless forgings. The simulation for flash and flashless forgings are applied axisy mmetric and plane-strain closed-die forging with rib-web type cavity. Inverse triangular and inverse trapezoidal elements are used to analyze flashless forging. The analysis is described for merit of flashless precision forging. Experiments have been carried out with pure plasticine billets at room temperature. Theoretical predictions of the forging load and the flow pattern are in good agreement with experimental results.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.837-841
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• 1997

An upper bound elemental technique(UBET) program has been developed to analyze forging load, die-cavity filling and optimum kinematically admissible velocity fields for flashless forging. The simulation for flashless forgings are applied plane and axisymmetric closed-die forging with rib-web type cavity. The kinematically admissible velocity fields for inverse triangular and inverse trapezoidal elements, are used to analyze flashless forging. Experiments have been carried out with pure plasticine billets at room temperature. Theoretical predictions of the forging load in plane-strain and axisymmetric forging are in good agreement with experimental results.

• 대한기계학회논문집A
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• 제27권10호
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• pp.1762-1771
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• 2003

In part of mechanical design analysis, quadrilateral mesh is usually used because it provides less approximate errors than triangular mesh. Over the decades, Paving method has been considered as the most robust method among existing automatic quadrilateral element mesh generation methods. However, it also has some problems such as unpredictable node projection and relatively large element generation. In this study, the aforementioned problems are corrected by updating the Paving method. In so doing, a part of node projection process is modified by classifying nodes based on the interior angles. The closure check process is also modified by adding more nodes while generating elements. The result shows well shaped element distribution in the final mesh without any aforementioned problems.

• Journal of Advanced Marine Engineering and Technology
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• 제23권3호
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• pp.379-388
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• 1999

Au upper bound elemental technique(UBET) program has been developed to analyze forging load die-cavity filling and optimum kinematically admissible velocity fields for flashless forging. The simulation for flashless forgings are applied plane-strain and axisymmetric closed-die forging with rib-web type cavity. The kinematically admissible velocity fields for inverse triangular and inverse trapezoidal elements are used to analyze flashless forging,. Experiments have been carried out with pure plasticine billets at room temperature. Theoretical predictions of the forging load in plane-strain and axisymmetric forging are in good agreement with experimental results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.402-407
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• 2008

We suggest a linear elastic flat shell element based on the HT(hybrid Trefftz) method. We formulate the membrane part of the proposed element as an HT plane element with the drilling DOF. For the bending part, we developed a thick HT plate element that can represent transverse shear deformations accurately. Because we derive both the membrane and the bending parts consistently using the HT functional, we can easily construct the triangular and the quadrilateral elements in a unified way. In addition, warping of quadrilateral element is compensated by force and moment equilibrium equations. We evaluate the performance of the new element in terms of accuracy and convergence.

• 소성∙가공
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• 제4권3호
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• pp.222-232
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• 1995

The planar anisotripic FEM analysis for predicting earing profiles and draw-in amounts in the deep-drawing process is introduced. An implicit, incremental, updated Lagrangian formulation with a rigid-viscoplastic constitutive equation is employed. Contact and friction are considered through the mesh-based unit vector and normal contact pressure. The consistent full set of governing relations, which is comprising euilbrium and geometric constraint equations, is appropriately linearized. Barlat's strain-rate potential is employed, whose in-plane anisotropic properties are taken into account with anisotropic coefficients and potential parameters. The linear triangular membrane elements are used for depicting the formed sheet. In the numerical simulations of deep drawing processes of a flat-top cylindrical cup for 2090-T3 aluminum alloy sheet show good agreement with experiments, although some discrepancies were observed in the directional trend of cup height and thickness strains.