• Steel and Composite Structures
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• 제23권6호
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• pp.737-746
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• 2017

In this paper the influence of aspect ratio, height ratio and material angle on static and free vibration behaviour of orthotropic elliptic paraboloid shells is studied by using a four-node hybrid stress finite element. The formulation of the element is based on Hellinger-Reissner variational principle. The element is developed by combining a hybrid plane stress element and a hybrid plate element. A parametric study is carried out for static and free vibration response of orthotropic elliptic paraboloid shells with respect to displacements, internal forces, fundamental frequencies and mode shapes by varying the aspect and height ratios, and material angle.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 추계학술대회논문집
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• pp.228-230
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• 2009

The moment-of-fluid (MOF) method is a new volume-tracking method that accurately treats evolving material interfaces. Based on the moment data (volume and centroid) for each material, the material interfaces are reconstructed with second-order spatial accuracy in a strictly conservative manner. The MOF method is coupled with a stabilized finite element incompressible Navier-Stokes solver for two fluids, namely water and air. The effectiveness of the MOF method is demonstrated with a free-surface dam-break problem.

• 한국자동차공학회논문집
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• 제4권2호
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• pp.183-188
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• 1996

The compressive stress-strain response of Low Density Polyurethane foam material is modeled using the finite element method. A constitutive equation which include experimental constants based on quasi-static and dynamic uniaxial compression test is proposed. Impact test with different impactor masses and velocities are performed to verify the proposed model. The comparison between impact test and finite element analysis shows good agreements.

• Advances in nano research
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• 제13권4호
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• pp.351-368
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• 2022

Recently, promising structural technologies like multi-function, ultra-load bearing capacity and tailored structures have been put up for discussions. Finite Element (FE) modelling is probably the best-known option capable of treating these superior properties and multi-domain behavior structures. However, advanced materials such as Functionally Graded Material (FGM) and nanocomposites suffer from problems resulting from variable material properties, reinforcement aggregation and mesh generation. Motivated by these factors, this research proposes a unified shape function for FGM, nanocomposites, graded nanocomposites, in addition to traditional isotropic and orthotropic structural materials. It depends not only on element length but also on the beam's material properties and geometric characteristics. The systematic mathematical theory and FE formulations are based on the Timoshenko beam theory for beam structure. Furthermore, the introduced element achieves C1 degree of continuity. The model is proved to be convergent and free-off shear locking. Moreover, numerical results for static and free vibration analysis support the model accuracy and capabilities by validation with different references. The proposed technique overcomes the issue of continuous properties modelling of these promising materials without discarding older ones. Therefore, introduced benchmark improvements on the FE old concept could be extended to help the development of new software features to confront the rapid progress of structural materials.

• 한국농공학회논문집
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• 제54권4호
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• pp.39-46
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• 2012

The objectives of this study is intended to analyze stresses using the boundary element method and probability analysis for agricultural structure. Loads and material properties are an important factor when analyzing the structure. Until now, designing structure, loads and material properties are applied deterministic value. However, load and material properties involve uncertainties due to those change probabilistic and deterministic methods could not consider uncertainties. To solve these problems, the reliability analysis based on probability properties scheme was developed. Reliability analysis is easy to approach to analysis frame structure, however it has limitation when solving plane stress strain problems a kind of agricultural structures. The BEM (Boundary Element Method) is able to analysis plane strain problems by boundary conditions. Thus, this study applied boundary element method to analysis plane strain problem, load and material properties as a probabilistic value to calculate the analytical model using Monte Carlo simulations were developed.

• 대한기계학회논문집A
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• 제25권11호
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• pp.1697-1704
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• 2001

A finite element model for polarization switching in electro-mechanically coupled materials is proposed and applied to predict the switching behavior of a two-dimensional ferroelectric ceramic. A complicated micro-structure existing in the material is modeled as il continuum body and a simple 3 node triangle finite element with nodal displacement and voltage degrees of freedom is used for a finite element analysis. The elements use nonlinear constitutive equations, switching criterion and kinetic relation, fur representation of material response at strong electric and stress fields. The polarization state of the material is represented by internal variables in each element, which are updated at each simulation step based on the proposed constitutive equations. The model reproduces strain and electric displacement hysteresis loops observed in the material.

• 한국해양공학회지
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• 제34권6호
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• pp.481-488
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• 2020

Composite materialsuch as glass-fiber reinforced plastic and carbon-fiber reinforced plastic (CFRP) shows anisotropic property and have been widely used for structural members and outfitings of ships. The structural safety of composite structures has been generally evaluated via finite element analysis. This paper presents a technique for updating the finite element model of anisotropic beams or plates via natural frequencies. The finite element model updates involved a compensation process of anisotropic material properties, such as the elastic and shear moduli of orthotropic structural members. The technique adopted was based on a discrete genetic algorithm, which is an optimization technique. The cost function was adopted to assess the optimization problem, which consisted of the calculated and referenced low-order natural frequencies for the target structure. The optimization process was implemented with MATLAB, which includes the finite element updates and the corresponding natural frequency calculations with MSC/NASTRAN. Material properties of a virtual cantilevered orthotropic beam were estimated to verify the presented method and the results obtained were compared with the reference values. Furthermore, the technique was applied to a cantilevered CFRP beam to successfully estimate the unknown material properties.

• 대한기계학회논문집A
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• 제26권12호
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• pp.2492-2502
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• 2002

A rubber-like material model is generally characterized by hyperelasticity and formulated by a total stress-total strain relationship because the material shows nonlinear elastic behaviour under large deformation. In this study, a pressure potential obtained by a separately interpolated pressure is introduced to the non-linear finite element formulation incorporating with incompressible or almost incompressible condition of the material. The present formulation is somewhat different from the general formulation using the pressure computed in the displacement field. A non-linear finite element analysis program is developed for the plane strain and the axisymmetric contact problems of a rubber-like material. Various examples with rubber material are analyzed for its verification. The results about deformed shapes and stress distributions thought to be meaningful in comparison with a commercial program, MARC.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 가을 학술발표회논문집
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• pp.217-221
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• 2000

Nonlinear stress analysis of nuclear containment building wall element is carried out using microscopic material model. The present study mainly focuses on the finite element analysis of the nuclear containment building wall element under biaxial tensile stresses and it evaluates the perfomance of adopted microscopic material model in the membrane energy dominant situation. From the numerical analysis, the adopted material model peforms well and has a good agreement with experiment result. Finally, the result of present study can be severed as a benchmark test when concrete material model is in need of evaluation.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 가을 학술발표회 논문집
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• pp.59-66
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• 2001

The post-peak analysis of concrete structures is carried out using a nine-node Reissner-Mindlin(RM) shell element which is formulated by using degenerated solid concepts. In order to avoid element deficiencies inherited in the standard RM shell element, assumed strains are adopted in the present shell element. A microscopic material model is adopted to represent the inelastic characteristic of concrete material. In particular, a concrete softening model is introduced to this material model. The arc-length control method is used to trace the post-peak behaviour of concrete structures. From the numerical test of the single-edge-notched beam, the present shell element shows a reasonable agreement with experimental data.