• Title/Summary/Keyword: solid elements

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Automation of Analysis for Stress Intensity Factor of 3-D Cracks (3차원 균열의 응력확대계수에 대한 해석의 자동화)

  • 이준성
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.04a
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    • pp.496-500
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    • 1997
  • This paper describes an automated system for analyzing the stress intensity factors(SIFs) of three-dimensional (3D) cracks. A geometry model, i.e.a solid containing one or several 3D cracks is defined. Several distributions of local node density are chosen, and then automatically superposed on one another over the geometry model by using the fuzzy knowledge processing. Nodes are generated by the bucketing method, and ten-noded quadratic tetrahedral solid elements are generated by the Delauuay triangulation techniques. The singular elements such that the mid-point nodes near crack fornt are shifted at the quarter-points are automatically placed along the 3D crack front. THe complete finite element (FE) model generated, i.e the mesh with material properties and boundary conditions is given to one of the commercial FE codes, and a stress analysis is performed. The SIFs are calculated using the displacement extrapolation method. To demonstrate practical performance of the present system, a semi- elliptical surface crack in a plate subjected to tension is solved.

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Analysis of Three-Dimensional Cracks in Inhomogeneous Materials Using Fuzzy Theory

  • Lee, Yang-Chang;Lee, Joon-Seong
    • International Journal of Fuzzy Logic and Intelligent Systems
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    • v.5 no.2
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    • pp.119-123
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    • 2005
  • This paper describes a fuzzy-based system for analyzing the stress intensity factors (SIFs) of three-dimensional (3D) cracks. 3D finite element method(FEM) was used to obtain the SIF for subsurface cracks and surface cracks existing in inhomogeneous materials. A geometry model, i.e. a solid containing one or several 3D cracks is defined. Several distributions of local node density are chosen, and then automatically superposed on one another over the geometry model by using the fuzzy theory. Nodes are generated by the bucketing method, and ten-noded quadratic tetrahedral solid elements are generated by the Delaunay triangulation techniques. The singular elements such that the mid-point nodes near crack front are shifted at the quarter-points, and these are automatically placed along the 3D crack front. The complete FE model is generated, and a stress analysis is performed. The SIFs are calculated using the displacement extrapolation method. The results were compared with those surface cracks in homogeneous materials. Also, this system is applied to analyze cladding effect of surface cracks in inhomogeneous materials.

Static and Dynamic Analyses of Bending Problems Using 3-Dimensional 10-Node Equivalent Element (3차원 10절점-상당요소에 의한 굽힘문제의 정적.동적해석)

  • 권영두;윤태혁
    • Computational Structural Engineering
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    • v.10 no.4
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    • pp.117-130
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    • 1997
  • In this paper, a modified 10-node equivalent solid element(MQM10 element), which has smallest degrees of freedom among 3-dimensional solid elements accounting bending deformation as well as extensional and shear deformations of isotropic plates, is proposed. The proposed MQM10 element exhibits stiffer bending stiffness due to the reduction of degrees of freedom from 20-node element or Q11 element. As an effective way to correct the relative stiffness stiffening phenomenon, the modification equation of Gauss sampling points is proposed. The quantity of modification is a function of Poisson's ratio. The effectiveness of MQM10 element is tested by applying it to several examples. It is noted that the results of static and free vibration analysis of isotropic plates using MQM10 elements show a good agreement with those using 20-node element.

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Analysis of Wave Responses in Harbor Using Boundary Damper Techniques (경계 damper를 이용한 항만 파낭응답 해석)

  • 정원무;박우선
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.5 no.1
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    • pp.39-44
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    • 1993
  • This paper is concerned with developing a finite element model incorporating boundary damper techniques which is applicable to the prediction of wave agitations in harbors. Based on the linear wave theory, a mild-slope equation is used. In order to consider the wave energy dissipations on solid boundary. the partial reflecting boundary condition is introduced. Radiating boundary condition is modeled by using tile second-order boundary damper developed by Bando et al. (1984). The near field region in harbor is discretized using 8-noded isoparametric elements, the boundary conditions are presented using 3-noded line elements. The numerical model is applied to a fully open rectangular harbor to prove its validity. Numerical experiments are also performed to investigate the effects of the wave reflection coefficients of solid boundary and the types of the dampers.

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The vessel collision load on bridge with fender system (방호공을 고려한 선박의 충돌하중)

  • 이계희;고재용;이성로
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2004.04a
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    • pp.193-200
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    • 2004
  • In this study, the impact load on bridge by vessel collision in consideration of fender system is evaluated by numerical method. The bow of object vessel(DWT5000) is standardized, and modeled by shell elements. The main body of objective vessel is modeled by beam elements that present mass distribution and stiffness of vessel. The buoyancy effect of vessel is considered as linear spring. The two types of fender systems, such as steel and rubber are analyzed in this study. In steel fender system, the steel plates that absorb collision energy by its collapse are modeled by shell element with stiffener. The steel is material modeled elastic-plastic material. In the rubber fender system, the rubber material is modeled hyper-elastic material and the main body of fender is modeled by solid elements. The global impact responses of vessel and fender system are evaluated by explicit dynamic scheme. The results show that the magnitude of vessel collision force are depended on the material behavior of fender system. Also the values of collision load are conservative compare to the those of design codes.

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Stresses analyses of shell structure with large holes

  • Tian, Zongshu;Liu, Jinsong
    • Structural Engineering and Mechanics
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    • v.6 no.8
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    • pp.883-899
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    • 1998
  • The strength, deformation and buckling of a large engineering structure consisting of four ellipsoidal shells, two cylindrical shells with stiffening ribs and large holes, one conical shell and three pairs of large flanges under external pressure, self weight and heat sinks have been analysed by using two kinds of five different finite elements - four assumed displacement finite elements (shell element with curved surfaces, axisymmetric conical shell element with variable thickness, three dimensional eccentric beam element, axisymmetric solid revolutionary element) and an assumed stress hybrid element (a 3-dimensional special element developed by authors). The compatibility between different elements is enforced. The strength analyses of the top cover and the main vessel are described in the paper.

Aggregation multigrid method for schur complement system in FE analysis of continuum elements

  • Ko, Jin-Hwan;Lee, Byung Chai
    • Structural Engineering and Mechanics
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    • v.30 no.4
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    • pp.467-480
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    • 2008
  • An aggregation multigrid method (AMM) is a leading iterative solver in solid mechanics. Recently, AMM is applied for solving Schur Complement system in the FE analysis of shell structures. In this work, an extended application of AMM for solving Schur Complement system in the FE analysis of continuum elements is presented. Further, the performance of the proposed AMM in multiple load cases, which is a challenging problem for an iterative solver, is studied. The proposed method is developed by combining the substructuring and the multigrid methods. The substructuring method avoids factorizing the full-size matrix of an original system and the multigrid method gives near-optimal convergence. This method is demonstrated for the FE analysis of several elastostatic problems. The numerical results show better performance by the proposed method as compared to the preconditioned conjugate gradient method. The smaller computational cost for the iterative procedure of the proposed method gives a good alternative to a direct solver in large systems with multiple load cases.

Infinite Elements for the Evaluation of Wave Forces (파랑하중 산정을 위한 무한요소)

  • 박우선;윤정방;편종근
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.1 no.1
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    • pp.71-80
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    • 1989
  • In this paper, the concept of the infinite element is applied to the linear wave diffraction and radiation problems. The hydrodynamic pressure forces are assumed to be inertially dominated, and viscous effects are neglected. The near field region surrounding the solid body is modelled using the conventional finite elements, and the far field region is represented using the infinite elements .In order to represent the scattered wave potentials in the far field region more accurately, the infinite elements are developed using special shape functions derived from the asymptotic expressions for the analytical eigenseries solution of the scattered waves. The system matrices of the infinite elements are constructed by performing the integration in the infinite direction analytically to achieve computational efficiency. Numerical analyses are carried out for vertical axisymmetric bodies to validate the infinite elements developed here. Comparisons with the results by other available numerical solution methods show that the present method using the infinite elements gives fairly good results. Numerical experiments are per-formed to determine the suitable location of the infinite elements and the appropriate size of the finite elements which directly affect accuracy and efficiency of the solution.

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Simplified Finite Element Model of an Anchor Bolt Inserted Through Concretes Considering Clamping Forces (체결력을 고려한 콘크리트 삽입 앵커볼트의 간편 유한요소 모델)

  • Noh, Myung Hyun;Lee, Sang Youl;Park, Kyu Sik
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.26 no.4
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    • pp.293-300
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    • 2013
  • In this study we proposed a simplified finite element model of anchor bolt system inserted through concrete structures considering clamping forces. The three different finite element types using LS-DYNA are applied for numerical efficiency of the anchor bolt modeling. Combined beam and solid elements are used to reflect the tension state at internal part of anchor bolt due to torques. The clamping forces due to torques are considered by introducing a compression for a nut plane modeled by beam elements. The numerical examples show good agreement with different element types. Parametric studies are focused on the various effects of different element types on the induced axial and shear forces of anchor bolts considering clamping forces.

Characteristics of the Bottom Ash in Municipal Solid Waste Incineration Ash (생활 폐기물 소각재 중 바닥재의 特性)

  • 안지환;한기천;김형석
    • Resources Recycling
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    • v.10 no.4
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    • pp.48-57
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    • 2001
  • The main consistent materials and main elements of the bottom ash in municipal solid waste incineration ash according to particle size were investigated and the environmental hazards were considered by investigating the content of dioxin and heavy metals in bottom ash and the concentration of heavy metals in its leachate. The main materials of bottom ash are glasses, ceramics, scraps of iron. As the particle size increases, their percentage weight also increases and their percentage weight was over 70% in 4 mesh~25 mm particle size fraction. The main elements of bottom ash are CaO, $SiO_2$, $Fe_2$$O_3$,$ A1_2$$O_3$and the content of CaO decreases and the content of $SiO_2$increases as particle size increases. The heavy metals accumulate in small particle size fraction. The concentration of heavy metals in each leachate by domestic leaching test is almost similar. As the aging period is prolonged, pH of bottom ash lowers gradually and the leached concentration of Cu and Pb diminishes.

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