• Title/Summary/Keyword: Hexahedral Element

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Three-Dimensional Finite Element Analysis for Hollow Section Extrusion of the Underframe of a Railroad Vehicle Using Mismatching Refinement with Domain Decomposition (영역분할에 의한 격자세분화기법을 사용한 철도차량 마루부재 압출공정의 3차원 유한요소해석)

  • Park, K.;Lee, Y.K.;Yang, D.Y.;Lee, D.H.
    • Transactions of Materials Processing
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    • v.9 no.4
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    • pp.362-371
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    • 2000
  • In order to reduce weight of a high-speed railroad vehicle, the main body has been manufactured by hollow section extrusion using aluminum alloys. A porthole die has utilized for the hollow section extrusion process, which causes complicated die geometry and flow characteristics. Design of porthole die is very difficult due to such a complexity. The three-dimensional finite element analysis for hollow section is also an arduous job from the viewpoint of appropriate mesh construction and tremendous computation time. In the present work, mismatching refinement, an efficient domain decomposition method with different mesh density for each subdomain, is implemented for the analysis of the hollow section extrusion process. In addition, a modified grid-based approach with the surface element layer is utilized lot three-dimensional mesh generation of a complicated shape with hexahedral elements. The effects of porthole design are discussed through the simulation for extrusion of an underframe part of a railroad vehicle. An experiment has also been carried out for the comparison. Comparing the velocity distribution at the outlet with the thickness variation of the extruded part, it is concluded that the analysis results can provide reliable measures whether the die design is acceptable to obtain uniform part thickness. The analysis results are then successfully reflected on the industrial porthole die design.

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Concrete fragmentation modeling using coupled finite element - meshfree formulations

  • Wu, Youcai;Choi, Hyung-Jin;Crawford, John E.
    • Interaction and multiscale mechanics
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    • v.6 no.2
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    • pp.173-195
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    • 2013
  • Meshfree methods are known to have the capability to overcome the strict regularization requirements and numerical instabilities that encumber the finite element method (FEM) in large deformation problems. They are also more naturally suited for problems involving material perforation and fragmentation. To take advantage of the high efficiency of FEM and high accuracy of meshfree methods, a coupled finite element (FE) and reproducing kernel (RK, one of the meshfree approximations) formulation is described in this paper. The coupling of FE and RK approximation is implemented in an evolutionary fashion, where the extent and location of the evolution is dependent on a triggering criteria provided by the material constitutive laws. To enhance computational efficiency, Gauss quadrature is applied to integrate both FE and RK domains so that no state variable transfer is required when mesh conversion is performed. To control the hourglassing that might occur with 1-point integrated hexahedral grids, viscous type hourglass control is implemented. Meanwhile, the FEM version of the K&C concrete (KCC) model was modified to make it applicable in both FE and RK formulations. Results using this code and the KCC model are shown for the modeling of concrete responses under quasi-static, blast and impact loadings. These analyses demonstrate that fragmentation phenomena of the sort commonly observed under blast and impact loadings of concrete structures was able to be realistically captured by the coupled formulation.

Periodic Mesh Generation for Composite Structures using Polyhedral Finite Elements (다면체 유한요소를 이용한 복합재 구조의 주기 격자망 생성)

  • Sohn, Dongwoo;Park, Jong Youn;Cho, Young-Sam;Lim, Jae Hyuk;Lee, Haengsoo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.27 no.4
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    • pp.239-245
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    • 2014
  • Finite element modeling of composite structures may be cumbersome due to complex distributions of reinforcements. In this paper, an efficient scheme is proposed that can generate periodic meshes for the composite structures. Regular meshes with hexahedral finite elements are first prepared, and the elements are then trimmed to fit external surfaces of reinforcements in the composite structures. The trimmed hexahedral finite elements located at interfaces between the matrix and the reinforcements correspond to polyhedral finite elements, which allow an arbitrary number of nodes and faces in the elements. Because the trimming process is consistently conducted by means of consistent algorithms, the elements of the reinforcements are automatically compatible with those of the matrices. With the additional consideration of periodicity of reinforcements in a representative volume element(RVE), the proposed scheme provides periodic meshes in an efficient manner, which are compatible for each pair of periodic boundaries of the RVE. Therefore, periodic boundary conditions for the RVE are enforced straightforwardly. Numerical examples demonstrate the effectiveness of the proposed scheme for finite element modeling of complex composite structures.

A Numerical Study on Hydrodynamic Interactions between Dynamic Positioning Thrusters (동적위치제어용 스러스터 사이의 유체역학적 상호작용에 대한 수치해석 연구)

  • Jin, Doo Hwa;Lee, Sang Wook
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.41 no.6
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    • pp.373-380
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    • 2017
  • In this study, we conducted computational fluid dynamics (CFD) simulations for the unsteady hydrodynamic interaction of multiple thrusters by solving Reynolds averaged Navier-Stokes equations. A commercial CFD software, STAR-CCM+ was used for all simulations by employing a ducted thruster model with combination of a propeller and No. 19a duct. A sliding mesh technique was used to treat dynamic motion of propeller rotation and non-conformal hexahedral grid system was considered. Four different combinations in tilting and azimuth angles of the thrusters were considered to investigate the effects on the propulsion performance. We could find that thruster-hull and thruster-thruster interactions has significant effect on propulsion performance and further study will be required for the optimal configurations with the best tilting and relative azimuth angle between thrusters.

Application of Grid-based Approach for Auto Mesh Generation of Vacuum Chamber (자동 요소망 생성을 위한 격자구성기법 적용)

  • Lee J.S.;Park Y.J.;Chang Y.S.;Choi J.B.;Kim Y.J.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.06a
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    • pp.844-847
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    • 2005
  • A seamless analysis of complex geometry is one of greatly interesting topic. However, there are still gaps between the industrial applications and fundamental academic studies owing to time consuming modeling process. To resolve this problem, an auto mesh generation program based on grid-based approach has been developed for IT-product in the present study. At first, base mesh and skin mesh are generated using the information of entities which extracted from IGES file. Secondly the provisional core mesh with rugged boundary geometry is constructed by superimposing the skin mesh as well as the base mesh generated from the CAD model. Finally, the positions of boundary nodes are adjusted to make a qualified mesh by adapting node modification and smoothing techniques. Also, for the sake of verification of mesh quality, the hexahedral auto mesh constructed by the program is compared with the corresponding tetrahedral free mesh and hexahedral mapped mesh through static finite element analyses. Thereby, it is anticipated that the grid-based approach can be used as a promising pre-processor for integrity evaluation of various IT-products.

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Design of Forming Path for Concave Steel Plate Using the Line Array Roll Set (선형 배열 롤 셋을 이용한 오목형상 강판 성형경로 설계)

  • Roh, H.J.;Kim, K.H.;Shim, D.S.;Yang, D.Y.;Chung, S.W.;Han, M.S.
    • Transactions of Materials Processing
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    • v.17 no.7
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    • pp.491-495
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    • 2008
  • Incremental forming path to manufacture a thick concave steel plate using the line array roll set is designed. To find the optimum forming path, the forming processes are simulated by the finite element method. A general-purpose commercial software, MSC MARC is used. A modeling with 8-node hexahedral elastic-plastic solid is performed to predict accurate springback and the analysis process was composed of 18 passes. The proposed forming paths are verified through experiments carried out in the prototype line array roll set. It is found that the process can be successfully applied to the fabrication of the dual curvature ship hull plate.

A study on Effects of Parameters in the Lagrangian Code based on F.E.M. through Oblique Dual-Plates Perforation Phenomena (관통자에 의한 경사복판의 관통현상에서 유한요소법을 근간으로한 라그랑지 코드의 변수의 영향에 관한 연구)

  • Kim, Ha-youn
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.55-60
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    • 2004
  • This study is concerned to the perforation phenomena of the oblique dual-plate by projectile. Experiment and simulation related to that was carried out. the variables considered in this phenomena include the electrolytic zinc coated steel sheet and carbon steel rod. In the former, the confirmation and projectile velocity possible phenomena of real phenomena is done, the latter, the effect of parameter such as time-step and grid space length is analized by using the three-dimensional Lagrangian explicit time-integration finite element code, HEMP. this code use the eight node hexahedral elements and in this study, Von-Mises Criteria is used as the strength model, Mie-Gruneisen is as the Equation of State. the simulation was performed by contrast with the experiment. through the calibration of the parameter of lagrangian code, reasonable result was approached.

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Large Scale Numerical Analysis for the Performance Prediction of Multilayered Composite Curved Actuator (적층 복합재료를 사용한 곡면형 작동기의 성능 예측을 위한 대규모 수치해석 연구)

  • 정순완;황인성;김승조
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2003.10a
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    • pp.167-170
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    • 2003
  • In this paper, the electromechanical displacements of curved actuators using laminated composites are calculated by finite element method to design the optimal configuration of curved actuators. To predict the pre-stress in the device due to the mismatch in coefficients of thermal expansion, the carbon-epoxy and glass- epoxy as well as PZT ceramic is also numerically modeled by using hexahedral solid elements. Because the modeling of these thin layers causes the numbers of degree of freedom to increase, large-scale structural analyses are performed in a cluster system in this study. The curved shape and pre-stress in the actuator are obtained by the cured curvature analysis. The displacement under the piezoelectric force by an applied voltage is also calculated to compare the performance of curved actuator. The thickness of composite is chosen as design factor.

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Three-Dimensional Simulation of a Rotor Pole Forging Process and Verification of the Results (로터 폴 단조 공정의 정밀 삼차원 시뮬레이션 및 결과의 검증)

  • 고병호;이민철;제진수;전만수
    • Journal of the Korean Society for Precision Engineering
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    • v.19 no.12
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    • pp.158-162
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    • 2002
  • In this paper, the usefulness of a three-dimensional forging simulation technique is verified through its application to process design in rotor pole forging. A simulator, AFDEX3D developed based on the rigid-plastic finite element method and hexahedral elements, is employed. The simulated results of an application example found in a precision forging company are compared with the actually forged ones in detail. It has been verified that the simulation results are in good agreement with the actual phenomena.

Natural Vibration Analysis of Thick Rings (두꺼운 링의 고유진동 해석)

  • Park, Jung-Woo;Kim, Sehee;Kim, Chang-Boo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.10 s.103
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    • pp.1186-1194
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    • 2005
  • In this paper, we have systematically formulated the equations concerned to the in-plane and out-of-plane motions and deformations of a thick circular beam by using the kinetic and strain energies in order to analyse natural frequencies of a thick ring. The effects of variation of radius of curvature across the cross-section and also the effects of bending shear, extension and twist are considered. The equations of motion for natural vibration analysis of a ring are obtained utilizing the cyclic symmetry of vibration modes of the ring. The frequencies calculated using thick ring model and thin ring model are compared and discussed with the ones obtained from finite element analysis using the method of cyclic symmetry with 20-node hexahedral solid elements for rings with the different ratio of radial thickness to mean radius.