• Title/Summary/Keyword: Explicit method

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A Study on the Behavior of Wrinkling in the Square Cup Deep Drawing of Al Alloy (Al합금의 사각용기 딥드로잉시 주름의 거동에 관한 연구)

  • Ko, Dae-Lim;Jung, Dong-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.3
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    • pp.276-282
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    • 2009
  • Wrinkling in the flange and wall of a deep-drawn part is one of the major defects in sheet metal processes. Wrinkling is influenced by many factors, such as material properties, shape of the body, forming conditions, stress state and thickness, etc. It is difficult to analyze the wrinkling initiation and growth according to the factors because the effects of the factors are very complex and the wrinkling behavior may show wide variation even though small deviation of factors. In this study, the influence of wrinkling parameters, such as material properties (Al1050, Al5052), the blank holding force and the drawing depth on the wrinkling initiation and growth is investigated by using the experimental method and the dynamic explicit finite element analysis. From the results, it is shown that the dynamic explicit finite element method can be used effectively to prevent the wrinkling problems advancely in the deep drawing process. Also, there is a good agreement between the experimental result and the dynamic explicit finite element analysis.

A Four-Node Assumed Strain Plate Element for Explicit Dynamic Transient Analysis (명시적인 동적 시간이력해석을 한 사절점 가변형도 평판요소)

  • 이상진
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.14 no.3
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    • pp.349-359
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    • 2001
  • An enhanced four-node plate element, which has been developed for explicit dynamic analysis of plate, is described in this paper. Reissner-Mind1in(RM) assumptions are adopted to consider transverse shear deformation effects in the present plate element. RM plate element produces a shear locking phenomena in thin plate so that the substitute natural strains based on assumed strain method are explicitly derived. The present plate element is applied into the explicit transient algorithm and the mass matrix of plate is formulated by using special lumping method proposed by Hinton et al. The performance of the element is verified with numerical examples.

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Explicit Design of Commercial Pipe on a Slope with Pumping Power (동력경사 상용관의 양해법 설계)

  • Yu, Dong-Hun;Gang, Chan-Su
    • Journal of Korea Water Resources Association
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    • v.30 no.5
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    • pp.495-501
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    • 1997
  • Pumping power being given, traditional method requires an iteration process for the solution of discharge and pipe diameter. Yoo and Kang (1996) have developed explicit equations for the estimation of discharge and pipe diameter for the cases of uniformly rough pipe on a sloping bed with a pumping power. The use of poser law for the estimation of friction factor enabled to develop the explicit form of equations. Yoo (1995a) has suggested the mean friction factor method for the estimation of friction factor of commercial pipe or composite surface pipe. With the same approach, the present work has developed the explicit equations of discharge or pipe diameter for the general case of commercial pipe on a sloping bed with a pumping power by adopting the mean friction factor method.

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Development of Sound Source Localization System using Explicit Adaptive Time Delay Estimation

  • Kim, Doh-Hyoung;Park, Youngjin
    • 제어로봇시스템학회:학술대회논문집
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    • 2002.10a
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    • pp.80.2-80
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    • 2002
  • The problem of sound source localization is to determine the position of sound sources using the measurement of the acoustic signals received by microphones. To develop a good sound source localization system which is applicable to a mobile platform such as robots, a time delay estimator with low computational complexity and robustness to background noise or reverberations is necessary. In this paper, an explicit adaptive time delay estimation method for a sound source localization system is proposed. Proposed explicit adaptive time estimation algorithm employs direct adaptation of the delay parameter using a transform-based optimization technique, rather than...

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A Program Development for Dynamic Characteristics of Material in SHPB with Explicit Finite Element Method (홉킨슨 압축봉에서의 동적 재료특성에 관한 수치해석적 연구)

  • Lee, Seung-U;Hong, Seong-In
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.6 s.177
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    • pp.1438-1445
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    • 2000
  • To determine dynamic characteristics of materials, a program was developed under base of stress wave propagation theory for SHPB with explicit finite element method. Through the program, all kinds of quasi-static stress-strain curves can be directly converted to dynamic stress-strain curves at any strain rate. This simulation results were compared with experimental results in the references and they are in a good agreement with each other.

Consideration of Damping Effect on Sheet Metal Forming (판재 성형에 미치는 damping의 영향 고찰)

  • 이상욱;양동열;정완진
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1997.03a
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    • pp.188-191
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    • 1997
  • In the recent sheet metal forming simulations, it increases to adopt the dynamic explicit method for an effective computation and the elastic-plastic formulation for stress recovery. It is inevitable in the dynamic explicit method that some noises occur and sometimes partly spoil results of simulations. It is severer when complicated contact conditions are included in simulations. An effective method to control these noises is introduction of damping effects. In this paper, the concept of contact damping is introduced in order to suppress noises due to complicated contact conditions. This is checked by analyzing a simple sheet metal forming process(U-bending). From the computational results, it is shown that the contact damping can effectively control the noises due to contacts and develop more reliable internal stress states.

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Ultimate load capacity of unit Strarch frames using an explicit numerical method

  • Lee, Kyoungsoo;Hong, Jung-Wuk;Han, Sang-Eul
    • Steel and Composite Structures
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    • v.13 no.6
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    • pp.539-560
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    • 2012
  • This study uses an explicit numerical algorithm to evaluate the ultimate load capacity analysis of a unit Strarch frame, accounting for the initial imperfection effects of the stress-erection process. Displacement-based filament beam element and an explicit dynamic relaxation method with kinetic damping are used to achieve the analysis. The section is composed of the finite number of filaments that can be conveniently modeled by various material models. Ramberg-Osgood and bilinear kinematic elastic plastic material models are formulated to analyze the nonlinear material behaviors of filaments. The numerical results obtained in the present study are compared with the results of experiment for stress-erection and buckling of unit Strarch frames.

Finite Element Analysis of Auto-body Panel Stamping (리어 힌지 패널 스템핑의 유한요소해석)

  • 정동원;이장희;양동열
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1996.06a
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    • pp.97-109
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    • 1996
  • In the present work computations are carried out for analysis of complicated sheet metal forming process such as forming of a rear hinge. Finite element formulation using dynamic explicit time integration scheme and step-wise combined Implicit/Explicit scheme are introduced for numerical analysis of sheet metal forming process. The rigid-plastic finite element method based on membrane elements has long been employed as a useful numerical technique for the analysis of sheet metal forming because of its time effectiveness. The explicit scheme in general use is based on the elastic-plastic modelling of material requiring large computation time. In finite element simulation of sheet metal forming processes, the robustness and stability of computation are important requirements since the computation time and convergency become major points of consideration besides the solution accuracy due to the complexity of geometry and boundary conditions. The implicit scheme employs a more reliable and rigorous scheme in considering the equilibrium at each step of deformation, while in the explicit scheme the problem of convergency is eliminated at the cost of solution accuracy. The explicit approach and the implicit approach have merits and demerits, respectively. In order to combine the merits of these two methods a step-wise combined implicit/explicit scheme has been developed.

Step-wise Combinded Implicit/Explicit Finite Element Simulation of Autobody Stamping Processes (차체 스템핑공정을 위한 스텝형식의 내연적/외연적 결함 유한요소해석)

  • Jung, D.W.;Yang, D.Y.
    • Journal of the Korean Society for Precision Engineering
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    • v.13 no.12
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    • pp.86-98
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    • 1996
  • An combined implicit/explicit scheme for the analysis of sheet forming problems has been proposed in this work. In finite element simulation of sheet metal forming processes, the robustness and stability of computation are important requirements since the computation time and convergency become major points of consideration besides the solution accuracy due to the complexity of geometry and boundary conditions. The implicit scheme dmploys a more reliable and rigorous scheme in considering the equilibrium at each step of deformation, while in the explict scheme the problem of convergency is elimented at thecost of solution accuracy. The explicit approach and the implicit approach have merits and demerits, respectively. In order to combine the merits of these two methods a step-wise combined implici/explicit scheme has been developed. In the present work, the rigid-plastic finite element method using bending energy augmented membraneelements(BEAM)(1) is employed for computation. Computations are carried out for some typical sheet forming examples by implicit, combined implicit/explicit schemes including deep drawing of an oil pan, front fender and fuel tank. From the comparison between the methods the advantages and disadvantages of the methods are discussed.

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Simulating flow-induced fiber motion with finite element based explicit coupling method

  • Diwei Zhang;Xiaobo Peng;Dongdong Zhang
    • Advances in Computational Design
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    • v.9 no.3
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    • pp.229-252
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    • 2024
  • This paper presents a finite element based explicit coupling method. The derived method is proposed to solve a certain type of fluid-structure interaction problem, which is the motion of a single or flexible fiber with the motion induced by the low-Reynolds-number fluid. The particle motion is treated as a non-linear geometric dynamic problem. The Total-lagrangian finite element method is applied to describe and discretize the particle domain. The Bathe method is used to integrate the time domain. The Stokes equation is used as the governing equation of the fluid domain. The inertia term of the Stokes equation is ignored, and Reynolds number flow is assumed as zero. Since the time term is also canceled, we solve it as a quasi-static problem. Mixed finite element is to solve the fluid equation. An explicit strategy is implemented to couple the particle and the zero-Reynolds number flow. Simulations with the proposed method are presented, including the motion of single and double rigid particle immersed in the double Couette flow and the Poiseuille flow. Simulation of single flexible fiber immersed in a Poiseuille flow is also presented. Effect of particle's density, aspect ratio, and geometry are discussed.