• Title/Summary/Keyword: global-finite element

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Effects of Cutting Angle on Kerf width and Edge Shape in the Hotwire Cutting of EPS Foam for the Case of Single-Sloped Cutting for VLM-s Process (VLM-s 공정을 위한 EPS 폼의 단순 경사 열선 절단시 절단 경사각이 절단폭과 모서리 형상에 미치는 영향)

  • 안동규;양동열
    • Journal of Welding and Joining
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    • v.21 no.5
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    • pp.525-533
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    • 2003
  • The dimensional accuracy and global roughness between successive layers of VLM-s, which is a new rapid prototyping process using hotwire cutter and EPS foam, depend significantly on the operating parameters of hotwire cutter. In the present study, the effect of cutting angle on the kerf width and edge shape in hotwire cutting of EPS foam for the case of single-sloped cutting with one cutting angle was investigated. Through single-sloped cutting tests, the modified relationship between kerf width and effective heat input, considering the effect of the cutting angle, and the relationship between the melted area and the cutting angle were obtained. In order to investigate the effect of cutting angles on the thermal field in EPS foam, transient heat transfer analyses using single-sloped volumetric heat flux model and locally-conformed mesh were performed. Through the comparison between experimental and numerical results, it was shown that the proposed analysis model is needed to estimate the three-dimensional temperature distribution of the EPS foam for the case of single-sloped hotwire cutting.

FPSO Collision Analysis Using a Simplified Analytical Technique (간이 해석 기법을 이용한 FPSO 충돌 해석)

  • Han, Sang-Min;Ito, Hisashi
    • Journal of Ocean Engineering and Technology
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    • v.24 no.2
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    • pp.25-33
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    • 2010
  • Collision between vessels may lead to structural damage and penetration of hulls. The structural damage of a hull may eventually bring about global collapse of the hull girder and outflow of oil, which would contaminate seawater. Therefore, various regulations require the strength of a vessel after collision to satisfy given criteria, and owners usually request collision analyses to confirm the structural safety of their vessels. In the process of designing a vessel to satisfy the collision strength criteria, the strength has been assessed mostly by conducting collision analyses using numerical techniques, such as dynamic, non-linear, finite-element analysis. Design is an inherently iterative process during which many changes are necessary due to the endless needs for reinforcement and modification. Numerical techniques are not adequate for coping with a situation in which collision analysis is frequently required to provide the revised results that reflect the repetitive changes in designs. Numerical techniques require a lot of time and money to conduct in spite of recent improvements in computing power and in the productivity of modeling tools. Therefore, in this paper, an analytical technique is introduced and a collision problem is idealized and simplified using reasonable assumptions based on appropriate background. The technique was applied to an example of an actual FPSO and verified by comparing the results with results from the numerical technique. A good correlation was apparent between the results of the analytical and numerical techniques.

Seismic behaviour of gravity load designed flush end-plate joints

  • Cassiano, David;D'Aniello, Mario;Rebelo, Carlos
    • Steel and Composite Structures
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    • v.26 no.5
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    • pp.621-634
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    • 2018
  • Flush end-plate (FEP) beam-to-column joints are commonly used for gravity load resisting parts in steel multi-storey buildings. However, in seismic resisting structures FEP joints should also provide rotation capacity consistent with the global structural displacements. The current version of EN1993-1-8 recommends a criterion aiming at controlling the thickness of the end-plate in order to avoid brittle failure of the connection, which has been developed for monotonic loading conditions assuming elastic-perfectly plastic behaviour of the connection's components in line with the theory of the component method. Hence, contrary to the design philosophy of the hierarchy of resistances implemented in EN1998-1, the over strength and the hardening of the plastic components are not directly accounted for. In light of these considerations, this paper describes and discusses the results obtained from parametric finite element simulations aiming at investigating the moment-rotation response of FEP joints under cyclic actions. The influence of bolt diameter, thickness of end-plate, number of bolt rows and shape of beam profile on the joint response is discussed and design requirements are proposed to enhance the ductility of the joints.

Engineering Estimation of Elastic-Plastic Fracture Parameter for Circumferential Surface Cracked Pipes: Part II (배관 원주방향 표면균열에 대한 탄소성 파괴 파라미터의 예측 (II))

  • Kim, Yun-Jae;Kim, Jin-Su;Kim, Young-Jin;Park, Yun-Won
    • Proceedings of the KSME Conference
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    • 2001.06a
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    • pp.310-315
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    • 2001
  • This paper provides validations of the reference stress based J and $C^*$ estimations, proposed in Part I, for inner, circumferential surface cracked pipes under internal pressure and global bending against detailed 3-D elastic-plastic and elastic-creep FE results. For this purpose, actual tensile properties of two typical stainless steels (TP304 and TP316) are used for elastic-plastic FE analyses and two realistic creep laws are used for elastic-creep FE analyses. For a total of twenty cases considered in this paper, agreements between the proposed reference stress based J and $C^*$ estimations and the FE results are excellent. More important aspect of the proposed estimations is that they can be used to estimate J and $C^*$ not only at the deepest point of the surface crack but also at an arbitrary point along the crack front.

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Study of Supporting Location Optimization for a Structure under Non-uniform Load Using Genetic Algorithm (유전알고리즘을 이용한 비균일 하중을 받는 구조물의 지지 위치 최적화 연구)

  • Kim, G.H.;Lee, Y.S.;Kim, H.K.;Her, N.I.;Sa, J.W.;Yang, H.L.;Kim, B.C.;Bak, J.S.
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.1322-1327
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    • 2003
  • It is important to determine supporting locations for structural stability of a structure under non-uniform load in space interfered by other parts. In this case, There are many local optima with discontinuous design space. Therefore, The traditional optimization methods based on derivative are not suitable. Whereas, Genetic algorithm(GA) based on stochastic search technique is a very robust and general method. This paper has been presented to determine supporting locations of the vertical supports for reducing stress of the KSTAR(Korea super Superconducting Tokamak Advanced Research) IVCC(In-vessel control coil) under non-uniform electromagnetic load and space interfered by other parts using genetic algorithm. For this study, we develop a program combining finite element analysis with a genetic algorithm to perform structural analysis of IVCC. In addition, this paper presents a technique to perform optimization with FEM when design variables are trapped in an incongruent design space.

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DYNAMIC MODELING AND REACTION WHEEL CONTROLLER DESIGN FOR FLEXIBLE SATELLITE AOCS (유연모드를 가진 인공위성의 자세제어를 위한 동역학 모델링 및 반작용휠 제어기 설계)

  • 우병삼;채장수
    • Journal of Astronomy and Space Sciences
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    • v.14 no.2
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    • pp.386-394
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    • 1997
  • In this study, a few of the modeling methods for flexible spacecraft were introduced and adopted to the modeling of a 3-axes stabilization satellite. The generated model was put into pre-built rigid body attitude control loop. A Lumped Parameter Model(Global Mode Model: GMM) was recommended for the absence of the Finite Element Method(FEM) model. Finally, GMM was compared with FEM in terms of designing a control filter. A 1st-order filter was designed to meet requirements of the controller since the new flexible model was applied, and that filter was added to motor controller and axis controller. MATLAB/Simulink was used as a tool for design and simulation of the control loop and filter.

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An Evaluation of Three Dimensional Finite Element Model on the Strength Prediction of Particles Reinforced MMCs (입자강화형 금속복합재료의 강도 예측에 관한 3차원 유한요소 모델의 평가)

  • 강충길;오진건
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.6
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    • pp.124-138
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    • 1998
  • Particles reinforced MMCs have many advantages over monolithic metals including a higher specific modulus, higher specific strength, better properties at elevated temperatures and better wear resistance. SiC$_p$/A16061 composites have good results in its mechanical properties. This work investigates SiC$_p$/A16061 composites in the microscopic view and compares the analytical results with the experimental ones. The discrepancy of the material properties between the reinforced particle, SiC$_p$, and the matrix material, A16061 appears to be so significant. Especially the coefficient of thermal expansion(CTE) of A16061 is 5 times larger than that of SiC$_p$. Thermal residual stress in MMCs is induced at high temperatures. The shape of particle is various but the theoretical model is not able to consider the nonuniform shape. Particle distribution is not homogeneous in experimental specimen. However, it is assumed to be homogeneous in simulation model. The shapes of particles are assumed to be not only perfect global but hexahedral shapes. The types of particle distribution are two - simple cubic array(SC array) and face-centered cubic array(FCC array).

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Prequalification of a set of buckling restrained braces: Part II - numerical simulations

  • Zub, Ciprian Ionut;Stratan, Aurel;Dubina, Dan
    • Steel and Composite Structures
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    • v.34 no.4
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    • pp.561-580
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    • 2020
  • Buckling restrained braces (BRBs) were developed as an enhanced alternative to conventional braces by restraining their global buckling, thus allowing development of a stable quasi-symmetric hysteretic response. A wider adoption of buckling restrained braced frames is precluded due to proprietary character of most BRBs and the code requirement for experimental qualification. To overcome these problems, BRBs with capacities corresponding to typical steel multi-storey buildings in Romania were developed and experimentally tested in view of prequalification. In the second part of this paper, a complex nonlinear numerical model for the tested BRBs was developed in the finite element environment Abaqus. The calibration of the numerical model was performed at both component (material models: steel, concrete, unbonding material) and member levels (loading, geometrical imperfections). Geometrically and materially nonlinear analyses including imperfections were performed on buckling restrained braces models under cyclic loading. The calibrated models were further used to perform a parametric study aiming at assessing the influence of the strength of the buckling restraining mechanism, concrete class of the infill material, mechanical properties of steel used for the core, self-weight loading, and frame effect on the cyclic response of buckling restrained braces.

Development and Validation of FE Adult Headform Impactor for Pedestrian Protection (성인 머리모형 임팩터의 FE 모델 개발)

  • Choi, Ji-Hun;Park, Bu-Chang;Kim, Jong-Sun
    • Transactions of the Korean Society of Automotive Engineers
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    • v.20 no.2
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    • pp.64-69
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    • 2012
  • Head injury is one of the most common cause of deaths in car-to-pedestrian collisions. To reduce the severity of such injuries, many international safety committees have performed headform impact test for pedestrian protection. In this paper, an adult headform impactor model is developed based on the finite element (FE) method and validated through the numerical simulation. The skin material of headform impactor is known as polyvinyl chloride skin (PVC) and its material was assumed as viscoelastic. The viscoelastic parameters of headform skin are identified by a series of trial and error methods. The new developed FE adult headform impactor is verified by the drop test and FE JARI adult headform impactor provided by Madymo program.

Design Optimization of Linear Actuator for Fast Response of Electromagnetic Engine Valve (과도시간 감소를 위한 전자기 엔진밸브 액츄에이터 형상 최적 설계)

  • Kim, Jin-Ho;Park, Sang-Shin
    • Journal of the Korean Magnetics Society
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    • v.20 no.1
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    • pp.24-27
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    • 2010
  • This paper presents the design optimization of a linear actuator for fast response of electromagnetic engine valve. The optimization is performed using generic algorithm which is one of global search techniques and not highly dependent on either initial conditions or constraints in the solution domain to maximize the mechanical frequency of the armature mass and valve spring stiffness for fast response of the engine valve. In the results, the mechanical frequency is improved by 30 %.