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Buckling analysis of functionally graded plates resting on elastic foundation by natural element method

  • Cho, J.R.
    • Steel and Composite Structures
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    • v.44 no.2
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    • pp.171-181
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    • 2022
  • Functionally graded material (FGM) has been spotlighted as an advanced composite material due to its excellent thermo-mechanical performance. And the buckling of FGM resting on elastic foundations has been a challenging subject because its behavior is directly connected to the structural safety. In this context, this paper is concerned with a numerical buckling analysis of metal-ceramic FG plates resting on a two-parameter (Pasternak-type) elastic foundation. The buckling problem is formulated based on the neutral surface and the (1,1,0) hierarchical model, and it is numerically approximated by 2-D natural element method (NEM) which provides a high accuracy even for coarse grid. The derived eigenvalue equations are solved by employing Lanczos and Jacobi algorithms. The numerical results are compared with the reference solutions through the benchmark test, from which the reliability of present numerical method has been verified. Using the developed numerical method, the critical buckling loads of metal-ceramic FG plates are parametrically investigated with respect to the major design parameters.

Thermal buckling analysis of metal-ceramic functionally graded plates by natural element method

  • J.R., Cho
    • Structural Engineering and Mechanics
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    • v.84 no.6
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    • pp.723-731
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    • 2022
  • Functionally graded materials (FGMs) have been spotlighted as an advanced composite material, accordingly the intensive studies have focused on FGMs to examine their mechanical behaviors. Among them is thermal buckling which has been a challenging subject, because its behavior is connected directly to the safety of structural system. In this context, this paper presents the numerical analysis of thermal buckling of metal-ceramic functionally graded (FG) plates. For an accurate and effective buckling analysis, a new numerical method is developed by making use of (1,1,0) hierarchical model and 2-D natural element method (NEM). Based on 3-D elasticity theory, the displacement field is expressed by a product of 1-D assumed thickness monomials and 2-D in-plane functions which are approximated by NEM. The numerical method is compared with the reference solutions through the benchmark test, from which its numerical accuracy has been verified. Using the developed numerical method, the critical buckling temperatures of metal-ceramic FG plates are parametrically investigated with respect to the major design parameters.

An investigation into the effects of voids, inclusions and minor cracks on major crack propagation by using XFEM

  • Jiang, Shouyan;Du, Chengbin;Gu, Chongshi
    • Structural Engineering and Mechanics
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    • v.49 no.5
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    • pp.597-618
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    • 2014
  • For the structures containing multiple discontinuities (voids, inclusions, and cracks), the simulation technologies in the framework of extended finite element method (XFEM) are discussed in details. The level set method is used for representing the location of inner discontinuous interfaces so that the mesh does not need to align with these discontinuities. Several illustrations have been given to verify that the implemented XFEM program is effective. Then, the implemented XFEM program is used to investigate the effects of the voids, inclusions, and minor cracks on the path of major crack propagation. For a plate containing cracks and voids, two possibly crack path can be observed: i) the crack propagates into the void; ii) the crack initially curves towards the void, then, the crack reorients itself and propagates along its original orientation. For a plate with a soft inclusion, the final predicted crack paths tend to close with the inclusion, and an evident difference of crack paths can be observed with different inclusion material properties. However, for a plate with a hard inclusion, the paths tend to away from the inclusion, and a slightly difference of crack paths can only be seen with different inclusion material properties. For a plate with several minor cracks, the trend of crack paths can still be described as that the crack initially curves towards these minor cracks, and then, the crack reorients itself and propagates almost horizontally along its original orientation.

Flutter Mechanism Analysis for Firefly Export Model (반디호 수출형 시제기에 대한 플러터 매커니즘 분석)

  • Paek, Seung-Kil;Lee, Sang-Wook
    • Aerospace Engineering and Technology
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    • v.6 no.1
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    • pp.35-44
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    • 2007
  • In this study was made the flutter analysis for the export model of Firefly(Bandi-ho), the small canard aircraft. Stiffness model based on internal load generation finite element model was generated. Mass model based on the weight DB for weight control was generated. Aerodynamic model based on Doublet Lattice Method was generated. Preliminary flutter analysis was made. Based on it, major vibration modes are identified and experimentally obtained via the ground vibration test. The obtained normal mode frequencies were used to correlate the finite element model. Flutter analysis was made again and major flutter mechanisms were summarized. The most important flutter root was identified as a coupled root between rigid body roll mode and anti-symmetric wing pitching mode.

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Numerical Study for The Critical-Flow-Characteristics of The Pressure Regulator and Considerations as a Pipe Network Element (I);Influence of the Inlet-Outlet Pressure Ratio (정압기 임계유동특성 및 배관망해석 요소로서의 고려에 관한 수치해석적 연구 (I);입출구 압력비 변화 영향)

  • Shin, C.H.;Ha, J.M.;Lee, C.G.;Her, J.Y.;Im, J.H.;Joo, W.G.
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.1448-1453
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    • 2004
  • The major parameters governing the fluid dynamical and thermo-dynamical behavior in the large pipeline network system are friction loss and the pipeline length. But in local pipeline networks and relatively short distance pipeline system, secondary loss and the considerations of the moving states of the fluid machine are also important. One of the major element in local pressure control system is pressure regulator. It causes the variations of the physical properties in that pipeline system. Especially, as there is not enough information to obtain reliable physical property values such as density, temperature etc. at the downstream of the pressure regulator, It is hard to calculate accurate solution in the pipeline network analysis. In this study, some numerical approaches to investigate the critical-flow-characteristics of the pressure regulator have been done and the detail examinations and considerations of the pressure regulator as a pipeline network elements according to the variations of the inlet-outlet pressure ratio have been carried. Finally the flow-flied distributions, relations and critical-flow-characteristics have been studied. in detail and the 1D analytic method to analyze critical pipe flow have been investigated

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Numerical Study for The Critical-Flow-Characteristics of The Pressure Regulator and Considerations as a Pipe Network Element (II);Influence of the Cross-Sectional-Area and Opening Ratio (정압기 임계유동특성 및 배관망해석 요소로서의 고려에 관한 수치해석적 연구(II);단면적 및 개도 변화)

  • Shin, C.H.;Ha, J.M.;Lee, C.G.;Her, J.Y.;Im, J.H.;Joo, W.G.
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.1454-1459
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    • 2004
  • The major parameters governing the fluid dynamical and thermo-dynamical behavior in the large pipeline network system are friction loss and the pipeline length. But in local pipeline networks and relatively short distance pipeline system, secondary loss and the considerations of the moving states of the fluid machine are also important. One of the major element in local pressure control system is pressure regulator. It causes the variations of the physical properties in that pipeline system. When it is under working, the accurate analysis of the flow properties is so difficult. In this study, some numerical approaches to investigate the critical-flow-characteristics of the pressure regulator have been done according to the variations of the opening ratio or cross-sectional area and the detail examinations and considerations of the pressure regulator as a pipeline network elements have been carried. Finally the flow-flied distributions and critical-flow-characteristics have been presented in detail and the critical flow phenomena and the relation to the opening ratio or cross-sectional-area ratio have been studied.

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The Study on the Development of Composite Robot Hand for TFT-LCD Glass Transport (대면적 TFT-LCD 유리기판 이송용 복합재료 로봇 손 개발에 관한 연구)

  • Choi, Gi-Han;Han, Chang-Woo;Lee, Sang-Ryong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.7
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    • pp.1357-1365
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    • 2002
  • A robot hand is used to transport the glass substrate in TFT-LCD manufacturing process. Carbon/epoxy composite is one of the best materials for this kind of robot hand application, due to their lightweight, high stiffness, and good damping characteristics. Major requirement of the robot hand is given as allowable deflection under weight loading of glass substrate and robot hand itself. In this thesis, a carbon/epoxy robot hand was analyzed using finite element method and beam theory to determine the deflection of the hand under the loading that is equivalent to actual weight. Because natural frequency is one of the major interests in robot hand design for TFT-LCD manufacturing process, modal analysis is also conducted using finite element method and beam theory. A robot hand was manufactured, and actual deflection and natural frequency were measured to verify the analysis results and compliance to requirement. The test results showed good agreement with analysis results.

Finite Element Analysis of a Ventilating Box Structure (통기성 상자 구조물에 대한 유한요소 해석)

  • 박종민;권순구
    • Journal of Biosystems Engineering
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    • v.27 no.6
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    • pp.557-564
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    • 2002
  • Corrugated board is an efficient low-cost structure material fur the boxes that are widely used for transporting, storing and distributing goods. Corrugated board is also considered as an orthotropic because the principal material directions are the same as in paperboard. The purpose of this study was to elucidate the principal design parameters of ventilating box through the FEA on the various types of ventilating hole. From the viewpoint of the stress distribution and stress level, the optimum pattern and location of the ventilating hole were vertically oblong, and symmetry position with a short distance to the right and left from the center of front and rear panel. And, the optimum location and pattern of hand hole were a short distance to the top from the center of both side panels, and modified shape to increase the radius of curvature of both side in horizontal oblong. In general, the optimum pattern and location of both the ventilating hole and hand hole based on the FEM analysis were well verified by experimental investigation. It is suggested that decrease in compressive strength of the box could be minimized in the same ventilating hole area under the condition of the length of major axis of ventilating hole is less than 1/4 of box length, the ratio of minor axis/major axis is 113.5∼l/2.5, and number of the ventilating holes is even and symmetrical.