List of FEA elements

Different types of finite elements can be used in the FEA module. In this page you can find a description of their properties.

  • An element connects N nodes.
  • Nodes are handled via std::shared_ptr shared pointers: you do not have to worry about deleting them.
  • Add elements to a mesh using ChMesh::AddElement()
  • Initialize the elements by telling which node are connected with SetNodes()
  • Set a material property to the element by using SetMaterial()

ChElementSpring

  • 2 nodes of ChNodeFEAxyz type
  • Large displacements allowed
  • Zero mass element
  • Parameters:
    • rest length L,
    • stiffness k,
    • damping r
  • Note: geometric stiffness not (yet) implemented
  • The simpliest element: a starting point to learn how to implement finite elements

ChElementBar

  • 2 nodes of ChNodeFEAxyz type
  • Very similar to ChElementSpring, except it has a mass
  • No torque at the ends (like two spherical joints)
  • Large displacements allowed
  • Parameters:
    • rest length L,
    • Section area A,
    • Young modulus E,
    • damping
  • Note: geometric stiffness not (yet) implemented

ChElementTetra_4

  • 4 nodes of ChNodeFEAxyz type
  • Linear interpolation, constant stress
  • 1 integration point
  • Corotational formulation for large displacements
  • Uses polar decomposition for corotated frame
  • Useful for solids
  • Fastest element for solids

ChElementTetra_10

  • 10 nodes of ChNodeFEAxyz type
  • Quadratic interpolation, linear stress
  • 4 integration points
  • Corotational formulation for large displacements
  • Uses polar decomposition for corotated frame
  • Note: initial position assuming nodes n>4 exactly at mid-length of edges
  • Useful for solids

ChElementHexa_8

  • 8 nodes of ChNodeFEAxyz type
  • Linear interpolation
  • 8 integration points
  • Corotational formulation for large displacements
  • Useful for solids, with structured grids

ChElementHexa_20

  • 20 nodes of ChNodeFEAxyz type
  • 8 at vertexes, 12 at edges midpoints
  • Quadratic interpolation
  • 27 integration points
  • Corotational formulation for large displacements
  • Useful for solids, with structured grids

ChElementBrick

  • 8 nodes of ChNodeFEAxyz type
  • Linear interpolation
  • 8 integration points
  • Use EAS Enhanced Assumed Strain
  • Large strains
  • Can use Mooney-Rivlin model for hyperelastic materials
  • Useful for solids, with structured grids

ChElementBrick_9

  • 9 nodes of ChNodeFEAxyz type (8 at the corners, 1 at the center)
  • Linear interpolation
  • 8 integration points
  • Strain formulations for large strains:
    • Green-Lagrange
    • Hencky
  • Plasticity:
    • J2 (metals)
    • DruckerPrager (soil, plastics)
    • DruckerPrager_Cap (soil, plastics)
  • Useful for solids, with structured grids

ChElementCableANCF

  • 2 nodes of chrono::fea::ChNodeFEAxyzD type
  • 3 integration point (stiffness), 4 (mass)
  • ANCF formulation for large displacements
  • Thin beam (no shear)
  • Does not model torsional stiffness (useful for wires, cables)
  • Section property: A, I, E, density, damping

ChElementBeamEuler

  • 2 nodes of ChNodeFEAxyzrot type
  • Linear interpolation
  • 1 integration point (default)
  • Corotational formulation for large displacements
  • Thin beam (no shear), based on the Euler-Bernoulli thin beam theory
  • Section property:
    • A, Iyy, Izz, E, density, damping
    • G, J for torsional stiffness, plus optional:
    • αe , ze , ye , for offset/rotated section
    • zs , ys for offset shear center

ChElementBeamANCF

  • 2 nodes of ChNodeFEAxyzDD type
  • ANCF formulation for large displacements
  • [recent feature – beta testing]

ChElementShellReissner

  • 4 nodes of ChNodeFEAxyzrot type
  • Bi-linear interpolation
  • 4 integration points (default)
  • Allows large displacements, exponential map used for SO3
  • Thick shells allowed
  • Based on the Reissner 6-field shell theory (w. drilling stiffness)
  • Can have multi-layered materials, using CLT thory
  • ANS, shear-lock free
  • Nodes need not to be aligned to shell (rotation offsets auto-computed in initialization)

ChElementShellANCF

  • 4 nodes of ChNodeFEAxyzD type
  • Bi-linear interpolation
  • 4 integration points (default)
  • Allows large displacements, using ANCF formulation
  • Thick shells allowed
  • Can have multi-layered materials
  • ANS-EAS, shear-lock free
  • Nodes D must be aligned to shell normal at initialization

Theory

Additional information regarding the implementation of finite elements in Chrono can be found at the whitepapers page.

Examples

See demos and examples at the tutorials page.