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Element Types

The following table shows the element types supported in the Exodus library, the IOSS library, nem_slice, and nem_spread.

Element Exodus IOSS nem_slice nem_spread
circle X X X X
sphere X X X X 
    |      |       |           |    |

beam2 | X | X | X | X | beam3 | X | X | X | X | | | | | | quad4 | X | X | X | X | quad5 | X | | | | quad9 | X | X | X | X | | | | | | tri3 (2D)| X | X | X | X | tri4 (2D)| X | X | X | X | tri6 (2D)| X | X | X | X | tri7 (2D)| X | X | X | X | | | | | | tri3 (3D)| X | X | X | X | tri4 (3D)| X | X | X | X | tri6 (3D)| X | X | X | X | tri7 (3D)| X | X | X | X | | | | | | shell2 | X | X | X | X | shell3 | | X | X | X | shell4 | X | X | X | X | shell8 | X | X | X | X | shell9 | X | X | X | X | | | | | | tet4 | X | X | X | X | tet5 | X | | | | tet7 | | X | | | tet8 | X | X | X | X | tet10 | X | X | X | X | tet11 | X | X | | | tet14 | X | X | X | X | tet15 | X | X | X | X | | | | | | pyramid5 | X | X | X | X | pyramid13| X | X | X | X | pyramid14| X | X | | | | | | | | wedge6 | X | X | X | X | wedge15| X | X | X | X | wedge16| X | X | X | X | wedge18| X | X | | | wedge20| X | X | X | X | wedge21| X | X | X | X | | | | | | hex8 | X | X | X | X | hex9 | X | | | | hex20 | X | X | X | X | hex27 | X | X | X | X |

The IOSS library, nem_slice, and nem_spread cannot correctly handle a mesh unless it contains elements of a known type.

However, the exodus library can store elements of an unknown type with a few limitations. For an unsupported element type, the exodus library will not:

  • return the side set node list.
  • return the side set node list node count.
  • convert side set nodes to sides or vice versa.

If none of the above functions are required, then an element unknown to the exodus library can can be written and read to/from an exodus file with no loss of information.

Exodus Node Ordering Convention

Node ordering follows the conventions illustrated in the figures below. The node ordering conventions follow the element topology used in PATRAN. Thus, for higher-order elements than those illustrated, use the ordering prescribed in the PATRAN Element Library Manual Manual https://web.mscsoftware.com/training_videos/patran/reverb3/index.html#page/Finite%2520Element%2520Modeling/elem_lib_topics.16.1.html#ww33606.

Circle and Sphere Element Types

For elements of type circle or sphere, the topology is one node at the center of the circle or sphere element. A circle or sphere element has no sides.

Circle Sphere

Bar, Truss, Beam Element Types

The element name for this element type can be "bar", "beam", "truss"

Bar2 Bar3

Triangular Element Types

These are usable in 2D or 3D meshes. In a 3D mesh, they would represent triangular shells. The element name is "triangle" or "tri" in either case.

Tri3 Tri4 Tri6 Tri7

The side numbering for a tri element is shown below. For a triangular shell, there are five sides. Side 1 is the "top" of the triangle given by nodes 1-2-3 and side 2 is the "bottom" of the triangle given by nodes 3-2-1. Sides 3,4,5 correspond to sides 1,2,3 of the 2D triangle.

Element Type Side # Node Order
TRI (2D) 1 1, 2 
          | 2     | 2, 3       |
          | 3     | 3, 1       |
Element Type Side # Node Order
TRI (3D) 1 1, 2, 3 
          | 2     | 1, 3, 2    |

(Edges) | 3 | 1, 2 | | 4 | 2, 3 | | 5 | 3, 1 |

Tri-Number

Quadrilateral Element Types

These are usable in 2D or 3D meshes. In a 3D mesh, they represent a quadrilateral shell element and the element name is "shell"; in a 2D mesh, the element name is "quad".

Quad4 Quad5 Quad8 Quad9

The side numbering for a 2D quadrilateral element and a 3D quadrilateral shell element are shown below.

Element Type Side # Node Order
QUAD (2D) 1 1, 2 
          | 2     | 2, 3       |
          | 3     | 3, 4       |
          | 4     | 4, 1       |

Quad-Number

Element Type Side # Node Order
SHELL (3D) 1 1, 2, 3, 4 
          | 2     | 1, 4, 3, 2 |

(Edges) | 3 | 1, 2 | | 4 | 2, 3 | | 5 | 3, 4 | | 6 | 4, 1 |

Shell-Number

Tetrahedral Element Types

Tet4 Tet5 Tet10 Tet11 Tet14 Tet15

The side numbering for a tetrahedral element type is shown below.

Element Type Side # Node Order
TETRA 1 1, 2, 4 
          | 2     | 2, 3, 4    |
          | 3     | 1, 4, 3    |
          | 4     | 1, 3, 2    |

Tet-Number

Pyramidal Element Types

Pyramid

The side numbering for a pyramidal element type is shown below.

Element Type Side # Node Order
PYRAMID 1 1, 2, 5 
   | 2 | 2, 3, 5 |
   | 3 | 3, 4, 5 |
   | 4 | 4, 1, 5 |
   | 5 | 1, 4, 3, 2 |

Pyramid-Number

Wedge Element Types

Wedge6 Wedge15 Wedge16 Wedge20 Wedge21

The side numbering for a wedge element type is shown below. Note that the face mapping for this element does not match the MSC/Patran face mapping. In exodus, sides 1,2,3 are quadrilateral and sides 4,5 are triangular; in MSC/Patran, sides 1,2 are triangular and sides 4,5,6 are quadrilateral. It is unclear when and why this digression occurred.

Element Type Side # Node Order Patran Side
WEDGE 1 1, 2, 5, 4 3 
          | 2     | 2, 3, 6, 5 | 5           |
          | 3     | 1, 4, 6, 3 | 4           |
          | 4     | 1, 3, 2    | 1           |
          | 5     | 4, 5, 6    | 2           |

Wedge-Number

Hexahedral Element Types

Hex8 Hex9 Hex20 Hex27

The side numbering for a hexahedral element type is shown below.

Element Type Side # Node Order
HEX 1 1, 2, 6, 5 
          | 2     | 2, 3, 7, 6 |
          | 3     | 3, 4, 8, 7 |
          | 4     | 1, 5, 8, 4 |
          | 5     | 1, 4, 3, 2 |
          | 6     | 5, 6, 7, 8 |

Hex-Number `