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The Patran template database file, template.db, contains a “generic” set of finite element topologies. By default, when opening a new database, the element topology library is included. Topology, in the context of a finite element, is the relative node, edge and face numbering scheme for each element of the same topology. The Patran library is compatible with earlier versions of Patran (PATRAN Release 2.5). Patran also provides additional information about each element topology which was not available in the earlier Patran versions:
• Nodal parametric locations
• Edge numbering
• Face numbering
• Face sense
• Corresponding degenerate element topology ID
Where possible, the ISO 10303-104, Application Resources: Finite Element Analysis document, which is part of International Standard ISO 10303-Product Data Representation and Exchange (STEP), was used to define the element topologies. If the ISO standard was found to be in conflict with earlier versions of Patran, the Patran convention took precedence. The ISO standard for numbering edges and faces of elements is used.
Face and edge numbering are important for assigning element attributes, such as pressures applied to a solid element face. In Patran, you may select an edge or a face of an element with the cursor. An example of the syntax, used in the Select Databox to describe an edge of hex element 1, would be elem 1.2.3, which refers to edge 3 of face 2 of element 1.
The element topology tables listed in sections 13.2 through 13.7 are used to construct and interpret the syntax of the Select Databox string.
Patran’s Element Library provides illustrations of each element type and topology, and their node locations.
Important: | The face sense is interpreted as positive if the normal is pointing away from (towards the outside) the element, using the right hand rule. This only applies to volume elements (element dimensionality = 3). |
Parametric coordinate systems
Rectangular
[Xi/Eta/Zeta] is used for Tet/Wedge/Hex elements. Values can either have a range of -1 to 1 or 0 to 1 depending on the case where an area or volume coordinate systems can apply (Tet/Wedge elements). [Xi/Eta] applies to a Tri or Quad element. Values range from 0 to 1 for the Tri, and -1 to 1 for the Quad. [Xi] applies to a Bar element. Values range from -1 to 1.
Area
[L1/L2/L3] is used for locating a point within a triangular area. Values range from 0 to 1, and the sum of all cordinates is equal to 1. The values correspond to the weighting with respect to the 3 corners of a triangle. For a Tri or Wedge element which will use [Xi/Eta] and [Xi/Eta/Zeta], the Xi/Eta value will range from 0 to 1, and we can determine L1/L2/L3 as :
L1 = 1.0 - Xi - Eta
L2 = Xi
L3 = Eta
Volume
[L1/L2/L3/L4] is used for locating a point within a tetrahedral volume. Values range from 0 to 1, and the sum of all cordinates is equal to 1. The values correspond to the weighting with respect to the 4 corners of a tetrahedron. For a Tet element which will use [Xi/Eta/Zeta], the Xi/Eta/Zeta value will range from 0 to 1, and we can determine L1/L2/L3/L4 as :
L1 = 1.0 - Xi - Eta - Zeta
L2 = Xi
L3 = Eta
L4 = Zeta