Element Types

This page lists the elements that can be used in FEA calculations.

FEA Element Types

The following elements are currently available in NairnFEA:

• 1 or "3 Node Triangle": 3-node constant-strain triangular elements (linear)
• 2 or "4 Node Quadrilateral": 4-node isoparametric rectangular elements (linear)
• 3 or "8 Node Quadrilateral": 8-node isoparametric rectangular elements (quadratic)
• 4 or "6 Node Triangle": 6-node isoparametric triangular elements (quadratic)
• 5 or "4 Node Interface": 4-node imperfect interface elements (linear)
• 6 or "6 Node Interface": 6-node imperfect interface elements (quadratic)
• 8 or "9 Node Lagrange": 9-node Langrangian rectangular element (quadratic) (9 point Gaussian quadrature)

XML Input Files

In XML input files, the first <Area> block must define an element type in an attribute and refer to it by number. Subsequent <Area> blocks can omit the type attribute unless the element type is changed to have an analysis with mixed elements. When mixed elements are used, they must be compatible elements. In other words, you can mix linear elements (types 1, 2, and 5) with each other or quadratic elements (types 3, 4, 6, and 8) with each other, but cannot mix linear elements with quadratic elements in the same mesh.

Finally, solid (or quadrilateral) areas can only use solid elements (types 1, 2, 3, 4, and 8) and interface areas can use only inteface elements (type 5 and 6).