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)

Scripted Input Files

In scripted input files, the element type is set using the Element command:

Element (elem)

where (elem) is a number or name from the above list. Once an element is selected, it remains the element used for all subsequent Area commands. If no Element command has be used, FEA calculations will default to "8 Node Quadrilateral" elements.

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 from the above list. Subsequent <Area> blocks can omit the type attribute unless the element type is changed to have an analysis with mixed elements.

Notes

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