The following element overview topics are available:
An element type is identified by a name of up to eight characters, such as PIPE288, consisting of a group label and a unique ID number. In this example, the group label is PIPE and the number is 288.
The element descriptions in Element Library are arranged in order
of the identification numbers. To select an element from the library for use in your
analysis, input its full name (such as pipe288)
or number (such as 288) via
ET.
Models may be either 2D or 3D depending upon the element types used.
A 2D model must be defined in an X-Y plane. They are easier to set up, and run faster than equivalent 3D models. Axisymmetric models are also considered to be 2D.
If any 3D element type is included in the element type (ET ) set, the model becomes 3D. Some element types (such as COMBIN14) may be 2D or 3D, depending upon the KEYOPT value selected. Other element types (such as COMBIN40) have no influence in determining the model dimensions. A 2D element type may be used (with caution) in 3D models.
In general, four shapes are possible: point, line, area, or volume.
A point element is typically defined by one node, such as a mass element.
A line element is typically represented by a line or arc connecting two or three nodes. Examples are beams, spars, pipes, and axisymmetric shells.
An area element has a triangular or quadrilateral shape and may be a 2D solid element or a shell element.
A volume element has a tetrahedral or brick shape and is usually a 3D solid element.
The degrees of freedom of the element determine the discipline for which the element is applicable: structural, thermal, fluid, electric, magnetic, or coupled-field.
Select an element type with the necessary degrees of freedom characterize the model's response.
Including unnecessary degrees of freedom increases the solution memory requirements and running time. Similarly, selecting element types with unnecessary features--for example, using an element type with plastic capability in an elastic solution--also increases the analysis run time.
You can create your own element type and use it in an analysis as a user-defined element.
User-defined elements are described in Creating a New Element in the Programmer's Reference.
All elements with structural degrees of freedom support traditional forward solving. The input geometry is undeformed, and the solution is the deformed geometry and the stresses/strains on the undeformed input geometry.
Some elements support inverse solving. The input geometry is already deformed with applied loads, and the solution is the undeformed reference geometry and its associated stresses/strains. For more information, see Nonlinear Static Analysis with Inverse Solving in the Structural Analysis Guide, INVOPT, and Inverse Formulations in the Theory Reference.