PLANE25 Element Description

PLANE25 is used for 2D modeling of axisymmetric structures with nonaxisymmetric loading. Examples of such loading are bending, shear, or torsion. The element is defined by four nodes having three degrees of freedom per node: translations in the nodal x, y, and z direction. For unrotated nodal coordinates, these directions correspond to the radial, axial, and tangential directions, respectively.

See Harmonic Axisymmetric Elements with Nonaxisymmetric Loads for a description of various loading cases. See PLANE25 in the Mechanical APDL Theory Reference for more details about this element. See PLANE83 for a multi-node version of this element.

Figure 25.1: PLANE25 Geometry

PLANE25 Input Data

The geometry, node locations, and the coordinate system for this element are shown in Figure 25.1: PLANE25 Geometry. The element input data includes four nodes, the number of harmonic waves (MODE on the MODE command), the symmetry condition (ISYM on the MODE command) and the orthotropic material properties. The MODE and ISYM parameters are discussed in detail in Harmonic Axisymmetric Elements with Nonaxisymmetric Loads.

The material may be orthotropic, with directions corresponding to the element coordinate directions. The element coordinate system orientation is as described in Coordinate Systems. Harmonically varying nodal forces, if any, should be input on a full 360° basis.

Element loads are described in Element Loading. Harmonically varying pressures may be input as surface loads on the element faces as shown by the circled numbers on Figure 25.1: PLANE25 Geometry. Positive pressures act into the element.

Harmonically varying temperatures may be input as element body loads at the nodes. The node I temperature T(I) defaults to TUNIF. If all other temperatures are unspecified, they default to T(I). For any other input pattern, unspecified temperatures default to TUNIF.

KEYOPT(2) is used to include or suppress the extra displacement shapes.

KEYOPT(3) is used for temperature loading with MODE > 0 and temperature-dependent material properties. Material properties may only be evaluated at a constant (nonharmonically varying) temperature. If MODE = 0, the material properties are always evaluated at the average element temperature. If MODE > 0, TREF must be input as zero.

KEYOPT(4), (5), and (6) provide various element printout options (see Element Solution).

A summary of the element input is given in "PLANE25 Input Summary". Element Input gives a general description of element input.

PLANE25 Output Data

The solution output associated with the element is in two forms:

Several items are illustrated in Figure 25.2: PLANE25 Stress Output.

In the displacement printout, the UZ component is out-of-phase with the UX and UY components. For example, in the MODE = 1, ISYM = 1 loading case, UX and UY are the peak values at θ = 0° and UZ is the peak value at θ = 90°. The same occurs for the reaction forces (FX, FY, etc.). The element stress directions are parallel to the element coordinate system. We recommend that you always use the angle field on the SET command when postprocessing the results. For more information about harmonic elements, see Harmonic Axisymmetric Elements with Nonaxisymmetric Loads

The sign convention on the surface shears is such that for a rectangular element that is lined up parallel to the axes with node J in the positive Y direction from node I, the shear stresses on surfaces I-J and K-L are analogous to the centroidal SYZ in both definition and sign. Stress components which are inherently zero for a load case are printed for clarity. Solution Output gives a general description of solution output. See the Basic Analysis Guide for ways to view results.

Figure 25.2: PLANE25 Stress Output

The Element Output Definitions table uses the following notation:

A colon (:) in the Name column indicates that the item can be accessed by the Component Name method (ETABLE, ESOL). The O column indicates the availability of the items in the file jobname.out. The R column indicates the availability of the items in the results file.

In either the O or R columns, “Y” indicates that the item is always available, a letter or number refers to a table footnote that describes when the item is conditionally available, and “-” indicates that the item is not available.

Table 25.2: PLANE25 Item and Sequence Numbers lists output available through the ETABLE command using the Sequence Number method. See The General Postprocessor (POST1) of the Basic Analysis Guide and The Item and Sequence Number Table for more information. The following notation is used in Table 25.2: PLANE25 Item and Sequence Numbers:

See Surface Solution for the item and sequence numbers for surface output for the ETABLE command.

PLANE25 Assumptions and Restrictions

PLANE25 Product Restrictions

There are no product-specific restrictions for this element.