CPT215 Element Description

CPT215 is a 3D eight-node coupled physics solid element capable of modeling coupled physics phenomena such as structural-pore-fluid-diffusion-thermal analysis and structural implicit gradient regularization using a nonlocal field. The element is defined by eight nodes and can have the following degrees of freedom at each node:

CPT215 has elasticity, stress stiffening, large deflection, and large strain capabilities. Various printout options are available.

For more details about this element, see CPT215 .

Figure 215.1: CPT215 Structural Solid Geometry

A higher-order version of this element is CPT216.

CPT215 Input Data

The geometry and node locations for this element are shown in Figure 215.1: CPT215 Structural Solid Geometry. A prism-shaped element can be formed by defining the same node numbers for nodes K and L, and nodes O and P. A tetrahedral-shaped element and a pyramid-shaped element can also be formed, as shown in the illustration. (CPT217 is a similar element, but is a 10-node tetrahedron.)

In addition to the nodes, for structural-pore-fluid-diffusion-thermal analysis, the element input data includes the orthotropic material properties. Orthotropic material directions correspond to the element coordinate directions. The element coordinate system orientation is described in Coordinate Systems.

Element loads are described in Element Loading. Loads can be input (SF and SFE) on the element faces indicated by the circled numbers in Figure 215.1: CPT215 Structural Solid Geometry. Positive pressures act into the element. Positive pressures act into the element. Body loads may be input (BF and BFE) at the element nodes or as a single element value. Nodal forces can be applied to the nodes directly (F).

CPT215 surface, body, and nodal-force loads are given in Table 215.1: CPT215 Surface, Body, and nodal-force loads. Also see Loading Types in the Coupled-Field Analysis Guide.

Most loads can be defined as a function of primary variables by using tabular input. For more information, see Applying Loads Using Tabular Input in the Basic Analysis Guide and the descriptions of individual loading commands in the Command Reference.

For problems that do not consider the optional temperature degrees of freedom, temperatures can 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 temperature pattern, unspecified temperatures default to TUNIF.

As described in Coordinate Systems, you can use the ESYS command to orient the material properties and strain/stress output. Use the RSYS command to choose output that follows the material coordinate system or the global coordinate system.

The element generally produces an unsymmetric matrix. To avoid convergence difficulty, use the unsymmetric solver (NROPT,UNSYM).

"CPT215 Input Summary" contains a summary of element input. For a general description of element input, see Element Input.

CPT215 Output Data

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

By default, the integration point results are copied to the nodes (ERESX).

The element stress directions are parallel to the element coordinate system, as shown in Figure 215.2: CPT215 Stress Output. A general description of solution output is given in The Item and Sequence Number Table. See the Basic Analysis Guide for ways to view results.

Figure 215.2: CPT215 Stress Output

The element stress directions are parallel to the global coordinate system.

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 number refers to a table footnote that describes when the item is conditionally available, and - indicates that the item is not available. All output is available only if calculated (based on input values).

Table 215.3: CPT215 Item and Sequence Numbers lists output available via ETABLE using the Sequence Number method. See Element Table for Variables Identified By Sequence Number and The Item and Sequence Number Table in this document for more information. The following notation is used in Table 215.3: CPT215 Item and Sequence Numbers:

CPT215 Assumptions and Restrictions

CPT215 Product Restrictions

There are no product-specific restrictions for this element.