CPT217 Element Description

CPT217 is a higher-order 3D 10-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 has a quadratic displacement, and linear pore-pressure and temperature behavior.

The element is defined by 10 nodes and can have the following degrees of freedom at each corner node:

and three degrees of freedom at midside nodes:

CPT217 has elasticity, stress stiffening, large deflection, and large strain capabilities. See CPT217 for more details about this element.

Figure 217.1: CPT217 Geometry

CPT217 Input Data

The geometry, node locations, and the coordinate system for this element are shown in Figure 217.1: CPT217 Geometry.

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 as described in the Material Reference.

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 217.1: CPT217 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).

CPT217 surface, body, and nodal-force loads are given in Table 217.1: CPT217 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.

As described in Coordinate Systems, you can use the ESYS command to orient the material properties and strain/stress output. Issue 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).

The following table summarizes the element input. Element Input gives a general input description.

CPT217 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 217.2: CPT217 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 217.2: CPT217 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 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 217.3: CPT217 Item and Sequence Numbers lists output available via the ETABLE command using the Sequence Number method. See The General Postprocessor (POST1) in the Basic Analysis Guide and The Item and Sequence Number Table in this document for more information. The following notation is used in the table:

CPT217 Assumptions and Restrictions

CPT217 Product Restrictions

There are no product-specific restrictions for this element.