CPT212 Element Description

CPT212 is a 2D four-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 four nodes and can have the following degrees of freedom at each node:

CPT212 can be used as a plane strain or axisymmetric element. The element has stress stiffening, large deflection, and large strain capabilities. Various output options are also available.

See CPT212 for more details about this element.

Figure 212.1: CPT212 Geometry

CPT212 Input Data

The geometry and node locations for this element are shown in Figure 212.1: CPT212 Geometry.

A degenerated triangular-shaped element can be formed by defining the same node number for nodes K and L. 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 212.1: CPT212 Geometry. 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).

CPT212 surface, body, and nodal-force loads are given in Table 212.1: CPT212 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.

Input the nodal forces, if any, per unit of depth for a plane analysis and on a full 360° basis for an axisymmetric analysis.

As described in Coordinate Systems, you can use ESYS to orient the material properties and strain/stress output. Issue RSYS 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. For a general description of element input, see Element Input.

CPT212 Technology

CPT212 uses the method (also known as selective reduced integration). This approach helps to prevent volumetric mesh locking in nearly incompressible cases. It replaces volumetric strain at the Gauss integration point with the average volumetric strain of the elements.

CPT212 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 212.2: CPT212 Stress Output. A general description of solution output is given in Solution Output. See the Basic Analysis Guide for ways to view results.

Figure 212.2: CPT212 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).

For axisymmetric solutions in a global coordinate system, the X, Y, XY, and Z stress and strain outputs correspond to the radial, axial, in-plane shear, and hoop stresses and strains, respectively.

Table 212.3: CPT212 Item and Sequence Numbers lists output available via the ETABLE command using the Sequence Number method. For more information, see Creating an Element Table and The Item and Sequence Number Table in this document. The table uses the following notation:

CPT212 Assumptions and Restrictions

CPT212 Product Restrictions

There are no product-specific restrictions for this element.