Using pyramid transitions with Simcenter Nastran

Simcenter Nastran uses the CPYRAM element to model pyramid element transitions. You use a PSOLID physical property table to define the properties for the element, including its material coordinate system. The CPYRAM element's geometry is shown below:

CPYRAM Element

The CPYRAM element has five corner nodes and up to thirteen total nodes, including eight optional midside nodes. Whether the CPYRAM element has some or all of its midside nodes depends on the orders of the meshes it connects. For example:

• If you use the CPYRAM element to connect parabolic tetrahedral elements to linear hexahedral elements, midside nodes 6, 7, 8, and 9 are missing.

• If you use the CPYRAM element to connect linear tetrahedral elements to linear hexahedral elements, midside nodes 6, 7, 8, and 9, as well as 10, 11, 12, and 13 are missing.

When you solve your model, Simcenter Nastran calculates element stresses (σx, σy, σz, τxy, τyz, and τzx) at the element's gauss points, then it extrapolates those stresses out to the corner nodes.

Supported solution sequences

In Pre/Post, pyramid elements are supported in SOL 101, 103, 105, 106, 108, 109, 111, 112, and 153, as well as in SOL 601 and SOL 701. However, the support for pyramid elements is currently different in SOL 601 and SOL 701 than it is in other Simcenter Nastran solution sequences. In SOL 101, 103, 105, 106, 108, 109, 111, 112, and 153, you can use CPYRAM elements to create transitions between elements of the same order as well as elements of different orders.

Using pyramid elements in SOL 601 and SOL 701 analyses

In SOL 601 and SOL 701 analyses, you can only use CPYRAM elements to connect elements of the same order.

• In a SOL 601 analysis, a CPYRAM element can have either 5 or 13 nodes. This means that you can use the CPYRAM element to connect a linear tetrahedral mesh to a linear hexahedral mesh or a parabolic tetrahedral mesh to a parabolic hexahedral mesh.

• In a SOL 701 analysis, a CPYRAM element can have 5 nodes. his means that you can use the CPYRAM element to connect a linear tetrahedral mesh to a linear hexahedral mesh.

In a SOL 601 analysis, you can use the ELCV=1 option on the NXSTRAT bulk data entry to convert 13-node CPYRAM elements to 14-node CPYRAM elements. With this option, when you solve your model, Simcenter Nastran inserts an additional node at the centroid of the quadrilateral face of the pyramid element. Because this node is added by Simcenter Nastran during the solution, you cannot display or manipulate this node in Pre/Post.

To insert this additional node in a CPYRAM element, create a Strategy Parameters modeling object. On the Translation page of the Strategy Parameters dialog box, select Convert Elements from the Element Conversion list. Then, on the Case Control page of the Create Solution or Edit Solution dialog box, select that Strategy Parameters modeling object to include it in your solution.

How do I

Use pyramid elements for hexahedral-tetrahedral mesh transitions

Learn more

Pyramid element transitions

Importing ANSYS models that contain pyramid elements

Look up more details

Supported element types for ANSYS pyramid transitions

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Using pyramid transitions with Simcenter Nastran, Simcenter 3D 2021.1 Series

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