Finite Elements in Patran allows the definition of basic finite element construction. Created under Finite Elements are the nodes, element topology, and multi-point constraints.

For more information on how to create finite element meshes, see Mesh Seed and Mesh Forms (p. 25) in the Reference Manual - Part III.

Nodes in Patran will generate unique *NODE entries. Nodes can be created either directly using the Node object, or indirectly using the Mesh object.

Finite Elements in Patran assigns element connectivity, such as Quad/4, for standard finite elements. The type of LS-DYNA element created is not determined until the element properties are assigned. See the Element Properties Form for details concerning the LS-DYNA element types. Elements can be created either directly using the Element object or indirectly using the Mesh object.

Multi-point constraints (MPCs) can also be created from the Finite Elements menu. These elements define a rigorous behavior between several specified nodes. The forms for creating MPCs are found by selecting MPC as the Object on the Finite Elements form. The full functionality of the MPC forms are defined in Create Action (Mesh) (p. 11) in the Reference Manual - Part III.

To create an MPC, first select the type of MPC to be created from the option menu. The MPC types that appear in the option menu are dependent on the current settings of the Analysis Code and Analysis Type preferences. The following table describes the MPC types which are supported for LS-DYNA.

Note that the LS-DYNA definition of joints requires the definition of coincident pairs of nodes. Coincidence is not required of the Patran model. The mean position will be calculated during translation.

Note that some of the LS-DYNA *CONSTRAINED entries are supported as LBC’s rather than MPC’s. This is generally because they require more data than can be entered for an MPC or for the sake of consistency with other analysis preferences.

Whenever a list of degrees-of-freedom is expected for an MPC term, a listbox containing the valid degrees-of-freedom is displayed on the form. A degree-of-freedom is valid if:

In most cases, all degrees-of-freedom, which are valid for the current Analysis Code and Analysis Type Preferences, are valid for the MPC type. The following degrees-of-freedom are supported for the various analysis types:

This subordinate MPC form appears when the Define Terms button is selected on the Finite Elements form, and the tied shell to solid type is selected. This form is used to create a *CONSTRAINED_SHELL_TO_SOLID entry. Note that a shell node may be tied to up to 9 brick
nodes lying along a tangent vector to the nodal fiber. Nodes can move relative to each other in the fiber direction only.

This subordinate MPC form appears when the Define Terms button is selected on the Finite Elements form, and the Rivet type is selected. This form is used to create one or more *CONSTRAINED_RIVET entries. Note that nodes connected by a rivet cannot be members of another constraint set that constrains the same degree of freedom, a tied interface, or a rigid body.

This subordinate MPC form appears when the Define Terms button is selected on the Finite Elements form, and Explicit is the selected type. This form is used to create a *CONSTRAINED_LINEAR entry. This MPC type is used to define a linear constraint equation.

This subordinate MPC form appears when the Define Terms button is selected on the Finite Elements form, and one of the joint types is selected. This form is used to create a *CONSTRAINED_JOINT_TRANSLATIONAL entry. The Relative Penalty Stiffness for this entry is defined on the main MPC form. The form will differ slightly for the 6 joint types. The spherical type requires only one dependent and one independent node. The translational joint requires 3 dependent and 3 independent nodes, and the other joint types require 2 dependent and 2 independent nodes.

This subordinate MPC form appears when the Define Terms button is selected on the Finite Elements form, and the Extra Nodes type is selected. This form is used to create a *CONSTRAINED_EXTRA_NODES_OPTION NODE/SET entry. This is the standard Rigid (Fixed) MPC type of Patran.