Bolt universal connections in the Nastran environment

In the Nastran environment, you can use the universal connection commands to define and mesh bolt connections between components.

Defining the bolt connection and generating the elements

• You can use the Bolt Connection command to specify the definition for the bolt connection. For example, you specify the parts (flanges) to connect, the locations of the spot welds, tolerance values for creating the connections, and properties of the connection such as the diameter of the bolt's head and shank and the bolt's material.

• You can use either the Automatic Elements or Connection Elements commands to generate the actual bolt elements from the connection definitions.If you use the Automatic Elements command, the software uses default values to create the bolt elements.Note: You can use options on the Bolt page of the Universal Connections customer defaults to control those default values.If you use the Connection Elements command, you can use options in the Bolt Element dialog box to control how the software creates the bolt elements.

Meshing Nastran bolt connections

You can use the Type option in the Bolt Element dialog box to specify the type of elements to use to mesh bolt connection definitions in the Nastran environment.

Option	Description
CBAR+RBE2 spider(s)	A CBAR element models the bolt and RBE2 rigid body elements model the interaction between the bolt and the connected components. The software creates a CBAR element between each set of flanges. For each intersection point between the CBAR element and a flange, the software creates RBE2 elements to connect that point to the surrounding nodes on the flanges.
CBEAM+RBE2 spider(s)	A CBEAM element models the bolt and RBE2 rigid body elements model the interaction between the bolt and the connected components. The software creates a CBEAM element between each set of flanges. For each intersection point between the CBEAM element and a flange, the software creates RBE2 elements to connect that point to the surrounding nodes on the flanges.
RBE2 Spider	An RBE2 rigid body element models both the bolt and connects it to the components. The software creates an RBE2 element between the connected flanges and connects the legs of that element to the surrounding nodes on the flanges.
RBE2+RBE2 spider(s)	An RBE2 rigid body element models the bolt and RBE2 elements in a spider configuration connect the bolt to the nodes on the flanges. The software always creates one RBE2 spider element on the top flange to connect the head of the bolt to the surrounding mesh. If the bolt connects more than two flanges, the software creates additional RBE2 spider elements to connect the nodes on the flanges to the shank of the bolt.

Bolt meshed with the CBEAM+RBE2 spider(s) option	Bolt meshed with the RBE2 Spider option

Mesh associated data for Nastran bolt elements

When you generate the bolt connection elements, the software automatically defines the mesh associated data for the elements.

• For CBEAM and CBAR elements, the software automatically defines the orientation vector and end offsets. You can edit the mesh associated data to modify these options and to set other options, such as the pin flags for ends A and B of the bar element.

• For RBE2 elements, the software automatically sets the degrees depending on the type of mesh on the flanges:For the RBE2 elements that connect flanges meshed with 2D elements, the software automatically sets the degrees of freedom for the core node and the leg nodes to On. For RBE2 elements that connect flanges meshed with 3D elements, the software automatically sets the translational degrees of freedom for the leg nodes to On.and sets all six degrees of freedom for the core node to On.

To modify mesh associated data, right-click the mesh in the Simulation Navigator and select Edit Mesh Associated Data.

Physical property data for Nastran bolt elements

If you select the CBAR+RBE2 spider(s) or CBEAM+RBE2 spider(s) option, during the meshing process, the software also creates a PBAR or PBEAM physical property table that defines the properties for the 1D elements that represent the bolt. The PBAR and PBEAM physical property tables define options, such as:

• The material to use for the CBAR or CBEAM elements.

• The nonstructural mass value for the CBAR or CBEAM elements.

• A circular Beam Section cross section that defines the shape and radius for the Fore Section of the beam element.

The options in the PBAR dialog box correspond to the fields on the PBAR bulk data entry. For more information, see PBAR in the Simcenter Nastran Quick Reference Guide.

The options in the PBEAM dialog box correspond to the fields on the PBEAM bulk data entry. For more information, see PBEAM in the Simcenter Nastran Quick Reference Guide.

Nastran bolt elements in the Simulation Navigator

The software stores the bolt connection elements as a new mesh or meshes in the appropriate collectors in the 1D Collectors node in the Simulation Navigator.

• CBAR elements are stored in a single mesh in the Bar Collector container.

• CBEAM elements are stored in a single mesh in the Beam Collector container.

• RBE2 elements are stored in RBE2 Collector container.

Where do I find it?

Application	Pre/Post
Prerequisite	A FEM or assembly FEM file as the work part and displayed partSimcenter Nastran or MSC Nastran as the specified solver
Command Finder	Bolt Connection Connection Elements Automatic Connection Elements

Bolt universal connection customer defaults

Menu	File→Utilities→Customer Defaults
Location in dialog box	Simulation→Pre/Post→Universal Connections→ Bolt tab

How do I

Simulate a bolt preload in ANSYS using universal bolt connections

Create large quantities of bolts in one connection

Learn more

Bolt universal connections

Override the length of bolt shanks

Extending the legs of spider elements in bolt connections

Bolt universal connections in the LS-DYNA environment

Meshing LS-DYNA bolt connections with rigid body elements

Meshing LS-DYNA bolt connections rigid body and beam elements

Quick links

Command reference

Pre/Post video examples

Bulk Entry Descriptions

Simcenter 3D tutorials

Browse Simcenter 3D help by product area

Bolt universal connections in the Nastran environment, Simcenter 3D 2021.1 Series

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