Initial forces on beam element axes (LS-DYNA)

Use the Initial Axial Beam Force command to pre-load certain types of beam elements to a prescribed axial force. The Initial Axial Beam Force command corresponds to the LS-DYNA *INITIAL_AXIAL_FORCE_BEAM keyword.

You can use options in the Initial Axial Beam Force dialog box to:

• Specify a load curve that defines the preload for the beam over time.

• Define the bending stiffness for the beam.

Creating the appropriate beam elements for the preload

In LS-DYNA you use the *INITIAL_AXIAL_FORCE_BEAM keyword to apply a pre-stress for a spot weld beam element. You define spot weld beam elements with element formulation type 9 (Hughes-Liu formulation for spot weld beams) and assign them a *MAT_SPOTWELD material. In Pre/Post to create spot weld beam elements, you:

1. Create a SECTION_BEAM modeling object dialog box to define the properties for the element. Use the Element formulation (ELFORM) list to select **(9) Spotweld beam (*MAT_SPOTWELD)**.

2. Create a PART (beam) physical property table and use the SECTION_BEAM option to select the modeling object. Use the Material Option to assign a *MAT_SPOTWELD type material.

3. Create the appropriate 1D connection elements and use the Mesh Collector dialog box to assign the PART (beam) physical property table to the element.

Defining the load curve to define the preload

You create a DEFINE_CURVE modeling object to specify the load curve data. When you define the load curve:

• You can specify a ramp function that starts at the origin to increase the force to the desired preload value. Ramping up the beam force can ease solution convergence.

• Typically, you apply the preload during the dynamic relaxation phase of the analysis. In the DEFINE_CURVE dialog box, use the Load curve used in (SIDR) list to select (1) Dynamic relaxation.

For more information, see Defining XY data for LS-DYNA solutions.

Where do I find it?

Application	Pre/Post
Prerequisite	A Simulation file as the work part and displayed partLS-DYNA as the specified solver
Command Finder	Initial Axial Beam Force

Learn more

Contact interference (Abaqus)

Constrained keywords for rigid body creation (LS-DYNA)

Enforced acceleration constraint (ANSYS)

Fixed and free boundary degrees of freedom (Nastran, ANSYS, and Abaqus)

Initial stress (LS-DYNA)

Initial velocity (LS-DYNA)

Rigid wall definition (LS-DYNA)

Single point constraints for boundary nodes (LS-DYNA)

Enforced velocity constraint (ANSYS)

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Initial forces on beam element axes (LS-DYNA), Simcenter 3D 2021.1 Series

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