Modal flexible body analysis

You can perform flexible body analyses in the ANSYS environment using the Modal Flexible Body solution. The solution reduces the dynamic behavior of the flexible body to a set of mode shapes, which are stored in the ANSYS structural results file (.rst). After you solve the solution, in Simcenter 3D Motion, you can associate the flexible body output file with a flexible body on which the component is defined in the motion simulation.

For more information about using the solution with Simcenter 3D Motion, see Flexible body analysis.

Types of ANSYS steps

The ANSYS modal flexible body solution performs three ANSYS steps in this order:

1. Generation PassCondenses a group of regular finite elements into a single superelement with the definition of master DOFs and other constraints.

2. Use PassUses the Generation Pass superelement in the modal analysis solve.

3. Expansion PassStarts with the reduced solution and calculates the results at all degrees of freedom in the superelement and saves them in the results file.

Flexible body connections and load degrees of freedom

You define the possible connection and load degrees of freedom in the finite element model that represents the flexible component using the Fixed Boundary Degrees of Freedom and Free Boundary Degrees of Freedom constraints.

For more information, see Fixed and free boundary degrees of freedom (Nastran, ANSYS, and Abaqus).

Output requests and parameters

You use modeling objects to define the solution results items to be output for the flexible body analysis:

• Use the ANSYS Structural Output Requests modeling object to define the solution results. The options in the Output Requests dialog box correspond to the options for the ANSYS OUTRES, OUTPR, ERESX, and HROUT commands.For more information about creating an ANSYS Structural Output Requests modeling object, see Request output for a modal flexible analysis (ANSYS).

• Use the Output Request Parameters modeling object to select the nodes or elements for which to output the selected solution results items. The options in the Output Request Parameters dialog box correspond to the CNAME and FREQ parameters for the ANSYS OUTRES command.

• Use the Transient Time Table modeling object to define an array of key times at which the specified solution results items are written. The options in the Transient Time Table dialog box correspond to the ANSYS TSRES command.

Use the options on the appropriate page in the Solution dialog box to include these modeling objects in the solution.

Where do I find it?

Modal Flexible Body options

Application	Pre/Post
Prerequisite	A Simulation file as the work and displayed partANSYS as the specified solverStructural as the specified analysis typeModal Flexible Body as the specified solution type

ANSYS Structural Output Requests, Output Requests Parameters, and Transient Time Table modeling objects

Application	Pre/Post
Prerequisite	A Simulation file as the work and displayed partANSYS as the specified solverStructural as the specified analysis typeModal Flexible Body as the specified solution type
Command Finder	Modeling Objects
Location in dialog box	Type→ANSYS Structural Output Requests, Output Requests Parameters, or Transient Time Table

How do I

Set up a modal flexible body solution (ANSYS)

Request output for a modal flexible analysis (ANSYS)

Quick links

Command reference

Pre/Post video examples

Bulk Entry Descriptions

Simcenter 3D tutorials

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Modal flexible body analysis, Simcenter 3D 2021.1 Series

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