Modal flexible body analysis (Abaqus)

You can perform flexible body analyses in the Abaqus environment using the Modal Flexible Body solution. The solution reduces the dynamic behavior of the flexible body to the following:

• A set of mode shapes stored in the Abaqus structural results file (.odb).

• Mass matrix information stored in a mass matrix file (.mtx). You must select to output a mass matrix file to use the results in a flexible body solution in Simcenter 3D Motion. The mass matrix information is used in the flexible body solution unless you select another way to handle the mass properties in the Mass Properties tab of the Flexible Body dialog box. For more information, see Add mass properties to a finite element flexible body.The .mtx file has the same base name as the .odb file with _MASS2 added to the end.

After you solve the solution, in Motion, you can associate the flexible body Simulation or output file with a flexible body on which the component is defined in the motion simulation. The solution only accepts constraints. It has no loads. Both the .odb and .mtx files are used in the flexible body solution in Motion.

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

The Modal Flexible Body solution corresponds to the Abaqus *SUBSTRUCTURE GENERATE keyword.

Flexible body connections and load degrees of freedom

You use the Fixed Boundary Degrees of Freedom constraint to define the connection degrees of freedom at the interface nodes for constraints.

The Fixed Boundary Degrees of Freedom corresponds to the *RETAINED NODAL DOFS keyword.

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

Output requests and parameters

Use the options on the appropriate page in the Solution dialog box to specify the following.

• Eigenvalue ExtractionOn the Eigenvalue Extraction tab, you can specify the number of complex eigenmodes to be extracted and the minimum and maximum frequency of interest.

• Matrix Substructure OutputUse the Output tab to output a substructure's recovery matrix, reduced stiffness matrix, mass matrix, load case vectors, and the gravity load vectors to a file. You must select to output a mass matrix file to use the results in a flexible body solution in Motion.

Where do I find it?

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

How do I

Set up a modal flexible body solution (Abaqus)

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Modal flexible body analysis (Abaqus), Simcenter 3D 2021.1 Series

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