Defining the Simcenter Nastran solution

Before you can create a Response Dynamics solution process, your finite element model must be reduced to a set of generalized coordinates (modal degrees of freedom). You generate this reduced mathematical representation of the model by creating and solving a solution. You can create a solution process using the results from these Simcenter Nastran solution types:

SOL 103 Real Eigenvalues

Modal analysis that evaluates normal modes and natural frequencies. Damping is not considered and loads are not relevant. You cannot use enforced motion boundary conditions or the Mode Acceleration data recovery method. The Quasi-Static event is not supported.

SOL 103 Response Dynamics

Full-featured modal analysis that generates normal modes, constraint modes, attachment modes, and/or effective masses. This solution type lets you use all of the Response Dynamics analysis features.

When you create the solution, you must define several output options. Some options are located in the Solution dialog box, and others are located in the Modeling Objects Manager dialog box.

Important note about units

Response Dynamics will produce incorrect results if the model for the Simcenter Nastran modal solution uses units different than one of the two base unit sets, either mN-mm or lb-in. To avoid getting incorrect results, do not change the Output File Units in the Advanced Solver Options dialog box. The units in the OP2 file must be consistent with the base units. If you create the Nastran input file using an application other than this software, export the model in the same units (specified in the UNITSYS parameter in the input file) as the base unit set to be used by Response Dynamics.

Additional setup for SOL 103 Real Eigenvalues solutions

SOL 103 Real Eigenvalues displacement modal results are expressed in the Absolute coordinate system (the Basic coordinate system in Nastran). This may cause errors with results. To generate modal results consistent for use with Response Dynamics, edit the solution Parameters, add the OUGCORD parameter, and set it to GLOBAL.

Additional setup for SOL 103 Response Dynamics solutions

For a random base excitation event to compute homogeneous and laminate element failure metrics, and to define valid residual vectors, select the Random Base Excitation Event check box in the Solution dialog box. When you select this check box, the software also verifies that the solution is set up correctly to solve the random base excitation without errors. For more information, see Random Base Excitation.

How do I

Define rigid-body mode tolerance for Simcenter Nastran

Define Response Dynamics result types

Define the frequency range and number of modes to solve

Filter out modes according to their modal effective mass fraction

Import results and event data from I-deas

Learn more

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Defining the Simcenter Nastran solution, Simcenter 3D 2021.1 Series

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