Response Dynamics

Response Dynamics Details View subpanel (Simulation Navigator)

Normal Modes details

The Response Dynamics Details View subpanel in the Simulation Navigator displays the dynamic characteristics for each normal mode, as well as details of each excitation you define.

To list information about all the modes, right-click the Modal Representation node and choose Information. The list that displays includes the following:

The types of results included in the solution (as defined in the Structural Output Request you added to the Dynamics subcase).
The frequency of each normal mode generated.
Information about the generated constraint modes, distributed attachment modes, equivalent attachment modes, and effective masses, as well as the types of results associated with each.

You can use right-click commands on this subpanel to adjust damping ratios, activate or deactivate modes from being used in your events, and plot your excitations.

By default, some columns are hidden.

To display them, right-click any column in the Response Dynamics Details View subpanel and select the desired column names from the Columns list, or, to enable multiple columns, right-click, select Properties and on the Simulation Navigator Properties dialog box enable the desired column names such as %RX_Mass, %RY_Mass, and %RZ_Mass.

Option	Description
# Mode	The mode identifier. For example, if you request 4 modes above 0 Hz in the solution, you see modes numbered 1–4. Active modes to be used in the event evaluation are indicated with an asterisk (). To exclude a mode from the event evaluation, right-click the selected mode and choose Deactivate*.
Frequency	The undamped modal frequency of the selected mode. The mode produces a resonance in the structure if excited at or near this frequency.
Damped Frequency	The damped modal frequency of the selected mode. The mode produces a resonance in the structure if excited at or near this frequency. This value includes the sum of these three damping values:The modal damping ratio you define in the Edit Damping Factor dialog box.Any viscous modal damping calculated by Rayleigh's Damping. Any physical damping calculated by Simcenter Nastran, scaled by the value you enter in the Physical Damping Settings dialog box. For more information, see Damping.
Stiffness	The modal stiffness of the selected mode.
Mass	The total modal mass of the selected mode in all six directions of the coordinate system. This column displays 1.000e+000 because by default, Simcenter Nastran normalizes the mode shapes to a mass of 1.0. To view the actual mass in this column, you must change the Method for Normalizing Eigenvectors option to Max in the Real Eigenvalue – Lanczos dialog box for the solution, and then re-solve and create a new Response Dynamics solution process (or you can edit the EIGRL bulk data entry in the Simcenter Nastran input file and change the MASS field (field 9) to MAX).
%X_Mass, %Y_Mass, %Z_Mass	The percentage of the total effective mass contributed by the selected mode in one of the three translational directions of the coordinate system.
%RX_Mass, %RY_Mass, %RZ_Mass	The percentage of the total effective mass contributed by the selected mode in one of the three rotational directions of the coordinate system. By default, these columns are hidden.
%Viscous	Percentage of the damping for this mode contributed by the user-defined viscous damping for the selected mode. To change the viscous damping, right-click the selected mode and choose Edit Damping Factor.
%Hysteretic	Percentage of the damping for this mode contributed by the user-defined hysteretic damping. To change the hysteretic damping, right-click the selected mode and choose Edit Damping Factor.
%Phys Visc	Percentage of the damping for this mode contributed by the physical viscous damping calculated by Simcenter Nastran (scaled by any scale factor you may have specified). By default, this column is hidden.
%Phys Hyst	Percentage of the damping for this mode contributed by the physical hysteretic damping calculated by Simcenter Nastran (scaled by any scale factor you may have specified). By default, this column is hidden.
Total Effective Mass (X, Y, Z, RX, RY, RZ)	The percentage of the effective mass contributed by all active modes (those modes indicated with an asterisk) in one of the six directions of the coordinate system. If this value is less than 80 percent for all of the active modes in the direction of interest, consider adding more modes to your analysis to ensure an accurate representation of your model. For example, if your excitation is defined in the X direction, but the total effective mass in the X direction is only 20 percent, the evaluation results may not reflect reality.Note: If you defined a large static component of load, and you use the Mode Acceleration data recovery method, you may be able to achieve accurate results with fewer modes.

Residual Vectors details

The Response Dynamics Details View subpanel on the Simulation Navigator displays details of the residual vectors when they are computed.

Option	Description
Vector	The vector identifier.
Frequency	The residual vector frequency.

Excitations details

The Response Dynamics Details View panel on the Simulation Navigator displays details of the excitations you have defined for a given event. You can right-click an excitation row and choose Plot to plot the excitation function in an XY graph.

Option	Description
Name	The name of the excitation as defined in the New Nodal Excitation, New Distributed-Load Excitation, or New DDAM Excitation dialog box.This column also lists the degrees of freedom to which the excitation is applied. 1=X, 2=Y, 3=Z, 4=RX, 5=RY, 6=RZ.
Node/Load Set ID	The ID of the node to which the excitation is applied.
Ordinate Type	The ordinate data type of the function used in the excitation (acceleration, displacement, velocity, and so on).
Scale Factor	The scale factor applied to this excitation. Use scaling to increase or decrease the overall excitation. The software multiplies the output of the excitation function by this factor to arrive at the actual excitation. For example, reduce your excitation by 50 percent by entering 0.5.
Phase Angle	For frequency excitation functions, this angle is used to define the phase difference between two excitations.
Record Name	The name of the excitation function's record in the AFU file.
AFU Name	The path and file name for the AFU file that contains this excitation function.

How do I

Create a Response Dynamics solution process

Clone a Response Dynamics solution process

Check validity of mode shapes

Select or remove modes to analyze in Response Dynamics

Clear the obsolete status of a Response Dynamics solution process

Learn more

Simcenter 3D Response Dynamics

Response Dynamics workflow

Simulation Navigator for Response Dynamics

Post processing response results after clearing the obsolete status

CBUSH element force in Response Dynamics

Random Base Excitation

Response Dynamics Function Toolkit

Look up more details

Response Dynamics status labels

Quick links

Command reference

Pre/Post video examples

Bulk Entry Descriptions

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