Data recovery

The data recovery method is a key attribute of each dynamic event. Depending on the type of analysis you perform, you can recover the dynamic physical responses of a model from its modal response using one of these data recovery methods:

• Mode Acceleration — Assumes the displacements are calculated by adding the acceleration effects (or the static results due to the inertia forces) to the static responses.

• Mode Displacement — Assumes the physical responses are the linear combination of modal contributions from normal modes.

Data recovery method	Characteristics	Suggested Uses
Mode Acceleration	Accurately determines the loads associated with the static component of a dynamic load.Guarantees full FE stiffness. Applies modal truncation to model inertia only. Uses attachment modes as well as normal modes for data recovery. Requires more disk space for data recovery than the mode displacement method (although may not require as many modes to be stored).	When performing a transient analysis (is generally more accurate). When using an enforced motion excitation in which the motion does not fluctuate about a mean of zero. For calculating the frequency responses away from the resonant frequencies. For structures that fly. With this type of problem, there is a steady acceleration with a dynamic fluctuation superimposed. Mode acceleration is more accurate for obtaining stresses and forces for this type of loading. For problems in which you are unsure of the number of modes needed to accurately capture the behavior of the structure. Note: When you use Mode Acceleration, you must set Residual Vectors to None in one of the following places:On the Case Control page in the Solution dialog box of your dynamics solution.In the Solution Step dialog box of the dynamics subcase for a SOL 103 Response Dynamics solution.
Mode Displacement	Applies modal truncation to both stiffness and inertia. Requires only normal modes for data recovery, but may require more normal modes than mode acceleration to represent the behavior of the structure. Is faster and requires less disk space than mode acceleration.	For frequency or random events, especially if you are interested only in displacement, acceleration, or velocity at a high frequency. When the excitation function has a mean of zero.When using an enforced motion excitation in which the motion is the vibration from a neighboring part (for example, the model is mounted on a shaking table). For constrained structures.

Note:

Random analysis always uses mode displacement. Response spectrum analysis uses approximate methods to calculate the peak responses, rather than using one of the methods above. Quasi-Static analysis uses superposition to combine the static loading results or attachment modes with the time history scaling function.

See Response functions for more information about modal and physical responses.

How do I

Create an event

Clone an event

Copy an event from one Response Dynamics solution process to another

Set up sequential transient events

DDAM reference acceleration and velocity

Define multipliers to adjust the standard DDAM shock coefficients

Define custom DDAM shock coefficients

Reduce response errors with residual vectors

Learn more

Events

Required modes for each event type

Excitations in cloned or copied events

Sequential transient events (continuation restart)

Quasi-Static events

Look up more details

Mode acceleration method

Mode displacement method

Quick links

Command reference

Pre/Post video examples

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Data recovery, Simcenter 3D 2021.1 Series

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