Altair SimSolid transient dynamics adds base excitation

Base Excitation is an optional load type available in Altair SimSolid dynamic solution capabilities. It is used to understand the behavior of a vibration isolation system. One or more structural supports are given a prescribed motion, causing the system to vibrate. This can be used to model a vehicle suspension system or the earthquake response of a structure. Read on to find out more.

Altair SimSolid transient dynamics

Transient dynamics in Altair SimSolid are based on the modal superposition method. A modal analysis is first run to determine the natural frequencies and modes shape of a structure. Three types of dynamic simulations are available:

  1. Time response – also sometimes called transient dynamics analysis, this determines the response of a structure to a series of time varying loads.
  2. Frequency response – also sometimes called harmonic analysis, this determines the response of a structure to harmonically varying loads.
  3. Random response – also sometimes called spectrum analysis, this determines the response of a structure to power spectral density (PSD) loads.

In Altair SimSolid, all dynamic analysis are linear and either modal or Rayleigh damping is used.

Base excitation

In Altair SimSolid, base excitation is supported for time, frequency and random response transient dynamic analyses. Restrictions are that base movement must be specified in the global XYZ coordinate frame and specified in terms of either displacement or acceleration amplitude histories.

For time domain analysis, an additional option is available which allows multiple supports to be excited independently. This can be useful for modeling traveling motion waves over a large structure, or independent forces acting on different locations on a vehicle.

Altair SimSolid base excitation is very easy to setup and do. Only a few simple steps are required:

  1. Create a new analysis – select either transient response, frequency response or random response from the analysis definition menu.
  2. Specify system settings – only three inputs are required. Select a previously run modal analysis as the modes source, specify the desired total simulation time and specify damping values.
  3. Create vibration functions – Create an time, frequency or PSD function by entering in XY data pairs. Values may be entered manually or read from an external CSV data file. Standard functions for triangular, rectangular, half sine, harmonic or uniform pulses are also available.
  4. Define the base excitation load or loads – define the global XYZ loading direction, the type of load (displacement or acceleration) and the time series to use.
  5. Run analysis and view results – dynamic analysis are very fast and typically run in only a few seconds. Altair SimSolid only retains internal analytic functions and does not store exhaustive time/frequency based displacement, stress, strain, reaction force results. This make the project file size much smaller than more traditional approaches. Results are then calculated on the fly during model opening or post-processing.

Check out the view example for more details.

Video example

Transient dynamics are available in Altair SimSolid Professional edition. Give it a try today.


Ken Welch
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Ken Welch

About Ken Welch

Ken was the cofounder and CEO at SIMSOLID corporation. He has over 30 years experience in the CAE industry in a variety of technical, sales and executive roles at companies including PDA Engineering, Rasna, Moldflow and MSC Software. Ken holds a B.S. and M.S. in civil engineering from the University of California, Davis.