Applying Selected Base Excitation for a Random Vibration Study

To apply selected base excitation for a random vibration study:

  1. Right-click the Load/Restraint folder and select Selected Base Excitation.
  2. Under Type, do the following:
    1. Select Displacement, Velocity, or Acceleration.
    2. For Restraint , select a restraint from the list of admissible restraints.
      Admissible restraints are defined with respect to the global coordinate system.
  3. Under PSD Displacement, PSD Velocity, or PSD Acceleration, do the following:
    1. For Unit , select the desired unit.
    2. Click the button for a global direction and enter a value for the power spectral density of excitation.
  4. Under Variation with Frequency, select:
    • Constant to specify constant excitation for the full range of operating frequencies.
    • Curve to specify your own variation or select a library curve. Click Edit to modify the curve.
    The base motion governed by the PSD curve is applied to the selected fixtures. Click View to view the input PSD curve. The software uses a Log-Log interpolation method to interpolate the frequency values that fall between the frequency curve input points. The software converts the input values of the curve to Log-Log scale and interpolates linearly (in the Log-Log domain) to find the values of frequencies that fall between the curve points.
  5. Under Symbol Settings, do the following:
    1. Click Edit Color to select a color.
    2. Set Symbol Size .
  6. Click .