Defining a Frequency Curve

To define a frequency curve:

  1. In the PropertyManager of a load or base excitation in a harmonic or random vibration study, under Variation with frequency, do one of the following:
    • Click Linear to use the default linear curve of load versus frequency. If you select this option, go directly to step 7.
    • Click Curve to specify your own variation of load versus frequency. If you select this option, continue with the next step.
  2. Click Edit.
    The Frequency Curve dialog box opens.
  3. In the Curve information box, type a name for the curve.
  4. Set the Units for the X (rad/sec or Hz) column. The Y values are dimensionless multipliers to the quantity specified in the PropertyManager for the associated load or base excitation.
    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. Edit the curve data as desired. To get the curve from an external file, click Get curve.
    The Function Curves dialog box opens.
    The X-Y columns show the default values based on the selected shape. You can edit the values in the cells as desired. To add a row, double-click in any cell in the Points column. To delete selected rows, right-click the selection and select Delete.
  6. To save the curve for subsequent use, click Save Curve, specify a name and a destination folder for the curve file and click Save.
    The program adds the extension .cwcur to the filename. The specified curve can be used in other documents.
  7. Click OK.
    You will return to the Load/restraint PropertyManager.
  8. To view the actual values of the specified load/restraint, under Variation with frequency, click View.
  9. Close the graph window.