Frequency Curve

The Frequency Curve dialog box lets you define or import a frequency curve to define frequency-dependent quantities for harmonic and random vibration linear dynamic studies.  You define X and Y pairs or read them from a text file. The Y value of the frequency curve is a multiplier to the associated quantity. For example, a force of 200 psi associated with curve A specifies a force as shown in curve B. At any frequency (f), the value of the force applied by the program is equal to the specified force value times the Y-value of curve A at frequency (f). You can define up to 5000 points.

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.

-or-

2. • Click Curve to specify your own variation of load versus frequency. If you select this option, continue with the next step.

3. 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.

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.

To use a frequency curve from an existing library:

1. In a load or restraint PropertyManager in a transient thermal or nonlinear study, under Variation with frequency, click Curve then click Edit.

2. In the Frequency curve dialog box, click Get Curve.

The Function Curves dialog box opens.

3. Select the desired curve library file (*.cwcur). The existing curve data files are listed under Frequency curve.  

4. Under Curve Library, select the desired  frequency curve.

The curve data appears in the dialog box.

5. If needed, modify the curve data then click OK.

You will return to the Frequency Curve dialog box.

6. Click OK.

You return to the PropertyManager.