# Create Power Spectral Density Function

Define power spectral density (PSD) versus frequency response curves.

PSD functions are referenced by dynamic loads. There are multiple methods for creating PSD functions in SimSolid.

1. In the Project Tree, click the Dynamics random analysis.
2. On the Analysis Workbench toolbar, click the icon.
3. Use one of the following processes to create the function:
ActionProcess
Import from external CSV
1. In the dialog, select the Import CSV button.
2. Browse to the desired file and click Open.
Note:

The file contents must have a header row followed by two or more rows of data. Each row has two to three values. Values must be separated with commas. The first is frequency and the second is amplitude.

Example: the file time-value.csv contains:
frequency,amplitude
0.0,0.0
0.1,1.0
0.2,0.0 
Create from standard template functions
1. In the dialog, select the Standard button.
2. In the Function type drop-down menu, choose the desired template.
3. For the Triangle, Rectangle, and Half-sine templates (pulses), specify Amplitude, Start, and duration.
Tip: You may optionally define Period to make the pulse repeat for the entire time history.
4. For the Harmonics template, define Amplitude, Period, and Phase of the harmonic function.
5. Click OK.
Create manually
1. In the dialog, select the Add row button. A new row will appear in the dialog's table.
2. Click in the row under Point #, Frequency, or Amplitude factor to activate a text box.
3. Enter the desired values.
Note:

You can set a periodic function by checking the option Set periodic in Create PSD function dialog. This will make the function repeat for the entire frequency span. To set a periodic function, the amplitudes at the first and the last points must be equal. The period of the function is always evaluated from 0.0 Hz, except for standard functions where the period can be defined in the dialog.

If this option is not checked and the frequency span is outside the range specified in the table, the corresponding amplitude is assumed to be equal to zero.

Options are available in the plotter dialog to change the scale to logarithmic or natural log from linear.

4. Click OK.