Create Random Response Dynamics Analysis

Before you can run a dynamics analysis, you must have a Modal analysis with results. See the Modal Analysis chapter to learn more.

  1. On the main window toolbar, click the (Dynamics) icon.
  2. Click Random response in the drop-down menu.
  3. In the dialog, specify Modal results to which the analysis will be linked.
    Note:

    The modal solution must exist in the current design study. In SIMSOLID, the time integration of the equations of motion is extremely fast and all modes are always included in the analysis.

  4. Specify the Frequency span upper limit and lower limit in the text boxes.
  5. Specify damping in one of the following ways:
    Action Process
    Use Rayleigh damping coefficients Assume the damping matrix is proportional to the mass and stiffness matrices.
    1. Click the Rayleigh damping tab in the dialog.
    2. Specify values for F1 (Mass) and F2 (Stiffness) in the text boxes.
    Use Modal damping Specify a damping ratio for each mode.
    1. Click the Modal damping tab in the dialog.
    2. In the table, under Damping ratio, click on a value to activate a text box. Input the desired damping ratio.
      Note: You can also enter a Default damping ratio and click Apply to use the same ratio for all modes.
  6. Click OK.
    You have finished creating the random response dynamics analysis. Next, you will need to create a power spectral density function.

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:
    Action Process
    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 3 or more rows of data. Each row has three values. Values must be separated with commas. The first is the row index (point), the second is time and the third is amplitude.

      Example: the file time-value.csv contains:
      point,frequency,amplitude 
0,0.0,0.0 
1,0.1,1.0 
2,0.2,0.0
    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 #, Time, orAmplitude factor to activate a textbox.
    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.

  4. Click OK.