Usually the most important measures in Random Vibration problems are the RMS measures. This is because all frequencies are acting simultaneously and the RMS values represent the square root of the area under the PSD curve. Statistically it represents the 1-sigma results.
When RMS measures are created or the option to calculate full RMS results is selected, Creo Simulate must calculate a full set of displacement and stress results at each frequency step. This will increase run time significantly sometimes by orders of magnitude.
Random vibration analysis will calculate RMS values for each displacement direction and component of stress. Since these values are Root-Mean-Square (RMS) they will always be positive. This means that combining these values to obtain a maximum resultant is not purely valid. Many FEA codes including Creo Simulate will calculate maximum displacement, Von Mises stress or Principal stresses based on Random Vibration results. It is important to remember that these calculations are based on all positive component values and will not be accurate.
