Hello All
This is the first time posting here. I've had a good amount ofexposure to Random Vibration and Shock (Modal Time Response)analyses performed in Simulation and its predecessor.
The displacement results of a R.V. or Hamonic Response analysis caneither be stated as RMS or through spectral response (PSD). (Ithink this is also true with Modal Time Response, but I can'tremember.) This is the displacement in Length^2/frequency over thefrequency band. For the PSD, one can elect to use sensor data andexport the data to spreadsheet. For the RMS, one can just look atthe contours in Simulation.
Parseval's Theorem implies that the Drms is simply the integral ofthe PSD curve, taken to the 1/2 power. This is no different thanthe area of the curve used to obtain the Grms for a randomvibration input spectrum.
My concern is that, when I calculate the area under the curve ofthe sensor's spreadsheet data (using Trapezoidal Rule), I getfactors of 3 to 4 less than the Drms expressed through the RMScontours in Simulation. Does anyone know how Simulationinterpolates and obtains the RMS displacement?
As an aside, I have done some hand calculations under RandomVibration for critically damped components and found that the PSD'sRMS jives very closely to estimates under random vibration, so Iwondering if the RMS calculator in Simulation has something in it.
Regards
Kirby M
SolidworksSimulation
This is the first time posting here. I've had a good amount ofexposure to Random Vibration and Shock (Modal Time Response)analyses performed in Simulation and its predecessor.
The displacement results of a R.V. or Hamonic Response analysis caneither be stated as RMS or through spectral response (PSD). (Ithink this is also true with Modal Time Response, but I can'tremember.) This is the displacement in Length^2/frequency over thefrequency band. For the PSD, one can elect to use sensor data andexport the data to spreadsheet. For the RMS, one can just look atthe contours in Simulation.
Parseval's Theorem implies that the Drms is simply the integral ofthe PSD curve, taken to the 1/2 power. This is no different thanthe area of the curve used to obtain the Grms for a randomvibration input spectrum.
My concern is that, when I calculate the area under the curve ofthe sensor's spreadsheet data (using Trapezoidal Rule), I getfactors of 3 to 4 less than the Drms expressed through the RMScontours in Simulation. Does anyone know how Simulationinterpolates and obtains the RMS displacement?
As an aside, I have done some hand calculations under RandomVibration for critically damped components and found that the PSD'sRMS jives very closely to estimates under random vibration, so Iwondering if the RMS calculator in Simulation has something in it.
Regards
Kirby M
SolidworksSimulation
