Sine on Random
Sine on Random
(OP)
I am doing a study on Combining Sine and Random vibration.
In test bench, component is tested by starting Sinusoidal testing then followed by Random vibration testing. Harmonic effect continues in Random vibration testing.
I wants to compare my test results with simulation. I performed separately Harmonic analysis and Random analysis then combined using square root of sum of squares method ( SRSS - is not advisable because it lost phase information).
Another method I performed a Random vibration analysis in frequency domain by combining sine and random spectra ( combined in time domain )
Is it possible to compare the combined spectra ( sine and random ) with the test results ( Sequence of harmonic followed by random testing).
If possible, how can the results be justified.
Arumuga Pandian
In test bench, component is tested by starting Sinusoidal testing then followed by Random vibration testing. Harmonic effect continues in Random vibration testing.
I wants to compare my test results with simulation. I performed separately Harmonic analysis and Random analysis then combined using square root of sum of squares method ( SRSS - is not advisable because it lost phase information).
Another method I performed a Random vibration analysis in frequency domain by combining sine and random spectra ( combined in time domain )
Is it possible to compare the combined spectra ( sine and random ) with the test results ( Sequence of harmonic followed by random testing).
If possible, how can the results be justified.
Arumuga Pandian





RE: Sine on Random
Tunalover
RE: Sine on Random
RE: Sine on Random
You can model very weird vibration modes through numerical analysis. Work out your applied forces and/or displacements. Do the numerical integration. When I did this, I was curious about non-linear damping.
This may be doable on a spreadsheet. It certainly can be done with MathCAD or Octave.
--
JHG
RE: Sine on Random
Harmonic effect is due to a too high level of the excitation.
Try to decrease the level of the signal till the harmonics disappear.
To understand, you can imagine a signal with a fixed sinus frequency. The FFT is just one Dirac.
Now, if the gain is too much, then the sinus is notched out. The sinus looks like a square signal and its FFT is a suite of decreasing Dirac (the harmonics).