converting to RMS value from Harmonic response spectrum

  • Last Post 03 May 2019
Hadi96 posted this 26 March 2019

Good Day,

Dear Guys,

I had a problem to converting spectrum data to Rms Value, i did not want the negative value to be appeared , how can i do it?

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kcao posted this 29 March 2019

I am not sure if I understand your question. RMS means root mean squared. You will square the value, so eventually everything is positive under square root.


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  • Hadi96
jj77 posted this 29 March 2019

RMS is more for summing stresses in response spectrum analysis (PSD or response spectra/earthquake say).


I think you mean amplitude.


The FRF is a complex function/number, and you are showing the imaginary part of that complex number.


Complex numbers and FRFS can be represented thus by a phase and an amplitude (positive number). Thus for complex number z:

z = x + i*y = ¦z¦*exp(i*phase),


So you need/mean the amplitude of the FRF which is:



You can set amplitude under details, options, and display in the frequency response.

Search the ansys help manual for:

Frequency Response and Phase Response

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Hadi96 posted this 30 March 2019

Thank you for your help sir, i had change to amplitude, are you sure it indicate the RMS value, since its look too different between the imiginary result before




vishavjeet062 posted this 03 May 2019

how can @Hadi96 ,you get a amplitude graph ?

have to apply the rotating force and fixed rotation