converting to RMS value from Harmonic response spectrum

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?


  • KaiKai Forum Coordinator
    edited 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.


  • jj77jj77 Member
    edited 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

  • Hadi96Hadi96 Member
    edited 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




  • vishavjeet062vishavjeet062 Member
    edited May 2019

    how can @Hadi96 ,you get a amplitude graph ?

    have to apply the rotating force and fixed rotation 

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