Random vibration analysis tutorial

Bala Reddy
Bala Reddy New Altair Community Member
edited January 2021 in Community Q&A

I have carried out the "OS-T: 1325 Random Response Analysis of a Flat Plate' tutorial, to mimic the real time project. However, I could not understand the steps used in the analysis as there was no explanation. It is quite difficult follow & carry out the analysis unless clear explanation in provided for each step. I request you please share the example with clear explain of each step logic behind each step.

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Answers

  • Adriano Koga_20259
    Adriano Koga_20259 New Altair Community Member
    edited January 2021

    you might want to take a look at this post. Maybe it helps.

    https://blog.altair.com/random-response-fatigue-analysis/

     

    Also try to look at other posts in the Community for more info.

    Do you have knowledge on Random Response? or is it the first time that you're using it?

  • Bala Reddy
    Bala Reddy New Altair Community Member
    edited January 2021

    Thank you Adriano for the response. However, i would like to understand the steps created while carrying out the analysis. Specially RNDPS card.

     

    what for this card is used. what's the significance of the X(1) ...Y(1) ... values. no Proper help is mentioned.

    It would be always good to provide the significance with the examples. Can some help to understand 

    image

  • Adriano Koga_20259
    Adriano Koga_20259 New Altair Community Member
    edited January 2021
    Bala Reddy said:

    Thank you Adriano for the response. However, i would like to understand the steps created while carrying out the analysis. Specially RNDPS card.

     

    what for this card is used. what's the significance of the X(1) ...Y(1) ... values. no Proper help is mentioned.

    It would be always good to provide the significance with the examples. Can some help to understand 

    image

    Ok. I agree. The Tutorial is more a step-by-step on how to build the analysis than going thorugh the physics.

    Essentially the RANDPS allows the user to input the PSDs and CrossPSDs as input for your random loadcases. You create the TABRND's for defining your input over frequency range.

    These tables are referenced by the RANDPS cards. All the RANDPS cards with same ID will be applied together into your loadcase. Repeated I and J indicate that your applying a single base PSD in that particular point, with X and Y being components of a complex number.

    When you see I and J different from each other, you're rather applying/calculating the Cross-PSDs o then.

    image

    Please take a look into the OS ebook for more details and equations of what is going on.

    https://altairuniversity.com/free-ebook-learn-dynamic-analysis-with-altair-optistruct/

    https://insider.altairhyperworks.com/wp-content/uploads/2018/01/T-T-1285-OptiStruct-Units-to-be-maintained-for-Random-response-analysis.pdf

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