STRUCTURAL DAMPING VS MODAL DAMPING

Nancy Jewel Mcdonie
Nancy Jewel Mcdonie Altair Community Member
edited June 10 in Community Q&A

Hello all experts, 

I want to know what is the difference between structural damping (direct transient frequency response) and modal damping (modal transient frequency response); why in direct transient frequency response we need to convert structural damping to equivalent viscous damping? 

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Answers

  • loistf
    loistf Altair Community Member
    edited June 5
    I can tell about the modal vs structural. When you are in direct transient , the damping matrix can be non-diagonal, anything you want. However, in modal analysis you need to stick to a diagonal matrix, otherwise you would lose the efficiency of the method.
  • Rajashri_Saha
    Rajashri_Saha
    Altair Employee
    edited June 10

    Hi Nancy,

    Transient Analysis does not allow the use of complex co-efficient. That is the reason structural damping is included by adding equivalent viscous damping.

    In Optistruct this can be done by adding the cards PARAM,W3 and PARAM,W4.

    Thanks

    Rajashri

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