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Contact in FRF

User: "Beta"
New Altair Community Member
Updated by Beta

Hi,

 

I am trying to perform a FRF analysis in a simple model. However, there are some contacts in this model.

 

I know that SLIDE contact type could only be used in a Nonlinear analysis so the it is not possible to use it for FRF anaylysis.

 

Is there any method or some way so I can solve this problem.

 

Thank you! 

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    User: "Rahul Rajan_21763"
    New Altair Community Member
    Updated by Rahul Rajan_21763

    You can run FRF with NLSTAT analysis type. PFA fem deck for same.

    Unable to find an attachment - read this blog

    User: "Beta"
    New Altair Community Member
    OP
    Updated by Beta

    Hi Rahul,

     

    Thank you for your answer. 

    User: "joseph_21332"
    Altair Community Member
    Updated by joseph_21332

    Hi Rahul R

    But however the Preloaded stress and strains are not carry forwarded from the NL substep to modal or FRF analysis.

    if SPC Forces are carry forwarded then the results who be different

    User: "Adriano_Koga"
    Altair Employee
    Updated by Adriano_Koga

    Hi Rahul R

    But however the Preloaded stress and strains are not carry forwarded from the NL substep to modal or FRF analysis.

    if SPC Forces are carry forwarded then the results who be different

    Just a quick coment in the first post:

    SLIDE contact can be used in both linear and non-linear analysis, but it will act differently.

    In linear models (static, modal, FRF,..), the contact status will not change during the analysis, meaning that it will not open or close due to traction/compression effects. There will be still sliding between the parts, frictionless, BUT they won't separate.

    For full NL models, the SLIDE contact will be a frictionless contact but its status might change depending on the loading conditions, if they tend to open or close the contact.

     

    Now, concerning PRELOAD.

    Using PRELOAD into your FRF loadcase will carry Geometric Stiffness resulting from the preload loadcase.

     Please take a look at the attached PDF from the Help.

    It is important to note that, while the prestressed linear analysis includes the
    effects of preloading as a weakening ora stiffening of the structure, the results
    from the prestressed analysis do not include the preloading results. Forexample,
    the displacements from prestressed linear static analysis do not include the
    preloading displacements. Inorder to get the overall deflection/stresses of the
    structure, the displacements/stresses from the prestressed linearanalyses have to
    be carefully superposed with the preloading displacements/stresses while
    post-processing.Particularly, while post-processing complex results from
    prestressed direct FRF, the correct approach would be tofirst obtain the complex
    results for a certain phase and then superpose the appropriate preloading result.
    Any othersuperposing approach would lead to incorrect results.