Linear transient analysis for rotate problem (SPC/SPCD)

Altair Forum User
Altair Forum User
Altair Employee
edited October 2020 in Community Q&A

Hi everyone,

 

My model is a die bonder arm which rotates 180° around Z direction of a central point in 0.1 second. And I try to perform linear transient analysis (direct transient response) to see all the nodal displacement. So I constrainted the central point with RBE2 and gave an enforce angular displacement using SPC and SPCD pair. (attached file is the input file)

 

However, the analysis result is strange. Because it seems that the arm rotates 90° around center of mass. And as it rotating, it becomes thinner and longer.

 

Thanks & Regards,

Super

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o_4.png        o_5.png

 

The linear transient analysis results are as following figures.(0s -> 0.05s -> 0.1s)

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Unable to find an attachment - read this blog

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Answers

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited April 2017

    Hi,

     

    In your model I see Transient heat transfer analysis and the load you have is a enforeced disp. Please correct this and try again. 

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited April 2017

    Hi @Prakash Pagadala, Thank you for replying.

     

    As the following figure shows, I used transient(direct) as load step type, not heat transfer(transient).

    And I have did the tutorial named [OS-1310: Direct Transient Dynamic Analysis of a Bracket]. What I did is using SPCD in place of DAREA to give the arm an enforce angular displacement.

     

    o_aaaaa.png

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited April 2017

    @ranranhihi

     

    OK, In the file it was heat transfer. I will run the analysis at my end and I will update you soon. 

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited April 2017

    @Prakash Pagadala

     

    What I want to do is to make the arm rotate 180° to see the displacement of the terminal point after the arm stops (or we can call it the residual vibration)

     

    However, I found this note - http://forum.altairhyperworks.com/index.php?/topic/13886-reason-for-large-rotations-in-analysis/&_fromLogin=1

     

    Before that, I think that its residual vibration is small after the arm stops. So I performed linear transient analysis on it.

     

    Maybe I should use non-linear transient analysis (NLGEOM). Could you give me some advises?

     

    Thanks & Regards.

  • Altair Forum User
    Altair Forum User
    Altair Employee
    edited April 2017

    @ranranhihi

     

    Yes, I noticed the same behavior when tuned to transient linear analysis. Due to large rotations the component is heavily deformed. 

     

    You can use NLGEOM instead or NLSTAT with LGDISP (Large displacement).

     

    There are tutorials available on Altair help which you can refer to understand modelling for NLGEOM or NLSTAT with LGDISP

     

     

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