Force Displacement Error

Gokul Ramarathnam_20422
Gokul Ramarathnam_20422 Altair Community Member
edited October 2020 in Community Q&A

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Hello, I am running an abuse test on a component with a simulated down load as seen in the curve. The load is distributed to a rigid plate by a very stiff spring. Force applied is Negative Z (in direction of gravity). The displacement of component is also expected to be same.    The  displacement of the node to which the load is applied is tracked in the plot.

 

My Question is, Why does the displacement reduce in between 100ms and 125ms? Theroretically, it should increase as long as force increases. Any ideas what and where I should check in my model?

 

Thank you!

 

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Answers

  • Simon Križnik
    Simon Križnik Altair Community Member
    edited April 2019

    Hi @Gokul Ramarathnam

     

    perhaps the load is applied too rapidly. Try applying a quasistatic load by ramping up the force in 300ms.



     

  • Gokul Ramarathnam_20422
    Gokul Ramarathnam_20422 Altair Community Member
    edited April 2019

    Hey @Hyperman

     

    Thank you for getting back to me on that! I think you are right, the load application is too rapid and my internal energy curve is too choppy. I have updated my load curve to reflect a slower loading rate.


    Thanks and Appreciate your help!

    Cheers,

    GR

  • Gokul Ramarathnam_20422
    Gokul Ramarathnam_20422 Altair Community Member
    edited April 2019

    Hello @Hyperman,

     

    I made my simulation quasi static, even increasing the loads in smaller steps with time to relax the load in between but the same issue persists. Any other ideas on why this is happening?

     

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  • Simon Križnik
    Simon Križnik Altair Community Member
    edited April 2019

    Can you share the model?

  • Gokul Ramarathnam_20422
    Gokul Ramarathnam_20422 Altair Community Member
    edited April 2019

    Hey @Hyperman,

     

    Unfortunately, I cannot share the model. Do you have any other pointers on where to look or investigate?


    Thanks!

  • Simon Križnik
    Simon Križnik Altair Community Member
    edited April 2019
    Altair Forum User said:

    The load is distributed to a rigid plate by a very stiff spring.

    The issue could be the undamped vibration of a spring used to distribute the loading.

     

    Try to replicate this load distribution method on a simple cantilever beam. If the issue persists share this simplified model provided it is generic enough not to breach any NDA's.  

  • Gokul Ramarathnam_20422
    Gokul Ramarathnam_20422 Altair Community Member
    edited April 2019

    Let me try that. 

    Thanks!

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