Why is the difference in displacement so big?

Felipe_20921
Felipe_20921 Altair Community Member
edited June 2022 in Community Q&A

Hello everyone,

i am analysing different methods for bolt modeling in HyperWorks and I found a big difference in displacement for two actually very similar models.

The models contain two plates with a bolted connection with pretension and an external force. The only difference between them is that for one model the plates consist of 2D Elements and for the other it is 3D Elements, therefore I expected fairly similar results.

imageimage

I found that in case of 2D Elements for the plates the pretension force is what causes the drop in displacement, but I dont understand why, it feels wrong.

Can someone explain this? The model files are attached, Thanks.

image

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Best Answer

  • Omar_NDIAYE
    Omar_NDIAYE
    Altair Employee
    edited June 2022 Answer ✓

    Dear Felipe,

    I haven't look closely to you model, but this might be related to the non-deformation through the thickness of the shell elements. While, using 3D elements, this deformation can happen through the thickness.

    Could you try to rerun a large displacement analysis (PARAM,LGDISP,1) and see if you reproduce such difference ?

    Thanks,

    Omar.

Answers

  • Omar_NDIAYE
    Omar_NDIAYE
    Altair Employee
    edited June 2022 Answer ✓

    Dear Felipe,

    I haven't look closely to you model, but this might be related to the non-deformation through the thickness of the shell elements. While, using 3D elements, this deformation can happen through the thickness.

    Could you try to rerun a large displacement analysis (PARAM,LGDISP,1) and see if you reproduce such difference ?

    Thanks,

    Omar.

  • Felipe_20921
    Felipe_20921 Altair Community Member
    edited June 2022

    Dear Omar,

    thanks for your reply. I ran a large displacement analysis and now the difference is in displacement is way smaller. Now it makes sense so thank you very much.

    Regards,

    Felipe

  • Felipe_20921
    Felipe_20921 Altair Community Member
    edited June 2022
    Baye Omar Ndiaye said:

    Dear Felipe,

    I haven't look closely to you model, but this might be related to the non-deformation through the thickness of the shell elements. While, using 3D elements, this deformation can happen through the thickness.

    Could you try to rerun a large displacement analysis (PARAM,LGDISP,1) and see if you reproduce such difference ?

    Thanks,

    Omar.

    Dear Omar,

    thanks again for your reply. I ran small and large displacement analysis for the 2D and also for the 3D Elements model and I found that only for the 2D Elements model there is a drastic change in maximum displacement.

    I further looked into the differences of small and large displacement non linear analysis, but I couldnt find out why I get these results.

    Would you mind trying to explain to me why exactly these differences between small and large displacement analysis occur only for 2D Elements but not for 3D Elements?

    Regards,

    Felipe

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