Element collapses during non-linear quasi static analysis

Sanjay Dinker_21074
Sanjay Dinker_21074 Altair Community Member
edited August 2022 in Community Q&A

Hello, 

 

I am solving a cantilever model using non linear quasi-static analysis. 

After a certain iteration, the model does not converge. I have attached (1.PNG) what happens in this particular step.

I edited the material curve for this component to have negligible stiffness after ultimate tensile strength. 

Strain 0.18232, UTS 540 MPa, next point

Strain 1, Stress 545

Is this the cause of the elements collapsing during the last iterations? If yes, how do I fix it?

Is there any other reason for the elements to behave in such a way?

 

Regards,

Sanjay

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Answers

  • Robinson Ferrari_20451
    Robinson Ferrari_20451
    Altair Employee
    edited August 2022

    Hi Sanjay,

    You are facing some element distortion probably due to some contact in your model.

    I could notice you are using EXPERTNL, CNTSTB. So, prefer using the CNTSTB load collector specifying any smaller value for S0 (0.01?), and you can try S1=0.001 to see if it helps. If not you can try increasing TFRAC to 1.0 (in CNTSTB as well).

    Also, try penalty=SOFT instead of penalty = AUTO which should help you to converge.

    Another important point is to adjust your material data to avoid WARNING # 3003. So, adjust your curves even using only plastic curves and TYPSTRN=1 in MATS1.

    Please let me know if works for you.

    Thank you very much,

  • Sanjay Dinker_21074
    Sanjay Dinker_21074 Altair Community Member
    edited August 2022

    Hello Robinson, 

     

    Thanks for the info. I have updated the contact set again.

    Initially I had node to surface contact, now I simulated using surface to surface contact. And I also changed back the material curve. The model simulates without any elements distorting. I need to check these results. 

    I will try changing CNTSTB and update the material curves later today and check if it helps out for the previous models.  

     

    Regards,

    Sanjay

  • Robinson Ferrari_20451
    Robinson Ferrari_20451
    Altair Employee
    edited August 2022
    Sanjay Dinker_21074 said:

    Hello Robinson, 

     

    Thanks for the info. I have updated the contact set again.

    Initially I had node to surface contact, now I simulated using surface to surface contact. And I also changed back the material curve. The model simulates without any elements distorting. I need to check these results. 

    I will try changing CNTSTB and update the material curves later today and check if it helps out for the previous models.  

     

    Regards,

    Sanjay

    Hi Sanjay,
    Thank you for your response.
    Ok, let me know if works for you.
    Thank you very much,
    Robinson

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