Continue Loads through subcases

Arno Heidkamp
Arno Heidkamp Altair Community Member
edited March 2023 in Community Q&A

I want to do a non-linear analysis with subsequent loading:

  • Subcase 1
    • Prestress
  • Subcase 2
    • cont. Prestress 
    • Load 1
  • Subcase 3
    • cont. Prestress
    • Continue load 1
    • add load 2

I found that CNTNLSUB carries over the stresses and strains from previous subcase, but not the load.

Then, if stresses&strains are carried over, but the load starts from scratch, there will be a discontinuity, won't there?

I wonder which combination is correct:

  • Subcase 1
    • Prestress
  • Subcase 2
    • CNTNLSUB(1)
    • Load 1

AND

  • Subcase 3 (I expect a different load path here, becaue Load 1 will start from zero again and will be lineary superimposed to Load 2)
    • CNTNLSUB(1)
    • LOADADD(Load 1, Load 2)

OR

  • Subcase 3 (if the above said is true, then the stresses and (linear) strains from Load 1 will have disappeared at the end of this subcase)
    • CNTNLSUB(2)
    • Load 2

OR

  • Subcase 3 (I expet a discontinuity here, because Load 1 will start from zero again, while the corresponding stresses & strain are carried over)
    • CNTNLSUB(2)
    • LOADADD(Load 1, Load 2)

 

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Answers

  • Robinson Ferrari_20451
    Robinson Ferrari_20451
    Altair Employee
    edited March 2023

    Hello Heidkamp,

    If you do your first example (LOADADD), load 1 will not start from zero. You will only add load 2 in this case. So, this should be the right option for your case.

    Please try this in a small deck and let me know if it works for you. Otherwise, attach your deck and I can take a look.

    Thank you,

  • Arno Heidkamp
    Arno Heidkamp Altair Community Member
    edited March 2023
    Robinson Ferrari_20451 said:

    Hello Heidkamp,

    If you do your first example (LOADADD), load 1 will not start from zero. You will only add load 2 in this case. So, this should be the right option for your case.

    Please try this in a small deck and let me know if it works for you. Otherwise, attach your deck and I can take a look.

    Thank you,

    Hello Mr. Ferrari,
    many thanks for the quick response.

    Just to make sure:

    Do you mean option 1 (CNTNLSUB(1)+LOADADD) or do you mean option 3 (CNTNLSUB(2)+LOADADD)

    Kind regards,

    Arno

  • Robinson Ferrari_20451
    Robinson Ferrari_20451
    Altair Employee
    edited March 2023
    Arno Heidkamp said:

    Hello Mr. Ferrari,
    many thanks for the quick response.

    Just to make sure:

    Do you mean option 1 (CNTNLSUB(1)+LOADADD) or do you mean option 3 (CNTNLSUB(2)+LOADADD)

    Kind regards,

    Arno

    Hello Arno,

    Subcase 1: pretension = ID_1

    Subcase 2: statsub(pretension=ID_1) + Load1=ID_2

    CNTNLSUB YES or CNTNLSUB=1

    Subcase 3: statsub(pretension=ID_1) + load3=ID_4 => (ID_4=LOADADD for Load1=ID_2 + Load2=ID_3)

    CNTNLSUB YES or CNTNLSUB=2

     

    PS: In OptiStruct, for continuing to use a load applied in a new subcase that continues from the previous one, you need to re-apply this load, the same for SPC, TEMP, etc.

    Thank you,

    Robinson

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