Coupling of different DOFs using a specific set of formulations
Coupling of different DOFs using a specific set of formulations
(OP)
Hi everybody,
I've faced a problem for which I've not been able to find a solid answer; hence, it would be so nice of you if you could help me with it.
01) Is it possible to define the Force-Displacement relation of a spring using a UMAT (let's say I need a one directional displacement behavior, like a spring, which follows a user-defined constitutive relation)?
02) Let's imagine I have a single point the the bottom of my model, which has just 2 translational DOFs (namely in X and Y directions). Is there a way to define the relation of these two DOFs (which are coupled) via a complicated set of formulations?
I hope it is not vague.
Thank you very much in advance.
I've faced a problem for which I've not been able to find a solid answer; hence, it would be so nice of you if you could help me with it.
01) Is it possible to define the Force-Displacement relation of a spring using a UMAT (let's say I need a one directional displacement behavior, like a spring, which follows a user-defined constitutive relation)?
02) Let's imagine I have a single point the the bottom of my model, which has just 2 translational DOFs (namely in X and Y directions). Is there a way to define the relation of these two DOFs (which are coupled) via a complicated set of formulations?
I hope it is not vague.
Thank you very much in advance.





RE: Coupling of different DOFs using a specific set of formulations
Perhaps *EQUATION keyword will do the trick. Please take a look here:
Abaqus Analysis User's Manual, 34.2.1 Linear constraint equations
Regards,
Bartosz
VIM filetype plugin for Abaqus
https://github.com/gradzikb/vim-abaqus
RE: Coupling of different DOFs using a specific set of formulations
thanks a lot for your answer.
Well, the relation between the two DOFs that I mentioned, is in fact a coupling defined by a specific relatively complex failure surface which has to be defined in a separate file, so I don't think the *EQUATION works in this case.
I'll look forward to any other opinions :)
Best Regards,
Reza
RE: Coupling of different DOFs using a specific set of formulations
b) MPC user subroutine is probably your best bet.
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RE: Coupling of different DOFs using a specific set of formulations
thank you very much for your reply. The MPC was something new for me actually, and I think it works! I need to spend some time on it and I'll update this "thread" with the result.
About your comment "a", I should say that I do not have a tabular data set, I need to implement the constitutive (material) law for the behavior in that DOF. Also a truss element would work, but just under the condition that I use a UMAT for it's material's behavior. Do you have any opinion?
thanks a lot :)
Best Regards,
Reza
RE: Coupling of different DOFs using a specific set of formulations
While they are fun and give you control, I try to avoid recommending user subroutines (unless there are no options) because just to get up and running with them can be a pain in the neck, let alone the actual FORTRAN coding (and the usual fun that comes with coding) for ABAQUS. Besides, many times, you can get away with some existing supported option.
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RE: Coupling of different DOFs using a specific set of formulations
I know how tedious and troublesome a subroutine can be, but I'm afraid I don't have any other options since I'm dealing with a complete set of constitutive relations!
Thank you very much for your fruitful answers :)
RE: Coupling of different DOFs using a specific set of formulations
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RE: Coupling of different DOFs using a specific set of formulations
Thank you very much for your support.
RE: Coupling of different DOFs using a specific set of formulations
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RE: Coupling of different DOFs using a specific set of formulations
RE: Coupling of different DOFs using a specific set of formulations
Now, coming to your latest post: Damage can be modeled with connectors.
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RE: Coupling of different DOFs using a specific set of formulations
I have not done it before, but to learn that, I have a good tutorial in PDF (which is easily found on the web) with examples, I think I'll start from that then.
Thank you very much for your support IceBreakerSours :)
RE: Coupling of different DOFs using a specific set of formulations
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RE: Coupling of different DOFs using a specific set of formulations
In fact, I have to do it, and I've got limited access to someone with the experience. Wish me luck then ;)
RE: Coupling of different DOFs using a specific set of formulations
Like I said, coding subroutines is fun but, under constraints, it isn't a practical venture. I can tell you I *rarely* code any subroutines anymore because it is not pragmatic for me (for many reasons).
Since it isn't straightforward to tell the skillset/level of the person you are interacting with on a forum like this, one has to go by how they frame their question, the jargon they might use, etc. to get a feel for where they might stand at the time of asking the question vis-a-vis their destination. I frame my response accordingly.
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RE: Coupling of different DOFs using a specific set of formulations
Thank you very much again :)
RE: Coupling of different DOFs using a specific set of formulations
By the way, I am not sure what 'macroelements' are but, just in case, you meant to speak of 'superelements', you should know that Abaqus prefers to call them substructures. Check the documentation for more.
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