Plastic Beam - Yield criterion

[dxvn818]

Dear all,

I have read the plastic beam model in the thesis of Inigo Terreros with the help of Google Translate because it is in French. Although I do not fully understand, his work was based on the calculation of Von-Misses stress at the middle of the beam, however, in GranOO v2.0, I don't see that calculation in libDEM/Bond/PlasticBeam, instead I saw the codes:

"...
if (plastic_ == false && GetCurrentElongation() > maxElasticElongation_)
        EnablePlasticMode();

...
"

and

"...
if (currentNormalForce > maxNormalForce_)
            {
              const Geom::Vector normalforce = maxNormalForce_*dir;
              Bond::forceOn1_ -= currentNormalForce*dir;
              Bond::forceOn1_ += normalforce;
             
              Bond::forceOn2_ += currentNormalForce*dir;
              Bond::forceOn2_ -= normalforce;

              // Adapt relaxed length
              const double dl = (currentNormalForce - maxNormalForce_)/_K;
              Bond::RelaxedLength() += dl;
              Beam::UpdateCoeff();

            }
...
"

I think GranOO v2.0 use different yield criterion compared to Terreros' work. Is it right ?

Thank you and regards,
Vinh

[Cédric Hubert]

Hi Vinh,

Yes, you are right.
I don't no the reason, I've not worked with Inigo.

But feel free to modify the beam class for your needs.
Stresses are already computed (principal), so you should be able to add your own criterion.

Best regards,
Cedric

[Damien André]

Hello All,
Yes you right, this is another "experimental" plastic beam. This implementation is not the same as inigo's plastic beam. I will try to update the inigo's sources for GranOO 2.0 on the next week. Please remind me if I don't do the job ^^

Damien.

[dxvn818]

Hello Cedric and Damien,

Thanks for your anwser.

Vinh