Foam Simulation law 33 , no densification region

sebmeca
sebmeca Altair Community Member
edited October 2020 in Community Q&A

Hi everybody !

I try to simulate a uniform compressive test with Radioss. I  have already do this with law 70 and I succced. But When I use law 33 ( visco_plas) I can't simulate the 'densification region ' : the difference between green et blue curves. Between law 70 et law 33 I keep the same model and I just change properties and material of foam.  Thanks in advance for your help. I copy my material law 33 and properties associated.  NB: I have blocked with a rigid body and boundary conditions the face without part in contact. The blue part is the impactor , which applies a constant velocity normaly to the face.

<?xml version="1.0" encoding="UTF-8"?>law33_force.PNG

<?xml version="1.0" encoding="UTF-8"?>material_law 33.PNG

<?xml version="1.0" encoding="UTF-8"?>model_law33.png

<?xml version="1.0" encoding="UTF-8"?>propeties_law 33.PNG

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Answers

  • Simon Križnik
    Simon Križnik Altair Community Member
    edited August 2020

    Hi,

     

    The crushing behavior of the foam cells is represented by a stress plateau with irreversible strains. An elasto plastic behavior is introduced in the deviatoric part of the stress tensor in order to represent this phenomenon.

    σ dev plas = A + B (1 + C * γvol) with γvol = (V / V0) − 1

    where σ dev plas is the plastic stress applied to the principal stress of the deviatoric tensor, γvol is the volume strain and A, B and C are modeling parameters.

     

    The densification phenomenon is modeled by a pressure term in the spherical stress tensor.

    σ spher ij = −P * δij with P = (− P0 * γvol) / (1 + γvol − Φ)

    where δij is the Kronecker symbol, Φ is the foam porosity and P0 the initial air pressure.

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