Foam Simulation law 33 , no densification region

sebmeca

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.

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Simon Križnik

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.