/MAT/LAW33 (FOAM_PLAS)

Format

Definitions

Example (Foam)

#RADIOSS STARTER
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/UNIT/1
unit for mat
                  Mg                  mm                   s
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#-  2. MATERIALS:
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/MAT/FOAM_PLAS/1/1
Foam
#              RHO_I
               2E-10
#                  E        Ka  func_IDf          Fscalecurv
                 200         1         0                   1
#                 P0                 Phi             Gamma_0
                   0                   0                   0
#                  A                   B                   C
                1E30                   0                   0
#                 E1                  E2                  Et            eta_comp           eta_shear
                   0                   0                   2                2E27                1E27
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#ENDDATA
/END
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

Comments

1. If the limiting yield curve is not defined, then the material follows a Maxwell-Kelvin-Voight visco-elastic model.

   
   
   

   Figure 1.

2. If the limiting yield curve is defined, then the material initially follows the visco-elastic law until it intersects the defined yield curve, which limits the visco-elastic stress in tension and compression. The material does not experience plasticity, but instead behaves in a visco hyperelastic way.
3. If the yield function fct_ID_f = 0, then(1)
   $${\sigma }_y=A+B(1+C\gamma )$$
   Where, $\gamma$ is the volumetric strain:(2)

   $$\gamma =\frac{V}{V_0}-1+{\gamma }_0=\frac{{\rho }_0}{\rho }-1+{\gamma }_0=\frac{-\mu }{1+\mu }+{\gamma }_0$$
4. If the yield function fct_ID_f ≠ 0, then $\sigma$ vs. $\gamma$ is read from input of the curve idenfier fct_ID_f. The curve can be defined for tensile ( $\gamma >0$ ) and compression ( $-1<\gamma <0$ ). The input stress should be positive for both tension and compression.

   
   
   

   Figure 2.

5. The optional air pressure, as a function of the volumetric strain can be added to the structural pressure. Pressure is applied only on the spherical part of the stress tensor.(3)
   $$P_{air}=-\frac{P_0\cdot \gamma }{1+\gamma -\mathrm{\Phi }}$$
6. Young’s modulus is used as the initial slope for unloading. It can be constant or variable, based on the strain rate.(4)
   $$E=\max (E,E_1\dot{\epsilon }+E_2)$$
7. The unloading or the loading direction change (tensile <-> compression) is following the current elastic modulus, like an isotropic elastic-plastic material or highly viscous foam material. However, there is no plastic strain accumulation.

   
   
   

   Figure 3.