Large-strain formulation

is based on the introduction of an intermediate local configuration, with respect to which the elastic response is characterized. This concept leads to a multiplicative decomposition of deformation gradient into elastic and plastic parts:

$\displaystyle \mbox{\boldmath$F$}$$\displaystyle =$   $\displaystyle \mbox{\boldmath$F$}$$\displaystyle ^e$$\displaystyle \mbox{\boldmath$F$}$$\displaystyle ^p.$ (46)

The stress-evaluation algorithm can be based on the classical radial return mapping; see [20] for more details. Damage is not yet implemented in the large-strain version of the model.

The model description and parameters are summarized in Tab. 10.

Table 10: Mises plasticity - summary.
Description Mises plasticity model with isotropic hardening
Record Format MisesMat (in) # d(rn) # E(rn) # n(rn) # sig0(rn) # H(rn) # omega_crit(rn) #a(rn) #
Parameters - material number
  - d material density
  - E Young's modulus
  - n Poisson's ratio
  - sig0 initial yield stress in uniaxial tension (compression)
  - H hardening modulus (can be negative in the case of plastic softening)
  - omega_crit critical damage in damage law (45)
  - a exponent in damage law (45)
Supported modes 1dMat, PlaneStrain, 3dMat, 3dMatF

VTKxml output can report Mises stress, which equals to $ \sqrt{3J_2}$. When no hardening/softening exists, Mises stress reaches values up to given uniaxial yield stress $ {\it sig0}$.

Borek Patzak