Deviatoric stress-strain: "deviatoric_strain"

Input

Reading an stress model of unknown type, the name is read first, followed by the data for that type. After the stress model, control data is read then finally a scalar equation of state.

In other words: 

type
parameters
strain_norm_factor stress_norm_factor
fraction_of_plastic_work_going_to_heat (usually ~0.9 to 1.0)
maximum_plastic_strain_per_subcycle (e.g. 0.01)
minimum_angle_for_rotations (e.g. 1.0e-6)
melt_model (see phase region documentation)
equation_of_state (see EOS documentation)
The stress and strain norm factors are used to select the metric convention. The strain convention relates equivalent plastic strain to the tensor strain, once plastic flow occurs. The stress convention is used when comparing the stress deviator with the yield stress. The effective magnitude of a strain or stress tensor t is sqrt(f norm(t)) where f is the apropriate factor. The Hill effective strain is obtained using f=2/3=0.6666667. The Hill effective stress has f=3/2=1.5. The von Mises effective stress has f=3/8=0.375 [Wallace] or f=1/2=0.5 [Dienes & Walsh in Kinslow]. The Wilkins effective stress has f= When performing a calculation using elastic-plastic parameters from any given source, it is important to check the convention used when deriving the parameters.

The maximum plastic strain increment is used to control subcycling of the strain integration algorithm. The minimum angle is used to decide when material rotation can be ignored.

Specific stress model types

State

eos_state
elastic_strain_deviator (real 6-vector: 3x3 matrix in Voigt notation)
equivalent_plastic_strain (real)