**process ductile_failure

Description

This post treatment is applied to predict ductile rupture under monotonic loading. The defines a damage variable \(D\) at the time \(t\) which is the integration of time between \(t_0\) and \(t\):

(128)\[D(t)=\exp\left[\int_{t_0}^t a \exp\left(b \frac{{\bf\rm Trace}(\ten S)/3.}{{\bf\rm Mises}(\ten S)}\right) dp\right]\]

where \(\ten S\) is a tensor and \(p\) is a scalar variable (normally the equivalent plastic strain).

One output is generated for each solution “map.” As the evaluation of this criterion is based on an integration, a sufficient number of result outputs are required for a precise answer. The user should therefore ask for a complete set of intermediate outputs (see output_number).

Syntax

**process ductile_failure \(~\,\) *stress name1 \(~\,\) *strain name2 \(~\,\) [*rice_tracey]

name1 is the name of the tensor, and name2 that for the scalar. With the option *rice_tracey the criterion is evaluated with the stress tensor sig and the cumulated plastic deformation ^{1 1}this assumes the name epcum for the cumulated plastic strain. Note that gen_evp behaviors name this variable according to the users input after a potential keyword.

The default values for the coefficients a and b are those used by the Rice-Tracey criterion: a=0.283 and b=1.5.

The variable names generated (in the problem.utp file, and appearing in the Zmaster results) is DAMAGE in the case of a general ductile criterion, and R_R0 if the particular case of Rice-Tracey was chosen.

Example

% Applying the Rice-Tracey criterion needs only:
**process ductile_failure
  *rice_tracey

% The following instructions allow the user to also compute
% Rice-Tracey criterion. sig and epcum are respectively
% the names of the stress tensor and of the
% cumulated plastic strain in the prob.utp file.
**process ductile_failure
  *stress sig
  *strain epcum

% The following syntax must be used in the material file :
**process ductile_failure
  a    0.283
  b    1.5

% This is another criterion:
**process ductile_failure
  *stress x1v
  *strain evcum

% ... with other values in the material file:
**process ductile_failure
  a    0.33333
  b    2.