STRAIN_NUCLEATION#
Description#
This option allows application of different methods from which the nucleation of porosity may occur.
Syntax#
The nucleation mechanisms are defined as follows:
[ crack_like ]
\(~\,~\,\) type
[ yield COEFFICIENT ]
[ porosity_yield COEFFICIENT ]
\(~\,~\,\) model_coefficient COEFFICIENT
\(~\,~\,~\,~\,\) …
crack_likekeyword indicating that the mechanisms of porosity creation takes the form of cracking or “loss of material.”
yieldallows to define a value of plastic strain below which there is no nucleation.
porosity_yieldDefines a value for the trace of the stress tensor below which there is no nucleation.
The law of nucleation is given by:
where \(\dot\lambda\) is the plastic multiplier. The form of the function \(A\) is variable according to the type of nucleation chosen. The table below summarizes the possible types of nucleation function:
CODE |
DESCRIPTION |
|---|---|
constant |
\(\dot f_n = A\dot\lambda\) |
gaussian |
\(\dot f_n = {\frac{f_n}{\sqrt{2\pi} s_n} \exp\left(-\frac{1}{2} \left( \frac{(p - \epsilon_n)}{s_n}\right)^2 \right)} \dot\lambda\) |
exponential |
\(\dot f_n ={\frac{B}{\epsilon_0}\exp\left(-\frac{p}{\epsilon_0} \right)}\dot\lambda\) |
The corresponding syntaxes are:
constant
\(~\,\) A COEFFICIENT % \(A\)
gaussian
\(~\,\) en COEFFICIENT % \(\epsilon_n\)
\(~\,\) fn COEFFICIENT % \(f_n\)
\(~\,\) sn COEFFICIENT % \(\sigma_n\)
exponential
\(~\,\) B COEFFICIENT % \(B\)
\(~\,\) e0 COEFFICIENT % \(\epsilon_0\)