Stress History Based Degradation With Custom Rules
This model implements the assuming the degradation factor depends on the stress history.
Syntax
material CustomStressDegradation (1) (2) (3) [4]
# (1) int, unique material tag
# (2) int, host intact material tag
# (3) int, tension degradation expression tag
# [4] int, compression degradation expression tag, default: (3)
Remarks
It is possible to assign different degradation evolution rules for tension and compression.
The degradation expression shall take one scalar input and return a vector of two scalars, of which the first is the degradation factor while the second is the derivative of the degradation factor with respect to the input.
The degradations for positive/negative stresses are defined separately.
Dpos=Dpos(σˉmax),Dneg=Dneg(σˉmin).
In which σˉmax is the maximum stress (positive) of the whole loading history, and σˉmin is the minimum stress (negative) of the whole loading history.
Example
To use this model, expressions of degradation evolution rules must be defined first. Assuming the degradation is an exponential function, and will be activated when the effective stress is larger than 20,
D=exp(−(σˉ−20)/20),
the corresponding derivative is then
dσˉdD=−201exp(−(σˉ−20)/20).
One can then define the expression in a plain text file as follows.