3. Parameters of the law#
The material parameters required to use the model in Code_Aster via the DEFI_MATERIAU command (see doc U4.43.01) are as follows:
ASTER |
Symbol |
Definition |
EPS0
|
\({\varepsilon }_{0}\) |
Parameter acting on the kinetics of viscoplastic deformation |
K |
\(K\) |
Parameter governing the hyperbolic sine behavior of the viscoplastic law |
H1
|
\({h}_{1}\) |
Work hardening module |
H2
|
\({h}_{2}\) |
Work hardening module |
DELTA1
|
\({\delta }_{1}\) |
Choice of the type of work hardening |
DELTA2
|
\({\delta }_{2}\) |
Choice of the type of work hardening |
H1ST
|
\({H}_{1}^{\text{*}}\) |
Saturation value of work hardening, in the non-linear case |
H2ST
|
\({H}_{2}^{\text{*}}\) |
Saturation value of work hardening, in the non-linear case |
BIGA
|
\({A}_{0}\) |
Parameter acting on damage kinetics |
SIG0
|
\({\sigma }_{0}\) |
Parameter governing the hyperbolic sine behavior of the law of damage |
ALPHAD
|
\({\alpha }_{\text{D}}\) |
Coefficient affecting the effective stress for the calculation of damage |
KC
|
\({k}_{c}\) |
Parameter governing microstructural damage kinetics |
S_EQUI_D
|
\({\alpha }_{\sigma }\) |
Choice of maximum hydrostatic or main stress |
Parameters \({\alpha }_{\text{D}}\), \({k}_{c}\), and \({\alpha }_{\sigma }\) are optional and have zero values by default.
The identification of the coefficients of the viscoplastic part of the model is carried out from creep tests at various stress levels.
Once this identification has been carried out, the coefficients driving the damage can be identified from long creep tests at low stress for which a drop in ductility is observed (drop in deformations at break).
A typical example of identification is detailed in [bib2].