by A. Assire et J.-M. Proix, EDF R&D / AMA
The parameters optimization of a model is carried out in Code_Aster thanks to the command MACR_RECAL, which offers several methods of optimization, in particular the traditional algorithm of Levenberg-Marquardt. The parameters to be identified can be coefficients of constitutive laws, loadings, thickness of shells, etc. or any other parameter of the modelization. Optimization consists in finding the values of the parameters which enable to minimize the difference between the numerical response, (in the form of n curves), and n experimental curved.
This command was improved mainly in order to optimize the performances.
Computation can now be carried out according to two modes:
Two traditional stopping criteria were added in the optimization algorithms:
To improve even more the identification performances of the constitutive laws parameters, the simulation command on material point - SIMU_POINT_MAT - was enriched with the key word SUPPORT=’ NOT’; it consists in directly calling the integration routine of the behaviors. It is usable in small strains, without linear research (otherwise it is necessary to use the old computation mode: SUPPORT=’ ELEMENT’). (cf U4.51.12).
The computations times are clearly decreased: for example the tests “compxxx” pass on average from 70s to 9s.
Overall these two evolutions lead to a factor 10 to 20 on the optimization tests of coefficients of constitutive laws. As an example, the test SSNA118A (optimization of 4 parameters of the behavior VISC_CIN2_CHAB on 4 curves) took:
on a local Linux machine.