UMAT routine is a well known input format for Abaqus users, used for constitutive laws integration. The contents of this routine should include the integration of the constitutive law, that is on an integration point, compute the stress tensor, internal variables and the tangent operator.
(see document [U2.10.01])
Creating dynamic library:
The dynamic library containing the UMAT routine must be prepared before running the calculation. For this, the user has a simple way to compile the library using the utility as_run [U1.04.00] (with a version of astk greater or equal than 1.8.3). The operation is as follows:
as_run --make_shared -o libumat.so umat.f
Writing command file:
The coupling between UMAT and Code_Aster in the command file is illustrated below:
With this mechanism, it is quite possible to have several different UMAT behaviors (several routines in a library or even different libraries, see for example the test umat002a).
The study is then launched as usual.
See tests :