A phenomenological model to simulate mechanical tests on ultrafine-grained aluminium produced by ECAE

Results of FEM simulations predicting the mechanical behavior at room temperature
of test specimens of ultrafine-grained aluminum produced by ECAE are presented. The
constitutive law is either based on a Hill model or on the Minty micro-macro model and coupled
with an isotropic hardening law and/or kinematic hardening law.
The yield locus shape, its size and its position during tension, compression and torsion tests
have been studied. Initial texture measurements allow the identification of a constitutive law
based on a set of representative crystals and crystal plasticity approach using a Full-
Constraint Taylor model.
Finite element simulations using the previous constitutive laws are compared with experimental
investigations. The results show that applying an initial back stress identified by tensile
and compression tests to the yield locus predicts the initial flow stress in torsion test. The
Minty micro-macro model coupled with a Voce type hardening model gives a good agreement
with experimental results for the prediction of the shape at different stages of deformation of
a compressed test specimen.
The simulation of tensile tests underline the need of inverse modeling as, due to the test
specimen shape, the test is far from being homogeneous. The link between test specimen
length and the necking appearance is studied.