A Phenomenological Model to Simulate Mechanical Tests on Ultrafinegrained Aluminum Produced by ECAE

Results of FEM simulations predicting the mechanical behaviour at room temperature of test specimens of ultrafine-grained aluminum produced by ECAE following route B

C

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] for 8 passes are presented. The constitutive law is either based on a Hill model or on the Minty micro-macro [2] 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 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 micromacro 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 modelling 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.