Polycrystal modelling of IF-Ti steel under complex loading path

Simple and complex loadings were performed on a IF-Ti steel in order to test different hardening laws. The different loading paths included uniaxial tension, plane strain, cyclic shear plane and plane strain tests followed by uniaxial tensile tests. Our aim was to determine the hardening law from these tests. For this purpose a polycrystalline self-consistent model was introduced. In this model an explicit concentration law and an intragranular behaviour based on the evolutions of physical parameters were proposed. Local objective frames were introduced to extend constitutive equations developed at small strains, to the finite strain framework. The identification of the physical parameters was performed thanks to an inverse method and led to values in good agreement with literature. For the different tests, macroscopic stresses and texture evolutions were computed and compared to experimental results. Initial and prestrain yield stresses surfaces were calculated. These different simulations pointed out for complex loading paths the necessity of an accurate description of the microplasticity mechanisms,in terms of slip systems, hardening matrix and evolution of dislocations densities on each slip system.