Polycrystal modelling of IF-Ti steel under complex loading path

Simple and complex loadings were performed on a IF-Ti steel in order to tes t different hardening laws. The different loading paths included uniaxial t ension: plane strain, cyclic shear plane and plane strain tests followed by uniaxial tensile tests. Our aim was to determine the hardening law from th ese tests. For this purpose a polycrystalline self-consistent model was int roduced. In this model an explicit concentration law and an intragranular b ehaviour based on the evolutions of physical parameters were proposed. Loca l objective frames were introduced to extend constitutive equations develop ed at small strains, to the finite strain framework. The identification of the physical parameters was performed thanks to an inverse method and led t o values in good agreement with literature. For the different tests, macros copic stresses and texture evolutions were computed and compared to experim ental results. Initial and prestrain yield stresses surfaces were calculate d. These different simulations pointed out for complex loading paths the ne cessity of an accurate description of the microplasticity mechanisms,in ter ms of slip systems, hardening matrix and evolution of dislocations densitie s on each slip system. (C) 2001 Elsevier Science Ltd. All rights reserved.