Mechanical behavior of ferritic grade 3Cr12 stainless steel-Part 2: Yield locus and hardening laws

In practice, the finite element method is quite successful in simulating the metal forming processes or the structural behavior of members carrying loads. The accuracy of such models largely depends on the mechanical laws used to describe the material behavior. Numerous authors have shown the effect of material anisotropy on deep drawing or the influence of non-linear hardening behavior on the resistance of structural members. Studies have also demonstrated how important the evaluation of the material parameters is during the theoretical calculation of the strength of stainless steel members for instance. Non-linear metallic materials emerge as an alternative to elastic perfectly plastic materials, be it for their stainless, ductility or strength properties. It is thus necessary to be able to accurately model their material behavior. In the present paper, prior to any computations, different laws are described: simple phenomenological law and micro–macro constitutive models based on crystal plasticity. Classical yield surface such as Hill one are combined with isotropic (Swift or Ramberg– Osgood) and kinematic (Armstrong–Frederick or Teodosiu–Hu) hardening models to define the material behavior. The material parameters included in each law are then carefully identified. For that purpose, the experimental equipment developed by Flores (2005) in the Structures Laboratory of the University of Liege was used to perform biaxial tests. Coupled with classical uniaxial tests, they provide the necessary data for the identification of the yield locus and the hardening models.