Metallic materials are widely used in industry. It is now classical to develop numerical simulation for their manufacturing processes in finite transformation and this is one of our laboratory specialities. In order to improve the predictivity of finite elements analysis (FEA), it is necessary to provide accurate constitutive models for mechanical behaviour, such as multi scale modelling. But measurements at small scales are not easy to obtain, especially measurements of damage. The aim of the present work is to develop experimental techniques and data treatments to study damage mechanisms (and necking) at small scale for polycrystalline materials, and identify the damage parameter evolution by families of grains orientation, for micromechanical modelling.