EXPERIMENTAL STUDY OF THE EFFECT OF TRIAXIALITY RATIO ONTHE FORMABILITY LIMIT DIAGRAM AND DUCTILE DAMAGEEVOLUTION IN STEEL AND HIGH PURITY COPPER

In this contribution, the effect of the stress state (by mean of the triaxiality ratio) on the equivalent plastic strain at fracture is experimentally investigated for different steels and high purity copper in the range of triaxiality from 0 (pure torsion) up to 1.2. This range of stress state is particularly meaningful for the majority of the mechanical applications. The prediction on the formability limit diagram for proportional loading paths (i.e. with constant triaxiality) is verified in the framework of Continuum Damage Mechanics (CDM) using the Lemaitre- Chaboche’s damage model. Furthermore the influence on triaxiality on the threshold plastic strain for damage initiation and for the critical damage at rupture is experimentally studied. The results are compared with the prediction of the aforementioned damage model. A very good agreement between experimental results and CDM prediction is achieved.