SIZE AND GEOMETRY-EFFECTS ON DUCTILE RUPTURE OF NOTCHED BARS IN A C-MN STEEL - EXPERIMENTS AND MODELING

The aim of this work was to investigate the effect of specimen size an d geometry on ductile fracture of a C-Mn steel with high sulphur conte nt. Uniaxial tensile tests were conducted at 300 degrees C on axisymme tric notched specimens having different sizes and geometries. Geometry effects were studied using specimens with various notch radii, thus i nducing different stress triaxiality levels. Size effects were evidenc ed using homothetic samples having the same geometry. Results show tha t ductility is reduced on specimens with sharp notches (which is a com mon observation). As specimen size increases, mean ductility as well a s scatter are reduced (showing a clear size effect). In order to predi ct rupture, locally coupled (post-processing type) and fully coupled ( continuum damage mechanics) Finite Element models were used. They are based on the plastic criteria introduced by Gurson and Rousselier. In order to model size effect (decrease of ductility and scatter), initia l distribution of inclusion volume fractions, measured by quantitative metallography, was accounted for in the simulations. Comparison of ex periments with simulations showed that both model types could predict mean values of ductility and scatter.