Issue 49

C. Bellini et alii, Frattura ed Integrità Strutturale, 49 (2019) 791-799; DOI: 10.3221/IGF-ESIS.49.70 794 Figure 2 : Geometry of the tested specimens. a) b) Figure 3 : a) Scheme of the equipment (punch and matrix) and of the sheet metal discretized with axisymmetric finite elements; b) achievement the necking condition. The sheet metal nodes on the outer edge are constrained to simulate the presence of the blank holder, while the nodes on the symmetry axis are not allowed to move along the direction orthogonal to the symmetry axis itself. The punch and the die are considered as rigid bodies. To analyse the influence of the friction coefficient on the formability of the aluminium alloy AA6060, the modified Coulomb friction model is considered, whose relationship between the tangential force f t and the normal one f n is as follows: 2 r t n sv v f f arctg R                (5)