Effect of Adhesion and Cohesion on Ductile Fracture in Cylindrical Upsetting Process

The lubricants employed at the die/billet interface reduce the adhesion and improve the formability of the AA 2014-T6 billets by avoiding cracks. The friction factor obtained from the ring compression test for different lubricants was correlated with the hypothesis of ductile fracture based on void failures to examine the damage rate with the increasing strain. Mohr–Coulomb criterion was employed for observing the cohesive failure for different aluminum alloys. The fitting parameters in the Mohr–Coulomb criterion were varied to study the influence of the process parameters on the fracture strain. The hardness variation in the billets for different stress triaxialities and Lode parameters was also investigated by constitutive modeling of the hardness with the equivalent strain.