FRACTURE PREDICTION IN PLASTIC-DEFORMATION PROCESSES

This paper describes the use of the finite-element technique to predict fracture initiation in a range of simple metalforming operations. These cover typical processes and enable deformation and fracture initiation to be examined under several different loading conditions. Three types of metalforming operation are considered, simple upsetting, axisymmetric extrusion, and strip compression and tension. Using a program developed to deal with metalforming analysis, the local stress and strain distributions are determined. These values are then used with previously published continuum fracture criteria to predict fracture initiation sites. The predictions so obtained are subsequently compared with experimental observations. Only one criterion has successfully predicted the fracture initiation site found experimentally in all the operations examined in this paper: that of a critical value of generalized plastic work per unit volume. This criterion was also used to predict the level of experimental deformation at which fracture should occur, but only with partial success. © 1990.