COMPARISON OF EXTRUSION STRAINS PRODUCED BY COSINE AND CONICAL DIES

Visioplastic analysis is used to compare strain fields produced in cyl indrical aluminum billets extruded at elevated temperature through axi ally symmetric dies that have either a cosine or a conical profile, Th e visioplastic method consists of computing strain rates from changes experienced in a flow function as a billet passes through the extrusio n die, The flow function is constructed using a grid that is stamped o n an axial plane of the billet before extrusion, After the partially e xtruded billet is removed from the die, numerical methods are used to determine the str ain rates from the deformed grid, The state of strai n over the extrusion region is computed using transformation and then integration of the strain rates, Results show that, unlike the conical die, the cosine die does not produce strains of reversed sign in the die entry region, The consequent benefits of using cosine dies for ext rusion of powder metals are discussed.