Extrusion analysis and workability prediction of three-layer composite hexagonal clad rods

This study uses upper bound method to predict the workability for the extrusion of three-layer composite hexagonal clad rods. A velocity field is generated with the assistance of a product's cross-section profile functions. The velocity component in the extrusion axis is expressed as a convex distribution. The simultaneous deformation of each constituent material with quite different mechanical properties may lead to fracture. A criterion for fracture based on the velocity deviation existing on the layer interface was proposed. Material fractures under extrusion are affected by a set of independent process parameters, including the initial area percentage of each layer, friction condition of die, mechanical characteristics of three constituent materials and reduction of area of billet. Finally, figures of extrusion limits containing safety and fracture zones for each process parameter are obtained for extrusion of three-layer composite hexagonal clad rods.