Upper bound and numerical analysis of cyclic expansion extrusion (CEE) process

Deformation of the material during cyclic expansion extrusion (CEE) is investigated using upper-bound theorem. The analytical approximation of forming loads agrees very well with the FEM results for different amounts of chamber diameter, friction factor and also for lower die angles. However, the difference between analytical and numerical solution increases at higher die angles which are explained by the formation of dead-metal zones at these angles. The results show that the forming load increases at higher friction coefficients, higher chamber diameters and lower amounts of corner fillet radius, but for the die angle there is a maximum value of laod at about 60o. Forming load enhanced by the increase of the die chamber diameter and friction factor. Increasing the die chamber diameter causes to higher strains and, therefore, higher rate of homogenous work. The load decreased slightly by an increase of die corner radius because of the lower and more homogeneous strain distribution in the material.