Upper bound analyses of novel backward extrusion

In this paper, an upper bound analysis for novel backward extrusion has been presented. Initially deformation zone has been divided to four separated regions and an admissible velocity field for them has been suggested. Then total power in this process has been calculated for every region and extrusion force has been gained. Moreover investigation of relevance of extrusion force and process powers (friction, deformation, velocity discontinuity) with process parameters has been revealed better understanding in load estimation and process efficiency in this method. Finite element analysis by DEFORMTM3D has been done for validation of upper bound results. Upper bound analysis showed, increasing of initial billet diameter enhances extrusion force by nonlinear relation. In addition big billet size remodels novel backward extrusion to conventional backward extrusion and it proves lower requirement extrusion load in novel backward extrusion in comparison with conventional backward extrusion. Moreover Increasing of first region’s thickness in this process diminishes extrusion force by exponential relation and no considerable change in extrusion force can be seen in a particular thickness domain. Investigation of process parameters in power efficiency shows that bigger extruded part’s diameter creates critical condition in process efficiency because of high friction power. But increasing of thickness enhances power efficiency. Finally upper bound analysis results have a good agreement with FEM.