Investigation into Lubricated Extrusion of Round Tubes through Streamlined Dies Considering the Plastic Flow

Abstract

In cold lubricated extrusion of round tubes the material properties and surface quality of the extruded products are influenced by the die profile. Streamlined dies induce less redundant work and render desirable distribution of strength. In the present general analysis the shapes of the die and the mandrel are expressed by continuous functions. A new general kinematically admissible velocity field for the metal flow is proposed which permits the prediction of metal flow. The upper-bound extrusion pressure is found by using the upper-bound theorem. The grid distortion is computed tracing metal flow along the stream lines. The effective strains are computed to know the workhardening pattern of the extruded tube products. Experiments have been carried employing A12024 as working material. The effect of process parameters such as area reduction, die length, tubular shape ratio (thickness to outer diameter) and friction condition etc. on extrusion power and metal flow has been studied extensively. The theoretical predictions both in extrusion load and metal flow have been shown to be in good agreement with the experimental results. The suggested streamlined dies are shown to be effective for extrusion of round tubes rendering less extrusion power and desirable flow patterns.