A stress ratio parameter for studying the workability of metals—Extrusion

The extrusion process has been simulated using the rigid-viscoplastic finite element analysis code ALPID 2.1. Various die geometries, billet materials, and ram speeds were included in the intrinsic workability studies. Conical dies, constant strain rate, and streamlined dies of different length with 9:1 as well as 4.4:1 reduction ratios were studied. Hypothetical materials with various strain rate sensitivities as well as aluminum 2024 and aluminum 1100 were used in the simulations. The rate of change of the square of the stress ratio (mean stress/effective stress) with respect to the log of strain rate as well as several other parameters were plotted for materials in the deformation region of the die. These plots are used to illustrate the stability of materials during the extrusion deformation process. Four different experimental process conditions were used with a streamline die to help confirm the results from the simulations.