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

A Stress Ratio Parameter for Studying the Workability of Metals-Tension and Compression

Axisymmetric tension and compression tests were simulated using the rigid-viscoplastic finite element analysis code ALPID 2.1. The tension test simulations were run for strain rate sensitivity parameters in the range of 0.2-–1.1. The compression test simulations were run for 0.2, 0.4, and 0.8 strain rate sensitivity parameters and for 0.0, 0.001, 0.150, and 0.800 friction factors. Variations of the stress ratiog (mean stress/effective stress) in combination with the strain rate and with respect to time have been studied. The rate of change of the square of theg parameter with respect to the log of the strain rate allows a useful description of the material workability within the simulated test specimens during the deformation processes