Numerical Modeling of Copper Tube Extrusion: Process and Eccentricity Analysis

In order to simulate copper extrusion more closely to industrial practices and to analyze the roots of the complicated issue of tube eccentricity, the material properties and the extrusion conditions were simulated using the finite element modeling (fem) software package, DEFORM^TM-3D. This allowed prediction of stress, strain, strain rate, and temperature conditions within the billet during various processing conditions. These state variables were considered when ascertaining the influence of degree of billet upset and tool misalignment on tube eccentricity. It was found that under ideal upset conditions and perfect tool alignment, the tube eccentricity was minimized. If the piercer (or mandrel) was aligned with an initial angular or parallel misalignment that was still within tolerance the impact on eccentricity initially is minor in comparison to the eccentricity produced toward the end of extrusion, with the angular misalignment scenario being the more severe case. As a result, an angular misalignment is more detrimental than a parallel misalignment for tube preform eccentricity with the given forming parameters.