Multiscale Simulation Study on the Anisotropic Behavior of Seamless Copper Tubes Processed under Varied Conditions

One of the most important parameters making the production of precision tubes a challenging process, is the inhomogeneity of mass flow in the pre-stage of processing leading to eccentricity, heterogeneity of residual stresses and crystallographic texture. This paper presents a multiscale modeling framework linking four disparate length scales for studying eccentricity and texture evolution in the tube drawing process with standard as well as tilted dies. The main aim of using this methodology was to comprise the anisotropic elastic and plastic behavior of the material and the crystallographic orientations in the FEM model. p This multiscale modeling framework starts with electronic scale calculations using the density functional theory approach to calculate the energy variation as a function of lattice parameters as well as the generalized stacking fault energy for copper. The calculated parameters are bridged to the next simulation scale, the atomic scale calculation. Where molecular dynamics simulations are performed to generate mobilities for dislocations and drag coefficients. The dislocation dynamics approach in the microscale then utilized the mobility values to compute the hardening parameters using the Palm-Voce hardening equation. The use of UMAT subroutine allowed to combine the crystal plasticity theory with the FEM model and calculated elastic and plastic parameters. These last ones were imported to the FEM simulations created for a two-step tube drawing process, performed with standard as well as tilted dies. The simulation results were validated using the measured eccentricity, texture, and mechanical properties: they were in a good agreement with the experimental results.