Study of Anisotropic Behavior in Tube Drawing Process Using Multiscale Simulation

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In the production of precision tubes, the reduction of eccentricity is a challenge even at an early stage of the process. The DFG project has shown that it and the residual stresses in drawn tubes can be controlled with tilting of the die or an offset between the die and tube. For this, Cu tubes of various dimensions were examined and their eccentricity, residual stress and texture changes were analyzed experimentally and simulatively. A 3D FEM model was developed and a UMAT subroutine was programmed to describe texture changes. The elastic and plastic hardening parameters required for the Chrystal Plasticity (CP) approach to describe the flow behavior were taken from the literature and imported into the FEM calculations. The simulation results obtained are in good agreement with the experimental data.Since these parameters are directly in conjunction with structure and properties of the material in lower scales, the main aim of this work is modifying the existing CP Finite Element (CPFE) model through multiscale simulation, so developing a simulation model based on the Integrated Computational Materials Engineering (ICME) concept to evaluate the anisotropic behavior of the material. However, the existing model will be first tested for Al tubes to check the feasibility of the model developed for Cu tubes for other materials. The multiscale methodology will be used to achieve all the necessary parameters for the final CPFE model. It will also provide a more precise and accurate predictive tool for analyzing the forming processes because the prediction of mechanical properties in structure level will be performed regarding the effect of features in smaller scales. Moreover, using ICME approach, a framework will be developed that is linking four desperate length scales (electronic-atomic-micro-meso) for the prediction of materials behavior during tube drawing. It should be also possible to be usable for other parameters like different materials, different amounts of reduction, and various tilting/offset values as well as – finally - for other forming processes. For this aim, Dislocation Dynamic (DD) simulations will be used to define the hardening rule constants. Therefore, the anisotropic hardening parameters for both Cu and Al will be calculated by DD simulations (microscale). An input for the DD calculations will be the dislocation mobility, which will be achieved by Molecular Dynamic (MD) calculations (atomic). Anisotropic elastic constants will be calculated by Modified Embedded Atomic Method (MEAM), to be used to achieve the required potentials for the MD calculations as well. At electronic scale, Density Functional Theory (DFT) approach will be used to get the generalized Stacking Fault energy (GSFE) and energy variations as a function of the lattice parameter. Finally, this framework to be developed will be validated with experimentally measured results.