Matthias Goerdeler

Integration of physically based models into FEM and application in simulation of metal forming processes

To obtain higher accuracy in FEM simulations the incorporation of microstructure evolution models becomes more and more important. From the point of view of metal physics it is well known that effects like recrystallization and deformation texture have a big influence on the material properties, especially the mechanical ones. The present article will give an overview about parts of the research activities in the Collaborative Research Centre (SFB 370) of the Deutsche Forschungsgemeinschaft (DFG). Three different types of microstructure models have been developed at the IMM and were coupled at the IBF to an implicit FEM code. The so-called flow-stress model is based on dislocation density evolution to describe the flow curve of metals, mainly at high temperatures. The Taylor-type model is able to describe deformation texture during metal forming. The third model is a modified cellular automaton to predict grain size and microstructure evolution during static recrystallization. The simulation of a rolling trial of the Al-alloy AA3104 including the named three models has been made and the results will be validated with experimental findings.

Through-process texture modelling of aluminium alloys

The complete through-process modelling of crystallographic texture evolution during aluminium sheet production is addressed. The texture determining processes deformation and recrystallization are analysed with respect to the underlying mechanisms. The advanced deformation texture model grain interaction (GIA) is coupled to a statistical analytical recrystallization texture model (StaRT). New concepts are described to model nucleation spectra for recrystallization with the GIA model and with a new model for the prediction of in grain orientation gradients. Orientation dependent recovery of the deformed structure is reflected based on substructure information extracted from the GIA model. A finite element (FE) model incorporating dislocation density based work hardening as well as texture serves as a process model to describe the macroscopic production parameters based on microstructural information. More detailed information on this integrative FE model can be found in a second paper presented at this symposium by Neumann et al. The excellent performance of the outlined through-process texture modelling concept is demonstrated in applications for two different aluminium sheet production lines?one laboratory and one industrial process?and displays for the first time the possibility of modelling texture evolution throughout various consecutive processing steps.

Modelling Set Up for Through‐Process Simulation of Aluminium Cup Production

In order to enable metal forming process optimisation through numerical simulation rather than trial and error, it is necessary to develop plasticity models of predictive character. The major disadvantage of frequently used phenomenological plasticity models lies in their limited validity which is defined by the experimental data ranges to which these models are fitted. The concept of phenomenological models may, however, be very successful if the plastic strains are small and if the strain path is not complex. This is often the case in sheet metal forming. Physical plasticity models, on the other hand, capture not only the true physical phenomena occuring during plastic deformation but also have the benefit of a ‘self evolutionary character’ which means that they are able to describe a considered phenomenon even outside of the experimental data range to which they have been adjusted. However, setting up physical models requires a significant amount of research and their adaptation to a specific alloy mak...

Integral Modelling of Texture Evolution in Multiple Pass Hot Rolling of Aluminium Alloys

The interaction of several physically based models for the development of crystallographic texture and microstructure during deformation and recrystallisation is exemplified in two cases of multiple pass hot rolling of commercial aluminium alloys. In this study streamlines output by the FE-code LARSTRAN/SHAPE and a model based on elementary rolling theory have been used respectively to calculate the evolution of material properties during deformation with a dislocation density based flow stress model and a Taylor type deformation texture model which considers grain interaction. To model the texture development during the interpass times between the rolling passes, an analytical recrystallisation model has been applied .

Modeling of Nucleation Spectra for Primary Recrystallization and Application to Through-Process Texture Modeling

Schemes to model deformation inhomogeneities and nuclei distributions based on the grain cluster model for deformation texture simulation GIA are presented. The orientation distributions of nuclei in stable orientations, nuclei in grains with orientation gradients and nuclei due to subgrain growth at grain boundaries are predicted. Additionally, nuclei with a random orientation distribution are considered, reflecting nucleation at shear bands or large constituent particles. Furthermore, models for a quantitative assessment of the participating nucleation mechanisms are proposed. The resulting nucleation texture was input to the static recrystallization texture model StaRT. The through-process texture development during a sequence of several hot rolling, cold rolling and annealing steps in industrial production of the aluminum alloy AA5182 is presented.