Christian Hortig

Application of Adaptive Mesh and ALE Method in Simulation of Extrusion of Aluminum Alloys

The purpose of this work is the modeling and simulation of the material behavior of aluminum alloys during extrusion processes. In particular, attention is focused here on aluminum alloys of the 6000 series (Al-Mg-Si) and 7000 series (Al-Zn-Mg). The material behavior of these alloys during extrusion is governed mainly by dynamic recovery and static recrystallization during cooling. The current material model is based on the role of energy stored in the material during deformation, as it acts as the driving force for microstructural development. The concept of internal variables is used to describe state quantities such as dislocation density, average grain size and average grain orientation. The focus of the current paper is on some of the numerical aspects of the extrusion process simulation such as contact problems and adaptive mesh refinement which should be considered in order to obtain more accurate and robust results.

Lengthscale-dependent modelling of ductile failure in metallic microstructures

The purpose of the current work is the application of a recent extension (Reusch et al., 2003a, 2003b) of the Gurson-Needleman-Tvergaard (GTN) model (e.g., Needleman and Tvergaard, 1984) to the simulation of ductile damage and failure processes in metal matrix composites at the microstructural level. The extended model is based on the treatment of void coalescence as a lengthscale-dependent process. In particular, we compare the predictions of the (local) with GTN model with those of the lengthscale-dependent extension for ductile crack initiation in ideal and real Al-SiC metal matrix microstructures. As shown by the current results for metal matrix composites and as expected, the simulation results based on the local GTN model for both the structural response and predicted crack path at the microstructural level in metal matrix composites are strongly mesh-dependent. On the other hand, those based on the current lengthscale-dependent void-coalescence modelling approach are mesh-independent. This correlates with the fact that, in contrast to the local approach, the predictions of the lengthscale-dependent approach for the crack propagation path in the real Al-SiC metal matrix composite microstucture considered here agree well with the experimentally-determined path.

Adaptiv modeling and simulation of shear banding and high speed cutting

The purpose of this short work is the thermomechanical modeling of shear band and chip formation during high‐speed cutting. Shear bands develop in areas of maximal mechanical dissipation in which temperature‐dependent softening dominates strain‐ and strain‐rate‐dependent hardening. In the simulations, the well‐known problem of the mesh‐dependence of the shear‐band development is addressed, involving both mesh size and mesh orientation. An example simulation is presented.

Non-Local Damage Simulation in Composites Using Crack Propagation and Mesh Adaptivity

The numerical analysis of ductile damage and failure in engineering materials and metal matrix composites is often based on a micromechanical description of the damage and failure process (Gurson [1], Needleman and Tveergard [2], Tveergard and Needleman [3]). In heterogeneous metal matrix composites, ductile crack extension occurs only in the ductile metallic phase, whereas cracks of rigid inclusions and decohesion is not necessarily experimentally observed.