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Projects |
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On this page you can see some of my research projects in different stages of progress. If you are interested in details, please feel free to contact me! Deformation of Polycrystalline Materials In experimental work and atomistic simulations of deformation of polycrystalline materials the sliding of dislocations in grains as well as the sliding of grain boundaries has been observed. It is obvious that such processes are becoming increasingly important with respect to the inelastic reaction of polycrystalline materials, whenever the grain size is reduced from micrometer to nanometer, since activities like dislocation motion inside the grains will then be restricted. Hence, the accurate modeling of deformation behavior of polycrystalline materials is of mayor interest. Here the Finite Element Method (FEM) is our tool of choice to analyze such complex problems. In addition, a second focus of research is on the microstructural evolutions during accumulative roll bonding of different materials systems investigated by experiments and computer simulations. Recrystallization of Polycrystalline Materials Modeling the microstructural evolution during recrystallization is a powerful tool for profound understanding of alloy behavior and for optimizing its engineering properties through an annealing process. In particular, the mechanical properties of metallic alloys are highly dependent not only upon the evolved microstructures but particularly also on the resulting texture from the softening process. In the framework of this project the recrystallization behavior, stored energy dissipation, and texture evolution are studied during static recrystallization depending on the initial conditions. The influence of the degree of deformation and on the annealing conditions such as heating rates are analyzed and the speed of recrystallization as well as the resulting microstructures are examined. Also the performance of Monte Carlo Potts model simulations will be compared to a coupled cellular automata—finite element—model, and it will be assessed, which of the two models is more suited for future applications. Grain Growth of Polycrystalline Materials When attempting to investigate the underlying mechanisms of grain boundary migration, one is faced with a profound problem: namely the 3D nature of polycrystalline materials. Current characterization techniques lack the spatial and temporal resolution to capture the kinetics of grain boundary migration at the atomic level. However, these limitations can be overcome by either studying a 2D material like graphene or retreating to mesoscopic considerations. This subproject is aimed at the task to bridge the gap from atomistic to mesoscopic simulations by treating grain growth behavior on different size scales:
Ostwald Ripening Ostwald ripening is a colloid-chemical process in disperse matter based on the curvature dependence of vapor pressure or solubility of a fine powder. The vapor pressure or concentration difference in a closed system is balanced by a flow of matter from the small to the large colloids. This results in shrinkage of the small particles, while the large particles grow. Once the radius of a small particle resp. colloid drops below a critical value, it becomes energetically unstable and dissolves completely. In the framework of the project Ostwald ripening is modeled by large three-dimensional Potts model simulations. Preliminary two-dimensional studies run very slow allowing the prediction that adding the third natural dimension to the model will lead to catastrophic simulation run times. Therefore, high performance computing will have to be used implementing the problem on the mesoscopic scale in a parallel programming language using, e.g., graphics processing units (GPUs). Multi-Scale Materials Almost everybody loves ice cream, and although it looks to be a very simple material it is indeed a very complex, composite material providing an excellent vehicle for discussing and demonstrating a broad variety of physical phenomena, such as Newton’s law of cooling, Boyle’s law and the relationship between a materials microstructure and its macroscopic properties (e.g., Young’s modulus). This multi-phase, multi-scale material is also excellently suited to study the relationship between a materials microstructure and thermal as well as mechanical influences building a particular bridge for the other projects above! In addition, a number of small projects are also pursued, e.g.,: Microstructure Generation, Discretization and Analysis Porous Media Fractal Interfaces Physikdidaktik: Experimentalpraktikum im Schuljahrgang 12 (deutsch/German) Diversity in Materials Science and Engineering |