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C. Pein:
"Microstructural Modelling of Diffusional Creep in Polycrystals";
Supervisor, Reviewer: H. Cerjak, E. Kozeschnik; Werkstoffkunde und Schweißtechnik, TU Graz, 2011; oral examination: 2011-07-15.

Creep deformation of modern materials such as 9-12% Cr steels is of major importance in terms of long-term behaviour and component stability. Thus, modelling and simulation of this phenomenon is an important topic in the area of materials science. The influence of the materials microstructure on creep is complex, thus, the objective of this work is to simulate creep behaviour on a microstructural basis.

To do so, a model is set up which comprises the microstructure as distinct, spatially resolved elements which are described by different physical properties. The deformation process is implemented with a visco-plastic approach which is capable to describe both linear and non-linear behaviour. Out of the different physical mechanism operating during creep loading, Nabarro Herring creep is studied in this work.

As mathematical framework the Finite Element Method is used. For the numerical implementation of the presented model, the general-purpose, commercial software MATLAB® is utilized. The chosen numerical algorithm to analyse creep deformation is a robust and efficient method to calculate stress and strain response to given boundary conditions. A short overview on the mathematical framework and a description of the code implementation is given as well.

The model approach is used to simulate several microstructural configurations. The results indicate that the microstructural elements have a distinct influence on local creep behaviour of a creep loaded material.