MSE Colloquium: Philip Eisenlohr, Versatility of Finite Strain Spectral Methods for Crystal Plasticity

Associate Professor, Department of Chemical Engineering and Materials Science, Michigan State University

Abstract

The mechanical properties of structural materials arise from the interplay of effects spanning a large spatial and temporal range from the electronic structure up to the engineering component scale and are most heavily affected by the defect content and material microstructure. A quantitative prediction of the overall material response in a closed or simplified form has proven very difficult for complex microstructures featuring multiple phases, strong property contrasts, or irregular grain shapes, for instance. Only a spatially resolved solution of the boundary value problem at the scale of the microstructure, which can then naturally account for the constitutive behavior of individual structure constituents, is presently able to quantitatively predict the overall response as well as identify local peculiarities from such full-field simulation.

We recently improved a fast solution strategy for these miromechanical simulations based on spectral methods by formulating the (direct and) mixed variational conditions for mechanical equilibrium and strain compatibility in a framework that couples them to a general class of non-linear solution methods. The selected solution method has a dominant influence on performance and stability at large material heterogeneities, and significant improvements are obtained when higher-order solution methods are employed over the conventional fixed-point approach. As examples illustrating the versatility of this novel formulation in conjunction with the open-source Düsseldorf Advanced Materials Simulation Kit (damask.mpie.de) serve dilatational plasticity, the micromechanical influence of increased deformation resistance close to grain boundaries, and the influence of the population of small grains on the mechanical response of a polycrystalline aggregate.

Bio

 

Dr. Eisenlohr studied Materials Science and Engineering at the University of Erlangen-Nürnberg, Germany, received his PhD in 2004, and continued to work there for about 2 years as Post-Doc and Lecturer. From 2006 until 2013, he was a senior researcher at the Max-Planck-Institut für Eisenforschung in Düsseldorf, Germany, where he headed the first-ever jointly established research group between the Fraunhofer and Max-Planck Societies investigating the topic of computational mechanics of polycrystals. In 2013, he joined the faculty of Michigan State University as an associate professor in the field of computational materials mechanics.

The research interests of Dr Eisenlohr are revolving around the link between material microstructure and mechanical properties. He is currently working on microstructure mechanics of complex materials, the influence of low- and high-angle boundaries on deformation resistance, and rare events in plastic deformation connected to damage initiation. He pursues constitutive and methodological advancements in dislocation-scale plasticity and crystal plasticity at the grain scale.