MSE Colloquium: Stephen Niezgoda, Computational Mechanics of Microstructures: Bridging simulation, characterization and material design

Post-doctoral Researcher, Los Alamos National Laboratories

All dates for this event occur in the past.

264 MacQuigg Labs
105 W. Woodruf Ave
Columbus, OH 43210
United States

Abstract

Impressive advances, both in materials characterization and physics-based multi-scale modeling tools, have given materials researchers unprecedented access to spatially and temporally resolved microstructure and local material response data. As a field, we are currently struggling with how to combine this deluge of data into useful materials knowledge. This will require working at the intersection of simulation and experiment; a fertile but largely unexplored research area. While this data crisis poses a significant technical challenge it is also a great opportunity to explore novel  approaches to materials development which rely heavily on coupled targeted simulation experiment and characterization, as was recently highlighted in the Materials Genome Initiative for Global Competitiveness.

In this seminar, several of the opportunities and computational challenges of working at this intersection, particularly in the area of mechanics of microstructures, will be highlighted. One developing area is that of “experiment and simulation co-design” or “computation assisted characterization”, where missing or incompletely measured data is estimated through simulation. This idea will be demonstrated through the application of full field crystal plasticity simulations for the estimation of equilibrated global absolute elastic stress/strain fields from incompletely measured relative strain information from cross-correlation or “high-resolution” electron backscatter diffraction. A second area that will be discussed, will be the ongoing development of stochastic multi-scale crystal plasticity models. In particular, a novel approach to incorporating multi-scale microstructure features and local stress fluctuations into homogenized plasticity (viscoplastic self-consistent) models in order to correctly predict twin variant selection in hexagonal metals will be shown. Finally, some of the challenges related to objectively comparing simulation and experimental data will be addressed, such as quantitative microstructure comparison and the generation of equivalent of representative microstructures for simulation will be addressed.

Bio

Stephen Niezgoda is currently a post-doctoral researcher with the Materials in Dynamic and Radiation Extremes group within the Materials Science and Technology Division at Los Alamos National Laboratory. Prior to joining Los Alamos, Stephen completed his graduate studies at Drexel University under the guidance of Surya Kalidindi, where his thesis work was on the statistical analysis of microstructure data and microscopy image processing techniques. At Los Alamos Stephen is currently working with Don Brown at the Los Alamos Neutron Science Center (LANSCE), where he is focused on the computational and experimental challenges of 3D High Energy X-ray Diffraction Microscopy (HEDM) (evolution of nuclear fuel assemblies during simulated reactor conditions). Prior to working at LANSCE, Stephen worked with Carlos Tome on developing the new technique of cross-correlation EBSD, as well crystal plasticity models for hexagonal and low symmetry materials. Before studying materials science, Stephen worked as an FAA certified airframe and powerplant mechanic as well as an industrial mechanic and machinist.