HOME

Left: Schematic of computational reconstruction with meshed sample plane, detector and projection geometry. Center: A sub-region of a reconstructed microstructure. Colors are coded to the local crystallographic orientations (J. Lind thesis, 2013). Right: Three dimensional reconstructed copper microstructure (R. Pokharel thesis 2013).
For information about Carnegie Mellon University, click here.
For information about the CMU Physics Department, click here.

Projects

• Towards optimal processing of additive manufactured metals for high strain rate properties. A joint project with A. D. Rollett of the CMU Materials Science and Engineering Department, starting in January 2016, in which we work with DOE National Laboratory personnel to understand the evolution of 3D printed metallic structures under post-processing. CMU has an active program in the AM field with which this projects will also interact; see the NextManufacturing Center for more information.
• Fatigue and failure in metals. A joint project with A. D. Rollett of the CMU Materials Science and Engineering Department, starting in January 2016, in which we study the evolution of fatigue cracks in industrially important nickel superalloys. We apply near-field and far-field HEDM and tomography (for early crack detection) to determine the evolution of microstructurally short fatigue cracks.
• Thermally induced coarsening in polycrystals. A continuation of work supported by the National Science Foundation to map the meso-scale evolution of metallic microstructures under thermal annealing. The work involves both novel measurements that track thousands of grains as they evolve and the development of advanced software for characterizing and tracking tens of thousands of grain boundaries in successive states of a sample.
• Intra- and inter-granular responses in ductile deformation under tension. Combined near-field, far-field, and tomographic measurements of samples at various levels of tensile deformation yield a detailed characterization of lattice strains, grain rotations and break-up, void formation and coalescence. The observations are directly compared to meso-scale models and are used to improve the accuracy of such models.
• Advancing HEDM measurement technologies. A collaboration with Air Force Research Laboratory, Advanced Photon Source, Lawrence Livermore National Laboratory, Los Alamos National Laboratory, and other scientists that is developing advanced hardware for in-situ sample manipulation as well as the integration of multiple measurement modalities. A Partner User Program (PUP) beam time allocation at 1-ID at the Advanced Photon Source has facilitated the first phase of this project.
• Characterization of systematic errors in nf-HEDM reconstructions. At what level of detail do near-field orientation maps become subject to systematic errors in the matching of simulated and actual experimental geometries? What are optimal experimental geometries and data collection protocols that minimize intrinsic errors? An extensive set of simulations and experimental observations of well characterized samples are being used to answer such questions.
• Interpretation of near-field intensity patterns. Traditional crystallography is built on observations of Bragg peak positions and intensities. Here, we ask how much local information can be deduced from the spatially resolved extended peaks that are resolved in nf-HEDM. Specifically, can lattice defect distributions be connected to the relative intensities within the roughly 100 observed peaks that emanate from each voxel location?

Updated August 25, 2020