Microstructure: Dislocations, Creases, and Grains

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9805422SethnaThis award supports research in the area of microstructure of materials that results from expulsion of external strain into sharp boundaries. This occurs at grain boundaries in crystals, at focal conic defects in smectic liquid crystals, at vortex lines in superconductors, and at creases in crumbled paper. The PI will focus on specific projects in three areas: frustrated crystals, nonlinearities and dispersion, and paper crumbling. The first focuses on new phases. Dislocation lines can relieve external strain, but can also form in response to frustration in the crystal structure. The PI will introduce a term in the free energy of anisotropic, chiral crystals and aim to predict and characterize the resulting defect-lattice phases. In the second area, the PI will study the perturbative effects of nonlinearity and disperson on the continuum interactions between microcracks and observe a hitherto ignored term in the continuum energy. This study is important to realistic simulation of interacting dislocation lines where connection between interactions at atomic scales to continuum elastic theory is required. The final area is concerned with the large scale dynamics of microstructure. The PI will study a model motivated by the acoustic emission found during martensitic transformations and during the crumbling of paper. %%%This talented PI will perform theoretical research aimed at a better understanding of the nature and formation of small scale structure that forms in association with defects in materials. The research will also focus on the dynamics of this microstructure that is relevant to how paper crumbles and a class of structural transformations. The proposed research also bears on how to include important information about materials at the atomic level to describe correctly dynamical phenomena at intermediate and macroscopic length scales. ***