Bassani, John L
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Publication Guided Assembly of Nanostructures via Elastic Interactions(2008-12-01) Bassani, John L; Lou, YoucunA solid solution can spontaneously separate into phases that self-assemble into patterns. This process can be guided via external fields to form ordered micro- and nanostructures. In this paper, we demonstrate that notions of interaction energies provide powerful insights into the coupling of these fields with the properties of the alloy. A phase-field model is developed that incorporates chemical, interfacial, and elastic energies, including heterogeneous elastic properties, and couples naturally to externally imposed mechanical fields. Aggregation in bulk and in thin films under patterned external load is investigated. The kinetics and morphology of phase separation are shown to depend significantly on elastic properties of the system, which include elastic heterogeneity and the misfit or transformation strain. Eshelby-type asymptotic estimates for interaction energies are shown to be very useful in understanding and predicting the trends observed from the simulations.Publication Snap Transitions in Adhesion(2008-06-01) Springman, Richard M; Bassani, John LEquilibrium adhesion states are analyzed for nonlinear spherical caps adhered to a rigid substrate under the influence of adhesive tractions that depend on the local separation between the shell and substrate. Transitions between bistable snapped-in and snapped-out configurations are predicted as a function of four nondimensional parameters representing the adhesive energy, the undeformed shell curvature, the range of the adhesive interactions, and the magnitude of an externally applied load. Nonuniform energy and traction fields associated with free-edge boundary conditions are calculated to better understand localized phenomena such as the diffusion of impurities into a bonded interface and the diffusion of receptors in the cell membrane. The linear Griffith approximations commonly used in the literature are shown to be limited to shells with a small height to thickness ratio and short-range adhesive interactions. External loading is found to alter the adhered configurations and the spatial distributions of both adhesive and elastic energies. An important implication of the latter analysis is the theoretical prediction of the pull-off force, which is shown to depend not only on the interface properties, but also on the geometric and material parameters of the shell and on both the magnitude and type of external loading.Publication Elastic Interfacial Waves in Discrete and Continuous Media(1996-04-01) Bassani, John L; Alber, E. S; Vitek, Vaclav; Wang, G. JPhonon spectra of bicrystals with relaxed grain-boundary structure display a variety of localized modes including long-wavelength acoustic modes. Continuum solutions for localized waves that incorporate atomic-level elastic properties of the interface via discontinuity relations agree well with the latter modes. In contrast, classical solutions that depend only on bulk elastic properties do not. This demonstrates that the distinct atomic structure of the interface is a controlling factor, and it is shown how local, atomic-level properties can be incorporated into continuum analyses of interfacial phenomena.