Modeling Dislocation Sources and Plastic Flow through Grain Boundaries in Mesoscopic Field Dislocation Mechanics

This work involves the modeling and understanding of mechanical behavior of crystalline materials using a continuum approach, Phenomenological Mesoscopic Field Dislocation Mechanics (PMFDM; Acharya and Roy, 2006). Specifically, this thesis contains three major parts. The first part involves the modeling of some aspects of dislocation sources that represent the emission of dislocation dipoles. The developed strategy is then used to investigate the dependence of mechanical response on the external dimensions of idealized single crystalline cubical samples with varying source and initial excess dislocation density distribution. The second part involves the modeling of plastic flow through grain boundaries in polycrystalline materials. The model is then used to analyze dislocation microstructure development in polycrystalline thin films and its effect on the mechanical response. The effect of thickness and the presence/absence of surface passivation on the plastic deformation of thin films is also studied. Results from these simulations are found to be in good qualitative agreement with experimental observations. The last part involves the numerical implementation of finite deformation PMFDM theory. The developed computational tool is capable of analyzing the deformation of crystalline materials under geometric and material nonlinearity.