Congratulations to Daniel Bugas for successfully defending his PhD dissertation, entitled “Network plasticity for multiscale modeling of deformation-driven microstructure evolution” at UCCS on August 7, 2023.
Abstract: Microstructural evolution in structural materials is known to occur in response to mechanical loading and can often accommodate substantial plastic deformation through the coupled motion of grain boundaries (GBs). Mechanically induced coarsening is one example of this phenomenon, which can result in less desirable properties. In this work we present a multiscale model for capturing the combined effect of plasticity mediated by multiple GBs simultaneously, which is referred to as “network plasticity” (NP). NP builds on the large body of prior work in crystal plasticity, combined with the unique behavior of GB shear coupling. It has been shown in prior work that there are many analogues between crystal plasticity and GB mediated plasticity, and here we extend that analog to polycrystal systems. The mathematical framework of graph theory is used to describe the microstructure connectedness, and the evolution of microstructure is represented as flows along the graph. By using the principle of minimum dissipation potential, which has previously been applied to grain boundary migration, it is then possible to construct a set of evolution equations for the flows along graph vertices. The effectiveness of the model is demonstrated through comparison to multiple bicrystal atomistic simulations, as well as a select number of GB engineered and non-GB engineered EBSD data. The network plastic effect is demonstrated through mechanical response tests and by examining the yield surfaces, and the transition from NP to other, simpler plasticity models is explored.
Thesis: The link will be posted here