RESEARCH

Molecular Dynamics (MD) and continuum dislocation models such as Dislocation Dynamics (DD) have been important tools for engineers and material scientists to further the understanding of the macroscale plastic deformation of metals; however, to date these simulations have been largely qualitative. A quantitative understanding of the nature of crystal plasticity from the fundamental level of the nucleation and motion of individual dislocations is a critical step in the design of new materials with tailored strengths and toughness. We have focused our research on the development of numerical methods which couple continuum and atomistic models of materials. This lead to the development of the XFEM-BDM framework for the simulation of cracks and dislocations. In the context of dislocation modelling, the XFEM-BDM allows for atomistic resolution of dislocation core behaviour while still modelling most of the domain with a computationally more efficient continuum model. The XFEM-BDM framework is illustrated below.

Simulation of the propagation of an edge dislocation using the XFEM-BDM. Displacements in the y-direction are shown. Results submitted to IJNME. See earlier XFEM-BDM article (Gracie and Belytschko, 2009)

Simulation of a nanoindentation process using the XFEM-BDM. Atoms are coloured by their energies. Atoms at the dislocation cores are coloured light blue. Results submitted to IJNME. See earlier XFEM-BDM article (Gracie and Belytschko, 2009)

In North America, abandoned wells from petroleum extraction are prolific in the same high-porosity, high-permeability sedimentary units that would be used for carbon storage. Because of the high uncertainty in subsurface material properties and structure, simulation models which can be used to accurately quantify CO2 leakage to the surface and/or aquifers used for drinking water are in high demand. We are working towards the development of accurate models of CO2 sequestration in multi-aquifer systems. For more information please see our recent article (recent publication)

Left: Head in an aquifer perferated by six abandoned wells and one injection well. The singularity in the head at the abandoned wells is captured by an Extended Finite Element Approximation. Right: Comparision of the convergence rate and accuracy of the Finite Element Method (FEM) and the Extended Finite Element Method (XFEM) for a model problem. Both the accuracy and the convergence rate of the XFEM are significantly superior to the FEM.

• Development of numerical methods for continuum based models of dislocations.
• Focus on prediction of plasticity and failure in bulk materials, thin films and MEMS devices.

Simulation of a threading dislocation in a SiGe thin film on an Si substrate. Simulation performed by Jay Oswald and published (doi: 10.1016/j.cma.2008.12.025)

• Development of soil-structure interaction models for simulating the effect of ice scours on pipelines
• Study of very large soil deformations

Left: Finite element mesh for an ice scour simulation. Right: Soil deformations due to ice scouring. Green material denotes soil initially in the trench.