My research is focused on developing novel micromechanical testing techniques, in order to quantify the mechanical properties of materials where only small volumes are accessible; the main application being structural materials used in nuclear power plants. The methods I develop will enable the extraction of bulk mechanical properties of very small volumes of materials exposed to irradiation, in order to predict their long term performance in operating conditions.
I primarily use nano-indentation with varying tip geometries along with EBSD for the microstructural analysis and strain mapping and FE modelling to extrapolate the bulk mechanical properties, up to and beyond the yield point. I am interested in advanced steels, particularly ferritic/martensitic steels and ODS varieties, exposed to reactor environments and irradiated using self-ions to emulate the damaged microstructure.
My work is in collaboration with several US research institutions including the University of Michigan and Oak Ridge National Laboratories, the UK Atomic Energy Authority and Rolls Royce Plc. I am currently funded via a Davis Clarke Fellowship award from the Energy Technologies Institute (ETI) and the EPSRC.
Scratching the surface: Elastic rotations beneath nanoscratch and nanoindentation tests
In this paper, we investigate the residual deformation field in the vicinity
of nano-scratch tests using two orientations of a Berkovich tip on an (001) Cu
single crystal. We compare the deformation with that from indentation, in an
attempt to understand the mechanisms of deformation in tangential sliding. The
lattice rotation fields are mapped experimentally using high-resolution
electron backscatter diffraction (HR-EBSD) on cross-sections prepared using
focused ion beam (FIB). A physically-based crystal plasticity finite element
model (CPFEM) is used to simulate the lattice rotation fields, and provide
insight into the 3D rotation field surrounding nano-scratch experiments, as it
transitions from an initial static indentation to a steady-state scratch. The
CPFEM simulations capture the experimental rotation fields with good fidelity,
and show how the rotations about the scratch direction are reversed as the
indenter moves away from the initial indentation.
A more holistic characterisation of internal interfaces in a variety of materials via complementary use of transmission Kikuchi diffraction and Atom probe tomography