The Oxford Micromechanics Group are interested in how materials (engineered and naturally occurring) respond, at the microstructural level, to externally applied loading - mechanical, thermal, and/or environmental (chemical, irradiation). The complex patterning of local stress and strain distributions and how they evolve, and are linked to particular aspects of the microstructure, provides many fascinating intellectual challenges. Technical impact comes from building sound understanding and models of how materials fail. This is central to setting safe performance windows, and developing new alloys and microstructures with greater capability.
Our centre of mass is in the Department of Materials, but we also span across to the Department of Engineering Science and Department of Earth Science. We work on a range of materials systems including those for nuclear, aerospace, and automotive sectors, as well minerals. We also have made significant contributions to development of new testing and characterisation methods allowing us to gain new insights.
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.
On the Brittle-to-Ductile Transition of the As-cast TiVNbTa Refractory High-entropy Alloy
Cold creep of titanium: Analysis of stress relaxation using synchrotron diffraction and crystal plasticity simulations