My research is directed toward the mechanisms of deformation in condensed matter at extreme strain-rates, from the bulk to sub micron scale. I focus on the transition between elastic and plastic behavior, with specific attention to the processes of ultrafast inelastic deformation (defect generation, plasticity, localisation, fracture, etc.). My work seeks to resolve the relationship between the structure of solid phases and their pathway through various defect states, from the early moments of loading to their bulk conclusions. Within this area, I am presently working on the effect of alloying and other impurities on ultrafast elastoplasticity, new analytical methods for simulating true dislocation dynamics under dynamic loading, and the temperature dependence of dynamic fracture mechanisms.
My work also involves the study of heterogeneous materials, and the statistical representation of non-uniform material response at various microstructural levels. This area extends my earlier work on powder systems into new territory through the coupling of novel experimental techniques and spatially-resolved diagnostics with 2D/3D numerical simulation. One of the primary drivers for this work is to establish a “Materials by Design” theme, whereby improved understanding of the role of defects/interfaces can lead to a new design capability for materials with predefined shock properties.
Since my research themes of dynamic strength and material heterogeneity have multi-scale origins, I coordinate experiments on platforms spanning many decades of length and time. These include the 100 mm bore and mesoscale gas guns within the ISP, through to high-power laser-shock drivers at Los Alamos and Lawrence Livermore National Labs, and shortly at Imperial College. My work also involves construction of in-house high-speed shock diagnostics (PDV, line VISAR) or exploring the unique capabilities for fast X-ray probing at various national and international facilities (Diamond Light Source, CLF, ESRF, LCLS). For example, I currently lead an effort to develop a dynamic high-energy X-ray imaging capability at the Diamond Light Source, for the study of extreme physical processes in high-Z materials.
et al., 2019, Insights into local shockwave behavior and thermodynamics in granular materials from tomography-initialized mesoscale simulations, Journal of Applied Physics, Vol:125, ISSN:0021-8979
et al., 2018, Ultrafast imaging of laser driven shock waves using Betatron x-rays from a laser Wakefield accelerator, Scientific Reports, Vol:8, ISSN:2045-2322
et al., 2018, Ultra-high-speed indirect x-ray imaging system with versatile spatiotemporal sampling capabilities, Applied Optics, Vol:57, ISSN:1559-128X, Pages:5004-5010
et al., 2018, Initial Results From a Simultaneous Pyrometry and Reflectivity Diagnostic, 20th Biennial Conference of the Topical-Group of the American-Physical-Society (APS) on Shock Compression of Condensed Matter (SCCM), AMER INST PHYSICS, ISSN:0094-243X
et al., 2018, On the Dynamic Response of Additively Manufactured 316L, 20th Biennial Conference of the Topical-Group of the American-Physical-Society (APS) on Shock Compression of Condensed Matter (SCCM), AMER INST PHYSICS, ISSN:0094-243X