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., Index of refraction measurements and window corrections for PMMA under shock compression, Aip Conference Proceedings, Vol:1426, ISSN:1551-7616, Pages:442-445
Eakins D, Chapman D, The influence of particle morphology on the dynamic densification of metal powders, Aip Conference Proceedings, Vol:1426, ISSN:1551-7616, Pages:1491-1494
et al., 2017, The effect of temperature on the elastic precursor decay in shock loaded FCC aluminium and BCC iron, International Journal of Plasticity, Vol:96, ISSN:0749-6419, Pages:135-155
et al., 2017, Spatially resolved measurements of grain size effects on the shock and spall response of quasi-Taylor wave loaded pure copper, Journal of Applied Physics, Vol:122, ISSN:0021-8979
et al., Interrogating Heterogeneous Compaction of Analogue Materials at the Mesoscale Through Numerical Modeling and Experiments, 20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter, AIP Publishing, ISSN:1551-7616