Freezing the supersonic: Revealing the mesoscale of dynamically compressed materials using real-time, synchrotron X-ray imaging
Daniel E. Eakins
Department of Engineering Sciences, University of Oxford, United Kingdom Abstract
Impact is a fundamental and ubiquitous process which subjects materials to rapid combinations of high pressure, temperature and deformation. These extreme conditions often drive behaviour not seen at ambient pressure in the form of novel deformation pathways (e.g. jetting, vorticity), failure modes (shear localization, brittle fracture), or nucleation of non-equilibrium phases. Enhancing the performance of materials in demanding environments relies upon better understanding of the link between these unique behaviours and the underlying mesoscale. This however has been experimentally inaccessible until recently, due to the short timescale (<100 ns) and subsurface nature of the processes of interest. In this talk, I discuss new capabilities for interrogating the sub-surface behaviour of materials under impulsive loading through real-time X-ray imaging at the European Synchrotron Radiation Facility. Using a bespoke single-stage gas gun designed for beamline ID19, materials can be subjected to impact stresses in the 10s of GPa range, with sequences of X-ray phase contrast images recorded at 5.68 MHz using a novel multi-camera indirect detection system. This new technique has enabled in situ visualisation of various extreme physical phenomena to be described, including void nucleation during rapid tensile failure, compaction of primordial astrophysical powders, and shock-driven cavity collapse. The transient mesoscopic details emerging from these new measurements have the potential to bridge the gap between bulk time-resolved diagnostics and mesoscale modelling, providing new insight into the hierarchical origins of dynamic material behaviour.