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Title: Studies of shock compression at the mesoscale with synchrotron X-ray phase-contrast radiography
Author: Rutherford, Michael Eric
ISNI:       0000 0004 7657 916X
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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Shock compression causes a nearly discontinuous change in thermodynamic conditions within a system, subjecting the shocked material to extremes of pressure, temperature and density. It is therefore a powerful tool with which to explore the high pressure-temperate states of matter found in aerospace, planetary, defence and nuclear fusion scenarios, and understand the fundamentals of mechanical deformation. This Thesis focuses on the development and application of a high spatial and high temporal resolution X-ray radiography diagnostic for the study of shock-compressed materials, which overcomes many of the existing limitations of surface-based diagnostics that the field has traditionally relied upon. The novel X-ray radiography method was used to directly probe dynamic granular compaction as it evolved from the mesoscale towards the macroscale in three granular systems, which were analogous to precursor chondritic asteroid material. Direct measurements of a normal distribution of shock wave positions and velocities, wavefront thickness and dispersion, and spatially-resolved mass density were made on the powder systems, many of which were quantities that could only be previously probed numerically or at the material surface. Indeed, the measurements made in this study represent the first direct, sub-surface measurements of high strain-rate granular compaction at the mesoscale. Experiments were supported by non-destructive sample characterisation using high-resolution X-ray tomography, which, for the first time, allowed dynamic results to be evaluated in light of a three-dimensional characterisation of that powder volume. A quantitative X-ray absorption model was also developed, which facilitated density measurements and an evaluation of the sensitivity of the radiographic method to shock-induced density changes. The work presented in this Thesis represents a step-change in the way granular materials may be studied under high strain-rate loading and demonstrates the capabilities of a novel X-ray radiography method that complements a growing number of existing methodologies in the field.
Supervisor: Eakins, Daniel ; Chapman, David Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral