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Title: Enhancement of temperature diagnostics with application to dynamically compressed materials
Author: Ota, Thomas
ISNI:       0000 0004 9351 6662
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2020
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The behaviour of materials at high pressure is relevant for a number of fields, including defence, aerospace and Earth and planetary science where understanding of material behaviour under high strain-rate conditions such as impacts is required. State variables such as pressure and density are readily accessible in shock experiments but determination of temperature remains challenging. Temperature affects material behaviour substantially, thus the determination of temperature in materials at high pressure (giga-Pascal range) enables progress in the fields noted above. This thesis outlines improvements to the technique of pyrometry which is a widely used diagnostic for determining temperature in shock experiments. Despite the popularity of pyrometry, concerns remain regarding the significance of different uncertainties and equivalence of independently-developed systems. The primary goal of this research has been to improve the technique of pyrometry; this has been accomplished in a number of areas. First, an extensive review of potential components and their impact on pyrometer operation has been completed which more clearly defines the sources of uncertainty in pyrometry systems. Second, collaborative experiments have allayed concerns about the validity of comparisons of measurements from differing pyrometry systems. Finally, an integrated reflectivity diagnostic has been developed and demonstrated which enables simultaneous measurement of radiance and reflectivity, removing reliance on assumptions to determine temperature. In addition to diagnostic development, equation of state (EoS) measurements on tin and lead have been made. Measurements of shock speed, particle velocity and radiance (converted to temperature) have been made during plate impact experiments. Results obtained from tin have validated existing EoS models however small but significant differences were identified. The measurements of lead temperature have been inconsistent, the results could indicate a phase transition. In summary, the work presented here provides a clear framework for understanding uncertainties in pyrometry and has demonstrated multiple practical improvements to the technique.
Supervisor: Eakins, Daniel ; Chapman, David Sponsor: Engineering and Physical Sciences Research Council ; AWE plc
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Shock waves ; Temperature measuring instruments