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Title: Shock-compression of porous materials and diagnostic development
Author: Chapman, David James
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2010
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A robust experimental design for measuring the shock-response of granular materials at ambient and higher densities is described. The method employed Lagrangian sensors embedded in anvils surrounding a sample cavity. The shock-consolidation of silica powders with a range of initial densities, structural forms of silica, morphologies, and water-content were investigated. Data on the principal Hugoniot and off-Hugoniot states were measured for: fused-silica powders of initial density ρ00 = 0.1, 0.25, and 0.77 g cm-3, quartz-sand of varying water-content (0%, 10%,20%, and 22% by mass), and statically compacted soil with initial density ρ00 = 2.29 g cm-3. The presence of a high water-content (20% and 22%) between the sand grains significantly altered the shock-response of the material. For most materials a dramatic stiffening in the material behaviour was observed upon reshock, an observation consistent with data from the literature. A phenomenological description of the compaction process in terms of grain re-arrangement, particle fracture, and plastic flow is offered. The P-α compaction model in various functional forms is applied to the fused-silica data. The exponential and power-law descriptions are observed to best fit the experimental results. The state of the art of measuring lateral stress using manganin gauges is reviewed, particularly in light of recent published results from hydrocode simulations. A series of recommendations for how best to use manganin gauges to measure lateral stress is presented. These suggestions result in small modifications to current analysis techniques. An experimental investigation of the behaviour of T-gauges, a manganin gauge commonly used to measure lateral stress, is presented. It is conclusively demonstrated that T-gauges behave approximately as wire gauges in the longitudinal orientation, and not as grid gauges as previously believed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available