The effects of microstructure and nanostructure upon dynamic ductile fracture
type: CreativeWork
description: Dynamic fracture is an important process in the behaviour of materials. However, the effects of material microstructure on dynamic fracture processes are not well understood. This thesis investigates the role of material microstructure and nanostructure in dynamic ductile fracture, such that the results can ultimately be used to improve fracture models. C110 OFHC copper was selected as a suitable material through which to investigate the role of microstructure and nanostructure in dynamic ductile fracture. The material was procured in a cold worked state. In order to control its microstructure, the copper was annealed to reduce the dislocation density, without altering its grain size. A novel method was developed to produce rings of pre-shocked material. The microstructures and quasi-static mechanical behaviour of all three states of copper (annealed, cold worked and pre-shocked) were characterised. An explosively loaded ring fragmentation experiment was developed, based upon an existing apparatus for brittle materials. The apparatus consisted of a mild steel driver cylinder containing an explosive charge. The copper ring was fixed to the outside of the cylinder over the centre of the charge. Diagnostics used to monitor the experiment included soft capture, photon Doppler velocimetry (PDV) and high-speed photography. A non-repeating pattern was marked on the rings and driver cylinders, enabling them to be reassembled and the precise location of the PDV measurement points known. Thus, information was obtained about velocity variation during the fragmentation process. A series of ring fragmentation experiments were performed on cold worked copper at strain rates of 10³ to 10⁴ s¯¹, which were controlled by varying the mass of the explosive charge. The experiments suggested a very slight decrease in the ductility of the copper at higher strain rates. The characteristic nature of the fracture surfaces varied with strain rate and showed different failure mechanisms on a s…
abstract: Dynamic fracture is an important process in the behaviour of materials. However, the effects of material microstructure on dynamic fracture processes are not well understood. This thesis investigates the role of material microstructure and nanostructure in dynamic ductile fracture, such that the results can ultimately be used to improve fracture models. C110 OFHC copper was selected as a suitable material through which to investigate the role of microstructure and nanostructure in dynamic ductile fracture. The material was procured in a cold worked state. In order to control its microstructure, the copper was annealed to reduce the dislocation density, without altering its grain size. A novel method was developed to produce rings of pre-shocked material. The microstructures and quasi-static mechanical behaviour of all three states of copper (annealed, cold worked and pre-shocked) were characterised. An explosively loaded ring fragmentation experiment was developed, based upon an existing apparatus for brittle materials. The apparatus consisted of a mild steel driver cylinder containing an explosive charge. The copper ring was fixed to the outside of the cylinder over the centre of the charge. Diagnostics used to monitor the experiment included soft capture, photon Doppler velocimetry (PDV) and high-speed photography. A non-repeating pattern was marked on the rings and driver cylinders, enabling them to be reassembled and the precise location of the PDV measurement points known. Thus, information was obtained about velocity variation during the fragmentation process. A series of ring fragmentation experiments were performed on cold worked copper at strain rates of 10³ to 10⁴ s¯¹, which were controlled by varying the mass of the explosive charge. The experiments suggested a very slight decrease in the ductility of the copper at higher strain rates. The characteristic nature of the fracture surfaces varied with strain rate and showed different failure mechanisms on a s…
author: Ward, Sarah
language: eng
keywords: Ring fragmentation, Dynamic fracture, Tensile SHPB, Copper, Ductile fracture, Microstructure, Nanostructure
license: http://purl.org/NET/rdflicense/allrightsreserved
date published: 2020-12-31
date modified: 2026-07-22T22:24:13Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.90275