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dc.contributor.authorJiang, Sheng
dc.date.accessioned2019-04-05T03:27:39Z
dc.date.available2019-04-05T03:27:39Z
dc.date.issued2018-11-08
dc.identifier.urihttp://hdl.handle.net/2123/20250
dc.description.abstractFracturing plays an important role in controlling the compaction behaviour of granular materials under impact. Associated effects include changes to porosity and permeability, especially along earthquake faults, and during mining and petroleum production processes. The overarching objective of this thesis is to understand the intrinsic fracture mechanisms of both pure brittle granular materials and cemented granular materials. Fracture mechanisms are quantitatively analysed in terms of energy dissipation during high speed grain fracture and fragmentation process. Furthermore, the effects of both inter-grain contact material and cement material on the fracture mechanisms are investigated at microscopic level. High strain rate experiments demonstrate that only a small portion of the input stress wave energy is dissipated through the fragmentation of the grain chain system. Micro-CT results validate that the fracture energy only accounts for a small portion of the chain system’s absorbed energy, even after including the undetected surface area of the micro-cracks. Comparisons between the glass bead chain systems, with and without contact materials, clearly indicate that the contact material changes the chain damage patterns. The contact material alters the initial contact state of the shielded grains and consequently restrains the initiation of cracks, governed by tensile stresses near the contact surface. However, different fracture mechanisms, namely, cement-focused and grain-focused fracture mechanisms can be activated for different cement materials covering a single glass bead, which is dependent on the cement/grain interface adhesion. Using measuring techniques based on Fourier transform, the locality of damage within the cemented bead is quantitatively analysed, as well as their preferential crack orientation. Several sporadic curved cracks come under observation near the interface region in the cement-focused fracture case, roughly along the cement/grain interface. By contrast, for the grain-focused fracture case, fracture is most likely to occur along the central loading axis area of the cemented bead and prevailingly forms diametric cracks along the impact direction.en_AU
dc.publisherUniversity of Sydneyen_AU
dc.publisherFaculty of Engineering and Information Technologiesen_AU
dc.publisherSchool of Civil Engineeringen_AU
dc.rightsThe author retains copyright of this thesis. It may only be used for the purposes of research and study. It must not be used for any other purposes and may not be transmitted or shared with others without prior permission.en_AU
dc.subjectRittle Granular Materialsen_AU
dc.subjectCemented Granular Materialsen_AU
dc.subjectDynamic Fractureen_AU
dc.subjectHopkinson baren_AU
dc.subjectX-Ray Tomographyen_AU
dc.subjectFourier Transformen_AU
dc.subject.otherincludes published articlesen_AU
dc.titleFracture and Fragmentation of Granular Materials Under Impacten_AU
dc.typePhD Doctorateen_AU
dc.type.pubtypeDoctor of Philosophy Ph.D.en_AU
dc.description.disclaimerAccess is restricted to staff and students of the University of Sydney . UniKey credentials are required. Non university access may be obtained by visiting the University of Sydney Library.en_AU


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