Under shock compression it is believed that crystalline materials undergo complex, rapid, micro-structural changes to relieve the large applied shear stresses. The mechanisms involved, such as dislocation flow and deformation twinning, under the generated high strain rates are not fully understood and in situ measurements of defects have proven elusive. This work presents the development of a nanosecond x-ray diffraction technique based on the white-light Laue method, and its first use in studying shock compressed copper. Observations of diffuse scattering are interpreted as stress-dependent lattice rotations due to dislocation glide. The results are compared with MD simulations of shocks in copper which are shown not to agree. Simulations of tantalum, shocked along the [001] axis, are demonstrated to undergo deformation twinning. A novel order parameter for identifying twin variants is developed and the deformation twinning mechanism under shock compression is identified.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:581151 |
| Date | January 2012 |
| Creators | Suggit, Matthew J. |
| Contributors | Wark, Justin S. |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:b98c48e9-1380-44ed-bd45-b399b693b97e |
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