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Title: Locally resolved adiabatic shear band formation in hexagonal close packed materials
Author: Patten, Jack Richard William
ISNI:       0000 0004 8499 4654
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2019
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This document will explain the process of developing systems and equipment to observe adiabatic shear bands as they form during experiments. This will involve explaining the scope of the problem which relies on the speed required to cause a system to effectively become adiabatic. The adiabatic nature of the deformation under shear loading at high rate is what allows the thermal softening to overwhelm strain and strain rate hardening. This requires a suitable test bed, and this thesis will explain the development of a suitable arrangement of a miniaturised Klosky Bar. This thesis will also explain a method of observing the deformation as it occurs, using a speckle pattern applied to a well-polished sample surface and digital image correlation to observe changes over the course of the experiment. This system needs a specific set of requirements be met for the sample so that shear bands can be preferentially formed in view of the imaging systems. The development of those samples is also explained. Additional methods of analysis are also preliminarily investigated, including x-ray phase contrast imaging and thermoreflectance temperature measurements. This thesis presents some of the results gathered during this investigation, conducted to attempt to find the ASB characteristics of Ti-6Al-4V. This project found the critical strain for as received Titanium-6- Aluminium-4-Vanadium is 0.25, and critical strain rate may be as low as 1x10^3, and showed that deformation through the shear region is not laminar. The directions this project's work could then be taken is explained in the final section.
Supervisor: Proud, William ; Eakins, Daniel Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral