UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

Improving X-ray CT Dimensional Metrology with Simple Holeplates

Corcoran, Hannah Clare; (2018) Improving X-ray CT Dimensional Metrology with Simple Holeplates. Doctoral thesis (Eng.D), UCL (University College London). Green open access

[img]
Preview
Text
Final_Corcoran.pdf - Accepted version

Download (47MB) | Preview

Abstract

X-ray computed tomography (XCT) is increasingly being used for the internal and external dimensional measurement of objects in many sectors. However, multiple factors affect the accuracy and precision of these dimensional measurements. Initial work found errors associated with the intensity and spectrum of the X-ray flux, both spatially and temporally over the imaging period. These variables were measured using a single ionisation chamber, an ionisation chamber array and a spectrometer, and their effects on dimensional metrology are discussed. The main focus of this work is on the apparent surface deformation of the reconstructed holes within a holeplate. Measurements of a complex holeplate with multiple holes highlighted systematic deformations in the reconstructed geometry (± 60 µm) for a 2 mm radius hole. Observed systematic deformation patterns were correlated with holeplate orientation. The simplification needed to understand the problem was achieved through practical testing and numerical simulation of simple holeplates, each containing a single hole. Similar trends in the systematic deformation patterns between complex and simple holeplates were found with deformations in the geometry of ±30 µm for a 2 mm radius hole. Algorithms using a ray tracing method were used to simulate X-ray images which were subsequently reconstructed. Results had the same trends in deformation as the experimental data but were of a smaller magnitude, probably due to scatter not being modelled in the simulation. Systematic deformation in the reconstructed geometry of the holes is caused by multiple factors: the orientation of the holeplate during imaging; the largest errors (<60 µm) were found when the holeplate was orientated at 45° to horizontal. The path length of the X-rays through the material and errors of <40 µm highlighted a correlation between the hole and the centre of rotation. Understanding these factors is essential to traceability in dimensional measurements using XCT.

Type: Thesis (Doctoral)
Qualification: Eng.D
Title: Improving X-ray CT Dimensional Metrology with Simple Holeplates
Event: UCL (University College London)
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2018. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
Keywords: X-ray computed tomography, metrology, holeplates, dimensional metrology, reference object
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Civil, Environ and Geomatic Eng
URI: https://discovery.ucl.ac.uk/id/eprint/10063941
Downloads since deposit
192Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item