Affiliations: Electro-Mechanical Engineering Group, The University
of Southampton, Southampton, UK | Singapore Institute of Manufacturing Technology,
Precision Measurements Group, Singapore
Note: [] Corresponding author: Joseph J. Lifton, Electro-Mechanical
Engineering Group, The University of Southampton, Southampton, UK. Tel.: +44
02380595568; Fax: +44 0238059301; E-mail: J.J.Lifton@soton.ac.uk
Abstract: X-ray computed tomography (CT) is a radiographic scanning technique
for visualising cross-sectional images of an object non-destructively. From
these cross-sectional images it is possible to evaluate internal dimensional
features of a workpiece which may otherwise be inaccessible to tactile and
optical instruments. Beam hardening is a physical process that degrades the
quality of CT images and has previously been suggested to influence dimensional
measurements. Using a validated simulation tool, the influence of spectrum
pre-filtration and beam hardening correction are evaluated for internal and
external dimensional measurements. Beam hardening is shown to influence
internal and external dimensions in opposition, and to have a greater influence
on outer dimensions compared to inner dimensions. The results suggest the
combination of spectrum pre-filtration and a local gradient-based surface
determination method are able to greatly reduce the influence of beam hardening
in X-ray CT for dimensional metrology.
