Industrial computed tomography
Industrial CT scanning
Industrial computed tomography (CT) scanning is
any computer-aided tomographic process, usually X-ray computed
tomography, that uses irradiation to produce three-dimensional
internal and external representations of a scanned object. Industrial CT
scanning has been used in many areas of industry for internal inspection of
components. Some of the key uses for industrial CT scanning have been flaw
detection, failure analysis, metrology, assembly analysis and reverse
engineering applications. Just as in medical imaging, industrial
imaging includes both nontomographic radiography (industrial radiography) and
computed tomographic radiography (computed tomography).
Contents
- 1Types
of scanners
- 2History
- 3Analysis
and inspection techniques
- 3.1Assembly
- 3.2Void,
crack and defect detection
- 3.3Geometric
dimensioning and tolerancing analysis
- 3.4Image-based
finite element methods
- 4See
also
Types of scanners
Line beam scanner
Line beam scanning is the traditional process of
industrial CT scanning.X-rays are produced and the beam is collimated to create
a line. The X-ray line beam is then translated across the part and data is
collected by the detector. The data is then reconstructed to create a 3-D volume
rendering of the part.
In cone beam scanning, the part to be scanned is
placed on a rotary table. As the part rotates, the cone of X-rays produce
a large number of 2D images that are collected by the detector. The 2D images
are then processed to create a 3D volume rendering of the external
and internal geometries of the part.
Cone beam scanner
History
Industrial CT scanning technology was introduced in 1972
with the invention of the CT scanner for medical imaging by Godfrey
Hounsfield. The invention earned him a Nobel Prize in medicine, which he shared
with Allan McLeod Cormack. Many advances in CT scanning have allowed
for its use in the industrial field for metrology in addition to the visual
inspection primarily used in the medical field (medical CT scan).
Analysis and inspection techniques
Various inspection uses and techniques include part-to-CAD
comparisons, part-to-part comparisons, assembly and defect analysis, void
analysis, wall thickness analysis, and generation of CAD data. The CAD data can
be used for reverse engineering, geometric dimensioning and tolerance
analysis, and production part approval.
Assembly
One of the most recognized forms of analysis using CT is for
assembly, or visual analysis. CT scanning provides views inside components in their
functioning position, without disassembly. Some software programs for
industrial CT scanning allow for measurements to be taken from the CT dataset
volume rendering. These measurements are useful for determining the clearances
between assembled parts or the dimension of an individual feature.
An industrial computed tomography (CT) scan conducted on an
aluminum casting to identify internal failures such as voids. All color
coordinated particles within casting are voids/porosity/air pockets, which can
additionally be measured and are color coordinated according to size.
Void, crack and defect detection
Flight through a 3D reconstruction of a disposable pepper
grinder. Glass in blue.
Traditionally, determining defects, voids and cracks within
an object would require destructive testing. CT scanning can detect internal
features and flaws displaying this information in 3D without destroying the
part. Industrial CT scanning (3D X-ray) is used to detect flaws inside a part
such as porosity, an inclusion, or a crack.
Metal casting and moulded plastic components are typically
prone to porosity because of cooling processes, transitions between thick and
thin walls, and material properties. Void analysis can be used to locate,
measure, and analyze voids inside plastic or metal components.
Geometric dimensioning and tolerancing analysis
Traditionally, without destructive testing, full metrology
has only been performed on the exterior dimensions of components, such as with
a coordinate-measuring machine (CMM) or with a vision system to map
exterior surfaces. Internal inspection methods would require using a 2D X-ray
of the component or the use of destructive testing. Industrial CT scanning
allows for full non-destructive metrology. With unlimited geometrical complexity, 3D
printing allows for complex internal features to be created with no impact
on cost, such features are not accessible using traditional CMM. The first 3D
printed artefact that is optimised for characterisation of form using computed
tomography CT
Image-based finite element methods
Image-based finite element method converts the 3D image data
from X-ray computed tomography directly into meshes for finite element
analysis. Benefits of this method include modelling complex geometries (e.g.
composite materials) or accurately modelling "as manufactured"
components at the micro-scale.
See also
- Industrial
radiography
- Cone
beam computed tomography
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