Non Destructive Testing
COMPUTED TOMOGRAPHY FOR
ADDITIVELY MANUFACTURED
AEROSPACE COMPONENTS
Additive Manufacturing (AM) is becoming an increasingly
important production technique for safety critical aerospace parts
// NILS ACHILLES
Conventional manufacturing techniques
can produce a large variety of shapes
and designs, but additive
manufacturing takes production design to
the next level. Complex designs and
internal features that cannot be
manufactured in one entire piece with
traditional means can easily be achieved
with AM. For example, shapes with a
scooped out or hollow center can be
produced as a single piece without the need
to weld or assemble individual
components, and weight can be reduced
more easily through internal structural
design changes. This has the added benefit
of being structurally stronger without
weak spots that can be compromised or
stressed.
These very complex parts require new
testing methods to assure their structural
health and integrity. Many different types
of anomalies, such as porosities, cracks,
inclusions, or residual powder, can occur
during the production process.
Furthermore, it is often important to verify
wall thicknesses or other inner structures,
e.g. measure the inner diameter of a
cooling channel. Computed Tomography
(CT) makes it possible to detect the
aforementioned anomalies and to perform
dimensional measurements, thus providing
a complete dataset of every scanned part.
Many additive manufacturers and
design engineers have already adopted
industrial computed tomography (CT) to
perform non-destructive testing (NDT) on
their products to ensure quality
throughout the research and development
phase as well as during production. A CT
scan consists of a high number of X-ray
images that are converted into a threedimensional
model through powerful
software. This enables a manufacturer to
look inside an object without destroying it,
which is most critical for complex
additively manufactured objects.
DETECTING FLAWS
Typical flaws from the powder bed fusion
process, such as porosity, lack of fusion,
balling (which is caused by surface tension
of the liquid metal), excessive surface
roughness, and micro-structural issues,
can be easily and quickly detected by CT.
Software programs for industrial CT
scanning allow for measurements to be
taken from the CT dataset
volume rendering. These
measurements are useful
for determining clearances
between assembled parts
or simply dimensions of an
individual feature. CT has
even become advanced
enough to conduct precise
measurements of internal
structures, which is
especially critical to quality
assurance in additive
manufacturing.
Other challenges,
including density variation,
176 SHOWCASE 2020 \\ AEROSPACETESTINGINTERNATIONAL.COM
1 // YXLON’s 3D-printed
specimen for internal tests
and developments in the
field of additive
manufacturing
2 // 3D CT volume and
section of the hydraulic
component to determine
wall thicknesses in the
curvature (Photo: Renault
F1 Team)
1
embedded features, organic part design,
dissimilar metals, or materials and surface
finishes, are more easily detected by CT
than any other NDT technique. Objects
can be scanned with CT and identified
issues can be fixed promptly and
efficiently.
Moreover, utilizing CT in R&D can avoid
many issues later in the production process
by identifying key information about part
design and raw materials to establish
early-on how suitable they are for the
intended geometry, which is vital to the
success of the final product.
In order to obtain information about
how a design will perform in future
production, we must start at the very
beginning. One of the key issues that
design engineers face in the development
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