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CT Scanning Vital for Airworthy Parts

Karl-Michael Nigge
By Karl-Michael Nigge Chief Product Officer, Volume Graphics
Karl-Michael Nigge

Engineers are on a never-ending quest to design and build products that are more fuel-efficient, stronger yet lighter, able to fly faster and travel greater distances than their predecessors. The mission parameters are essentially no different than those of the first hot-air balloons or winged craft; what’s changed are the manufacturing technologies and materials used to achieve these lofty objectives.

For instance, many of today’s aircraft parts are made of advanced polymers and carbon-fiber composites. These ultra-light materials make it possible to reduce component weight without sacrificing strength. Superalloys, such as Inconel and Hastelloy, offer similar benefits, which explains why they’re found in gas turbine engines and other flight-critical components. Both allow aerospace designers to meet structural or thermal integrity requirements with less metal, thereby increasing vehicle efficiency.

The challenge in each of these examples is achieving qualification of both the part’s design and the materials needed for its construction. Without such prerequisites, aircraft, satellite and rocket-engine components would remain forever earthbound.

The methods used to make aircraft components have also changed. Most are now produced via automated machining, casting, forming, and layup equipment, with an increasing number of parts made via additive manufacturing. Here, again, the manufacturing processes must also be validated before parts can be certified as flight-ready.

The question then becomes: What’s the most cost-effective, reliable way to meet these requirements? The answer depends on factors like part size, complexity, surface or interior inspection goals and level of flight-criticality. But in many cases, inspection requirements entail a powerful, comprehensive metrology and non-destructive testing (NDT) solution known as industrial computed tomography (CT).

Consider all the blades found in a jet engine. Though produced using a reliable investment-casting process and made of a tough, heat-resistant nickel-based alloy, the loss of even a single blade during flight can lead to catastrophic results. With CT scanning—along with the use of scan-data analysis and visualization software—a quality engineer can peer deep inside these and other flight-critical components and identify the porosity, cracks and other flaws that could ultimately lead to component failure.

CT technology is also used to measure internal part features. The only alternative is destructive testing, painfully cross-sectioning each component to see if any defects or dimensional non-compliance lie within. Capabilities like these are of particular importance for the qualification of 3D-printed aerospace parts because AM opens the door to nearly complete design freedom. The only catch is these features must be validated before the FAA and other governing bodies will approve the use of 3D-printed components. CT scanning and data analysis meet that need.

The tech meets the needs of composite manufacturers, too. CT data analysis makes it easy to quickly query fiber orientation or identify delamination, without damaging the workpiece. This NDT testing method lets manufacturers correlate in-process measurement data with that obtained via CT scanning, thus furthering the development of repeatable processes across a wide variety of manufacturing methods.

These are just a few of the reasons why manufacturers look at CT scanning as an indispensable part of their NDT toolkit. When coupled with robust analysis and visualization software, it allows them to validate a host of flight-critical components as well as the processes used to make them.

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