Non – destructive testing (NDT) takes on various forms from very simple liquids and dyes to more sophisticated methods involving the application and analysis of heat and vibration.

simple Yet sophisticated component testing

Thermal Wave Imaging’s EchoTherm blade inspection station.

Non-destructive testing (NDT)takes on various forms from very simple liquids and dyes to more sophisticated methods involving the application and analysis of heat and vibration.Thermal Wave Imaging,Inc.(TWI), a leader in thermal NDT, offers products and services for fast, repeatable and cost effective solutions suitable for manufacturing, Q/A, service and R&D.

The company’s EchoTherm and Thermo- Scope systems offer reliable and accurate detection of defects, such as wall thinning, cooling channel blockages or anomalies, thermal barrier coating (TBC) delamination, and porosity.“The trend we’ve seen is that customers are getting more sophisticated and rather than look for a one size fits all NDT tool, which might be only thermography or ultrasonics or X-ray, they realize it takes a multi-pronged approach to develop and implement an effective NDT solution,” said Bharat Chaudhry, general manager for the Ferndale, Michigan, U.S.A-based company.

“Our products are based on the pulsed thermography approach,”Chaudhry noted.
“For example, our core products, which are based on flash thermography,utilize high intensity flash lamps as the heat source. The inspection process involves precise and uniform deposition of a small amount of heat at the surface of a component, capture of surface temperature variations as a result of heat diffusion in the material and reconstruction of internal features with our software and tools offering detection and measurement of subsurface flaws.

What makes TWI’s software packages so unique and powerful is that they all feature our patented signal reconstruction process, referred to as Thermographic Signal Reconstruction (TSR) resulting in an unprecedented increase in resolution, quantitative measurement and material characterization over conventional techniques.” In effect, a thermal map of the internal structure of the material is created and can be viewed as a snapshot or time sequence of images. Images at later times present information at greater depths. “We also offer turnkey inspection solutions based on the vibrothermography technique.

Instead of using flash lamps to heat the part, we mechanically excite it with the aid of an ultrasonic actuation system (20 KHz),” he said. “This process can be beneficial for detection of cracks in certain metallic and composite components.“The potential real world benefits our technology offers has prompted broad-band investigation of our solutions to replace legacy inspection methods for advanced applications involving turbine engine components such as blades and vanes,” he said. “In many

gas turbine blade graph

Thermal Wave Imaging’s EchoTherm blade inspection station.

instances, we provide clients with high value-add, fully automated dedicated
inspection cells to increase efficiency and product quality.” The potential of thermographic methods for nondestructive evaluation of turbine engine components has been widely acknowledged. The wide area, noncontact and curvature-tolerant aspects of thermography make it an appealing alternative to point detection inspection methods.

Thermographic NDT systems are currently used by turbine manufacturers, component vendors and endusers for a variety of in-service and manufacturing inspection applications. Recent advances in infrared camera and computer technology and the development of new algorithms and methodologies that fully exploit underlying heat transfer phenomena have given rise to a new generation of active thermographic NDT equipment with unprecedented capability for precise, quantitative inspection of turbine components, for applications ranging from detection of thermal barrier coating delamination to measurement of coating and wall thickness.

“Some applications require only detection of TBC delaminations and spallation,” Chaudhry said. “Certain OEMs are taking it one step further by actually wanting the TBC thicknesses measured as well. Also, before TBCs are sprayed on, we can accurately measure wall thickness of the base metal substrate, blocked cooling holes and channels of blades and vanes. “There are several advantages our technology has to offer over other conventional NDT techniques currently being utilized,” said Chaudhry.

“Our process is non-contact, non-invasive, very rapid, highly repeatable and tolerant of curvature and geometric changes in a component.Data interpretation and flaw detection can be as simple as examining a detailed image rendition of the internal structure of a component.And, under a majority of operating conditions, our equipment does not require any special safety or environmental considerations.”

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