Case StudiesInspection/NDTMetal Additive Manufacturing

Theta Technologies proves NDT capabilities

Using a nonlinear resonance technique to find flaws in HiETA's 3D printed heat exchanger samples

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Theta Technologies is developing a game-changing, non-destructive testing (NDT) solution that is proven to detect the presence of flaws in 3D printed components. The nonlinear resonance technique is designed to excite components using a variety of different sources. Once the component is excited, a detector system watches for non-linearity within the tested component.

With the metal additive manufacturing industry rapidly evolving and subsequently allowing manufacturers to design and create much more complex metal components, this unique non-destructive testing technique is emerging at a convenient time for those wanting to manufacture bespoke metal parts – particularly for safety-critical applications. Theta’s solution offers several crucial benefits over other NDT solutions on the market – such as saving time, reducing overall costs, and freeing up resources by identifying flawed components before post-processing is completed.

Theta Technologies proves NDT capabilities. Using a nonlinear resonance technique to find flaws in HiETA's 3D printed heat exchanger samples.
HiETA’s 3D printed heat exchanger sample

There is, however, no better way to prove that a new technology lives up to its promise than by putting it to the test.

Thermal engineering company, HiETA Technologies Ltd, is well-known in the additive manufacturing industry for their production of heat exchangers. The complex geometry of these parts has resulted in other non-destructive testing technologies being relatively ineffective when it comes to identifying flaws within the components. With this in mind, Theta decided to prove that the company had the solution to this common additive manufacturing problem.

Theta Technologies proves NDT capabilities. Using a nonlinear resonance technique to find flaws in HiETA's 3D printed heat exchanger samples.

Theta’s nonlinear resonance, non-destructive testing technology was used to assess two additively manufactured heat exchanger samples, created by HiETA Technologies. Using nonlinear resonance to excite each component, Theta was able to exploit microscopic flaw behavior to identify whether either of the samples showed signs of a flaw within its complex structure. By increasing the excitation of the parts, Theta is able to identify whether the part is flawed – as defective samples show an amplitude-dependent frequency response. In this case, a nonlinear signature could be an indicator of trapped powder.

Theta Technologies proves NDT capabilities. Using a nonlinear resonance technique to find flaws in HiETA's 3D printed heat exchanger samples.
Error bars showing two standard deviations obtained in reproducibility tests – identifying the ‘Damage Index’ for both samples S8 and S9

HiETA was already aware that one of the sample heat exchangers was flawed and challenged Theta’s nonlinear resonance NDT technology to identify this. The blind test of each of the Inconel samples was undertaken using the same parameters, with repeatability and reproducibility of the part examinations being key features in determining the overall outcome. The error bars seen in the graph above are two standard deviations obtained in reproducibility tests, and identify the ‘Damage Index’ for both samples S8 and S9. As Theta discovered, there were very clear distinctions between flawed and flawless samples based on the nonlinear signature.

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Edward Wakefield

Edward is a freelance writer and additive manufacturing enthusiast looking to make AM more accessible and understandable.

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