Non-Destructive Evaluation Techniques in Additive Manufacturing

Non-destructive evaluation (NDE) encompasses a suite of methods designed to assess the integrity and performance of additively manufactured parts without impairing their functionality. As layer-by-layer fabrication gains traction in sectors such as aerospace, medical devices and automotive, ensuring defect-free production is vital to maintain safety and reliability. Traditional post-process inspection methods—including X-ray computed tomography and conventional ultrasonic testing—offer high resolution but can be time-consuming and costly. Recent advances focus on integrating inspection into the build process, enabling in-process or in-situ monitoring that can detect and correct defects such as porosity, lack of fusion or cracks as they form. Techniques based on ultrasonic waves and eddy-current induction provide rapid, volumetric scanning of metal builds, while laser-based approaches generate and detect acoustic signals remotely, minimising interference with the build environment. Complementary methods such as infrared thermography and acoustic emission capture thermal signatures or stress waves associated with defect formation. The convergence of robotics, machine learning and digital twins now allows real-time data fusion and automated decision-making, reducing scrap rates and accelerating qualification. Together, these non-destructive strategies underpin a shift towards smart manufacturing, where continuous quality assurance is embedded in the additive process, delivering higher yield, lower cost and enhanced performance for critical applications.

Research from Nature Portfolio

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Research from all publishers

A recent study demonstrated the integration of ultrasound and eddy-current techniques within a multi-robot deposition cell for directed energy wire-and-arc additive manufacturing. By embedding artificial reflectors in metal builds, investigators showed that layer-wise in-process scans could detect sub-millimetre defects immediately after deposition. This approach merges fabrication and inspection in real time, enabling prompt repair strategies and reducing scrap.

Laser Induced Phased Arrays (LIPA) have emerged as a viable on-line ultrasonic method for inspecting complex internal geometries. Using pulsed lasers to generate ultrasound and synthesise a phased-array response in post-processing, researchers have located features as small as 0.2 mm in diameter tens of millimetres beneath the surface. Validation against X-ray computed tomography confirms its potential for remote, high-resolution defect mapping within parts.

Laser ultrasonic testing has been applied to titanium alloy components to detect sub-millimetre internal holes. A Q-switched pulsed laser induces surface and bulk acoustic waves, which are captured by a Doppler vibrometer. Variations in wave amplitude correlate with defect size, achieving precise resolution in pulse-echo mode. Cross-validation with computed tomography underscores laser ultrasonics as a high-throughput, non-contact NDE route for critical AM builds.

Non-Destructive Evaluation Techniques in Additive Manufacturing publication trend

The graph below shows the total number of articles in non-destructive evaluation techniques in additive manufacturing across all publications each year (not limited to Nature Index journals).

Technical terms

Non-destructive evaluation (NDE): Assessment of material integrity without causing damage or altering functionality.

Ultrasonic testing: Use of high-frequency acoustic waves to probe internal structures and detect anomalies.

Eddy-current testing: Electromagnetic induction method that identifies surface and near-surface defects from impedance changes.

Phased array: Arrangement of multiple transducers enabling dynamic beam steering and focus for improved resolution.

Laser ultrasonics: Generation and detection of ultrasonic waves using laser pulses and optical sensors for non-contact inspection.

X-ray computed tomography (XCT): Three-dimensional imaging technique reconstructing internal geometries from X-ray projections.

References

1. In-process non-destructive evaluation of metal additive manufactured components at build using ultrasound and eddy-current approaches. Journal of Manufacturing Processes (2023).
2. Laser Induced Phased Arrays (LIPA) to detect nested features in additively manufactured components. Materials & Design (2020).
3. Detection of Internal Holes in Additive Manufactured Ti-6Al-4V Part Using Laser Ultrasonic Testing. Applied Sciences (2020).