<p class="MsoNormal">As a potential breakthrough technology, the additive manufacturing of metallic parts has raised tremendous interest. It is thus not surprising that methods are highly sought after, that can provide information on the quality of the manufactured parts in a non-destructive way. Laser-based ultrasonics is a potential candidate to provide insight into fabricated parts either in-line or as quality check after fabrication.&nbsp; The method is based on the excitation of ultrasonics signals, i.e., acoustic pulses or eigenvibrations of samples, by a ns-pulsed laser and subsequent readout of the induced dynamics or propagating acoustic pulses by optical interferometry. In particular, two-wave mixing interferometry has been proven as helpful detection approach with its robustness to optical scattering induced by surface roughness.</p><p class="MsoNormal">We provide here a study of ultrasonics measurements on Ti-6Al-4V parts with controlled defects of different sizes and depths under the sample surface. The defects are printed as spheres with radii ranging from 0.1-1mm which are embedded in depths from 0.1 to 5mm. We apply a spatial scanning scheme and record the time-resolved response for each individual position. The time-position data then reveals backscattered signals from individual defects. We also use reconstruction methods to learn about the accuracy we can provide in the defect location as well as in detectable sizes. Our results are finally compared with measurements provided by micro-computer tomography and we discuss potential improvements of the applied methodology.</p>

Defect Detection in Additively Manufactured Parts by Laser Ultrasonics

Paper Proceedings: https://asmedigitalcollection.asme.org/qnde/QNDE2021/volume/85529

ASME 2021 48th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE2021)

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