Enhancing ML Particle Distribution Via Surface PEO in Complex Metal Geometries

Mechanoluminescence can be used as a contact-free visualisation of deformation, but particle integration in complex geometries is challenging. The paper demonstrates a proof-of-concept approach, in which plasma electrolytic oxidation (PEO) is used to create a porous alumina layer capable of hosting SrAl₂O₄: Eu, Dy mechanoluminescent particles on aluminium substrates. A 15-minute PEO treatment produced an optimal microstructure for particle retention and mechanical stability. While embedded particles showed limited mechanoluminescence due to outward pore expansion during bending, applying a thin epoxy glaze enabled strong and repeatable luminescent responses during both loading and unloading. The mechanoluminescence contrast ratio remained stable across long delay intervals, indicating robustness against afterglow decay. CMOS imaging confirmed the feasibility of spatial strain mapping, though surface inhomogeneity currently limits resolution. These results establish PEO-based particle integration as a promising route toward wire‑free, full‑field stress visualisation in metal components and highlight key microstructural factors for future optimisation.