A Prediction Model for Porosity and Pore Size Distribution of Metal Additive Manufactured Parts Based on Laser Ultrasonic Surface Waves

This study develops a simulation-assisted nondestructive characterization approach using laser-excited surface acoustic waves to quantify porosity and extract pore size distributions in additively manufactured metallic components. A finite-element model, covering a porosity range of 1–6% together with representative pore-size statistics, is established to systematically analyze how pore- size statistics influence surface wave velocity and frequency-domain attenuation. A quantitative porosity evaluation model based on surface wave velocity is constructed, while an inversion approach combining Rayleigh-scattering theory with the frequency-domain attenuation of surface waves is proposed for estimating pore-size-distribution parameters. Simulation results show that surface wave velocity decreases with increasing porosity and exhibits relatively low sensitivity to variations in pore-size distribution. In contrast, frequency-domain attenuation is strongly affected by porosity and also varies with pore-size statistics within the investigated parameter range. Laser-ultrasonic experiments were conducted on two additively manufactured 316L stainless steel samples with different porosities. After correction for the systematic discrepancy between the simplified numerical model and the experimental response, the measured attenuation exhibits the same overall trend as the simulation-calibrated inversion model. This work provides a feasible non-contact approach for porosity evaluation and attenuation-based estimation of pore-size-distribution parameters in metal additive manufacturing.