Resonant Ultrasonic Testing can Quantitatively Assess the Microscopic Porosity of Complex-Shaped Additively Manufactured AlSi10Mg Components

Abstract

The utility of resonant ultrasonic testing for quality control of complex-shaped additively manufactured (AM) components in terms of porosity variations is investigated. A fully non-contact test setup is used to investigate differences in the volumetric porosity between AM AlSi10Mg samples. A set of 96 samples with programmatically induced pores varying in nominal total porosity between 0% and 2% is tested: one half of the samples are prismatic, and the other half have a complex internal Triply Periodic Minimal Surface (TPMS) structure. In addition, a subset of the samples is scanned using X-ray micro-computed tomography (µ-CT). It is found that the resonance frequency corresponding to the 1st compressional mode can predict the total nominal porosity even in TPMS samples. From statistical analysis, the smallest detectable porosity difference is found to be 0.25% for the prismatic samples and 0.5% for the TPMS samples. The experimental results agree well with the predictions of finite element (FE) simulations and analytical models. However, X-ray µ-CT appears to underestimate the porosity, possibly due to its inability to resolve the small pores. Our findings suggest that resonant ultrasonic testing can quantitatively assess the total porosity of AM parts having complex geometries.