Statistical characterization of low-porosity, additively manufactured metal foams measured in an acoustic impedance tube

Abstract

This work focuses on the acoustic response of aluminum foams with different porosities additively manufactured using powder bed fusion. Emerging voxel-by-voxel additive manufacturing, which further expands the achievable microstructure design space through localized spatial control of the printing properties, allows for direct fabrication of samples with varying percent porosities. Unlike traditional, rigid-frame foams with very high porosities, the samples range from fully dense to approximately 50% porosity. This work utilizes normal incidence acoustic impedance tube measurements and the Johnson–Champoux–Allard–Lafarge analytic model, which are common characterization methods for traditional rigid-frame porous media. For the reflection and transmission coefficients measured in an acoustic impedance tube, Bayesian statistical inversion is performed with the Johnson–Champoux–Allard–Lafarge model to obtain distributions of the possible values for the six required model parameters. By using a statistical characterization approach, the applicability of these common acoustic measurement and modeling methods for lower porosity additively manufactured foams is also assessed. [This work was supported by the Office of Naval Research.]