NOTICE: Due to a lapse in annual appropriations, most of this website is not being updated. Learn more.
Form submissions will still be accepted but will not receive responses at this time. Sections of this site for programs using non-appropriated funds (such as NVLAP) or those that are excepted from the shutdown (such as CHIPS and NVD) will continue to be updated.
An official website of the United States government
Here’s how you know
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Sensitivity of acoustic nonlinearity and loss to residual porosity in additively manufactured aluminum
Published
Author(s)
Ward L. Johnson, Jake Benzing, Orion Kafka, Newell Moser, Derek Harris, Jeremy Iten, Nik Hrabe
Abstract
Acoustic nonlinearity and loss are found to be positively correlated with porosity at industrially relevant levels of less than half a percent in commercially pure aluminum produced by laser powder bed fusion (L-PBF) with several different power levels. The technique employed for acoustic measurements involves nonlinear reverberation spectroscopy (NRS) with noncontacting electromagnetic-acoustic transduction, which offers advantages of adaptability to complex part geometries and short inspection times for industrial qualification of additively manufactured (AM) parts of arbitrary size. Porosity and microstructure are characterized with the Archimedes technique, X-ray computed tomography, and scanning electron microscopy. Fit parameters of nonlinearity and loss vs. porosity are found to vary significantly with the height of material in the build, consistent with an hypothesis that the correlations are indirect and involve dislocations as the principal nonlinear/anelastic elements. Nonlinearity and loss decrease with time under acoustic excitation, while being relatively insensitive to pauses in excitation of similar duration, indicating that acoustic excitation at inspection levels induces changes in nonlinear/anelastic defects without predominant involvement of thermal excitation. This remarkable behavior is not seen as a fundamental impediment for the application of the technique to nondestructive AM part qualification because of the brief time required for a measurement.
Johnson, W.
, Benzing, J.
, Kafka, O.
, Moser, N.
, Harris, D.
, Iten, J.
and Hrabe, N.
(2023),
Sensitivity of acoustic nonlinearity and loss to residual porosity in additively manufactured aluminum, Ndt & E International, [online], https://doi.org/10.1016/j.ndteint.2023.102801, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=935566
(Accessed October 9, 2025)