Using BB-gun or Acoustic Excitation to Find High Frequency Modes in Additively Manufactured Parts

Abstract

Additive manufacturing (AM) considers parts that are produced at a low volume or with complex geometries. Identifying internal defects on these parts is difficult as current testing techniques are not optimized for AM processes. The resonant frequency method can be used to find defects in AM parts as an alternative to X-ray or CT scanning. Higher frequency modes at approximately 8000 Hz and above cannot be tested with a traditional modal hammer or shaker since they do not provide enough excitation. The goal of this paper is to evaluate creative testing techniques to find internal defects in parts with high frequency modes. The two types of testing methods considered are acoustic excitation provided by two speakers and high velocity impact testing produced by a BB – gun. Although the frequency ranges of interest are part dependent, these techniques were able to reach up to 16,000 Hz, which is an additional 8000 Hz above what the traditional modal hammer is able to reach. This work was funded by the Department of Energy’s Kansas City National Security Campus which is operated and managed by Honeywell Federal Manufacturing Technologies, LLC under contract number DE-NA0002839.