Monitoring the build history of a wire-arc additively manufactured part using structural resonances

Wire arc additively manufactured parts can take a significant amount of time to fabricate from several hours to days. During this process, the part is exposed to a steady localized heating at the build zone, and rapid cooling away from the arc contact point. The heated zone is constantly moving across the part geometry during the build resulting in spatially localized heating and cooling throughout the part geometry. In this investigation, we utilize the broadband emission signal from the wire arc to measure the acoustic response of the part build. Experimental results are obtained using contact emission transducers mounted such that they are isolated from the direct heat to avoid damage. Transient acoustic signals are recorded throughout the entire build process and evaluated using Fourier analysis. Acoustic spectra are utilized to capture modal data which slowly track the parts construction. In a second effort the modal response of the part is modeled as a function of each build layer and the two modal structures are compared. The emphasis is to understand and track the modal response of the structure of the part as it is fabricated and develop a real time process monitoring capability.