Process monitoring of Wire-Arc Additively Manufactured (WAAM) parts by tracking the evolutionary nature of structural resonances

Wire arc additively manufactured parts can take a significant amount of time to fabricate from several hours to days. 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. An example is presented were an arc-out of the welder pauses the build which resulted in a cooling of the part and an abrupt shift in the resonance paths of structural modes.