Linear and Nonlinear Analysis of Additively Manufactured Material With Different Porosity Induced by Varying Material Printing Speed Using Guided Acoustic Waves

Abstract

Guided acoustic wave based techniques have been found to be very effective for damage detection, and both quantitative and qualitative characterization of materials. In this research, guided acoustic wave techniques are used for porosity evaluation of additively manufactured materials. A metal 3D printer, Concept Laser Mlab 200 R Cusing™, is used to manufacture 316L additively manufactured (AM) stainless steel specimens. Two levels of porosity are investigated in this study, which was controlled by a suitable combination of scan speed and laser power. The sample with lower level of porosity is obtained with a low scanning speed. Lead Zirconate Titanate (PZT) transducers are used to generate guided acoustic waves. The signal is excited and propagated through the specimens in a single sided transmission mode setup. Signal processing of the recorded signals for damage analysis involves both linear and nonlinear analyses. Linear ultrasonic parameters such as the time-of-flight and magnitude of the propagating waves are recorded. The nonlinear ultrasonic parameter, the Sideband Peak Count Index (SPC-I) is obtained by a newly developed nonlinear analysis technique. Results obtained for both specimens are analyzed and compared using both linear and nonlinear ultrasonic techniques. Finally, the effectiveness of SPC-I technique in monitoring porosity levels in AM specimens is discussed.

Application of nonlinear ultrasonic analysis for in situ monitoring of metal additive manufacturing

“…The SPC technique was first used by Park et al to monitor porosity in additively manufactured metal parts. 28,29 In this study, the SPC technique was further improved by performing nonlinear ultrasonic analysis in the time-frequency plane through synchrosqueezed wavelet transform (SWT), and the proposed new SPC technique was applied to in situ porosity monitoring during the DED process by leveraging the unique layer-by-layer deposition mechanism of DED. The uniqueness and advantages of the proposed technique can be summarized as follows: (1) SPC is optimized for transient nonstationary ultrasonic signals through SWT.…”