Session: Research Posters

Paper Number: 173241

Acoustic Characterization of L-Pbf Process Interruptions Using Rus and Ultrasonic Testing 

Process interruptions during Laser Powder Bed Fusion (L-PBF) are relatively common but often overlooked issues that can cause localized changes in microstructure, affecting the consistency and mechanical performance of additively manufactured (AM) metal components. Interruptions can occur due to various number of factors such as power loss, Recoater malfunctions and pauses within the prints. Such disruptions interfere with the thermal gradients and solidification behavior within the melt pool, leading to inconsistencies in grain structure, density, and residual stress. Ultimately impacting mechanical properties such as strength, stiffness and fatigue life. Therefore, there is a critical need for reliable non-destructive evaluation (NDE) techniques that can identify and quantify these effects both during and after the build process.

In this study, a combined acoustic NDE approach is used to assess stainless steel 316L samples produced by L-PBF with deliberately introduced process interruptions. The method integrates Resonant Ultrasound Spectroscopy (RUS) and ultrasonic wave velocity measurements to characterize changes in mechanical behavior caused by these disruptions. To replicate realistic manufacturing conditions, the samples were printed under controlled settings with varied process parameters such as laser power, scan speed, and layer thickness. These parameter changes were intentionally applied to induce a range of defects and inconsistencies typically seen in interrupted builds.

RUS was employed to extract elastic moduli by analyzing shifts in the natural vibration modes of the samples. These resonance shifts are sensitive to internal changes in stiffness, providing a means to detect structural anomalies not visible on the surface. In parallel, longitudinal ultrasonic wave velocity measurements were performed to assess local changes in density and elastic behavior along the build direction. Ultrasonic velocity is directly related to the material’s elastic modulus and density, making it an effective tool for identifying zones affected by thermal instability or lack of fusion.

The results show a strong correlation between acoustic responses and variations in print parameters, particularly in regions surrounding the interruptions. Notable changes in wave velocity and resonance frequency were observed, especially in samples fabricated at lower scan speeds or under insufficient laser energy densities.

The acoustic responses observed in this study proved to be reliable indicators of changes in mechanical properties, such as reductions in stiffness and the presence of density gradients. These shifts reflect the influence of process interruptions and parameter variations on material behavior. Overall, the results highlight the value of combining RUS with ultrasonic wave velocity measurements for a more thorough assessment of L-PBF components affected by build disturbances. This dual-method approach not only strengthens post-process inspection capabilities but also holds strong potential for integration into real-time monitoring systems during fabrication. As additive manufacturing continues to scale toward industrial production, the adoption of such acoustic NDE techniques could significantly improve quality assurance, facilitate early defect detection, and ultimately lead to more reliable parts with reduced waste and rework.

Presenting Author: Hossein Taheri Georgia Southern University

Presenting Author Biography: Dr. Taheri is a Associate Professor at Georgia Southern University who's focused to see his students succeed in the NDT and Advanced Manufacturing Industry. His commitment to help students and the industry is impeccable. He's also the Director of LANDTIE Lab at GSU.

Authors:

Poojith Chowdary Chigurupati Georgia Southern Unviersity
Hossein Taheri Georgia Southern University