Determining unfused powder threshold for optimal inherent damping with additive manufacturing

Abstract

The practicality of inherent damping with the Laser Powder Bed Fusion (LPBF) Additive Manufacturing (AM) process is strengthened with the identification of a threshold value for unfused powder volume. This approach provides the ability to design parts with inherent damping that can suppress vibration by 88–95% compared to fully-fused counterparts, and the damping achieved is a product of only 1–4% unfused powder volume. Inherent damping with LPBF has also addressed conventional shortcomings like manufacturing feasibility, high cycle fatigue (HCF) endurance, and a predictive tool that helps optimize damping by configuring unfused powder volumes. Despite the proven capability of the approach, a threshold unfused powder volume for optimizing damping performance and minimizing structural integrity impact has not been identified. The work in this manuscript addresses this gap in the inherent damping with LPBF capability by leveraging damping data from a varied collection of Nickel Alloy 718 and Stainless Steel 316 L specimens and assessing the trend in vibration suppression with respect to unfused powder volume. Results from this study show a trend in the effects of unfused powder volume on inherent damping performance. With the application of regression and probability distribution analyses, a rule-of-thumb comparison between undamped and passively damped systems has allowed for systemic identification of a threshold value for unfused powder volume.