Nonlinear behavior of additively manufactured steel beams with trapped-powder dampers.

Jonathan K. Black; Brooklyn Andrus; Derek Koski; Matthew S. Allen; Nathan Crane; Tracy Nelson

Journal of Structural Dynamics

A Diamond Open Access Journal for High-quality Papers in the Field of Structural Dynamics

2684-6500

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Jonathan K. Black, Brooklyn Andrus, Derek Koski, Matthew S. Allen, Nathan Crane & Tracy Nelson

Nonlinear behavior of additively manufactured steel beams with trapped-powder dampers.

(Issue 3)

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Abstract

Additive manufacturing has gained popularity for its ability to produce complicated geometries that distribute material optimally and allow several parts to be consolidated into one.

Part consolidation often comes with a large reduction in damping, however, due to the elimination of frictional losses at interfaces between parts.

This reduction of damping can be problematic in applications where resonant vibrations lead to early fatigue failure or undesirable noise emission. In recent years, a promising technique for increasing damping in parts made by laser powder bed fusion (LPBF) has been introduced, in which pockets of retained, unfused metal powder act as embedded dampers. This work presents an experimental study of the nonlinear behavior of several 316L stainless steel rectangular beams made by LPBF with embedded powder dampers. In addition to amplitude-dependent nonlinearity, a significant memory effect is observed, thought to be caused by powder settling and unsettling in response to external agitation. A procedure was developed to measure the full range of damping behavior by causing the system to transition between high-damping and low-damping states. This procedure is applied to six beams with varying pocket thicknesses, resulting in a rich dataset that provides insight into the factors that most influence the effective modal damping and natural frequency of these parts.

As pocket thickness increases, the damping increases, together with the amount of nonlinearity and the variance in damping and natural frequency. This uncertainty can be reduced by controlling the amplitude range of interest, the powder state, the drive point, the impact force, and the hammer tip. The relative importance of each of these factors is quantified, and each factor is found to be significant in certain cases. Some of the parts are shown to exhibit significant modal interactions, as well as time-varying phenomena, for some modes.

Additionally, a study which varied the operating temperature is presented, confirming that the behavior of trapped-powder dampers is largely temperature-independent.

Implications of these findings for design and modeling are discussed.

Index by keyword : Damping, Additive Manufacturing, System Identification, LPBF, Particle Damper

To cite this article

Jonathan K. Black, Brooklyn Andrus, Derek Koski, Matthew S. Allen, Nathan Crane & Tracy Nelson, «Nonlinear behavior of additively manufactured steel beams with trapped-powder dampers.», Journal of Structural Dynamics [En ligne], Issue 3, URL : https://popups.uliege.be/2684-6500/index.php?id=285.