Abstract

Laser Powder Bed Fusion (LPBF) can be used to create metal parts with pockets of retained, unfused powder that serve as mechanical dampers. These trapped-powder dampers show promise for reducing the amplitude of vibrations at resonance by orders of magnitude. However, little is currently understood about the nonlinearity and repeatability of trapped-powder dampers, meaning that the design process currently consists of expensive trial-and-error prototyping and iteration. The present work contributes a corpus of experimental measurements for rectangular beams with trapped-powder dampers of various dimensions and locations. Preliminary testing revealed the presence of a memory effect which we hypothesize to be caused by powder settling and unsettling, and subsequent testing accounted for this effect by seeking to identify the upper and lower bounds of damping behavior by controlling the powder state. The measurements were processed with a nonparametric system identification technique to extract amplitude-dependent damping and natural frequency, and testing with several replicates of every measurement enabled estimates of uncertainty. A finite element model (FEM) was developed in which the trapped-powder damper was represented by a region with linear viscoelastic damping. This computationally inexpensive model was updated to match the linearized behavior of a beam at low and high vibration amplitudes and used to predict the behavior of beams with powder pockets of different sizes. Accurate predictions are made for most of the modes of interest. We hypothesize that those modes for which large discrepancies exist are dominated by damping mechanisms besides sliding friction, such as impacts, and we suggest that another model be used in those cases. This work represents a significant contribution to the existing literature on the behavior of LPBF trapped-powder dampers. It also proposes and evaluates the applicability and limitations of a computationally inexpensive model that could be used as a design tool.

Degree

MS

College and Department

Ira A. Fulton College of Engineering; Mechanical Engineering

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2025-08-12

Document Type

Thesis

Keywords

Additive Manufacturing, Damping, System Identification, Finite Element Modeling, LPBF

Language

english

Download

Included in

Engineering Commons

Share

COinS