Session: 01-02-01: Passive, Semi-Active, and Active Noise and Vibration Control

Paper Number: 112553

112553 - Optimal Design of Magnetic (Eddy Current) Dampers for Tuned Damping Applications 

Damping is an essential element of any structure prone to vibration. The energy dissipation provided by dampers reduces structural vibration, enhancing serviceability of the structure and in some cases prevents damage caused by fatigue.  In this study, magnetic damping (also known as an eddy current damping) which is generated by the eddy current induced in a conductive material subjected to a time-varying magnetic field (normally created by several rare earth permanent magnets) is explored. The eddy current in the conductor generates its own magnetic field resulting in an electromagnetic force opposing the force of the original time-varying magnetic field.

The motivation for conducting this study is to explore the use of eddy current as an alternative to liquid-based viscous and solid-based viscoelastic damping mechanisms in tuned mass dampers as well as stand-alone viscous dampers, in large structures. The main contribution of this effort is development of a numerical tool for designing eddy current dampers and optimizing them for particular applications.

Two designs of eddy current dampers (ECDs) are investigated in this paper. The first design is made up of a stack of eight Neodymium NdFeB (N42) permanent magnets separated by seven pole pieces made of nearly pure iron, assembled on an Aluminum shaft moving back and forth in the confines of an aluminum tube. The interaction between the magnetic field of the permanent magnet assembly moving inside the aluminum tube and the magnetic field of the electromagnet created by the eddy current within the aluminum tube results in energy dissipation.

 The second version of the eddy current damper contains a conductive copper plate and five NdFeB (N50) magnet plates two of which are axially and the remaining three radially magnetized.  The magnets are placed in Halbach array arrangement, on two iron plates that move in parallel and close vicinity of the copper plates. In this damping scheme, the relative motion between the copper and magnet plates produces a repulsive force that opposes the changing in the magnetic flux density. The damping effectiveness is much higher in this damper configuration than the first one.

The two configurations of eddy current damper are modeled and simulated in COMSOL finite element environment. To verify the FE models, the damper with the first configuration has been built and its damping effectiveness measured. The experimental results have shown a strong agreement between the measured data and model predictions.

The corresponding author.  Reza Kashani at Email address: reza.kashani@udayton.edu

Presenting Author: Ahmad Kashani University of Dayton

Presenting Author Biography: Dr. Kashani received his Ph.D. in Mechanical Engineering from the University of Wisconsin-Madison in 1989.
From 1989 to 1994 he was an assistant professor at Mechanical Engineering-Engineering Mechanics Dept. of Michigan Technological University. He joined The University of Dayton in 1994 where he currently is a full professor at the Mechanical and Aerospace Engineering Department.
Dr. Kashani’s research interests are mainly in control of dynamic systems with special interest in passive and active control of sound and vibration. He has numerous publications in these areas.

Authors:

Abdulrhman Mohmmed H. Farran The University of Dayton
Ahmad Kashani University of Dayton