Non-Contact Eddy Current Excitation Method for Vibration Testing

Abstract

When a conductive material is subjected to a time changing magnetic field, eddy currents are induced in that structure. The eddy currents circulate inside the conductor resulting in a magnetic field that interacts with the applied field. The eddy current field is such that it opposes the change in flux resulting in a force between the source and conductor. The time changing magnetic field necessary to induce an electrometric force in the materials can be generated through a variety of different ways. In the present study, a permanent magnet will be mounted to the tip of an electromagnetic shaker such that the motion of the magnet relative to the structure will cause a time changing field and the formation of eddy currents. The actuator will be demonstrated to be beneficial due to its ability to apply actuation forces without contacting the structure. This study will show that the non-contact nature of the system eliminates mass loading and added stiffness which are downfalls of traditional excitation techniques. Additionally, it will be shown that the use of a non-contact device preserves the mode shapes of the structure, whereas a stinger results in distortions due to the added constraint. Using this concept, a model of the actuation system will be developed, allowing the beams response to be simulated. The actuation system will then be used to excite a cantilever beam to obtain the modal parameters without contacting the structure. The novel noncontact actuation system developed in this paper provides a new method performing vibration testing of on lightweight or flexible structures while preserving their dynamics.

Simulation and Analysis of an Eddy Current Damper

“…Sodano [1] mounted a PM on the tip of an electromagnetic shaker such that the relative motion between the magnet and the conductive structure causes a time changing magnetic field to induce eddy currents in the structure. Saxena and Patel [3] have also theoretically simulated the response of a vibrating cantilever beam in the absence as well as presence of a time changing magnetic field provided by an electromagnet.…”

Modeling and analysis of magnetic impedance sensor with circuitry integration for damage detection

“…At the same time, the effect of the defect can be reflected by analyzing the coil impedance change resulting from the change of magnetic fluxes throughout the coil. The eddy current phenomena are also utilized in developing passive (Sodano, 2006;Sodano et al, 2005Sodano et al, , 2006 and active controls (Bau et al, 2007). In these studies, the eddy currents induced and the resulting Lorentz forces are explicitly modeled.…”

Performance Analysis of a Hybrid One-Sided Magnetic Exciter Mounted on a Piezoelectric Stack

“…Sodano [3] has used eddy currents in a conducting plate for non-contact excitation of a beam. A permanent magnet is attached to a standard electrodynamic exciter.…”