Novel Method for the Characterization of the Electrical Conductivity and Eddy Current Damping of Aluminum Foams

In this article, we present a novel method for the indirect characterization of eddy currents damping and loss coefficients, as well as the equivalent electrical conductivity of metal foams. The proposed method is based on the measurement of the braking torque when the metal foams are exposed to an alternating magnetic field generated by a set of rotating permanent magnets (PMs). Measurements are carried out in a low-frequency range (< 50 Hz) and for high amplitude magnetic fields (up to 0.4 T), both typical values observed in electromechanical devices. This method was used for the accurate characterization of a set of open-cell aluminum foams with different compositions and porosities. Experimental results, in good agreement with the theoretical models, confirm the viscous damping behavior of aluminum foams in the tested frequency range. The quadratic dependency of the damping coefficient on the magnetic flux density is also confirmed in the measurement range.