Measurement of the electrical conductivity of open-celled aluminium foam using non-contact eddy current techniques

This paper studies the electrical properties of open-celled aluminium foams manufactured by a novel sintering-dissolution process (SDP) using non-destructive eddy current testing. Experimental measurement results are first presented by means of an impedance analyser under swept frequency testing for the determination of electrical conductivity of Al foams. A double air-cored solenoidal sensor has been constructed for the purpose of evaluating cylindrically shaped samples used in the investigations. The effects of porosity (relative density) and pore size, which are the principle parameters of the foams, on the conductivity are examined. The results demonstrate that the electrical conductivity of Al foam is strongly dependent on both porosity and pore size. The sensor geometry is further simulated electromagnetically using finite element methods, by which the mutual impedance between two coils is calculated to solve the forward electromagnetic (EM) induction problem to provide a calibration curve relating the mutual impedance change with the electrical conductivity of the sample. The results obtained from experimental measurements are found to be in good quantitative agreement with the finite element simulations. q 2004 Elsevier Ltd. All rights reserved.