Detection of metallic cylindrical inclusions by thermoelectric coupling

Abstract

In this paper, we present a technique that can give information on surface metallic inclusions embedded in a host material, i.e. by the magnetic sensing of local thermoelectric currents produced when a temperature gradient is established in the material. These thermoelectric currents generate flux magnetic densities that are detected by a highly sensitive magnetometer. A comparison between reported analytical results with experimental data of the magnetic field produced by thermoelectric currents around surface-breaking cylindrical tin inclusions in copper under external thermal excitation for different lift-off distances between the sensor and the surface of the specimen is presented. The diameter of the inclusions varied from 4.76 to 12.7 mm at different lift-off distance magnetometer probe and the specimen 1 to 8 mm respetively. A fairly modest 1.46$^{\circ}$C/cm temperature gradient in the specimen produced magnetic flux densities ranging from 60 to 1460 nT.