Detection of Elliptical Cylindrical Inclusions by Magnetic Sensing

A comparison between reported analytical results with experimental data of the magnetic flux density produced by weak thermoelectric currents around cylindrical inclusions of elliptical cross-section embedded in a copper matrix under external thermal excitation for different aspect ratios b/a of the elliptical inclusions is presented. The aspect ratio of the elliptical cylindrical inclusions varied from 0.5 to 3.250. By changing the aspect ratios b/a of the elliptical inclusions, a wide range of real situation such as slender inclusions, cracks and even porosity can be simulated. A fairly modest 2.3°C/cm temperature gradient in the specimen produced magnetic flux densities ranging from 2 to 100 μT at 2 mm lift-off distance between the tip of the magnetometer probe and the specimen. The experimental magnetic field distribution illustrated the potential for the non contacting thermoelectric technique to detect and characterize metallic inclusions of different geometries based on their magnetic signature.