A proposal for magneto-thermal NDT in conducting materials

A method for non-destructive testing in conducting materials is proposed by combining electromagnetic excitation and transient infrared thermography. In the conducting material under inspection, which is isolated thermally, a time-varying magnetic field induces eddy currents. The heat generated by the eddy currents, flows mainly from the border to the center of the specimen, crossing the current flow. Thus, the specimen is "swept" by current flow and heat flow in two different directions. Because of this property, a crack in the specimen with arbitrary orientation, will modify the heat flow either directly or indirectly and, consequently, the temperature distribution. The numerical analysis shows that the temperature gradients developed around the crack, permit the determination of its position and, in most cases, its shape Obviously, this proposal needs experimental verification.