Magnetic particle inspections work by running a magnetic current through the material that is being inspected. When the current is interrupted by a defect magnetism spreads out from that point, indicating its presence and allowing inspectors to identify its location in the material.
This method is used for the detection of surface and near-surface flaws in ferromagnetic materials and is primarily used for crack detection. The specimen is magnetised either locally or overall, and if the material is sound the magnetic flux is predominantly inside the material. If, however, there is a surface-breaking flaw, the magnetic field is distorted, causing local magnetic flux leakage around the flaw. This leakage flux is displayed by covering the surface with very fine iron particles applied either dry or suspended in a liquid. The particles accumulate at the regions of flux leakage, producing a build-up which can be seen visually even when the crack opening is very narrow. Thus, a crack is indicated as a line of iron powder particles on the surface.
Continue reading below for more information about the motivations behind these projects and how these "experiments" that have already begun large-scale testing are being carried out.
