In terms of flaw detection, what does the magnetic particle method specifically target?

The magnetic particle method is a non-destructive testing technique primarily used for detecting surface and near-surface flaws in ferromagnetic materials. This method relies on the application of magnetic fields and the use of ferromagnetic particles, which cluster around discontinuities in the material when it is magnetized. Since these particles accumulate at the surface of the detected flaws, they provide a visual indication of surface defects.

Surface flaws such as cracks, laps, seams, and other discontinuities can be effectively identified due to the way magnetic fields interact with these imperfections. Internal flaws, on the other hand, may not be adequately revealed because the magnetic field does not penetrate very deeply into the material. Thus, the method is not suitable for identifying flaws located deep within the material, limiting its application.

In addition, the magnetic particle method is designed for use on magnetic materials, and does not work on non-magnetic materials, which further narrows its scope to surface detection.