Magnetic Particle Inspection is able to be used for the detection of surface breaking and slightly sub-surface (up to 2mm) discontinuities.
Bench type crack detectors and portable units can be employed which produce various waveforms (i.e. A.C, HWDC and induced magnetic flow) to provide both circular as well as longitudinal magnetism.
Visit the Keighley Laboratories Group Ltd website for more information on Magnetic Particle Inspection (MT)