About Magnetic Particle Testing
Magnetic Particle (MP) Testing is primarily used for crack detection in ferromagnetic materials. The specimen is magnetized, either locally or overall, and if 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 for very narrow cracks. It is indicated as a line of iron powder particles on the surface.
The magnetic particle testing method is applicable to all metals which can be strongly magnetized – ferritic steels and irons, but not generally austenitic steels. The method is fast, and evaluation of the material is done instantly. The equipment used is portable and easy to get to the area of inspection. Magnetic particle testing can be applied to relatively rough and dirty surfaces, but the flaw sensitivity may be impaired.
The method is very sensitive and able to detect narrow and small defects. It is widely used during manufacturing and testing of welds and material in the Industry including train industry.
DEKRA’s magnetic particle testing experts also use a range of fluorescent methods, using fluorescent particles which require UV-A illumination.