Magnetic particle inspection - for basic

A way of knowing the existence of cracks or defects that exist on the surface (surface or sub surface discontinuities) in ferromagnetic materials. The working principle of this test is based on the nature of ferromagnetic objects that will give the poles of a magnet if the object is in the magnetization, the magnetic pole that will cause the flow of the magnetic field from North Pole to South Pole. If there are defects in the test object such defects will cause a new magnetic field, if the defect is located perpendicular to the direction of the magnetic field.

The advantages of this method include:
-Can detect very small defects.
-Detecting defects on complex objects.
-To examine surface and subsurface defects.
Can check-ring-shaped objects and pipes.
-Portable.

Disadvantages of this method include:
-The object is examined only ferromagnetic objects.
-Requires an electrical current.
-For large test objects in great need of a yoke as well.

source : letheg