|Nondestructive Testing Encyclopedia|
- Magnetic Particle Inspection -
|Two separate fields, having different directions, cannot exist in a part at the same time. But two or more fields in different directions can be imposed upon a part sequentially in rapid succession. When this is done magnetic particle indications are formed when discontinuities are located favourably with respect to the directions of each of the fields, and will persist as long as the rapid alternations of field direction continue. This, in effect, does constitute two or more fields in different directions at the same time, and enables the detection of defects oriented in any direction in one operation.|
Multidirectional methods can provide reduced inspection times, improved sensitivity and simple quick demagnetiztions. However, since the field is constantly changing the field direction that is optimum for a particular orientation of defect is there only momentarily. This requires the inspection medium (particles) to be applied constantly during magnetization. This means observation must be continuous as well since the indication formed will not have the magnetizing force fixed to hold the particles in place. The fluid bath used to apply the particles could wash the indication away.