ABSTRACT
Many inspected parts have an axis of symmetry, and can be easily magnetized in the circumferential direction so as to produce MFL from longitudinally oriented flaws. Three methods are commonly used. Where the part is solid, or only an outer surface inspection is needed, and the specifications permit, the passage of current along the part is often used. Where a more uniform flux density is required in hollow parts, an internal conductor method may be used, with either direct or pulse current. 21 , 22 Finally, for round bars and tubes, rotating yokes are sometimes used. These techniques are discussed in this chapter.
