Does circular magnetization detect faults across or lengthwise in a part?

• A. Across
• B. Both
• C. Lengthwise
• D. Neither

Answer: (C)

In magnetic particle inspection, the detectability of a flaw depends on how the magnetic field interacts with the flaw’s orientation. Circular magnetization creates a magnetic field that runs around the circumference of a cylindrical part. A flaw that runs along the length of the part presents a long path perpendicular to that circumferential field, causing flux leakage along the crack and producing a visible indication along the crack's length. That makes circular magnetization especially effective for detecting cracks that extend lengthwise along the part. Cracks that go across the part aren’t as readily revealed by this orientation because the field lines don’t intersect them in the same way, so the leakage is less pronounced.