Under continuous longitudinal magnetization with a cable, which type of defect is detected?

Under continuous longitudinal magnetization with a cable, which type of defect is detected?

• A. Defects perpendicular to the long axis of the part
• B. Defects parallel to the long axis of the part
• C. Defects parallel to the concentric circles of magnetizing force within the part
• D. Defects only on the surface of the part

Answer: (A)

When magnetization runs along the length of the part, the magnetic field flows longitudinally. A flaw that crosses this field—meaning its plane is perpendicular to the long axis—interrupts the magnetic circuit and causes leakage of flux to the surface. That surface leakage is what you detect with magnetic inspection, so defects oriented across the length show up most clearly. If a defect runs parallel to the long axis, the field can pass by with less disruption, making it harder to detect. Defects that align with the concentric circular paths around the magnetizing current don’t create the kind of leakage that the inspection relies on. Surface-only flaws can be detected, but the type most readily identified with longitudinal magnetization is a flaw perpendicular to the long axis.

When magnetization runs along the length of the part, the magnetic field flows longitudinally. A flaw that crosses this field—meaning its plane is perpendicular to the long axis—interrupts the magnetic circuit and causes leakage of flux to the surface. That surface leakage is what you detect with magnetic inspection, so defects oriented across the length show up most clearly. If a defect runs parallel to the long axis, the field can pass by with less disruption, making it harder to detect. Defects that align with the concentric circular paths around the magnetizing current don’t create the kind of leakage that the inspection relies on. Surface-only flaws can be detected, but the type most readily identified with longitudinal magnetization is a flaw perpendicular to the long axis.