Circular magnetization of a part can be used to detect which defects?

Circular magnetization is particularly effective for detecting defects that are oriented parallel to the long axis of the part. When a part is magnetized circularly, the magnetic field lines form closed loops around the circumference of the component. This orientation allows the field to interact with defects that run parallel to this direction, creating a leakage field at the location of the defect.

The detection of such defects relies on the principle that when the magnetic field encounters a flaw, such as a crack or inclusion aligned in the same direction, it can lead to a disturbance in the magnetic field, which can then be detected by suitable instruments.

In contrast, defects that are oriented perpendicular to the long axis may not create significant leakage fields that can be easily identified with circular magnetization. This aligns with the limitation of detecting defects that are not oriented in the same direction as the applied magnetic field. The method’s effectiveness primarily targets defects that are in line with the magnetization, which is why the correct choice highlights the alignment of defects parallel to the part's long axis.