What are the two main types of magnetic fields used in MPI?

The two main types of magnetic fields used in Magnetic Particle Inspection (MPI) are longitudinal and circular magnetic fields.

Longitudinal magnetic fields are created along the length of the test specimen, which provides good sensitivity to surface and near-surface flaws, such as those that might occur in the length of welds or throughout the body of a component. In contrast, circular magnetic fields are established in a plane perpendicular to the long axis of the part and are particularly effective for detecting flaws that are oriented around the circumference of a cylindrical object.

This combination of longitudinal and circular magnetic fields allows for a comprehensive assessment of the component’s integrity, making MPI a versatile and effective nondestructive testing method for identifying surface and near-surface discontinuities.