What is a major limitation of MPI in detecting certain types of defects?

The statement that Magnetic Particle Inspection (MPI) cannot detect defects within non-ferromagnetic materials accurately reflects a significant limitation of this method. MPI relies on the use of magnetic fields to detect surface and near-surface discontinuities. This technique is effective with ferromagnetic materials, where magnetic fields can be induced and the particles can accumulate at defect locations, indicating their presence.

In contrast, non-ferromagnetic materials, such as aluminum or brass, do not support magnetic fields in the same way. As a result, MPI is not suitable for detecting defects in these materials, as the magnetic particles will not respond to the induced magnetic field, and therefore, any defects present will remain undetected.

Understanding this limitation emphasizes the need for selecting appropriate NDT (Non-Destructive Testing) methods based on the material properties when assessing components for defects. This ensures that the most effective inspection method is used for the specific materials and types of defects one suspects may be present.