How does the strength of the magnetic field affect the inspection outcome in MPI?

The strength of the magnetic field is critical in Magnetic Particle Inspection (MPI) because it directly influences the ability to detect surface and near-surface defects in ferromagnetic materials. An insufficient magnetic field may not produce a strong enough magnetization in the part being inspected, which can result in missed defects. These defects may remain undetected because the magnetic particles used in the inspection process rely on the magnetization of the material to congregate at areas of magnetic flux leakage, which is caused by discontinuities such as cracks or voids.

When the magnetic field strength is appropriate, the particles can effectively cluster at these discontinuities, providing a clear indication of potential defects. Conversely, if the field is too weak, the particles may not respond adequately to the magnetic anomalies, leading to false conclusions about the integrity of the material. Therefore, maintaining an adequate magnetic field strength is essential for accurate and reliable inspection outcomes in MPI.