What does the "particle flow" refer to in the context of MPI?

The term "particle flow" in the context of Magnetic Particle Inspection (MPI) specifically relates to how the magnetic particles behave in the liquid suspension during the inspection process. This behavior is crucial for ensuring that the particles can effectively gather at and indicate any surface and near-surface discontinuities in a material.

In MPI, a magnetic field is applied to the part being inspected, causing the ferromagnetic particles suspended in a liquid medium to align along the magnetic field lines and cluster at areas of discontinuity, such as cracks or voids. This behavior—how well the particles move and aggregate within the suspension—is vital for achieving accurate and reliable inspection results. Understanding particle flow helps operators control the inspection parameters effectively to enhance sensitivity and detection capabilities.

Factors such as viscosity of the suspension, concentration of particles, and the magnetic field strength can influence particle flow, making knowledge of this concept integral to the effective execution of MPI procedures.