Electromagnetic testing emt-mft chapter 9b

Finally, the flux leakage method has also been adapted to the inspection of
steel reinforcement in concrete beams. The basic function of the magnetic
field disturbance (MFD) inspection equipment is to provide maps of the
magnetic field across the bottom and sides of the beam. An electromagnet on
an inspection cart, which is suspended on tracks below the beam, provides a
magnetic field that induces magnetization in permeable structures in its
vicinity, such as steel rebars, cables, and stirrups. An array of Hall effect
sensors distributed across the bottom and sides of the beam measures the
field produced by magnetized structures within the beam. If a flaw is present
in one of these magnetized structures, it will produce a disturbance of the
normal magnetic field pattern associated with the unflawed beam. Thus, the
idea behind the MFD system is to search the surface of the beam for field
anomalies that indicate the presence of flaws in reinforcing steel within the
structure.
Keywords:
magnetic field disturbance (MFD)
Charlie Chong/ Fion Zhang