ACFM (Alternating Current Field Measurement)
Alternating Current Field Measurement (ACFM) is an electromagnetic inspection technique that introduces an alternating current to the surface of a component to detect cracks that break the surface.
Surface and subsurface crack detection occurs when the presence of a crack disturbs the electromagnetic field induced in the part and the disturbance signal is transmitted to the equipment resulting in the detection of defects.
Difference from other Non-Destructive Testing for crack detection such as Penetrating Liquids and Magnetic Particles, ACFM technique requires less surface preparation, the amount of lost and false signals is significantly less, it can be applied under water. With fewer requirements for cleaning the area to be inspected and fewer false indications, inspections are significantly shorter, saving time in applying the technique.