Review of developments in ACPD and ACFM

The Alternating Current Potentiel Drop (ACPD) and Alternating Current Field Measurement (ACFM) techniques were developed in response to a fracture mechanics requirement for accurate and reliable crack sizing. In many components and thick walled structures the cracks are surface breaking and it is the crack depth that is required. Both the ACPD and the ACFM techniques are particularly suited for measurement of the size of surface cracks and the ACFM technique can also be used for detection. This Review describes developments in these two related fields of study