Researchers at Vanderbilt University in Nashville, Tennessee, and the University of Alaska's Fishery Technology Center are developing ultra-sensitive magnetic field detectors which are already finding applications in the aircraft maintenance business, even though the technology was originally aimed at improving efficiency in the fishing industry.
Known as Superconducting Quantum Interference Devices, or SQUIDs, the detectors are many times more sensitive than conventional magnetometers and work by measuring the electrical resistance of the subject to strong alternating magnetic fields.
SQUIDs can be used to detect the minute electromagnetic fields generated when aluminium atoms dissolve, thereby releasing electrons. The system can evaluate total corrosive damage, but can also provide information on the rate at which the joint is degrading. SQUID use is most valuable in analysing corrosion in aircraft lap joints - the area where two overlapping aluminium plates are bolted together - but it can also be used on other plates because it is more sensitive to conventional tests.
A test works by mapping the plate according to its electrical resistance. Any area signalled as having a different resistance than the normal resistance of the aluminium plate is considered an anomaly which can then be further identified.
The test is sensitive enough to spot the very first sign of corrosion before other methods can.
Source: Flight International
