Detecting corrosion with ultrasound

Citation

(1998), "Detecting corrosion with ultrasound", Aircraft Engineering and Aerospace Technology, Vol. 70 No. 3. https://doi.org/10.1108/aeat.1998.12770cab.033

Detecting corrosion with ultrasound

Detecting corrosion with ultrasound

Keywords Aircraft industry, Corrosion, Ultrasound

Commercial jets regularly undergo routine inspections to check for corrosion, sometimes requiring the time-consuming and laborious task of taking the airplanes apart. Now a safety inspection required for T-caps in the wing boxes of DC-9 airliners can be performed more thoroughly and about 15 times faster than with previous methods using an ultrasonic technique developed by a team headed by the Airworthiness Assurance Non-destructive Inspection Validation Centre (AANC) at the Sandia National Laboratories in Alburquerque, New Mexico.

Using ultrasound, inspectors can inspect the plane's wing attachment area in about 48 hours, compared with the previous average of about 800 hours. Sound waves projected through the aircraft's aluminium skin are reflected back in distinctive patterns that reveal whether corrosion is damaging the inside of the structure. The system also provides information on the length and depth of any cracks in the structure, even those missed during visual inspections.

The new technique, which involves equipment developed at Northwestern University and SAIC/UItra Image International, uses two wedge-shaped transducers operating in a pitch-and-catch configuration to shoot sound waves at an angle into the multilayered structure and to receive echoes bouncing back to the surface. The result is a colour image on a screen in which the hues represent different thicknesses of metal in the T-cap. Thinning is a result of corrosion.

The automated technique could save airlines about $9,000 per plane compared with manual inspection. In addition, the reduction of downtime for each DC-9 during maintenance amounts to savings of about $20,000 per day.