Rapid ultrasonic inspection of ageing aircraft

The requirement for rapidly detecting corrosion and disbands in large areas of lap joints in transport aircraft has prompted the development of various new NDT methods and large-area imaging systems. QinetiQ has developedultrasonic array technology in collaboration with Diagnostic Sonar Ltd and evaluated the inspection performance and the potential speed of inspection. The crucial factors in this development were the achievement of high speed as well as high spatial and depth resolution to allow interrogation of sealant and adhesive layers and the characterisation of corrosion. A highly-innovative ultrasonic array probe has been developed that is capable of the high frequency response and broad bandwidth required for lap-joint inspection of ageing aircraft. The array covers a 124 mm swathe and scans at a speed of 4 m (13 ft) per minute with a I mm scan pitch. Scanning software was developed to allow scanning at the maximum pulse-repetition frequency allowed by the ultrasonic flaw detector. Another critical issue was the coupling of a long array into the structure. Data on the latest focused array will be presented, with images scanned on real aircraft structure. Technology transfer of the array has been a successful part of this project. The ultrasonic array is commercially available front Diagnostic Sonar Ltd, an NDT manufacturer in the UK, and the software to control it is available as an upgrade of current commercially-available equipment.

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