DEVELOPING FIELDABLE NDT TOOLS FOR AIRCRAFT INSPECTION

摘要

This paper describes the experience of developing two nondestructive inspection techniques and testing the prototype systems at airline maintenance facilities. It is written from a researcher's perspective and stresses the lessons learned from the field tests and from the interaction with the airline inspection and maintenance community. The two systems developed are the dripless bubbler ultrasonic scanner and the instrumented tap test and image system (hereafter the Bubbler and the Tapper respectively for short). The Bubbler represented a capability of performing water-coupled, immersion-quality ultrasonic B-scans and C-scans on an aircraft with a focused beam of ultrasound. It addressed the inspection problems of corrosion detection in fuselage skin lap splices, intergranular corrosion detection and characterization around wing skin fasteners, and disbond detection of adhesively bonded joints and tear straps. Although the system was developed for NDI of metal structures on aircraft, it was applied to a number of inspection problems for composite structures during the field and betasite tests. The Bubbler was the result of transferring a laboratory technology, namely the immersion ultrasonic scan with a focused beam, to a system that can be deployed on an aircraft. The Tapper, on the other hand, was the result of identifying an NDI practice currently in use at the airlines and substantially improving it by conducting R&D in the laboratory. In essence, a subjective, qualitative practice was made operator independent, quantitative, and image-based while keeping the simplicity, easy-to-use and cost effective advantages of a tap test. The system is still under development, but a manual version has already gone through four field tests at airline maintenance facilities and several more on military aircraft.