Analysis of corrosion of aircraft fluid pressure lines using eddy current

Abstract

The metal tubes are often used in aircraft to convey fluids to one or more destinations as they are capable of withstanding high levels of internal pressure and hoop stresses. The internal surfaces of fluid carrying metal tubes are frequently corroded once the inner walls are contacted with stagnated fluid for a long period of time. Once corroded, the fluid lines are to be replaced as they become unairworthy. The detection is difficult as there is no method developed for the corrosion detection of small diameter Aluminium metal tubes. This study is to carry out eddy current inspections on small diameter metal tubes and to carry out a qualitative analyze on eddy current impedance plane displays, building up a relationship on the resultant signals. It is also to distinguish the different characteristics of impedance plane displays of internal corrosion and crack signals. A qualitative analysis is the objective in this study as detection of corrosion is the prime objective for the aircraft fluid pressure lines. Since, neither the aircraft manufacturer nor pressure lines manufacturer has given any tolerances for corrosion, irrespective of the depth and the spread of corrosion, the fluid lines are to be replaced with new lines, if the corrosion is detected. Therefore, this study is limited only for a qualitative analysis and will be an eye opener for another study for a quantitative analysis.