Abstract: Fatigue damage monitoring of aircraft metallic structure is critical to flight safety. Based on the previous work of ref.[13], a kind of rosette eddy current sensor is proposed, and monitoring experiment of 2A12-T4 aluminum alloy under constant load based on constructed fatigue-crack monitoring system is carried out, which intends to validate the quantitative crack-monitoring capability of rosette eddy sensor through comparison between experimental result and fractographic quantitative analysis result. The comparison result shows that amplitude ratio of sensing-channel signal is sensitive to the crack propagation, and has step feature. When the crack extends from the position of sensing-channel to adjacent channel position, the amplitude ratio of sensing-channel signal increases sharply, and then increases slowly after the adjacent channel position. Viewing the changing-point as indication of crack position, the quantitative-monitoring capability of fatigue crack is achieved by rosette eddy current sensor with precision of 1 mm, and the sensing-channels near fatigue source are capable of qualitative-monitoring of accumulated fatigue damage.

Key words: Aircraft metallic structure, Fatigue damage, Fractographic quantitative analysis, Rosette eddy current sensor, Structural health monitoring