Figure 7 The history of crack length increasing with test time 2.3.3. Full-scale aircraft structure tests Based on the above coupon and component verification experiments, ICM system has been verified in several full-scale aircraft structure fatigue tests with most sensors spliced at fatigue critical locations where are hidden in the structure and hard to access by the conventional non-destruction inspection methods. For example, ICM sensors were mounted on a full scale central wing fatigue testing aircraft. Figure 8 shows the sensor splicing between two repaired Al-alloy parts with a piece region of rivets which can give alarm signals when the cracks appear at this location. The other example is a full-scale fatigue test for a fighter structure. Total 110 sensors were fixed in 80 key locations inside structures including fuselage frames, wings, empennages and landing gears which formed a net after connected with interrogators for monitoring all locations prone to crack. With the aid of ICM system, some cracks were detected in time. Figure 9a shows sensors distributed in one frame and figure 9b gives the history of crack length increasing with test time in the fractured locations of the frame. Fig.8. ICM Sensors Monitoring on Central Wing Figure 9 Sensors distributed in one frame (a) and the history of crack length increasing with test time in the fractured location of the frame (b) At present, ICM system has become an indispensable measure for monitoring damage in most full
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