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10 April 2007 Structural health monitoring of an aircraft fuselage lap joint
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Fatigue crack growth in a lap joint specimen extracted from a retired aircraft fuselage was monitored using bonded continuous acoustic emission sensors. The specimen lasted nearly 350,000 cycles of tension-tension cyclic loading. During this period a large number of acoustic emission signals were collected. Two distinct classes of events were observed during this test. The first group of events consist of low amplitude, long rise time and long duration events which could be attributed to fretting between various surfaces. The second group of events had short rise time and short duration and is thought to be from fatigue cracks. This interpretation is based on the waveform characteristics observed during this test and patterns seen in acoustic emission signals from known fatigue cracks in previous studies. Based on this assumption the crack growth process appear to have initiated after 200,000 cycles of fatigue load and accelerated during the final 20,000 cycles. The final fracture of the specimen occurred in the grip area and indications of this impending failure were evident in the acoustic emission data. In addition, acoustic emission data also suggest fatigue crack growth in an area inaccessible for visual examination.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
G. Grandhi, F. Nkrumah, M. Jacques, and M. Sundaresan "Structural health monitoring of an aircraft fuselage lap joint", Proc. SPIE 6530, Sensor Systems and Networks: Phenomena, Technology, and Applications for NDE and Health Monitoring 2007, 65300K (10 April 2007);

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