A validation study for a new SHM technology (ICM) under operational environment Zhi Wang1,*, Jiakun Cai1, Jinshan Li1, Mabao Liu2 1Beijing Aeronautical Technology Research Center (BATRC), Beijing 100076,China 2 Xi’an Jiaotong University, Xi’an, 710049, China * Corresponding author: wangzhi6022@sohu.com Abstract A new invented SHM technology, named as Intelligent Coating Monitoring ( ICM), was verified by various lab-scale experiments as along with full-scale fatigue tests to inspect ICM capability for monitoring crack initiation and propagation in metal substance. In order to apply the technology to fighter aircrafts, ICM system was validated at real service condition. Firstly, ICM is briefly introduced, including the principle of sensor, the make-up of the system and various lab-scale experiments as well as full-scale fatigue tests for verification and application. Then the installation of ICM system on an operational aircraft structure was given which includes the determination of critical locations that needs monitoring, the selection of sensors corresponding to each monitoring point with certain geometry, the method of sensors splicing and main-/sub- interrogation units fixing and the connection of the above hardware through wires laying to form a ICM system. Finally, the operating situation and the effectiveness of the ICM system under operational environment were validated and summarized. Keywords Crack monitoring, Aircraft Structure Health, Intelligent coating, Fracture 1. Introduction At present, the safety of aircraft structures in most of countries is generally maintained by periodic inspection utilizing traditional nondestructive testing (NDT) techniques such as eddy-current, ultrasound, radiography, thermograph etc. However, these inspections often require the disassembly of the structure, which is a difficult and time-consuming procedure. As many locations of fighter aircraft in which cracks are prone to generate or form during full-scale fatigue in aging airframes are hidden in the structure, it is impossible to access for some certain areas. It is reported that recent aircraft crashes such as C-130A and F-15C in USA were resulted from catastrophic structural failure [1], suggesting that the current NDT is not reliable and is not adequate for aircraft safety. Moreover, the catastrophic risk of critical components also increases with the continued operation of aging fighter aircraft beyond its initial design life and in more severe service environments. Consequently, a desired solution is to implant a structural health monitoring (SHM) system on fighter aircraft which have the huge potentials to improve aircraft safety and reduce operational and maintenance cost. Currently, several candidates of sensors suitable for SHM application have been widely investigated through lab-scale experiments, which include piezoelectric, fiber-optic, MEMS, strain-gages, CVM etc. To validate the effectiveness, some technologies based on different sensors have already installed in the service civil airplanes. For example, Bragg Fibre Gratings, impact and crack monitoring facilities, such as acoustic emission, eddy current and CVM sensors have installed in an AIRBUS A320 and an AIRBUS A340-600. In addition, diverse SHM technology such as crack wires, CVM or acoustic emission sensors were used during the full-scale fatigue test of the fuselage of the Airbus A380 [2]. Moreover, some structural health monitoring (SHM) systems have matured in recent years, allowing SHM systems to be tested on experimental flight tests [3-6]. However, there is a huge gap for SHM technology to translate these laboratory outcomes to practical application on the fighter aircrafts.
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