Damage Diagnosis of Complex Connection Structures of Aircraft Fuselage Stringers with Guided Wave-Based Method

Abstract

For civil aircraft, structural forms of its components like fuselage and wing are very complicated. Usually, these structural components are manufactured separately and then riveted together. These connection parts, such as stringer joints and skin lap joints, are prone to be cracked and failure. In addition, most structures are inaccessible, making manual maintenance difficult. Therefore, it is of great significance to reliably monitor the fatigue crack damage of complex connection structures. Guided wave (GW) based structural health monitoring (SHM) has attracted wide attention in the aerospace field since it has the characteristics of being sensitive to small damages, and capable of monitoring large areas. However, the complex configuration, the limited space, and the interference of bolts and rivets make sensor deployment difficult. Moreover, during propagation in complex connection structures, guided waves will undergo reflection, transmission, and mode conversion, resulting in mode aliasing and wave packet deformation of response guided wave signals. The structural damage information contained in the signal will also be masked, which brings difficulties to crack monitoring in complex connection structures. Although there have been some related studies on crack monitoring of metal joint structures such as lap joints, there are still other parts in the complex joint structure of the actual fuselage, such as long stringers and belt plates. At present, especially for the multi-layer riveted butt joint structure with stringers, the research is still very limited. In this paper, the amplitude and mode of the guided wave signals of different types of channels between the components of the single strap butt joint structure with stringer are analyzed. By imposing simulated damage, the effect of the damage scattering signal on the damage identification ability after guided waves pass through multiple rivet holes or multi-layer structures of the complex structure is studied. The crack damage diagnosis method for the complex connection structure of aircraft fuselage stringer is studied and verified by the experimental results of real cracks. The diagnostic results demonstrate the effectiveness of the method.