飞机机身蒙皮均布增压疲劳裂纹扩展研究

In order to study the fatigue crack propagation of the fuselage skin under uniform pressurized cyclic load, experiments were carried out with the self-made aircraft fuselage skin uniform pressurized fatigue device. Firstly, the stress intensity factor was calculated by the extended finite element method. Then, the deflection angle of the crack was calculated based on the maximum circumferential stress criterion and the strain energy density factor criterion, and the fatigue crack propagation path of the fuselage skin was predicted. Finally, the fatigue fracture was analyzed under scanning electron microscope. The results show that the crack propagation paths predicted by the two criteria are basically consistent with the crack propagation path obtained by experiment.The surface cracks of the fuselage skin are mixed mode cracks. With the increase of the crack length, K_Ⅰ first increases and then decreases, K_Ⅱ first decreases rapidly to around 0, then oscillates around 0, and finally increases rapidly when the lower hole is about to penetrate. Observing the fatigue fracture shows that the fatigue cracks are initiated by multiple fatigue sources. The crack propagation zone has typical quasi-cleavage fracture characteristics, and the fatigue crack growth rate first increases and then decreases with the increase of crack length. The instantaneous fracture zone is a typical dimple feature with different sizes.