Evaluation For The Residual Strength Of Multiple Cracks In Typical Skin Connecting

The aircraft will suffer widespread fatigue damage(WFD) after long time operation, it is one of the main damage form of aging aircraft. Compared with a single crack damage, the WFD crack growth rate is more faster, and it can lead to accelerated deterioration of the structure residual strength, thus it seriously affect the aging aircraft operation safety. At present, the WFD are not mature enough in the theoretical calculation and experiment research, therefore, there is necessary to conduct further research of WFD structure in the crack growth and residual strength.On the basis of the existing related research, this paper analyzes the law of crack propagation under the different influence factors, and the residual strength of multiple crack structure is assessed.First of all, the fracture criterion used for modeling and calculation is determined, based on the basic theory of fracture mechanics.the model containing multiple collinear crack are set up, then change the initial crack angle, the shape and aperture size of model hole respectively, the integral stress intensity factors(SIF) of each model are obtained by using the Contour integral method, using the extended finite element method(XEFM), it is concluded that crack propagation path, then analysis the influence of different variable factors on the crack extension. Secondly, based on extended finite element method, get the structure failure load process under the crack growth rule, and analyzes the mutual influence between the cracks. Finally, combining with the ligament area plastic connected criterion and the average stress criterion, the change law of residual strength of structure with different crack spacing are evaluated. The results show that simulation analysis are all coincide with the associating theoretical result.