Three-dimensional weight function analyses and stress intensity factors for general surface and corner crack emaninating from circular hole

icaf2023 Tracking Number 23

Comprehensive study of aircraft structural failures showed that the most prevalent failure is due to cracks originating from fastener holes, where stress concentration takes place. Stress intensity factors (SIFs) for these crack configurations are the prerequisite for evaluation of the critical crack sizes and fatigue lives of components during which the initial cracks would grow to the critical size. The computational efficiency for SIF is critical, since for every crack growth step, the crack size changes and so are the SIFs. Much work has been done to obtain SIFs of a single and double symmetric 3D cracks at riveted holes subjected to typical loadings. However, due to the complexity of the problem, limited work has been done for the SIFs of the crack configurations as shown in Fig.1 subjected to arbitrary load cases. These crack configurations are very common, but are too complicated to be analytically tackled. The SIF solution is still highly demanded for the damage tolerance analyses of various flaws at fastener hole. In this paper, the 3D slice synthesis weight function method (SSWFM) is further developed to calculate the 3D SIFs for more general and complex case, eccentric and asymmetric surface and corner cracks, and combination of surface and corner cracks subjected to arbitrary load cases. The resulting 3D SIFs are extensively compared to those obtained from FEM/Franc3D; very good agreement is achieved as shown in Fig.2. However, the developed SSWFM is about 450 times faster than FEM/Franc3D in calculation of the 3D SIFs for the present complex crack geometry. It can be used to obtain 3D SIFs of most of the surface and surface-corner crack configurations from a hole in practical engineering, and would be useful for 3D fatigue crack growth analysis of rivet joint structures subjected to various load cases.