Mode-I stress intensity factors for cracked R-fluted shells under complex loads

Highlights: • J2-integral can estimate the different SIFs of complex stress fields under bending. • The geometric relationship of the crack tip can express the relationship between the stress intensity factors of the crack tip. • Simplifies the calculation of stress intensity factors for complex cracks. • Deduced the calculation process of the stress intensity factor at the crack tip under complex loads. Based on the conservation law and bending theory, a technique to determine complicated stress intensity factors on three-dimensional components is proposed, A series of closed form expressions of stress intensity factor are derived for cracked shells under different loads, such as bending, tension. The method requires the geometric relationship between multiple singular stress fields from the crack section, and the relationship between the stress at different crack tips can be estimated. In the expression of the stress intensity factor K, K is proportional to the stress σ at the crack tip, and we can get the supplementary equation of between different stress fields K according to the ratio of the stress at the crack tip, then use the J-integral method to calculate the stress intensity factors of different stress fields. In order to verify the feasibility of this method, a cracked R-fluted shells model was constructed. Under the action of the bending moment, the corner crack propagation is simulated through the reserved corner crack, and two crack tips with different stress fields are generated during the simulation. The research result indicates that the proposed method is effective for cracked R-fluted shells, and has universal applicability for solving complex stress intensity factors on three-dimensional components.