Global–Local Collaborative Optimization Method for Stiffened Cylindrical Shells with Cutout

In the cutout reinforcement for a stiffened cylindrical shell, the layout optimization of global stiffeners and the stiffeners around the cutout are generally separated. However, considering the two optimizations separately is noncollaborative. To solve this problem, a global–local collaborative optimization method is proposed. Based on the sequential sampling method, a set of sampling points is obtained in the design space. Local optimization is carried out to optimize the stiffener layout around the cutout for each sampling point along with its strain energy and stress. The radial basis function surrogate model is constructed based on the aforementioned sampling points. Based on the surrogate model, global optimization is carried out to obtain the optimal global stiffener layout and the stiffener layout around the cutout. In this way, the layout of the global stiffener and the layout of the local stiffener can be designed collaboratively. An illustrative example of the stiffened cylindrical shell with the cutout is carried out to verify the effectiveness of the proposed method. An innovative stiffened cylindrical shell with the cutout is obtained by a collaborative optimization method. The weight of the innovative design is reduced by 8.70%, and the maximum von Mises stress is reduced by 14.47% when compared with the optimal design by a noncollaborative optimization method.