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To resist external pressure, stiffened spherical domes have been widely used in underwater vehicles. In traditional design of these thin-walled structures, uniform stiffeners are usually utilized and overly conservative safety factor method is employed to envelop the multi-source uncertainties mainly caused by manufacturing. In this study, a concept of non-uniformly stiffened spherical dome (NUSPD) is developed to improve the structural buckling capacity. Furthermore, an efficient reliability-based design optimization (RBDO) framework is established for NUSPD, which includes a deterministic optimization loop to fix the stiffener layout, and subsequently followed by a RBDO loop to determine the detailed stiffener dimensions and decrease the structural weight under geometric and material property uncertainties. Since the RBDO of stiffened spherical domes is very complex, an improved enhanced chaos control method together with surrogate model is proposed to improve the convergence rate. Finally, the efficiency of the proposed RBDO framework is demonstrated by the NUSPD example. [ABSTRACT FROM AUTHOR]

Aiming at the optimization of aircraft panels, a modified version of harmony search (HS) algorithm is proposed based on the information of the harmony memory (a memory location where all the solution vectors are stored) for improvisation procedure, named as adaptive dynamic harmony search (ADHS) algorithm. In order to reduce the amount of calculation, response surface method is employed, and second-order polynomial with cross terms is used to construct the model. To demonstrate the advantage of the proposed algorithm, typical aircraft panels under buckling constraint are established, and several existing HS algorithms are compared. The effects of the number of improvisation ( NI ) and harmony memory size ( HMS ) are investigated and discussed in detail. Results indicate that the proposed ADHS can provide an optimum design in a robust manner, and local optimum solutions may be reduced based on the ADHS for optimization problems with multiple local minima. Finally, several useful information is obtained for the design of stiffened panels with cutouts. [ABSTRACT FROM AUTHOR]

• An efficient bi-stage RBDO framework of composite structures is established. • Lamination parameters are used to obtain an approximated optimal layer number. • IGA is utilized for buckling analysis and derivation of analytical sensitivity. Composite variable-stiffness (VS) panels with curvilinear fiber paths are very promising for aerospace structures. Due to the inherent complexity of VS laminates, buckling analysis and design optimization are extremely time-consuming and challenging, especially when uncertainties are considered, i.e. reliability-based design optimization (RBDO). In this study, an efficient bi-stage RBDO framework via isogeometric analysis (IGA) is established to release the tremendous computational burden. In Stage I, the layer thickness and lamination parameters are used as design variables to obtain an approximated layer number, which greatly reduces the design variable size. In Stage II, intermediate density variables are introduced, and IGA is employed for the buckling analysis and derivation of the analytical sensitivity. Furthermore, the augmented step size adjustment (ASSA) algorithm is used to enhance the efficiency and robustness of the RBDO process. Numerical results of VS panels are used to validate the performance of the proposed RBDO framework. The optimal results indicate that the proposed framework can find the optimal lightweight design that satisfies the manufacturing constraints in an efficient and accurate manner. [ABSTRACT FROM AUTHOR]