High-stiffness Oriented Hierarchical Topology Optimization Of Stiffened Shell

With the advanced design targets of large airspace,super high speed and high maneuverability,the main structure construction of the high-speed aerocraft is to pursue an ultimate lightweight design.In order to reduce the redundant mass,the main structure construction,thin-walled structure,is presented as a design characteristics of highly integrated with load-bearing and aerodynamic dimension,which results in that this kind of thin-walled structure requires high stiffness indices for fulfilling both huge in-plane load brought by engine thrust and out-plane load caused by the aerodynamic inflow,which brings great challenge for light-weight design.In addition,the complicated features of the structure form make it more difficult to meet the lightweight design under bearing behavior being satisfied.The bottleneck problems of high-stiffness thin-walled structure design mentioned above have restricted the tactical indicators such as the cruising distance and maneuverability of China's aerospace vehicles.Focusing on the above problems,this dissertation proposes a high-stiffness oriented hierarchical stiffeners design method for thin-walled structures: by arranging the primary sparse stiffeners and secondary dense lattice,the stiffness of the thin-walled structure reinforced hierarchically,which improve the in-plane and out-plane stiffness of the structure effectively,meanwhile,the lightweight design of the structure is achieved.To achieve the above research objectives,the main works of this dissertation are given as followed:1.To achieve the design of complicated stiffened thin-walled structures,this dissertation proposes a stiffened constraint implementation scheme based on the traditional SIMP topology optimization method.For different structural features,variable connection and Helmholtz anisotropic filtering technology is employed to fulfill the purpose of load bearing complicated stiffened shell design of structured mesh and unstructured mesh.2.Aiming at the problem of the low efficiency of periodic lattice analysis due to the large scale of the aerocraft cabin structure and the complicated geometric features,an engineering scheme of efficient equivalent processes for periodic structure is proposed,order-reduced method based on surrogate model for engineering periodic lattice and modified AH method for inverse homogenization unit cell are applied respectively to realize the high efficiency analysis for periodic structure in complicated structure.3.A high-stiffness oriented hierarchical topology optimization method for thin-walled structure is proposed: By arranging the primary stiffeners and secondary lattice,the global and local stiffness of the thin-walled structure is enhanced and the material utilization of different levels is effectively improved,the dual effects of weight reduction and performance improvement are achieved.The result shows that,given the complicated geometry or loads boundary,the high-stiffness hierarchical design has significant mechanical performance advantages.Numerical example indicates that,under the same quality index,compared with the traditional design,the hierarchical design proposed can improve both the in-plane and out-plane stiffness of the thin-walled structure,which verifies the effectiveness of the method.