A new integrated layout optimization method is proposed here for the design of multi-component systems. By introducing movable components into the design domain, the components layout and the supporting structural topology are optimized simultaneously. The developed design procedure mainly consists of three parts: (i). Introduction of non-overlap constraints between components. The Finite Circle Method (FCM) is used to avoid the components overlaps and also overlaps between components and the design domain boundaries. It proceeds by approximating geometries of components and the design domain with numbers of circles. The distance constraints between the circles of different components are then imposed as non-overlap constraints. (ii). Layout optimization of the components and supporting structure. Locations and orientations of the components are assumed as geometrical design variables for the optimal placement. Topology design variables of the supporting structure are defined by the density points. Meanwhile, embedded meshing techniques are developed to take into account the finite element mesh change caused by the component movements. Moreover, to account for the complicated requirements from aerospace structural system designs, design-dependent loads related to the inertial load or the structural self-weight and the design constraint related to the system gravity center position are taken into account in the problem formulation. (iii). Consistent material interpolation scheme between element stiffness and inertial load. The common SIMP material interpolation model is improved to avoid the singularity of localized deformation due to the presence of design dependent loading when the element stiffness and the involved inertial load are weakened with the element material removal. Finally, to validate the proposed design procedure, a variety of multi-component system layout design problems are tested and solved on account of inertia loads and gravity center position constraint.

No / This paper studies the selective maintenance problem for multi-state systems with structural dependence. Each component can be in one of multiple working levels and several maintenance actions are possible to a component in a maintenance break. The components structurally form multiple hierarchical levels and dependence groups. A directed graph is used to represent the precedence relations of components in the system. A selective maintenance optimization model is developed to maximize the system reliability in the next mission under time and cost constraints. A backward search algorithm is used to determine the assembly sequence for a selective maintenance scenario. The maintenance model helps maintenance managers in determining the best combination of maintenance activities to maximize the probability of successfully completing the next mission. Examples showing the use of the proposed method are presented.