Design Optimization Of Concentrated Force Diffusion Structures

Launch vehicle is a complex structure assembled by several sections. In the actual design, the transmission form of external force is usually determined by the connection form of different sections in the launch vehicle. In the process of internal transfer, the external force is often converted to concentrated force loading. In order to reduce the damage and adverse effect of structural stiffness, strength, and stability caused by concentrated force, Designers often need to decorate specific structure in the designated area in order to diffuse the concentrated force loading. This paper mainly explores the conceptual design and detailed design optimization of concentrated force diffusion structures under several kinds of design requirements in practical engineering.Michell truss theory is the classical theory of truss structures topology optimization, it studied that how to transfer the concentrated force to the given support using optimal truss structures. The relation of concentrated force direction and the line supports is critical to the resulting Michell truss configuration. When the concentrated force is perpendicular to the support boundary, the solution of traditional Michell truss theory is a straight-bar, but the actual engineering need to design the optimal transmitting path of concentrated force, which can diffuse the concentrated force to the support as uniformly as possible. Thus, although the optimization design of concentrated force diffusion structure is also to seek the optimal transmission path, Michell truss theory does not provides solution for this problem. In this paper, the minimum structural compliance is taken as the object function subject to structural volume constraint. Constraint on uniformity of the internal force is also considered in this model. Two-dimensional and three-dimensional examples are presented to illustrate the effectiveness of the formulation and algorithm.The above-mentioned continuum topology optimization presents the conceptual optimal layout design of concentrated force diffusion structure, but practical engineering wishes to obtain a more detailed and manufacturable design, and need us to research the interpretation method of structural topology optimization results, that is the feature extraction of structural topology. This work starts from the density contour of topology optimization results, and interprets the topological characteristic using the common structural form in engineering. On the basis of interpreted results, we adopt the simple understanding of topology optimization combined with the common structural form, further regularize the interpreted results and obtain two possible structural forms, one is making holes structure and the other one is truss-like structure. Based on these two forms, the present work proposes a novel design process from conceptual design, result interpretation and then to detailed design.Finally, based on the proposed design process, a feasible design optimization technique is presented for plane concentrated force structure and the short shell of a rocket’s storage trunk, and the both of optimal results satisfy the requirements in engineering. This work has an obvious engineering significance, the optimal designs have been used as a reference design by some design institutes, moreover, the novel design process, in which the optimal design could be acquired from conceptual design, result interpretation and then to detailed design, can be applied in the design of some other engineering structures.