Stress-related Multi-Scale Concurrent Optimization Of Lattice Structures

Lattice material as a new lightweight multi-functional materials are widely aerospace field^ Marine engineering, automobile manufacturing because of their high specific strength and stiffness. At the same time, due to lattice materials include high porosity, which can effectively heat insulation sound absorption energy absorption. However, the load carrying structures of aerospace vehicles composed of periodic lattice materials are often with large numbers of micro-components, the workload of structural modeling and response analysis is enormous. The traditional FEM technology no longer apply.So we introduce a new multi-scale method of Extended Multi-scale Finite Element Method(EMsFEM).A series of studies about multi-scale analysis and concurrent optimization design of structures composed of lattice materials, about the structural intensity, stiffness and stability and so on.In view of the micro bar of lattice structure different failure modes about local strength and buckling failure, Two different lattice structure optimization models are established about local bar strength failure optimization model I and strength and stability failure optimization model II.Calculation result shows that with the increase of n size factor calculation, strength constraint is not obvious effects on the lattice material lightweight design with the increase of size factor n for the optimization model I, so the basic structure of minimum weight essentially unchanged, but due to stability constraints imposed, structure of minimum weight reduced with the increase of size factor n for optimization model II.When the large complex structural mechanics analysis. Anyone component or unit could be maximum stress. Due to the rapid increase of constraints number, lead to consider local stress constraints optimization model no longer apply. In this paper, we provide a new coagulation function that can effective condense to a global constrain for large-scale local constraints and solve the "more peak" difficulty. Lattice material structure lightweight design has been implemented considering the global strength and stability constraints.In order to make the minimum weight smaller in optimization design for lattice material structure. This paper provide new optimization design model considering micro scale and macro scale influence each other of the lattice material structure. The cross-sectional area of micro bar as micro design variables and relative density of discrete macro units as macro design variables, the multi-scale concurrent optimization design has been implemented considering the structural strength and stiffness constraints.Study thermal buckling characteristics of the negative poison’s ratio grid materials, stiffened plate structure, sandwich panel structure by numerical simulation. The negative poison’s ratio grid material is higher than orthogonal grid in thermal buckling critical buckling load in the same volume material. But the orthogonal stiffened plate is better than the negative poison’s ratio stiffened plates. However negative poison’s ratio sandwich board is better than that of orthogonal sandwich board. So to efficient use of materials, it is necessary to reasonable decorate material in structure design.