Dynamic Topological Optimization Design Of The Heavy Commercial Vehicles' Frame In The Full Structure

Along with the rapid development of the economic, people's requirement for the comprehensive performance of commercial vehicle, like speed, carrying capacity, ride comfort, security and so on, is getting higher and higher. The frame is the most important part of the commercial vehicle with dominant effects on the whole function. The frame dynamic characteristics in the whole vehicle situation have significant difference with those in the single frame situation. The vibration modes of the frame have great discrepancy between the two situations. However, the frame is always assembled into vehicle in actual operation. Consequently, considering the situation of whole vehicle is essential to study optimal design of the frame.Per iteration of the topology optimization consists of three steps:finite element analysis, sensitivity analysis and parameters' change. This paper focuses on a new sensitivity calculation method in the process of dynamic topological optimization. We propose the new method of modal stiffness sensitivity, based on the finite element theory combined with the vibration equation. Meanwhile, we present the relevant criterion of element's cancel and addition, and the semiautomatic iterative process of finite element analysis and optimization. These contents offer theory foundation for topology optimization of the frame in the whole vehicle situation.In this paper we establish the whole vehicle finite element model by use of HyperMesh. The actual commercial vehicle is mostly made of various steel plates; hence we mainly utilize the shell elements to build the finite element model. The finite element mesh of the frame is enough fine and integral, whereas the mesh of the cab and van carriage is relatively coarse. The spring elements are used to simulate the wheels and the suspensions. Considering the entire vehicle FE model's complexity and hugeness, we employ the substructure reduction method to reduce the computation of finite analysis in the iterative process.This paper study the topological optimization method based on the proposed dynamic topological optimization theory. The weight of the frame is the optimal objective, and the frequencies are the optimal constrains. We calculate the sensitivity parameter of each part of the frame according to their modal stiffness sensitivities. We choose appropriate design variables from the sensitivity parameters, and propose rational design plan of the new structure. The modal analysis of the frame in the whole vehicle situation is studied to compare with the original frame and obtain the final optimal design result. The result validate the topological optimization theory is effective and practical.