Lightweight Design Of HMCVT Box Based On Multi-objective Topology Optimization Method

Currently,the development of agricultural mechanization has been already an inevitable trend in the field of agricultural modernization,and tractors are playing a pivotal role in the process of agricultural mechanization.Reducing the manufacturing costs of tractors and improving fuel efficiency have become urgent for tractor design.Thus,many tractor manufacturing companies are striving to invest heavily in the research and application of lightweight tractor technology.With the rapid development of computer technology,the application of lightweight design technology in the field of agricultural mechanization engineering has become increasingly widespread.Lightweight design technologies mainly include two aspects: lightweight materials and structural optimization.With the development for more than two decades,structural optimization techniques have become more sophisticated.The innovation,creativity and advantage of structural optimization can help engineer break away the regular thinking pattern.In particular,the topological optimization technology leads the trend.The design of a transmission box of Hydro-Mechanical Continuously Variable Transmission(HMCVT)for an intelligent heavy tractor studied in this paper.The transmission system plays a crucial role in the tractor system,and its box that drives as a vital component in the system of the tractors.This paper takes the HMCVT box as the research object,proposes a multi-objective topology optimization design method based on the compromise programming method,and the lightweight design is conducted by considering both the natural frequency and the rigidity of the box.The main research content is as follows:(1)Theoretical research on structural optimization methods based on multi-objective topology optimization.Studying on the topology optimization theory,topological optimization method: SIMP method,the origin and solution of numerical instabilities in topology optimization,and formulization of topology optimization.Besides,based on the multi-objective topology optimization method and the multi-objective Pareto solution,a multi-objective topology optimization objective function combining targets of stiffness and frequency is proposed.(2)The multi-objective topology optimization design method based on the compromise programming method is adopted to optimize the structural topology of the HMCVT box.According to the structure and characteristics of the HMCVT box,the initial design of geometric mode of the HMCVT box is designed,and the boundary load of the HMCVT box under pure hydraulic start working conditions is obtained through simulation analysis.The multi-objective topology optimization design method based on the compromise programming method is implemented.Taking both the natural frequency and the stiffness into consideration,the objective function of the lightweight design is determined and the structure of box is optimized.Based upon the results of multi-objective topology optimization design,a detailed design of the HMCVT box is developed.The reinforcement ribs are applied on the bearing seat hole to reduce the concentrated stress at the bearing seat,to achieve the purpose of improving the structural strength of the bearing seat.The results show that compared to the initial design,the weight of the optimized HMCVT box is reduced by 41%(from 418.2Kg to 243.4Kg),the maximum displacement is decreased by 27%(from 0.219 mm to 0.158mm),and the maximum stress is decreased by 32%(from 441 MPa to 298MPa).