Lightweight Design Of Bus Body Frame Based On Multi-objective Optimization

Bus body is an important and the main bearing part of the bus.Since the body weight accounts for a large proportion of the total vehicle quality, the reasonable body frame lightweight design has a very important significance to reduce the vehicle quality.This paper takes the G610A-PD type electric bus of Hebei Jieshen Amperex Technology Co., Ltd.as the research object. A lightweight design platform of the body frame based on multi objective optimization is established. The main research contents include the following aspects:(1)The body frame structure of the pure electric bus is analyzed, and the model is simplified according to the characteristics of the bus body frame. Subsequently, the finite element model of the body frame is established. The general driving conditions and the technical index of electric bus body are determined.(2)The load and constraint of the bus in various conditions are analyzed. In addition, the strength and stiffness of the bus in all conditions are analyzed. The torsional rigidity and the opening deformation of the vehicle body frame under different conditions are focus researched and the relevant technical evaluation is accomplished. Based on the modal analysis theory, the analysis and evaluation of the modal frequencies and shapes of the body frame are carried out. The dynamic stiffness characteristics of the body frame are analyzed, and the first ten modes are analyzed emphatically, which provide an important basis for the further structural improvement and a reference for the body frame lightweight design.(3)Based on the advantages of ISIGHT in the multi-objective optimization design, the optimization of the bus body frame is carried out. Through the integration of ANSYS large finite element analysis software, a multi-objective optimization design platform is set up. The visual model of body frame is built by APDL language so as to realize automatic modeling, automatic simulation and thus achieve the effect of automatic optimization. A new method for lightweight design of vehicle body frame based on multi objective optimization is proposed.(4)After solving the multi-objective optimization problem, a series of Pareto solutions will be obtained. According to the practical engineering demand to determine the optimal solution, the body frame of the multi-objective optimization design is completed. Since the main consideration is the body mass in the process of optimization, the final choice of the Pareto solution is to make the body frame to reach the lightest quality. According to this principle, the final design variables are obtained. The body frame lightweight optimization algorithm based on ISIGHT is easy to choose, the result is easy to be obtained, and the optimization method is clear. It can improve the optimization efficiency and reduce the unnecessary human error in the whole body frame multi-objective optimization design process. For the large and complex body frame multi-objective optimization design, using this method has obvious advantages and prospects.(5)The structure improvement scheme of the body frame is determined, and the size of the optimized member is given. The optimization results show that the lightweight have been achieved in the case of the body frame torsional stiffness and first-order torsional vibration frequency without reducing.The body frame strength, rigidity and the opening-deformation are verified after the structure improvement in each driving condition. The dynamic stiffness characteristics of first ten modes of the body frame are verified. Eventually, the body frame quality drop from 1840 kg to 1717 kg. Body weight loss of about 123 kg, which accounts for about 6.7% of the body frame.The torsional stiffness is increased from 56.4k N.m/(o) to 60.1 N.m/(o).The first-order torsional vibration frequency is increased from 6.3HZ to 6.5HZ. Finally, the lightweight design of the body frame is finished, and the feasibility of the lightweight scheme is determined.