基于ANSYS及灵敏度分析的客车结构轻量化设计

Design of Lightweight Bus Structure Based on ANSYS and Sensitivity Analysis

电动客车发展迅速,社会对电动客车的需求日益增加。客车满载时对动力需求高,电池组的数量多,车身总质量偏大,导致电池损耗加快,客车行驶里程降低。优化车架的结构设计,实现轻量化是延长电池使用寿命、提高行驶里程的有效途径之一。为达到某型电动客车在满足各工况强度要求的前提下实现轻量化的目的,选取4种典型工况,包括匀速直线行驶工况、弯扭工况、紧急制动工况和紧急转弯工况,建立了客车车身结构的有限元模型。由ANSYS Workbench分析计算得到了4种不同工况下的应力、变形。以有限元分析结果为依据,对车架进行了优化设计。根据优化设计理论,以车身质量最小为目标函数,以构件厚度为设计变量,以底架应力和扭转刚度作为设计约束,利用NASTRAN软件计算了车架刚度对关键构件厚度的灵敏度。对刚度相对灵敏度较低的部件进行了轻量化设计,如将车门支撑部件、车架侧围等部件型材厚度由3 mm减薄至2 mm,对刚度相对灵敏度较高的部件进行了加厚处理,如将车架主要受力部件厚度由4 mm加厚至5 mm,以此来提高整车的扭转性能,提出了较为合理的车架轻量化设计方案。更新了优化后的车架模型,再利用有限元分析对比了优化前后最大应力及变形结果。经对比分析,在满足各工况强度要求的前提下,整车质量下降52 kg,车架质量降幅达2%。

The development of electric buses is rapid and the demand for electric buses in society is increasing. When the bus is fully loaded, the demand for power is high, the number of battery packs is large, and the total weight of bus body is heavy, which results in the battery being depleted faster and the mileage of bus reduced. One of the effective way to extend the battery life and increase mileage is to optimize the structural design of frame and achieve lightweight. In order to achieve the goal of reducing the weight of an electric bus under the premise of meeting the requirements of various conditions, 4 typical conditions including the conditions of uniform straight running, bending and twisting, emergency braking and emergency turning are selected, and the FE model of bus body structure is established. The stresses and deformations under the 4 conditions are calculated and analyzed by ANSYS Workbench. Based on the FE analysis, the frame is optimized. According to the theory of optimization design, taking the minimum body mass as the objective function the component thickness as the design variables and the chassis stress and torsional stiffness as the design constraints, the sensitivity of frame stiffness to the thickness of key components is calculated by NASTRAN. Thinning the components which have lower relative sensitivity of rigidity, for example, the thicknesses of parts from door support and frame side are thinned from 3 mm to 2 mm. Thickening the components which have high relative sensitivity of rigidity, for example, the thicknesses of the main force components of the frame are increased from 4 mm to 5 mm, so as to improve the torsional performance of the vehicle and to propose a more reasonable frame lightweight design scheme. After updating the optimized frame model, the maximum stress and deformation before and after optimization are compared by FE analysis. The comparative analysis shows that under the premise of meeting the strength requirements of all working conditions, the mass of the vehicle is reduced by 52 kg, and the mass proportion of the frame is reduced by 2%.