【作者】 王群；

【导师】 李建国；

【作者基本信息】 清华大学 ， 材料科学与工程， 2009， 硕士

【摘要】 汽车轮毂生产过程的开始环节是工艺和工装设计,但目前存在的主要问题是设计周期长、劳动强度大,特别是不能在设计阶段进行较精确的计算,出现问题和缺陷只能事后改进,难以实现设计的优化。本文运用多元统计方法分析了影响轮毂辐条力学性能的主要因素,研究了轮毂形状对辐条力学性能的影响规律。通过对从轮毂辐条中间部位取样测得的力学性能数据进行因子分析,来推出隐藏在背后支配这些变量行为的更本质却又是不可观测的公共变量。由因子分析结果可知,影响辐条抗拉强度、屈服强度和伸长率变量的因素主要有两个,经分析验证可知其分别为Si相和Mg2Si相,并推出了这两个因子的定量表达式:据此公式评价Si相形貌和热处理后Mg2Si相的析出情况,也即对硅相变质和时效处理的效果进行评估。同时,又深入分析了Si相、Mg2Si相形貌变化对力学性能的影响。通过主成分回归,建立了辐条力学性能变量与轮毂形状参数之间的回归方程。首先根据轮毂辐条数对轮毂进行分类,在每类轮毂中又分别通过抗拉强度、屈服强度和伸长率这三个力学量对轮毂形状参数进行主成分回归分析。根据回归方程的系数,分析了轮毂形状对辐条力学性能的影响规律:轮毂的半径大小对轮辐力学性能影响较小,设计时可以忽略;通过增大轮心和辐条相交部位的面积和周长可以增加合金液向轮辋、轮辐部位凝固时的补缩;而热节的增大却使得热节处的壁厚增大,不利于热节处合金的快冷,合金Si相粗大,性能较差。当轮毂形状已定时可知辐条力学性能的期望值及置信区间。更多还原

【Abstract】 The beginning phase in the auto wheel hub production is process and mold design, but the main problem in the design cycle is long, labor-intensive, especially cannot carry on the precise computation in the design stage. It is difficult to achieve the optimal design. In this paper, the main factors that influencing the mechanical properties of wheel spoke were analyzed and the impact of the mold shape on the mechanical properties was studied by multivariate statistical methods.Through factor analysis for the measured data of mechanical properties in the middle of wheel spokes to get the essence variables which are hidden behind the surface variables and dominate them. It is found that there are two major factors influencing tensile strength, yield strength and elongation of the spokes, which are Si phase and Mg2Si phase after analysis and verification. At the same time, the quantitative analysis formulas of two phases concluded can be given as follow:These can be used to evaluate Si phase morphologies and the precipitation of Mg2Si phase, namely evaluate the corresponding process flow. Meanwhile, the impacts of Si phase and Mg2Si phase on the mechanical properties were analyzed deeply.The principal component regression analysis was used to establish the regression equation between the mold wheel shape parameter and the mechanical properties. The wheel was classified according the number of wheel spokes. In each type, regression analysis was carried out between wheel shape parameter and tensile strength, yield strength, elongation separately. According to analysis the coefficient of the regression equation, the main obtained results that the effect of the shape of the wheel hub on the mechanical properties are as follows: the impact of the radius of wheel spokes is weak, the parameter can be ignored; increasing the size of the intersection position of wheel boss and spokes can increase the alloy feeding solidification to wheel felloe and spoke; enlarging the hot spot will make it more difficult to achieve the flash set, and this can lead to reduce the mechanical properties. According to the shape parameter, it gives the mechanical properties forecast range of spokes.更多还原