【作者】 任旭春；

【导师】 姚振汉；

【作者基本信息】 清华大学 ， 力学， 2005， 博士

【摘要】 充气轮胎是轿车、卡车、飞机等交通工具的不可或缺的部件,这些交通工具的性能与轮胎的特性密切相关。研究轮胎的力学性能、改进轮胎结构设计一直受到轮胎工业和汽车工程界的密接关注。轮胎的力学性能分析涉及到多重非线性,包括超弹性橡胶和帘线-橡胶复合材料的材料非线性、有限变形带来的几何非线性、轮胎与地面、轮辋接触产生的边界条件非线性,因此即使在功能强大的CAE软件的帮助下,轮胎的分析和优化设计也是高度复杂的。为了提高轮胎分析和优化设计的效率,本文研究了以下几个关键问题。应用数字散斑相关法和单向拉伸实验测定了胶料的Mooney-Rivlin本构参数;分析了轮胎的整体变形、接地法向力分布和等效Cauchy应力分布。提出一种新的等效横观各向同性超弹性的帘线-橡胶复合材料模型来提高分析的效率。等效的均匀材料模型的应变能由反映橡胶基体性能的Mooney-Rivlin型的各向同性超弹性部分和附加的体现帘线增强作用的横观各向同性超弹性部分组成。针对帘线-橡胶复合材料的特点,设计了材料参数的识别方案,通过代表体元精细划分有限元网格的数值实验识别模型的6个参数。算例证明该横观各向同性超弹性模型的实用性、效率和精度。为改进轮胎胎冠形状优化的寻优算法,基于响应面方法,提出了一阶、二阶自适应序列局部响应面的迭代格式,对原优化问题进行逼近;借鉴桁架尺寸优化的满应力方法中的射线步调整,给出了非线性迭代过程中的增量射线步公式,同时调整违背约束的情况和坏点的情况,以避免振荡的产生。给出算例验证了求解方法的适用性。为求解目标函数和约束条件均为非凸隐函数的优化问题的全局最优解,通过广义回归网络构造目标函数和约束条件的全局响应面,离散放松的可行域得到全局近似最优解,结合局部搜索的策略,得到全局最优解。更多还原

【Abstract】 Pneumatic tire is an indispensable part of most vehicles, including car,truck and even airplane, and the performances of vehicles are closely relatedto the properties of tires. The investigation of their mechanical properties andthe improvement of their structural designs have attracted much attention allthe time in vehicle engineering, not only tire industry. The mechanicalanalysis of tire involves multiple nonlinearities, including the materialnonlinearity caused by the hyperelasticity of rubber and rubber-cordcomposites, the geometrical nonlinearity related to finite deformation, and theboundary nonlinearity comes from the contact of the tire with ground and rim,which make the analysis, design and optimization highly complex, even withthe help of powerful CAE software. To enhance the efficiency of the analysis,design and optimization, some related key problems are investigated in thisthesis.Digital speckle correlation method is adopted to measure parameters ofMooney-Rivlin model of rubber in the simple tension experiment. The globaldeformation of tire, distribution of equivalent Cauchy stress and distributionof normal contact forces between tire and ground are analyzed.To enhance the efficiency of tire analysis, a new equivalent transverselyisotropic material model of rubber-cord composites is presented. The strainenergy of the equivalent homogenized material is consisted of a Mooney-Rivlin type isotropic hyperelastic part to formulate the properties of rubbermatrix, and an additional transversely isotropic part to formulate thereinforcement of the cord. The total six material parameters in the model areidentified based on numerical experiments of the representative volumeelement divided into refined finite elements. Numerical examples are given toshow the feasibility, efficiency and accuracy of the presented model.To improve the numerical method for the shape optimization of tire tread,a response surface method is adopted. A self-adaptive iteration scheme ofsequential first order and second order local response surfaces is presented toapproximate the original optimization problem. Referred to the ray-stepapproach in full-stress method for the size optimization of truss, a formula toadjust the incremental ray-step is proposed to treat the violation of constraintand bad design-point, in this way the iteration oscillation is suppressed.Numerical example has shown the feasibility of presented approach.To solve the optimization of tire with non-concave objective function andconstraint, a method based on the generalized regression neural network isproposed, which is used to construct the global response surface of objectivefunction and constraint function. The relaxed feasible domain is discretized tofind the coarse global optimum, and then combined with the local search toget the global optimum.更多还原