轮胎稳态运动学与六分力预报Ⅰ:理论与方法

提出一种新的轮胎运动学描述和六分力预报理论。滚动接触是汽车轮胎力学、轮轨动力学的核心问题,由于涉及刚体转动与有限变形,滚动接触运动学与动力学的描述与求解非常困难。用拉格朗日—欧拉混合描述法分析大变形滚动接触结构的速度场、加速度场和接触变形。以车轮定位角为卡尔丹角,用拉格朗日描述,得到了包含刚体转动和弹性变形的轮胎速度场。而接触区域的变形和受力用欧拉描述,通过欧拉网格和拉格朗日网格的信息传递,完成滚动结构动力学分析。所提出的理论可以退化到Fiala模型,并可以从理论上解释子午线轮胎的伪侧偏和伪侧倾现象。基于所建立的运动学理论和非线性有限元,建立轮胎六分力预报方法。针对某轿车子午线轮胎,分析轮胎接地面滑移速度、接地面积、接地压力、侧向剪力分布等随着侧偏角的变化规律,并研究该轮胎侧偏力和回正力矩随着胎面刚度和摩擦因数的参数敏感性。结果表明轮胎侧偏刚度和回正刚度主要受结构刚度控制,而峰值侧偏力和峰值回正力矩主要受摩擦因数控制。将利用所建立的方法和试验,探讨带束层结构对大规格子午线轮胎侧偏特性的影响规律,进一步验证所提出的理论和方法的正确性。所提出的理论和方法开辟了直接从轮胎设计预报轮胎六分力的新途径。

Theory and Method of Tire Rolling Kinematics and Prediction of Tire Forces and Moments

A new method to describe the tire rolling kinematics and calculate the tire forces and moments is presented.The rolling contact is the core problem of tire/vehicle mechanics as well as wheel/track dynamics.It is extremely difficult to model rolling contact because of the rigid body rotation and the finite deformation occurred.The mixed Lagrange-Euler method is introduced to deal with the calculation of the velocity,acceleration,and contact deformation of rolling contact structure.By using Lagrange framework,the tire velocity and acceleration which include the rigid body rotation and elastic deformation can be obtained by treating the wheel position angles as Cardanic angles,while the Euler method is used to analyze the deformation and forces in the contact area.The dynamic analysis of the rolling structure is thus performed by transferring information between these two kinds of grids in the contact area.Not only can the presented principle be degenerated into Fiala tire model but it can explain the tire ply steer and ply camber phenomenon as well.The method to predict the tire forces and moments is built up by using the proposed kinematic theory and nonlinear finite element method.The detailed analysis of the slipping velocity,contact forces,contact areas,lateral forces of a radial tire have been performed.Study on the parametric sensitivity of the tire lateral forces and self-aligning torque on the tread stiffness and friction coefficient is also carried out.The results show that the tire cornering stiffness and self-aligning stiffness are mainly controlled by the structure stiffness,while the peak lateral force and peak self-aligning torque are mainly controlled by the friction coefficient.The effect of the belt structure to the cornering properties of the large radial tires will be studied by using related experiments and simulations,to verify the principles and methods mentioned above.The proposed methodology provides a new tool to predict tire forces and moments.