Hydroplaning simulations for tires using FEM,FVM and an asymptotic method

Hydroplaning tires have been frequently simulated using commercial explicit FEM (Finite Element Method) codes. However, these simulations are slow, and the result of the lift force is so oscillatory that the hydroplaning speed cannot be accurately determined. Thus, in the author’s previous study, a new methodology using FDM (Finite Difference Method) code and an FE tire model iteratively was proposed. However, this full iteration method still required a long computation time, especially for patterned tires. Thus, in this study, the full iteration methodology was modified such that no iteration or only one additional iteration was needed at each speed. Then, by applying the full iteration method, no iteration method and one iteration method, the hydroplaning speeds of a straight-grooved tire were determined, and it was noted that the hydroplaning speed obtained from the one iteration method was almost the same as that obtained from the full iteration method. Moreover, the hydroplaning speeds of two patterned tires were determined using the one iteration method, and they were compared with the hydroplaning speeds obtained experimentally.     

基于车路系统的事故现场轮胎印迹强度参数化研究

为明确事故现场可视轮胎印迹强度与车辆动力学特性、轮胎橡胶磨损特征及道路表面灰度之间的关联特性,提出基于车路耦合的事故现场轮胎印迹强度参数化研究方法。通过结合动态滑动摩擦因数模型及轮胎非线性模型,建立车辆路面9 DOF非线性系统动力学模型,运用VBOX惯性测量技术验证模型的有效性。运用胎面磨损能量模型,从车路系统角度确定车辆、轮胎和路面特性对轮胎全局摩擦力及胎面磨损特性的影响。结合印迹强度特征模型提出轮胎印迹强度参数研究方法,选取不同制动、转向角工况及3组路面、胎面特性对轮胎路面接地力学特性、胎面橡胶磨损量、可视轮胎印迹特征进行仿真分析。结果表明：印迹强度仅与全局摩擦力大小有关,与轮胎路面滑移方向无关;滑移工况下胎面橡胶磨损量随着全局摩擦力和滑移速度的增大而增大,而印迹强度变化不明显;制动力矩和道路表面灰度对产生可视轮胎印迹起决定作用,转向角主要影响不规则可视轮胎印迹的产生;前轮轮胎最先出现可视印迹,且可视印迹长度和强度均高于后轮轮胎;采取可视印迹起点作为事故车辆速度判定具有一定的误差,应根据具体情况进行具体分析;研究成果能够为基于可视轮胎印迹的交通事故重建提供理论基础。     

带复杂花纹的轮胎滑水显式动力学分析

以205/55R16型半钢子午线轮胎为参考轮胎,利用组合类保角映射簇建模法构建了3种不同胎面花纹的轮胎有限元分析模型.利用该模型进行载荷一下沉量及流体压力一行驶速度分析结果表明.轮胎有限元模型和骨架材料的等效简化方法以及滑水求解策略有效.在此基础上,考察了胎面花纹形态对轮胎滑水性能的影响.结果表明.S型轮胎和V型轮胎由于横向花纹沟的存在,滑水性能优于纵沟胎.     

湿滑条件下基于真实纹理道面的机轮着陆滑水行为解析

湿滑条件下的着陆滑跑是航空事故的高发区。为较为真实地反映湿滑条件下机轮的滑跑行为，需要建立包含真实道面纹理特征的滑跑模型。在提取真实道面形貌特征的基础上，通过解析湿滑条件下的机轮滑跑行为进一步反算其遵循的摩擦关系，以获得更加接近真实条件的摩擦模型；然后运用欧拉-拉格朗日（CEL）算法建立基于真实纹理形貌特征的道面-水膜-轮组的流固耦合模型，以摩擦因数、动水压力为分析指标来探讨速度、滑移率、水膜厚度以及道面类型对机轮滑水行为的作用规律，进而为提高飞机着陆的安全性提供理论参考。研究结果表明：A320型飞机着陆可能滑漂的危险区段为刚刚着陆阶段，随着速度的降低，道面支撑力会逐渐增大，而动水压力将逐渐减小；随着滑移率的增加，动水压力呈现出先减小后增大的趋势，当滑移率为0.15时，动水压力达到最小；关于水膜厚度的影响，水膜厚度小于3 mm时不会发生滑漂，而水膜厚度大于10 mm时极可能发生滑漂；当水膜厚度为7 mm时动水压力与飞机滑行速度、滑移率的相关性较大，可视为机轮发生滑漂的临界状态；最后，在其他条件一致的情况下，各道面类型的抗滑性排序为SMA > OGFC > AC > 平滑道面。因此，湿滑条件下，控制飞机着陆的初始速度和滑移率是减小航空事故、提高机场安全运行的有力保障。     

Recycling technology of tire rubber

Material recycling technology for automotive tire rubber waste was developed by the continuous devulcanization method. The deodorization during the recycling process has become possible by the newly developed method. The devulcanized rubber obtained by these methods from tire rubber waste, generated from both the manufacturing products and scrap tires, shows excellent mechanical properties applicable to the new tire rubber compounds in engineering practice. Furthermore, it was confirmed by actual road tests that a test truck tire containing 10 wt % of the devulcanized rubber in the tread might exhibit tread wear behavior almost equal to that for the standard type with the new rubber compound.     

基于径向刚度法的车辆翻新轮胎使用寿命判定

为了有效判定车辆翻新轮胎的剩余使用寿命，需要科学确定废旧轮胎胎体橡胶老化程度对翻新轮胎使用寿命的影响。在分析废旧轮胎胎体橡胶老化规律的基础上，通过橡胶老化试验测试及回归分析，确定了胎体弹性模量随着橡胶老化年限增加近似线性增大的影响规律；结合计算机仿真技术及试验测试技术，基于轮胎径向刚度法提出了翻新轮胎剩余使用寿命不安全系数计算方法，其计算数值大小与翻新轮胎径向刚度和新轮胎径向刚度之差成正比，与新轮胎径向刚度值成反比；构建了由橡胶加速老化系统、弹性模量测取系统、承载-变形计算机模拟系统和承载-变形测试系统等组成的翻新轮胎剩余使用寿命判定系统；基于径向刚度法和判定系统提出了车辆翻新轮胎剩余使用寿命判定规则，确定了翻新轮胎胎体剩余使用寿命判定具体流程；根据剩余使用寿命不安全系数计算方法和判定规则，将翻新轮胎确定为可正常使用、需降速使用和需报废处理3个级别，并利用11.00R22.5载重车辆翻新轮胎进行了剩余使用寿命判定与评价，依据判定规则分别计算了不同使用年限3条翻新轮胎的剩余使用寿命不安全系数，确定出3条翻新轮胎所对应的级别，判定与评价结论与实际使用情况相吻合。研究结果表明：废旧轮胎胎体橡胶老化程度对翻新轮胎剩余使用寿命影响显著，翻新轮胎径向刚度与剩余使用寿命之间存在较大影响关系；废旧轮胎胎体橡胶老化程度越严重和径向刚度越大，翻新轮胎的剩余使用寿命将会越短。     

考虑动压与路面粗糙度时轮胎湿牵引性能研究

根据流体动力润滑理论,将轮胎黏性滑水问题模拟为胎面单元与路面之间的动压、挤压膜问题,同时考虑了路面粗糙度的影响,建立了轮胎胎面单元黏性滑水问题的数学模型,并进行数值求解。以矩形胎面单元为例分析了胎面单元对轮胎黏性滑水性能的影响。结果表明,轮胎的薄膜湿牵引性能与滑动速度成反比;在考虑路面粗糙度的情况下,引入了膜厚比作为轮胎的薄膜湿牵引性能衡量标准,得出湿牵引性能与路面粗糙度成正比的结论。     

家用汽车轮胎使用分析

汽车轮胎的状况对车辆的动力性、制动性、舒适性、驾驶稳定性、燃油经济性都有着直接影响,因此文章主要介绍了汽车轮胎的具体构造及其在日常使用中的常见问题,并共同探讨轮胎的正确使用方法及保养手段。     

轮胎制动力—滑移率特性的动态模型研究

轮胎制动力及滑移率对制动力矩的响应存在着显著的低频衰减振荡现象，这从制动力－滑移率特性曲线上看，表现为一系列的以稳态点为中心的旋涡状过渡曲线。这是稳态的轮胎模型所不能描述的。本文在稳态ｂｒｕｓｈ轮胎模型基础上，通过印迹前端蹼处胎冠一阶变形模型，建立了轮胎制动力－滑移率的动态模型，并根据转鼓试验台上的轮胎制动试验，验证了该模型的仿真效果。     

基于 FLUENT 软件轮胎滑水现象模拟研究

基于FL U EN T软件模拟了轮胎滑水产生过程,并计算了不同轮胎花纹、不同车速及不同水膜厚度等条件下轮胎所受动水压强的大小。模拟分析结果表明:①复合花纹轮胎最不易发生滑水,横向花纹次之,纵向花纹最易滑水;②当水膜厚度不变时,同一轮胎所受动水压强随车速的增加而增加,且增长速度随着车速的增加而增加;③当车速不变时,同一轮胎所受动水压强随水膜厚度的增加而增加。以动水压强等于轮胎内部压强时轮胎发生滑水为判断标准,建立了轮胎临界滑水速度与水膜厚度的关系,并根据已有水膜厚度方程,推算出了临界滑水速度与降水量的关系。      

干燥路面上轮胎制动距离的FEM仿真

介绍了装有ABS系统汽车的轮胎制动性能仿真方法.把整个制动过程按速度离散为若干个均匀的子区间,用有限元法计算在每个子区间的离散速度下制动器摩擦热损失率和轮胎与地面间摩擦能量损失率,然后根据能量守恒定律求出每个子区间上的制动时间增量,最终求得整个制动时间和制动距离.其中ABS的作用通过控制轮胎的角速度使其始终保持最佳滑移...     

Hydroplaning simulation of a tire in thin water using fem and an estimation method and its application to skid number estimation

To simulate the hydroplaning of a tire, many analytical studies have been performed using commercial explicit FE (Finite Element) codes such as MSC.DYTRAN and LS-DYNA. However, most previous studies on this subject have addressed simulation of hydroplaning for water more than 5 mm deep. Additionally, because a great number of Eulerian elements and Lagrangian elements are typically used to analyze hydroplaning and because multiple analyses should be performed for various water depths, long CPU times are required. In this study, it was found that the traction force and the lift and drag forces between the tire and the road surface could be easily estimated for water shallower than 5 mm using an exponential function based on tire rolling FE simulation results. Furthermore, changes in skid resistance, expressed as SN (skid number), could be estimated for various water depths and vehicle speeds using the method proposed in this study, and the results were proven to be in good agreement with results obtained using the ASTM E274 Pavement Friction Tester.     

Dynamic Friction Models for Road/Tire Longitudinal Interaction

Summary In this paper we derive a new dynamic friction force model for the longitudinal road/tire interaction for wheeled ground vehicles. The model is based on a dynamic friction model developed previously for contact-point friction problems, called the LuGre model. By assuming a contact patch between the tire and the ground we develop a partial differential equation for the distribution of the friction force along the patch. An ordinary differential equation (the lumped model) for the friction force is developed, based on the patch boundary conditions and the normal force distribution along the contact patch. This lumped model is derived to approximate closely the distributed friction model. Contrary to common static friction/slip maps, it is shown that this new dynamic friction model is able to capture accurately the transient behaviour of the friction force observed during transitions between braking and acceleration. A velocity-dependent, steady-state expression of the friction force versus the slip coefficient is also developed that allows easy tuning of the model parameters by comparison with steady-state experimental data. Experimental results validate the accuracy of the new tire friction model in predicting the friction force during transient vehicle motion. It is expected that this new model will be very helpful for tire friction modeling as well as for anti-lock braking (ABS) and traction control design.     

Dynamic Friction Models for Road/Tire Longitudinal Interaction

Summary In this paper we derive a new dynamic friction force model for the longitudinal road/tire interaction for wheeled ground vehicles. The model is based on a dynamic friction model developed previously for contact-point friction problems, called the LuGre model. By assuming a contact patch between the tire and the ground we develop a partial differential equation for the distribution of the friction force along the patch. An ordinary differential equation (the lumped model) for the friction force is developed, based on the patch boundary conditions and the normal force distribution along the contact patch. This lumped model is derived to approximate closely the distributed friction model. Contrary to common static friction/slip maps, it is shown that this new dynamic friction model is able to capture accurately the transient behaviour of the friction force observed during transitions between braking and acceleration. A velocity-dependent, steady-state expression of the friction force versus the slip coefficient is also developed that allows easy tuning of the model parameters by comparison with steady-state experimental data. Experimental results validate the accuracy of the new tire friction model in predicting the friction force during transient vehicle motion. It is expected that this new model will be very helpful for tire friction modeling as well as for anti-lock braking (ABS) and traction control design.     

Integrated Control of Active Rear Wheel Steering and Direct Yaw Moment Control

SUMMARY

An integrated control system of active rear wheel steering (4WS) and direct yaw moment control (DYC) is presented in this paper. Because of the tire nonlinearity that is mainly due to the saturation of cornering forces, vehicle handling performance is improved but limited to a certain extent only by steering control. Direct yaw moment control using braking and/or driving forces is effective not only in linear but also nonlinear ranges of tire friction circle. The proposed control system is a model matching controller which makes the vehicle follow the desired dynamic model by the state feedback of both yaw rate and side slip angle. Various computer simulations are carried out and show that vehicle handling performance is much improved by the integrated control system.     

橡胶沥青对路面抗滑性能的影响研究

在柔性路面设计、养护和修复中,抗滑性和构造是应当考虑的重要的安全特征。主旨是优化橡胶沥青路面的表面构造特性,宏观上减少溅水、喷射及滑水现象;微观方面增强低、高速行驶时的摩擦力。采用英式摆式仪法和体积法来测量摩擦表面特性,取试验室制备的试件代表实际道路表面。研究采用两种级配和三种沥青结合料:常规沥青;湿法橡胶沥青;干法橡胶沥青。在相同的混合料配比基础上,以增加1%的橡胶沥青来测试其含量对路面质量的影响。研究结果用来评价橡胶沥青的生产工艺和混合料级配对路表面特性的影响。结果表明间断级配橡胶沥青混合料比密级配具有更大的构造深度。与常规混合料相比,橡胶沥青混合料能提高路面抗滑性。该研究表明,用不同工艺生产的橡胶沥青对路表面特性的影响不同。     

轮胎胎面与柔性路面摩擦接触的数值分析

应用有限元软件ANASYS建立了包括橡胶胎面和柔性路面结构的有限元模型,探讨了车辆处于自由滚动和紧急制动过程中在不同轮胎／路面界面摩擦系数下的胎面、路表的变形特性和接触应力分布状态。研究结果表明,界面摩擦系数是影响胎面与柔性路面摩擦性能的主要原因,随其值的增加路面弯沉减小,摩擦应力先增加然后保持稳定,但轮胎的磨耗增加,接触压应力增加。适当地丰富路表构造、提高界面摩擦系数能降低路面弯沉,增强紧急制动状态下的抗滑性能;但是当摩擦系数超过某临界值时,随其数值的增大所对应制动状态下的抗滑性能不再提高,且路面压应力明显增加。摩擦特性对路表抗滑性能和路面力学响应的研究提供了一定的理论基础。     

轮胎半经验模型中摩擦系数切换问题

介绍了2种简单的摩擦系数模型(库仑摩擦定律、静摩擦力模型)，并将其与轮胎统一刷子理论模型结合起来分析轮胎的摩擦问题。在此基础上引入了满足轮胎刷子理论模型边界条件的轮胎稳态半经验模型，给出了应用轮胎半经验模型实现摩擦状态切换的方法。通过轮胎在2种滚动速度下的侧偏试验，证明了轮胎半经验模型可实现2种速度下的摩擦系数切换。     

浅谈汽车轮胎磨损谈及有效保养

汽车轮胎每天都要和粗糙的路面接触,发生磨损自然是在所难免的事情。但是,绝不能因此就对轮胎的磨损掉以轻心,因为可以从轮胎的磨损程度发现汽车隐藏的故障。一般来说,如果汽车没有问题,轮胎的磨损就应该是均匀的;如果磨损不均,那可能就是有问题了。在汽车的行驶过程中,如果操作使用不当或维护保养不及时,将导致轮胎的异常损伤,直接影响汽车的动力性、经济性和各种使用性能的发挥,甚至造成严重的行车事故。汽车轮胎不仅影响整车动力性、经济性和轮胎使用寿命,而且直接影响汽车的操纵稳定性、汽车行驶方向的可控性,关系到人的生命和财产安全。因此,要科学地按技术要求控制轮胎气压,减少或避免轮胎异常磨损,合理维护和正确使用轮胎。     

Sideslip angle estimation based on input–output linearisation with tire–road friction adaptation

An adaptive sideslip angle observer considering tire–road friction adaptation is proposed in this paper. The single-track vehicle model with nonlinear tire characteristics is adopted. The tire parameters can be easily obtained through road test data without using special test rigs. Afterwards, this model is reconstructed and a high-gain observer (HGO) based on input–output linearisation is derived. The observer stability is analysed. Experimental results have confirmed that the HGO has a better computational efficiency with the same accuracy when compared with the extended Kalman filter and the Luenberger observer. Finally, a road friction adaptive algorithm based on vehicle lateral dynamics is proposed and validated through driving simulator data. As long as the tires work in the nonlinear region, the maximal friction coefficient could be estimated. This algorithm has excellent portability and is also suitable for other observers.