【作者】 张莹；

【导师】 朱思洪；

【作者基本信息】 南京农业大学 ， 农业机械化工程， 2015， 博士

【摘要】 与小汽车、客车和载重车相比,农用车辆、林业车辆、拖拉机和部分工程车辆等都存在着剧烈的振动现象。随着车辆行驶速度的逐渐提高,这一问题愈加的突出,同时随着车辆向着大型化、高速化、舒适性方向发展,车辆的舒适性已经成为消费者关注的主要内容之一。研究表明,减振器是车辆进行振动的衰减的重要元件。基于车辆对减振器阻尼特性的要求,结合当前国内外在减振器方面的研究现状,选用减振器的主流使用型号S30型阀片式减振器,研制了可拆卸式阻尼可调减振器以及试验台架。对减振器的结构进行深入分析,基于流体力学理论,建立了减振器的理论数学模型。对减振器的活塞阀系节流阀片的变形进行理论分析,采用有限元方法和流固耦合计算方法对节流阀片的变形进行深入研究,对小挠度理论中,减振器节流阀片计算公式中的阀片变形系数进行了修正。选择CAISIM软件,分析减振器复原阻尼大小、阻尼特性的非对称性和减振器阻尼的不同数学模型,对汽车动力学的影响,主要完成的工作和取得的结论归纳如下:1、减振器内特性的阻尼特性研究。在分析减振器阻尼结构的基础上,建立减振器阻尼数学模型。设计并研制了可拆卸式的阻尼可调减振器,对影响减振器阻尼特性的活塞节流孔直径、节流阀片的片数、限位阀的外径和旁通可调节节流孔直径进行了详细的试验研究。研究结果表明,活塞节流孔直径、限位阀的外径和旁通可调节节流孔直径对减振器阻尼特性的影响较大。其中,当节流阀片的数量超过一定范围时,其数量的增加,对减振器阻尼的影响较小。限位阀的外径的调整,是对减振器阻尼调节影响最大。旁通节流孔直径在0～φ3mm范围内,复原阻尼力减小幅度最大,在φ3mm～Φ4mm范围内次之,当旁通孔直径大于Φ4 mm时,其阻尼力变化不再明显。2、采用有限元方法,对减振器节流阀片变形量的研究。根据减振器的工作过程,结合减振器实体结构尺寸和试验结果,对减振器节流阀片的变形计算进行深入分析。根据减振器实体建立减振器单片阀片与叠加阀片的有限元模型,采用ANSYS平台的STRUCTURE模块,对减振器阀片的变形大小进行细致研究。研究结果表明,采用小挠度理论及大挠度理论对减振器阀片的变形量进行计算都有其局限性。定义新的变形系数:"C_n",对减振器阀片的变形计算公式中的阀片变形系数进行修正。3、采用流固耦合方法,对减振器节流阀片变形量的研究。基于流体力学和固体力学等相关理论,建立减振器节流阀片变形计算的流固耦合模型。运用ANSYS平台的STRUCTURE模块、FLUENT模块和SYSTEM COUPLING模块,对减振器节流阀片的变形进行单向流固耦合和双向流固耦合仿真,进一步的分析了阀片在流体载荷作用下的变形规律。并对三种不同方法计算减振器阀片变形的大小进行比较分析。研究结果表明,采用有限元法对阀片变形的计算数值较流固耦合计算的数值最大。4、减振器阻尼特性对汽车动力学特性影响规律的研究。基于CARSIM软件,开发了减振器阻尼特性对汽车动力学影响的模拟试验程序,选取四种不同的典型工况,分别进行了减振器复原阻尼的大小、减振器阻尼特性的非对称性和减振器不同数学模型对汽车动力学的影响。研究结果表明,通过阶跃输入的路况时(小障得和大坡),减振器的复原阻尼力大小对车辆的振动影响较大。随着复原阻尼力的增加,车辆的振动能量减少,车辆的舒适性增强。车辆在粗糙的路面上(搓板路)运动时,随着减振器复原阻尼的减少,车辆的振动先减小后增加,说明对地在粗糙路面上运动时的汽车,阻尼过大过小都会引起振动情况的加剧。车辆进行双移线运动时,随着减振器的阻尼值增加,车辆垂向振动和俯仰振动能量减少,车辆的侧倾角、摇摆角、摇摆角速度、动载荷均受其影响较小。采用非对称阻尼的车辆,较采用对称性阻尼时的车辆舒适性有明显增强。建立了减振器的三种数学模型:线性模型,两段非对称模型和多项式模型。随着减振器数学模型复杂程度的增加,车辆的振动响应值越接近减振器实际阻尼特性引起的响应值。其中,两段非对称模型和多项式模型的响应值较为接近。通过本课题的研究,为非公路车辆及公路车辆悬架设计中的减振器选型,减振器的结构设计,可调减振器的结构设计,被悬架的匹配,可控制悬架中可调阻尼的变化区间的设置和控制策略的制定,以及车辆减振理论的发展提供了理论基础和技术支持。更多还原

【Abstract】 The vibration of off-road vehicle,such as agricultural vehicles,forestry vehicles,tractors and some engineering vehicles,is more poignant than cars,buses and trucks.With the increasing of running speed,the problem is increasingly outstanding.More attention will be paid to the comfort.The influence of the internal components of the shock absorber is deeply studied.Based on the requirements of the vehicle to the damping characteristics of the shock absorber,combined with the current research situation of shock absorber,taken the S30 type valve type shock absorber as prototype.Based on the parameter of it,the removable damping adjustable shock absorber and test rig is design and manufactured.The structure of the shock absorber is deeply analyzed.Based on the theory of fluid mechanics,a theoretical mathematical model of the shock absorber is put forward in the paper.The deformation of the throttle slice of the piston valve is analyzed,and the deformation of throttle slice is studied by using the finite element method and fluid structure coupling method.CAISIM software is chosen to analyze the influence of the damping of shock absorber,the asymmetry characteristic of the shock absorber,and the different mathematical models of shock absorber on the vehicle dynamics.The finished work and achieved results are generalized as following:1.On the basis of analyzing the structure of the shock absorber,the mathematical model of the shock absorber is established.The detachable adjustable shock absorber is designed and developed.It is detailed experimental studied that the damping variation law which is influenced of the diameter of the piston orifice,,the diameter of the piston,the number of the throttle valve,the diameter of the limiting valve and the diameter of the bypass valve.The results show that the diameter of the piston orifice,the diameter of the limiting valve and the diameter of the bypass have large influence on the damping characteristics of the shock absorber.The number of the orifice plate is out of a certain range,with the increase of the number of the throttle orifice plate,the influence of the damping is small.The adjustment of the outer diameter of the limiting valve is the greatest influence on the damping of the shock absorber.Bypass throttle hole diameter in theφ0～φ3 mm range and recovery damping force decreases greatly.In diameterφ3 mm～φ4mm,the damping force change is smaller.When the bypass hole diameter with a diameter larger than中4 mm,the damping force change is no longer obvious.2.Using the finite element method,the deformation of throttle slice of the shock absorber.According to the working process of the shock absorber,the deformation calculation of the throttle slice of the shock absorber is analyzed with the results of the experiments.The finite element model of the single chip valve and the valve plate is built according to the vibration absorber.The STRUCTURE module is used to study the deformation of the valve plate.The results show that the deformation of the valve plate is limited by the small deflection theory and the large deflection theory.Define the new coefficient of deformation:"C_n",the deformation of the valve plate in the deformation calculation formula of the valve plate deformation coefficient.3.Use of fluid solid coupling method,the throttle valve of the shock absorber is developed.Based on the theory of fluid mechanics and solid mechanics,fluid solid coupling model is established to calculate the deformation of throttle slice of shock absorber.Using the STRUCTURE module,FLUENT module and COUPLING SYSTEM module,the deformation of throttle slice of shock absorber is simulated,and the deformation law of valve plate is further analyzed.The comparison analysis of three kinds of different methods for calculating the deformation of the valve plate is made.Calculation results of valve plate that use of the finite element method is largest.4.The influence of the damping characteristics of the shock absorber on the vehicle dynamic characteristics is studied.Based on CARSIM software,the simulation test program is developed for the influence of damping characteristics of shock absorber on the vehicle dynamics,and the influence of four different kinds of typical operating conditions,respectively,are carried out.The results show that the damping force of the shock absorber has a greater effect on the vibration of vehicle.By step input of the road conditions(small obstacle and large slope),as the recovery of the damping force increases,the vibration energy of the vehicle decreases.The comfort of the vehicle increases with the increase of the damping force.At the situation of vehicle(washboard road)movement on the rough road,with the shock absorber damping recovery increased,the vibration of the vehicle decreases first and then increases.It indicate that on the rough road sports car,damping greater or smaller cause the aggravation of the vibration.In the condition of double lane change movement of vehicles,with the increase of the shock absorber damping values,vehicle vertical vibration and pitch vibration energy reduction,vehicle roll angle,roll angle,yaw angular velocity,dynamic load were less affected.The vehicle with asymmetric damping is obviously enhanced than the vehicle has a symmetrical damping.Three kinds of mathematical models of shock absorber are established:linear model,the two section of asymmetric model and polynomial model.With the increase of the complexity of the mathematical model of the shock absorber,the vibration response of the vehicle is close to the actual damping characteristic of the shock absorber.Among them,the response value of the two segment asymmetric model and the polynomial model is close.This work can provide the theoretical basis and technical support for the structure design of the shock absorber,the matching of the suspension,the setting and controlling strategy of the controllable suspension,and the development of the theory of vehicle.更多还原