机械弹性车轮径向刚度和阻尼模型的分析

针对新型机械弹性车轮刚度特性,利用曲梁理论建立了弹性基础封闭圆环曲梁模型,对车轮刚度与輮轮抗弯刚度、铰链组弹性基础刚度及激振频率之间的关系进行了分析。结合车轮静态和动态试验分析结果,验证了根据曲梁理论所建模型的正确性,并分析了车轮刚度与车轮变形量、变形速率及激振频率之间的解析关系。根据分析结果建立了车轮刚度和阻尼的非线性解析模型,该模型反映了车轮变形量和激振频率对车轮刚度的影响,以及车轮变形速率和激振频率对车轮阻尼的影响,从而为车轮结构振动的进一步研究提供指导。     

基于解析弹性基础的重载轮胎动力学建模与分析

以重载大扁平比轮胎为研究对象,基于弹性基础的柔性胎体模型为基础,分别从大扁平比胎侧曲梁的刚度建模、基于解析弹性基础的轮胎动力学建模两方面开展研究。建立考虑预紧力弦效应和结构弯曲效应的大扁平比胎侧曲梁解析刚度模型,并研究胎侧曲梁非均匀截面特性和几何、结构参数对解析刚度的影响规律。结果表明：（1）重载轮胎在0～180 Hz范围以结构周向弯曲振动为主,与基于弹性基础的柔性梁模型一致;（2）大扁平比胎侧曲梁的解析刚度与胎侧的几何、结构和充气压力参数直接相关;（3）轮胎充气压力影响柔性胎体梁的轴向预紧力和胎侧的弦刚度,进而影响轮胎弯曲振动特性。     

技术文摘专栏

轮胎静态及侧偏刚度有限元分析 【摘要】：考虑子午线轮胎的材料非线性、接触非线性以及大变形等复杂的力学特性,采用Abaqus软件建立轮胎三维有限元分析模型,研究充气压力和负荷对轮胎静态刚度（径向刚度、侧向刚度、纵向刚度、扭转刚度）和稳态侧偏刚度的影响,并给出了相应的负荷与变形之间的关系。     

基于动态特性的伸缩臂叉车驾驶舒适性分析

基于运动微分方程,分别建立整机底盘总成和驾驶室总成简化振动系统数学模型.同时,考虑叉具的柔性变形,借助Adams和HyperMesh建立整机刚柔耦合动力学模型.通过样机试验测试,获取轮胎的径向刚度和径向阻尼参数.借助振动测试仪,测试减震垫的动刚度和阻尼因子参数.以搭建的简化振动系统数学模型指导驾驶舒适性的分析方向,以A...     

电动汽车机-电-路耦合系统建模及动力学分析

轮毂电机驱动的电动汽车簧下质量大导致轮胎动载荷增加,电机电磁力也会加剧车辆振动,同时车辆和道路通过动态轮胎力相互耦合.为了探究电动汽车的振动机理,建立电动汽车机-电-路耦合系统非线性动力学模型,考虑悬架刚度、阻尼和轮胎刚度的非线性,并在传统路面不平顺激励的基础上叠加了轮毂电机的电磁激励和车路耦合引起的路面二次激励.解析...     

汽车轮胎的有限元分析

利用SolidWorks三维设计软件根据汽车子午线轮胎的实际结构特征,经过合理简化,建立汽车轮胎实体简化模型,然后运用ANSYS有限元仿真软件,通过对轮胎模型定义单元属性、接触状态和载荷状态建立合理的轮胎有限元模型,并对模拟轮胎与路面在不同充气压力接触状态下产生的接触应力进行分析,得出汽车轮胎在不同充气压力状态下应力主要分布在轮胎与路面的静态接触部分,且胎侧和胎冠部分变形较大。由不同充气压力变形情况得出轮胎使用充气压力应在220 kPa左右。     

刚度突变转子系统的动力学研究

根据转子动力学理论,建立了具有突变刚度特性的Jeffcott转子力学模型及动力学方程.通过解析方法得到了刚度突变后的转子系统振动解析表达式,分析了刚度突变前后稳态振幅之间的关系及刚度突变对轴心最大位移的影响,定义了刚度突变后的暂态过程时间并确定了碰摩参数区域.结果表明,刚度突变会导致转子系统振动幅度增大,无论工作频率如何,刚度突变所引起的轴心最大位移均位于暂态运动阶段,暂态过程时间与系统阻尼、刚度突变时的轴心位置及系统工作频率有关,碰摩参数区域随着刚度突变幅度及质量偏心距的增大而增大.     

非线性耦合油气悬架系统动力学建模与仿真研究

针对某型工程车辆的油气悬架系统,确定了含非线性刚度和阻尼的油气悬架和轮胎的数学模型,并根据虚位移原理推导了油气悬架恢复力和轮胎恢复力之间关系的解析表达式.结合工程实际,基于有限元动力学方法,采用连接单元来模拟非线性刚度和阻尼特性,建立了油气悬架和轮胎耦合的非线性悬架系统动力学模型,并通过施加正弦载荷、冲击载荷和阶跃载荷,揭示了油气悬架系统的特性.该方法为同类型悬架系统动力学建模提供了借鉴,结果为悬架系统和汽车系统动力学的研究提供了参考.     

轮胎物理参数对接地压力分布非对称性的定量影响研究

提出接地压力非对称指数的概念,利用轮胎环模型来定量研究接地压力分布的不对称性,分析了物理参数对非对称指数的非线性影响规律。结果发现影响轮胎接地压力分布非对称性的主次因素依次为:角速度、阻尼、带束层有效密度、充气压力、垂向载荷、侧壁径向弹簧参数、带束层径向弹簧参数及带束层有效抗弯刚度。在参数±40%变化范围内,垂向载荷、充气压力和侧壁径向弹簧参数对接地压力分布非对称指数的影响最大。     

机械结合面法向接触刚度和阻尼的理论模型

基于统计接触理论和等效粗糙接触表面假设,考虑微凸体在加卸载及动态载荷下的变形特征,建立了结合面法向静、动态接触模型,获得了单位面积法向静、动态接触刚度与接触阻尼(基础特性参数)。基于Kadin和Etsion的粗糙表面弹塑性卸载接触模型,通过引入微凸体卸载过程中残余变形与最大变形量及最大接触载荷之间的函数关系,建立静态加卸载接触模型。针对结合面间简谐动态相对位移,利用泰勒公式对静态接触载荷和接触刚度进行展开,得出了动态接触载荷、接触刚度的增量以及动态接触载荷下的能量损耗,建立了法向动态接触刚度和接触阻尼的计算模型。分析了结合面面压、动态位移幅值及振动频率对动态接触刚度和接触阻尼的影响规律,研究表明:法向动态接触刚度相对静态接触刚度有微小偏移增量,动态接触刚度增量和接触阻尼随法向面压及动态位移幅值的增大而非线性增大,动态接触刚度增量随振动频率增加呈非线性增大,而接触阻尼则随振动频率增加呈非线性减小。通过理论计算与试验结果的对比分析,证明了本文建立的结合面法向静、动态接触刚度及接触阻尼理论模型的正确性。     

On the Dynamics of Lubricated Cylindrical Roller Bearings,Part I: Evaluation of Stiffness and Damping Characteristics

The stiffness and damping coefficients of a single roller-to-race contact of lubricated cylindrical roller bearings are numerically evaluated using a linearized perturbation method for both elastohydrodynamic lubrication (EHL) finite and infinite contact theories. A steady-state pressure equation is solved by a multilevel method and the elastic deformation is evaluated with the multilevel multi-integration method. Dynamic pressures are obtained by solving a set of perturbed pressure equations and are used to calculate the stiffness and damping coefficients. The influence of various nondimensional parameters (load parameter, speed parameter, material parameter, edge radius, and geometrical parameter) on the stiffness and damping are studied. The results show that a finite line contact gives higher values of stiffness and damping coefficients compared to an infinite contact, particularly at higher load and lower speed values. Based on the numerically evaluated data, curve-fitted relations for the stiffness and damping coefficients of a single roller-to-race contact are developed that can be used in the dynamic analysis of rotor–bearing systems.     

轮毂直驱电动车轮胎刚度及滚阻匹配研究

研究轮毂直驱电动车轮胎垂向刚度与滚阻特性相匹配问题,揭示轮毂直驱电动汽车非簧载质量负效应产生机理,提出利用胎压改变轮胎垂向刚度进而改善悬架特性的方法。设计出四组不同胎压的轮胎垂向刚度试验,并将轮胎实际垂向刚度应用到悬架特性分析上。结果表明,通过调节轮胎垂向刚度改变了悬架特性的二阶共振频率使其远离人体敏感振动频率,并在一定程度上抑制其振动幅值。为解决轮毂直驱电动汽车轮胎刚度与滚阻特性匹配问题,研究胎压对轮胎滚阻特性和能量损耗的影响,并对四组胎压的轮胎进行滚阻特性及滞回特性试验。试验结果表明,胎压对轮胎滚动阻力有很大影响,胎压升高,轮胎滚动阻力系数和能量损耗变小。进一步表明,胎压与轮胎滚阻系数的关系及能量损耗的关系两者之间基本是一致的,揭示了轮胎滚动阻力产生机理。因此,利用胎压调节轮胎垂向刚度抑制了电动汽车非簧载质量负效应,兼顾了胎压对轮胎滚阻及能耗的影响,实现了轮胎垂向刚度与滚阻特性的匹配,为轮胎与悬架的相互作用机理提供了理论依据。     

离心压缩机蜂窝阻尼密封动力特性及转子稳定性*

新一代蜂窝阻尼密封在提升透平机械转子稳定性方面有优越的表现,其动力特性是评价转子稳定性的重要参数。应用非定常动网格技术和多频涡动模型,研究蜂窝密封动特性系数随转子涡动频率的变化规律,并与迷宫密封进行对比。结果表明：蜂窝密封动特性受转子涡动频率影响较大,直接刚度系数和交叉阻尼系数随涡动频率增大而增大,交叉刚度和直接阻尼系数随涡动频率增大而减小;迷宫密封动特性系数随涡动频率变化特征不明显;在低频率区蜂窝密封的有效阻尼远高于迷宫密封。在实际压缩机转子上的应用结果表明,蜂窝密封能显著提升转子稳定性。     

磁力轴承系统PID控制特性的研究

叙述了磁力轴承的主动控制原理及控制系统的组成;分析了磁力轴承系统的刚度阻尼特性与其控制器特性之间的关系;同时分析了采用PID控制的磁力轴承刚度阻尼与控制系统各参数之间的关系,提出一种简便的PID参数设计方法.     

圆柱腔小孔节流空气静压轴承动力学性能研究

为研究轴承参数对气膜刚度、阻尼特性的影响,以圆柱腔小孔节流空气静压支承轴承为例,基于动网格方法,采用数值仿真计算分析轴承气膜在外激励下的动载荷响应特性,计算气膜承载力、刚度和阻尼;考虑气膜厚、气腔尺寸、小孔孔径、供气压与激励特性,基于正交试验设计构造正交表,进行采样计算,采用径向基神经网络模型拟合得到承载力、刚度和阻尼与轴承参数的相关性数学模型;基于得到的数学模型,分析气腔尺寸对轴承动力学性能的影响。研究表明:由于挤压膜效应,激励频率的增加可使气膜刚度增加、阻尼降低;当轴承间隙气容更小时,刚度随激励频率的增加更快。     

Dynamic characteristics of the rotor in a magnetically suspended control moment gyroscope with active magnetic bearing and passive magnetic bearing

For a magnetically suspended control moment gyroscope, stiffness and damping of magnetic bearing will influence modal frequency of a rotor. In this paper the relationship between modal frequency and stiffness and damping has been investigated. The mathematic calculation model of axial passive magnetic bearing (PMB) stiffness is developed. And PID control based on internal model control is introduced into control of radial active magnetic bearing (AMB), considering the radial coupling of axial PMB, a mathematic calculation model of stiffness and damping of radial AMB is established. According to modal analysis, the relationship between modal frequency and modal shapes is achieved. Radial vibration frequency is mainly influenced by stiffness of radial AMB; however, when stiffness increases, radial vibration will disappear and a high frequency bending modal will appear. Stiffness of axial PMB mainly affects the axial vibration mode, which will turn into high-order bending modal. Axial PMB causes bigger influence on torsion modal of the rotor.     

Practical behavior of advanced non-linear hydraulic servo system model for a mold oscillating mechanism depending on line volume

We studied a mold oscillating mechanism for continuous casting. An equivalent hydraulic servo system model was established including a non-linear property and line volume near the hydraulic cylinder. The analysis focused on a practical behavior of the system. To observe an oscillated object and dynamic responses, an equivalent stiffness, damping ratio and simple mass-damper-spring 1-DOF model were established by Karl-Erik Rydberg’s research, and showed hydraulic cylinder pressure and line volume near the hydraulic cylinder. Especially, hydraulic pressure including statue of a mechanical and hydraulic cylinder was analyzed in the time and frequency domain. The results were validated by comparing responses between the 1-DOF model and the nonlinear hydraulic servo system model. The line volume that connects the hydraulic cylinder and the hydraulic servo valve has great effect on damping ratio and natural frequency of the hydraulic servo system. When the line pipe has high volume compared to normal statue, the hydraulic cylinder pressure has sharp peak frequencies that are located on natural frequency and its duple-harmonic terms with sideband peaks; (±2×exciting frequency) space. Based on this fact, we investigated the model using sensitivity analysis, and explained an oscillating mechanism about the mold oscillator by applying additional spring. A design of robust control for the mold oscillator was suggested by Negative strip time criterion, and maximum additional spring stiffness was shown.     

A novel negative dislocated seal and influential parameter analyses of static/rotordynamic characteristics

This paper proposes a new type of negative dislocated seal (NDS) based on the dislocated bearing theory to investigate the influential parameters of static rotor eccentricity and dislocated ratio on the static and rotordynamic characteristics of an example seal solved with computational fluid dynamics (CFD) the flow field. The rotordynamic characteristics of the NDS were investigated in respect of the effects of rotor whirling frequency on response force, stiffness coefficients, damping coefficients and rotor system stability, by multifrequency elliptical orbit rotor whirling model. Based on the studies, we reached the following conclusions. The circumferential pressure distribution of NDS and conventional labyrinth seal (LS) presents sine periodic variation approximately, while relative to the LS, the NDS has two divergent wedge gaps and reduces the hydrodynamic pressure effects, then the circumferential pressure difference and tangential force on rotor surface decreases by about 40 %~190 %. The leakage of the NDS linearly increases with the rising eccentricity ratio and dislocation ratio approximately, and is larger (about 0.9 %~1.5 %) than the LS. The direct stiffness coefficients of the two seals increase with the rise of rotor whirling frequency, while the absolute values of both the cross-coupled stiffness coefficients and the damping coefficients decrease with raising rotor whirling frequency. Compared with the LS, the NDS has smaller (about 28.8 %~206.2 %) cross-coupled stiffness coefficient, larger (about 26.15 %~60.39 %) effective damping coefficient, and good stability of rotor system. This study has developed a novel seal structure to improve the seal performance of turbomachinery such as aeroengine.