踏面制动尖叫噪声的有限元分析

利用ABAQUS软件建立铁路货车车轮踏面制动系统有限元模型,对其进行制动摩擦尖叫噪声的有限元复特征值分析.根据复特征值实部的正负判断系统发生尖叫噪声的可能性,如果有实部为正的特征值,则可判断系统有发生尖叫噪声的趋势.在ABAQUS建模方法中,闸瓦与车轮之间的法向力根据接触计算确定,不需假设接触弹簧,可以方便处理非平面滑动接触尖叫噪声问题.利用该模型,研究滑动摩擦因数、闸瓦压力角、闸瓦压力和转动方向对尖叫噪声的影响.研究结果显示,闸瓦压力角对制动尖叫噪声有重要影响,当闸瓦压力角α=5°时,制动系统发生尖叫噪声的影响.研究结果显示,摩擦因数越大,系统发生尖叫噪声的趋势就越大;闸瓦压力越大,尖叫噪声发生的趋势就越大.车轮逆时针转动比顺时针转动更容易引起尖叫噪声.     

轮轨曲线尖叫噪声有限元预测方法的研究

利用ABAQUS有限元软件,对车辆经过小半径曲线时的尖叫噪声进行有限元预测分析.建立了包括车轮、钢轨和钢轨支撑弹簧的有限元动力学模型.根据车轮通过小半经曲线时横向蠕滑力饱和的实际情况,假设横向蠕滑力等于摩擦因数乘以法向力,通过摩擦力耦合建立车轮和钢轨耦合的动力学方程.对此动力学方程进行稳定性分析,得出耦合系统动力学特征方程的复特征值.根据是否存在实部为正的复特征值,从而判断系统是否有发生曲线尖叫噪声的趋势.计算结果显示,当轮轨摩擦因数比较大时,系统存在实部为正的复特征值,说明此时轮轨系统存在发生曲线尖叫噪声的可能性.此外,钢轨端部不同约束条件对曲线尖叫噪声预测结果有一定的影响.     

制动力对制动尖叫噪声及磨损特性的影响

在自行研制的新型摩擦制动噪声试验台上,采用锻钢制动盘和铜基粉末冶金制动片作为摩擦副,研究制动力对制动尖叫噪声特性和界面磨损特征的影响。结果表明:随着制动力的增大,摩擦系统不稳定振动加强,系统产生高强度制动尖叫噪声的倾向增强;制动力的增大导致摩擦界面磨损更加严重,黏着撕裂和剥落、犁削、磨屑堆积等"不平顺"因素对接触界面产生连续激励并加剧系统的不稳定振动,进一步诱导高强度制动尖叫噪声的产生。     

约束对盘形制动摩擦噪声影响的有限元研究

建立了铁路车辆盘形制动装置的三维实体有限元模型,分别为该模型中的制动盘、闸片和夹钳等部件设置了不同的材料特性。利用线性弹簧力模拟制动摩擦面间的法向力,摩擦力取为线性弹簧力与摩擦因数的乘积。通过对系统有限元运动方程进行复特征值分析,根据复特征根实部为正值判断系统发生失稳的模态,这也是可能产生摩擦噪声的模态。仿真结果显示,系统的约束条件对摩擦噪声的形成有显著的影响。改变模型的约束条件,可以抑制制动系统的摩擦噪声发生趋势,说明通过优化设置约束条件来提高摩擦系统的运动稳定性从而抑制摩擦噪声的发生是可行的。     

CRH2盘形制动系统制动尖叫噪声研究

为了研究高速动车组的制动尖叫噪声,建立CRH2拖车盘形制动系统的摩擦耦合有限元模型,对其进行运动稳定性和制动自激振动的瞬态动力学分析,研究了摩擦因数、闸片以及制动盘弹性模量对制动系统尖叫噪声的影响。结果表明：随着摩擦因数μ的增大,盘形制动系统发生制动尖叫噪声的趋势增加;随着闸片弹性模量的增大,制动系统发生制动尖叫噪声的趋势增加,并且激发的噪声频率也明显变大;随着制动盘弹性模量增大,制动系统发生制动尖叫噪声的趋势先降低后增大。     

盘式制动器复模态摩擦耦合制动稳定性分析

为研究影响汽车制动噪声的因素,以通风盘式制动器为研究对象,应用有限元软件ABAQUS,建立制动尖叫有限元模型,通过自由模态试验及制动尖叫台架试验验证了模型正确性,进行复特征值分析和自由模态分析,探讨系统部件自由模态与摩擦耦合模态的关系,摩擦系数及制动系统关键部件刹车盘刹车片的弹性模量对制动稳定性的影响,结果显示在摩擦耦合作用下,系统中固有频率接近的部件产生模态耦合,导致系统不稳定振动;系统摩擦系数越大,摩擦耦合程度也越大,系统不稳定性越大,但主振频率不变;刹车盘和刹车片弹性模量增大分别起到增强和削弱摩擦耦合对系统不稳定性的影响。     

转向节特性对盘式制动器尖叫影响的研究

考虑到目前关于盘式制动器尖叫噪声的仿真研究通常忽略了转向节的影响,建立包含转向节部件的盘式制动器有限元模型,利用复特征值分析法对该制动器的振动尖叫特性进行预测分析,重点探讨了转向节的特性对制动尖叫行为的影响.结果表明增大摩擦因数会增强制动系统产生尖叫的倾向和强度,转向节对制动系统不同部件之间的耦合具有重要影响,其模态将...     

摩擦片偏磨引起的汽车制动低鸣噪声

建立后盘式制动器有限元模型,对其进行制动低鸣噪声的有限元复特征值分析。根据系统的负阻尼比预测系统出现制动噪声的趋势。利用该模型,研究摩擦片切向偏磨对制动噪声的影响。研究结果表明,切向偏磨是引起制动低鸣噪声的主要原因。当偏磨量大于0.5 mm时,系统的负阻尼比突变,说明发生制动低鸣噪声的可能性极大;同时该噪声的出现与制动压力、摩擦滑动方向、摩擦因数有特定的关系。该计算结果与噪声试验结果完全一致,为消除该制动低鸣噪声提供了理论依据和指导。     

基于ABAQUS的车辆盘形制动系统仿真分析

制动盘和摩擦片之间产生共振时会影响二者之间的接触状况,从而导致摩擦副之间的接触恶化,严重时会引起制动失效.文中基于三维实体软件SoIidWorks建立了轨道车辆盘形制动系统.针对车辆盘形制动系统振动噪声问题,利用ABAQUS建立了车辆盘形制动的有限元模型.利用模态分析方法,分别对制动盘、摩擦片和盘形制动耦合系统进行模态...     

稳恒磁场作用下摩擦制动尖叫发生率及其预测分析

为了研究稳恒磁场作用下制动尖叫发生率随制动工况的变化规律,提出一种基于长短时记忆(LSTM)网络的摩擦制动尖叫发生率的预测模型。设计制动尖叫信号的测量方案,并开展大量的模拟制动试验;通过LSTM门控循环单元的深度学习网络,构建对不同制动工况下制动尖叫发生率的智能预测模型;通过预测模型及摩擦界面的微观特性分析稳恒磁场对制动尖叫行为的影响规律及机制。结果表明：建立的模型可以实现对制动尖叫发生率的准确预测;稳恒磁场可有效降低制动尖叫发生率,但当磁感应强度增大到一定阈值后,磁场对摩擦行为的影响程度趋于饱和,制动尖叫发生率也逐渐趋于稳定。研究结果为探索发展基于磁场的制动器制动尖叫主动抑制技术提供了理论基础和数据模型。     

Comparative Study on the Complex Eigenvalue Prediction of Brake Squeal by Two Infinite Element Modeling Approaches

The complex eigenvalue analysis is currently a common approach to predict squealing vibration and noise. There are two methods for modeling friction contact in the complex eigenvalue analysis of friction systems. In one method, contact springs are used to simulate friction contact. In another method, no contact spring is used. However, it has been uncertain whether these two modeling methods can predict approximately identical results. In order to clarify the uncertainty, two finite element models of the same brake system for the brake squeal prediction are established and simulated by using ABAQUS and NASTRAN software tools, respectively. In the ABAQUS model, friction coupling is applied to determine normal contact force and no contact spring is assumed. Whilst in the NASTRAN model, the contact spring is assumed by the penalty method to simulate contact connection. Through the numerical simulations, it is recognized that even if the same mesh geometry is applied, generally, these two finite element approaches are not capable of predicting approximately identical unstable frequencies. The ABAQUS approach can predict instabilities of high frequency up to 20 kHz or more, while the NASTRAN approach can only predict some instabilities of high frequency, not all. Moreover, the simulation results also show that both the contact spring stiffness and mesh size have influences to some extent on the prediction results of squeal. The present comparative work illuminates that the modeling method without contact springs is more suitable to predict squealing vibration and noise, comparing to the modeling method with contact springs. It is proposed that one should prefer using the modeling method without contact springs to predict squealing vibration and noise. The proposed study provides the reference for predicting squealing vibration and noise.     

摩擦块形状对制动盘摩擦温度及热应力分布的影响

列车制动产生的摩擦热在制动盘表面的分布与闸片结构密切相关,并影响到制动盘的耐热疲劳程度.基于实际应用的圆形、六边形、三角形3种形状摩擦块的制动闸片,利用有限元分析软件ABAQUS,模拟制动时制动盘的温度及热应力分布情况.结果显示:制动盘摩擦表面温度及热应力呈环形带状分布,沿周向变化不明显,在径向上分布的均匀程度差异较大;其变化程度与摩擦块形状和位置有关,摩擦块为圆形时,盘面的温差和热应力最小,摩擦块为三角形时,盘面的温差和热应力最大;摩擦块的位置分布影响到摩擦副接触弧长度,接触弧长度增加,对应的摩擦环带温度升高;各环带对应的接触弧长度偏差越小,制动盘温度越低,分布也越均匀.     

Frictionally excited thermoelastic instability in disc brakes—Transient problem in the full contact regime

Exceeding the critical sliding velocity in disc brakes can cause unwanted forming of hot spots, non-uniform distribution of contact pressure, vibration, and also, in many cases, permanent damage of the disc. Consequently, in the last decade, a great deal of consideration has been given to modeling methods of thermoelastic instability (TEI), which leads to these effects. Models based on the finite element method are also being developed in addition to the analytical approach.The analytical model of TEI development described in the paper by Lee and Barber [Frictionally excited thermoelastic instability in automotive disk brakes. ASME Journal of Tribology 1993;115:607-14] has been expanded in the presented work. Specific attention was given to the modification of their model, to catch the fact that the arc length of pads is less than the circumference of the disc, and to the development of temperature perturbation amplitude in the early stage of breaking, when pads are in the full contact with the disc. A way is proposed how to take into account both of the initial non-flatness of the disc friction surface and change of the perturbation shape inside the disc in the course of braking.     

Squeal analysis of gyroscopic disc brake system based on finite element method

In this paper, the dynamic instability of a car brake system with a rotating disc in contact with two stationary pads is studied. For actual geometric approximation, the disc is modeled as a hat-disc shape structure by the finite element method. From a coordinate transformation between the reference and moving coordinate systems, the contact kinematics between the disc and pads is described. The corresponding gyroscopic matrix of the disc is constructed by introducing the uniform planar-mesh method. The dynamic instability of a gyroscopic non-conservative brake system is numerically predicted with respect to system parameters. The results show that the squeal propensity for rotation speed depends on the vibration modes participating in squeal modes. Moreover, it is highlighted that the negative slope of friction coefficient takes an important role in generating squeal in the in-plane torsion mode of the disc.     

A friction model for dry contacts during metal-forming processes

In a metal-working process, the friction between the material and the tools influences the process by modifying the strain distribution of the workpiece. This frictional behavior is often taken into account by using a constant coefficient of friction in the finite element simulations. However, friction coefficient varies in time and space with many parameters. This paper aims at modeling of friction in dry contacts which happens at metal-forming processes in the lack of lubricant. The coefficient of dry friction in this model is a function of contact area ratio (which is a function of surface contact characteristics) and strain hardening exponent (material property). The V-bending process of aluminum alloy 6061-T4 sheets was studied experimentally and numerically using ABAQUS/Standard with two kinds of friction models: Coulomb friction and newly developed dry friction models. The results clearly showed that the developed dry friction model has better results in predicting load-stroke curves and springback compared to traditional Coulomb friction model. The FE prediction error for 6061-T4 AA is 16.9% using Coulomb friction model and 9.2% using dry friction model.     

盘式制动衬片力学模型的特性分析

通过对盘式制动衬片的受力分析 ,建立盘式制动衬片表面受力的力学模型 ,并计算出总摩擦力的作用中心。通过对底板与摩擦材料之间的受力分析 ,说明在各种应力作用下 ,在制动过程中有可能出现制动不稳定状态 ,为了避免这一现象 ,应合理设计衬片的几何尺寸。同时对如何设计底板上抗剪力孔的位置进行简单的分析。定性的说明了由于摩擦热而引起底板的弯曲变形 ,对摩擦面受力情况的影响。     

动态摩擦因数对蝶式制动器温度场影响的试验和模拟研究

针对蝶式制动器制动过程中温度场研究的需要,利用相似原理研制定速制动试验台,用以模拟摩托车匀速下长坡时的制动工况。制动试验台用车床的三爪卡盘控制固定在旋转轴上的制动盘做定速旋转运动,内外摩擦片通过液压力夹紧制动盘,使制动盘与摩擦片发生摩擦运动,通过热电偶、拉压力传感器、压力表、热成像仪分别测出定速制动50 s的摩擦片上固定点的温度变化、制动扭矩(经计算得出)的动态变化、制动力的均值、制动盘摩擦区域的温度场变化,实时显示并记录下来。定速制动摩擦试验机能实现不同转速、不同制动力等条件下,制动过程中的各变量的动态测量。试验还选取热成像仪测得的最大的温度为变量,研究摩擦因数随温度的变化。在试验的基础上,用ABAQUS对制动盘与摩擦片的相互作用做了一些仿真和分析。仿照实际模型1∶1建模,加载与边界条件与实际模型相同,将测得的摩擦因数随温度变化的数据输入接触条件,仿真得到制动盘与摩擦片温度场的变化。仿真与试验的结果对比表明摩擦因数动态变化的接触模型能很好的模拟制动的实际工况。     

基于虚拟样机技术的行星齿轮传动系统分析

利用实体建模软件UG建立了减速器行星齿轮传动系统的虚拟样机,并利用UG与动力学仿真分析软件ADAMS,将虚拟样机导入到ADAMS中建立仿真模型。齿轮啮合中轮齿间除了滚动接触外还存在相应的滑动接触,使轮齿间具有较大的摩擦了,针对传统赫兹理论形成的齿面接触力计算没有考虑齿间摩擦,将摩擦系数引入计算,得到了齿轮之间的接触力曲线变化。应用UG NX的"高级仿真"模块,建立行星轮有限元模型,通过解算器NX NASTRAN对有限元模型进行分析求解,得到行星轮在接触力作用下应变和应力分布情况,再根据设计要求对零件参数进行优化,使行星轮的结构既满足设计要求,又达到体积小和成本低。     

料仓结构的有限元分析与优化设计

假定料仓内散体是服从Mohr-Coulomb屈服准则的理想弹塑性介质[1],散体与仓壁之间的摩擦属于Coulomb摩擦接触问题.通过ABAQUS有限元软件对料仓在静载作用下进行应力分析,将有限元分析的结果与实际测试结果相校核,在此基础上得到料仓的力学性能,进而优化设计.