Brake squeal analysis by coupling spectral linearization and modal identification methods

Brake squeal is induced by self-excited vibrations, consequences of local nonlinearities at the contact interface. This paper deals with a new way to analyze the brake squeal behavior. The proposed method is based on a spectral linearization of the brake nonlinear dynamic response with unilateral contact and friction conditions. The approach enables to identify modal parameters of an equivalent linear system by a combination of the random decrement technique and the Ibrahim time domain method. It is applied to the analysis of a pad/beam squealing contact. The obtained results are compared to the classical complex eigenvalues analysis and nonlinear temporal dynamic finite element analysis ones.     

闸片沟槽织构对盘式制动尖叫的影响

为研究制动闸片沟槽织构对盘式制动系统制动尖叫的影响,基于摩擦自激振动理论,建立盘式制动系统普通闸片和沟槽闸片有限元模型,采用复特征值分析法研究该盘式制动系统的摩擦自激振动特性。利用该有限元模型开展沟槽的宽度和深度的参数化分析,获得其对制动尖叫的影响规律。结果表明：制动闸片与制动盘间的摩擦自激振动是导致制动尖叫发生的主要原因,沟槽型闸片对抑制制动尖叫具有明显效果;当闸片沟槽深度在5~20 mm区间内,盘式制动系统的稳定性随沟槽深度的增大而呈现逐渐降低的趋势,表明沟槽深度越小,发生摩擦自激振动的可能性越小;在沟槽宽度5~20 mm范围内,随沟槽宽度的增大,盘式制动系统的稳定性先增大后降低,在沟槽宽度为10 mm时,系统发生制动噪声的可能达到最大。     

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。     

Evaluation of Disc Brake Materials for Squeal Reduction

A nontraditional evaluation tool is introduced to examine the effects of different materials, in practical applications, that are used in fabricating disc brake components for commonly used or special requirements such as heavy-duty performance and racing cars. As an extension to earlier finite element (FE) disc brake models, a detailed FE model of the whole disc brake corner that incorporates the wheel hub and steering knuckle is developed and validated using experimental modal analysis. Stability analysis of the disc brake corner using the finite element software ABAQUS is carried out to predict squeal occurrence also taking into account the negative and positive damping effects and friction material real surface to increase the accuracy of prediction. A Taguchi method–based design of experiment is used to better assess the contributions of different materials and its interaction effects for effective reduction of brake squeal. The results showed that the pad friction material contributes 56% to the total system instability (squeal generation). The rotor material contributes 22% of the system instability. Caliper and bracket materials participate 11 and 11%, respectively.     

盘式制动器的结构场有限元分析

首先探讨盘式制动器在制动过程中的摩擦接触和非线性动力学问题.具体的分析方法包括:摩擦接触算法,非线性有限元方法.按照制动盘与摩擦片的实际几何尺寸,建立了具有速度可变效应的三维瞬态结构应力有限元模型,利用非线性有限元方法,较真实地模拟了制动器的制动过程.通过以上分析得出制动过程的一些结构上的性能变化.将同相同制动条件下的实心盘式制动器和通风盘式制动器对比,得出通风盘式制动器在制动过程中的接触应力,各向位移等.     

采用全联热-机械有限元模型计算盘式制动器尖叫声的预测工具(二)

本文提出一个制动器尖叫模拟的新的综合方法,它集中开发采用全考虑制动器结构响应热负荷的影响的正确的热-机械有限元模型.该综合研究包括实现与时间有关的非线性接触和全联瞬态热分析,在进行不稳定研究前,采用复杂固有值技术,提供在制动器内的接触和温度分布.其结果依次通过制动全部系统固有值证实制动尖叫性质的变化.     

A numerical investigation into the squeal instability: Effect of damping

Between the NVH issues, brake squeal is a harmonic acoustic emission (between 1 and 20 kHz) caused by friction induced vibrations. The onset of squeal is due to an unstable behaviour of the system leading to limit cycle vibrations. A general approach used by several authors to determine the system instabilities is the CEA: Complex Eigenvalues Analysis. This work presents a numerical investigation into the squeal instability on a simplified disc-brake system addressed to analyse the effect of damping on the squeal instability.The mode lock-in instability is reproduced by a parametrical analysis. The relationship between the distribution of damping on the system components and the propensity of the brake to develop squeal is investigated. The numerical results are validated by the experimental ones, presented in a previous work. The behaviour of the system eigenvalues highlights that, while a homogenous distribution of damping stabilizes the system, a non-uniform repartition of damping can increase the squeal propensity.     

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.     

鼓式制动器振动与啸叫的研究

对于干摩擦引 分析汽车制动啸叫噪声,提出了鼓式制动器啸叫时振动的特性仅取决于制动鼓和蹄征 的观战建立了一种三种解析模型,用以分析制动鼓的固有模态及其稳定性,判 断动器是否发生啸叫。理论分析和试验结果吻合良好,表明该方法具有足够的准确度和工程实用性。     

Analytical formulation of mode-coupling instability in disc-pad coupled system

This paper describes the mode-coupling-type squeal mechanism in a disc brake system. The mode shapes of a disc and a brake pad (an annular sector plate) are obtained using the component eigenvalue analysis and the Rayleigh-Ritz method, respectively. The disc-pad coupled system subject to friction-couple is discretized by the truncated set of system component modes. Mode-coupling instability is determined in closed form resulting from a reduced-order friction-coupling model, which subsequently defines the modal stability index. The proposed index parameter determines the necessary condition for flutter instability without solving system complex eigenvalues. The numerical investigation shows that the disc-pad modal interaction has a strong squeal tendency when two pads are not identical.     

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。     

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.     

汽车盘制动器优化设计热和机械特性的研究(一)

由于热量集中于制动盘的表面造成热弹不稳定性(TEI)而引起热变形.这样可能发生大家知道的低频强烈振动.因为在盘和衬块的接触面间的摩擦系数变化,在摩擦衬决发生尖叫声.通过对热聚集和尖叫现象的联合分析,对高热和机械特性可设计一最佳的盘和摩擦衬块.本文同时考虑了热和机械不稳定性按照盘的厚度,卡钳的加压方式,衬片弧长进行了数值...     

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。     

Advanced Friction–Wear Behavior of Organic Brake Pads Using a Newly Developed System

The objective of this study was to investigate the influence of an advanced performance system on the tribological behavior of brake pad material using a specially designed brake pad tester system following standard SAE J-661. The tribological behavior and friction and wear characteristics of the organic brake pad samples were evaluated. During braking tests, the samples, in contact with a cast iron disk, were studied at different disc speeds, temperatures, and braking cycles under a constant pressure. In order to understand the friction and wear behavior, the unworn surfaces, worn surfaces, and wear debris were characterized by means of scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). Furthermore, the surface characteristics and differences in the wear modes of the brake pad samples were examined. Wear debris was permitted to deform the brake pad surfaces, leading to friction layers and enabling the estimation of the friction behavior of the brake pads. The results showed that the best friction–wear behavior was obtained with lower braking cycles at low speeds and temperature. Thus, the newly developed brake pad tester system proved very effective in evaluating the performance of the brake pad samples.     

On the dry and wet sliding performance of potentially new frictional brake pad materials for automotive industry

In this work, dry and wet continuous sliding performances of newly developed four different non-commercial frictional brake pad materials (NF1, NF2, NF4, and NF5) were evaluated and compared with other two chosen commercial brake pad materials (CMA and CMB) using a small-scale tribo-tester of pad-on-disc type.Results showed that under dry continuous braking, friction coefficients for all non-commercial brake pad materials including the CMB were insensitive to the type of brake pad materials. In addition, all brake pad materials showed a slight increase in the friction coefficients (5–19%) with increasing pressure or speed. Meanwhile, the wear rates were substantially dependent on the type or ingredient of brake pad materials and the pressure. Conversely, under wet sliding condition, the friction coefficients were decreased by a factor of 2. Moreover, no evidence of HD water film could be evidenced as the measured friction coefficient values were in the order of dry friction. Thus, the wet results suggested that the friction behaviour was influenced by factors other than HD film, and the values of friction coefficient were in the range of dry friction, mixed and boundary lubrication friction. Qualitative assessment of the SEM morphologies of brake pad surfaces showed that tribofilms were easily formed in dry braking and hardly formed in wet braking. Besides, all brake pad rubbing surfaces showed contact plateaus “patches” and disintegrations of various sizes and locations depending on the braking condition. Furthermore, the removal of material was associated with either mechanical crushing action performed by entrapped wear debris or due to disintegration of plateaus which were accelerated by spraying the water.     

Finite element modeling for stick-slip pattern of squeal modes in disc brake

This paper provides the finite element modeling for describing the nonlinear stick-slip response of squealing modes in a disc brake system. The analytical nonlinear contact kinematics is applied to each contact node of the finite element disc and pads. Numerical results show that a portion of the contact area can undergo the stick-slip oscillation. Depending on the size of the stick-slip zone, the corresponding squeal vibration can be either the pure harmonic or periodic oscillation. Particularly, the squeal mode arising from the pad rigid mode generates the periodic stick-slip limit cycle in its steady-squealing response, as opposed that the disc squeal modes become the pure harmonic response.     

盘式制动器中热问题的研究概况

摩擦热是影响摩擦副材料性能变化的最直接因素。过高的摩擦热不仅使摩擦副材料的摩擦学性能发生变化,而且导致热弹性不稳定性（TEI）、局部过热点现象等发生,制动盘发生热变形。目前研究认为,热弹性不稳定性是制动器发生热颤振和噪声的主要来源,最终可能导致制动器过早失效。本文针对这些方面的研究进行了综述,最后进行总结并对未来研究工作提出了展望与建议。     

摩擦副组合对摩擦磨损性能的影响

在1：1惯性力矩制动试验台上研究了两种不同石墨形态的铸铁制动盘与两种混杂纤维增强的酚醛基制动闸片配副时的摩擦磨损性能。结果表明，对于某一配方的制动闸片，使用灰口铸铁盘的摩擦副具有较高的摩擦系数，但制动盘表面温度较高，闸片磨损量较大；对于某一种制动盘，使用B配方制动闸片时，制动盘表面的温度较高，但闸片的磨损量较小；在所有四种组合中，B配方制动闸片与灰口铸铁盘配副的瞬时摩擦系数能够完全满足有关技术要求。     

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。