空调转子压缩机摩擦噪声的有限元分析

为探讨空调转子压缩机摩擦噪声的产生机制,提出一种利用有限元软件对空调压缩机相关摩擦副进行摩擦噪声预测的方法.利用复特征值分析法对空调转子压缩机摩擦系统的有限元模型进行模态分析,获得摩擦系统的固有频率以及相应振型的变化特性,据此推断可能导致摩擦噪声的频率.有限元模型计算结果与实测数据具有很好的一致性,验证了该预测方法的有...     

摩擦噪声系统的振动特性研究

建立了一个往复滑动摩擦系统1∶1实体装配模型,采用有限元方法对该系统的振动特性进行研究,获得了系统的自然频率和振动模态。将得到的系统振动频率与系统的试验噪声的频率进行比较,发现它们的一些结果有很好的一致性。对系统的计算模态分析显示,发生噪声的模态同时具有切向和法向振动特征。     

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.     

降低制动摩擦振动的制动器结构拓扑优化设计

本文建立起某车型盘式制动系统三维有限元模型,分析了该制动系统的摩擦振动噪声特性,并基于ABAQUS/Optimization模块对该制动系统进行结构拓扑优化设计,在满足轻量化的目标要求下改善摩擦振动噪声问题.结果表明:制动系统在摩擦力作用下可能出现四种振动模态,且产生频率为3632.4 Hz的振动噪声的倾向和强度最大.产生该频率摩擦振动噪声的原因是由于制动钳的第4阶模态频率与制动盘的第11阶模态频率非常接近,在摩擦力作用下容易产生共振.通过对制动钳进行结构拓扑优化设计,移除制动钳两侧区域的材料,使其在满足重量最小的目标前提下将第4阶模态频率降低到2804 Hz,从而避免与制动盘发生共振,且制动钳的重量减轻了17.1％.进一步采用复特征值分析对结构优化后的制动系统进行摩擦振动噪声特性预测,结果表明制动系统仅有两组相邻模态出现模态耦合现象,且原始制动系统出现的3632.4 Hz的振动噪声频率已经消失,制动系统摩擦振动噪声问题得到显著改善.     

摩擦尖叫噪声有限元预测分析的可靠性研究

使用相同的制动系统,分别建立了基于ABAQUS和NASTRAN的制动摩擦尖叫噪声有限元预测分析模型.基于ABAQUS的摩擦尖叫噪声模型利用接触耦合关系计算法向力,不需要在接触界面假设接触弹簧.基于NASTRAN的摩擦尖叫噪声模型根据罚函数法计算法向力,需要在接触界面假设接触弹簧.比较了这2种模型的计算结果,发现即使这2个模型采用相同的有限元网格,计算预测到的不稳定频率(即实部为正的复特征值虚部)通常不同,且NASTRAN建模方法只能部分预测到中高频尖叫噪声.计算结果显示,当接触弹簧刚度大于等于3.2×109 N/m时,NASTRAN模型的预测结果基本相同;有限元网格尺寸和单元类型对计算结果也有较大的影响.     

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.     

滑动摩擦振动噪声的非线性显式动力学分析

利用有限元软件ABAQUS/Explicit(显式动态求解器)对球-平面接触条件下的滑动摩擦振动噪声进行了数值模拟分析。对比试验结果,探讨了摩擦噪声的发生机制,并分析了摩擦噪声发生时接触界面的运动特性。结果表明,摩擦噪声主要是由摩擦系统的自激振动引起的,法向振动与切向振动的耦合是系统产生自激振动和摩擦噪声的一个重要因素。当摩擦系统发生自激振动时,从面节点与主面的接触并不是连续不变的,两者在相对运动的过程中具有黏着-滑动-分离-黏着的特性。     

基于盘-销系统的摩擦尖叫条件下的动态时滞摩擦特性分析

为研究摩擦副间摩擦特性,建立盘-销模型台架试验系统,采用三向力传感器在发生和不发生摩擦尖叫条件下测量摩擦接触作用力,并利用小波分解方法将摩擦接触力分解为准静态分量和动态分量;在此基础上提出摩擦因数传递函数的概念,进行传统摩擦因数和新摩擦因数传递函数的计算与分析.对比分析发现:在系统发生摩擦振动或者噪声的条件下,采用摩擦因数传递函数评价摩擦特性更加合理.研究结论有助于深化摩擦因数特性的认识以及摩擦振动和噪声发生机理的研究.     

水润滑引起摩擦噪声的机制及实验研究

水润滑摩擦噪声是一种较为常见的现象,会影响产品性能和环境舒适性.分析水润滑引起的摩擦因数一速度特性与摩擦振动系统稳定性的关系,对橡胶块与玻璃片的水润滑摩擦噪声进行实验研究.结果表明:水润滑引起的摩擦特性对系统具有负阻尼作用,当系统等效阻尼为负时,系统失稳,形成摩擦自激振动,是产生水润滑摩擦噪声的根源;摩擦元件的固有频率决定摩擦噪声频率,不同的支撑方式会改变系统模态频率,从而影响摩擦噪声频率.     

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。     

Numerical study of friction-induced vibration and noise on groove-textured surface

A numerical study was performed to predict the squeal instability when a sphere sliding on a groove-textured surface through complex eigenvalue analysis, which was discussed with the experimental results. It is shown that the friction system had a propensity to cause squeal instability. Mode coupling was found when squeal occurred. The calculated dominant frequency of squeal was close to the experimental measured one. The numerical model created can be used to predict the squeal instability of the friction system. Sphere sliding along groove showed potential in reducing squeal instability compared to the case of sphere sliding across groove.     

Experimental investigation into squeal under reciprocating sliding

Experiments on squeal under reciprocating sliding were performed by means of a ball against a block. Vibration accelerations, sound pressure level of squeal and tangential force were measured simultaneously. Under certain test conditions, the reciprocating sliding can create a whole process from squeal generation to disappearance. Based on power spectral density (PSD) and short-time Fourier transform (STFT) analyses on the vibration accelerations in that process, it was found that the dominant frequencies of the friction-induced vibrations associated with squeal is not varied. Examination of the friction–velocity slope shows that there is no invariable correlation between the negative friction–velocity slope and occurrence of squeal. Squeal can occur in regions with both negative and positive friction–velocity slopes.     

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.     

旋转滑动摩擦高频噪声产生机理的实验研究

为了深入研究金属旋转滑动摩擦高频噪声的产生机理,以多功能摩擦磨损试验机为平台,采用单因素实验法来研究相对滑动速度、接触压力、表面形貌等影响因素对摩擦高频噪声的影响规律。实验发现：金属旋转滑动高频摩擦噪声多发生在相对滑动速度低、接触压力较大以及摩擦因数-速度负斜率处;摩擦副间相对滑动速度、接触压力和表面粗糙度的变化几乎不会对高频噪声的频率产生影响,但高频噪声声压级随表面粗糙度的增大呈现明显减小趋势。对摩擦噪声声压信号和法向、切向振动加速度信号进行互相关分析,结果表明,法向振动加速度信号和摩擦噪声声压信号之间具有更高的相关性,从而为进一步理解摩擦高频噪声的产生机理和预测模型的建立提供了参考。     

摩擦系数影响摩擦噪声发生的机理研究

结合摩擦系数测量和磨痕表面形貌的观察，认为摩擦力的波动成分是引发摩擦噪声的主要机理。对于往复滑动过程，在摩擦系数一往复循环次数的关系图上一般有一个驼峰状的变化。应用Suh的理论，说明了在摩擦系数的驼峰状上升沿靠顶部的地方既是摩擦力接近最大值，又是摩擦力波动最激烈的地方，因而在这地方很容易出现摩擦噪声。     

沟槽和圆坑织构抑制摩擦尖叫噪声研究

在列车制动盘试样表面加工出不同宽度的发散型沟槽织构和不同直径与间距的发散型圆坑织构后,将其与光滑表面进行摩擦噪声对比试验,并利用数值分析方法进行模拟分析,研究织构表面对摩擦尖叫噪声特性的影响及作用机理。结果表明,两种织构表面均能降低摩擦系统高频尖叫噪声,且尺寸分布合理的沟槽织构能明显地抑制噪声的产生。利用数值分析方法能较好地揭示织构影响界面摩擦噪声的机理,即对摩材料滑过织构表面并碰击其棱边时,所产生的作用力能起到主动控制界面摩擦噪声的作用,且能抑制某些特定频率的尖叫噪声的产生。     

基于小波变换的摩擦噪声激励源的研究

在往复滑动试验机上作了金属摩擦噪声试验,试验期间同时测量了摩擦噪声、摩擦振动三维加速度和名义摩擦力等动态信号,这些信号含有与摩擦振动激励源有关的信息。应用小波变换技术对这些信号进行了分解,在对应摩擦振动主频的小波分解细节分量中,可以清楚地看出激励摩擦振动的摩擦力动态分量,从而说明了摩擦噪声是由波动变化的摩擦力所引发。     

Friction-Induced Vibration by Stribeck’s Law: Application to Wiper Blade Squeal Noise

This paper is concerned with the squeal noise of a wiper/windscreen contact. It is shown that squeal noise stems from friction-induced self-excited vibrations in the context of Stribeck’s law for friction coefficient. The study is specifically focussed on the instability range of velocities and not on the amplitude of limit cycles. The studied dynamic system consists of a single degree-of-freedom mass-spring-damper oscillator submitted to a velocity-dependent frictional force which follows the Stribeck law. The local stability is analyzed by the first Lyapunov method and results in a stability criterion. Experiments have been performed on a glass/elastomer contact lubricated with water. The tribometer ‘LUG’ provides measurements of the vibrational velocity and friction force versus sliding speed. It is found that the instability appears during the transition between boundary and elastohydrodynamic regimes where the negative gradient of the friction versus velocity curve is steep. The apparition and vanishing of instability are correctly predicted by the steady-state stability criterion.