闸瓦几何参数对制动尖叫噪声的影响

目的 研究车辆制动时闸瓦摩擦体与车轮踏面间摩擦力诱发的自激振动现象,获得抑制制动尖叫噪声的有效措施.方法 建立带踏面制动系统的车辆转向架模型,分别模拟了当闸瓦与车轮间摩擦系数(μ)为0、0.25、0.4时,闸瓦摩擦体与车轮踏面间接触力的波动情况.采用踏面基础制动装置有限元模型研究了闸瓦摩擦体宽度、磨耗程度和几何形貌对制动尖叫噪声发生趋势的影响.应用复特征值法对制动系统的稳定性进行分析,获得摩擦自激振动在频域上的分布情况.根据不稳定系数(TOI)判断系统发生尖叫噪声的可能性,TOI值越大,则系统发生尖叫噪声的趋势就越大.结果 踏面制动时,闸瓦与车轮间的摩擦力可能引起不稳定振动,导致尖叫噪声.随着闸瓦摩擦体宽度从75 mm增大到90 mm,制动系统的TOI值从4.226减小到2.819.在闸瓦摩擦体磨耗区间内(10～40 mm),相同磨损程度下,采用无缺口闸瓦摩擦体对应的制动系统TOI值均大于采用有缺口闸瓦摩擦体对应的制动系统TOI值.结论 在75～90 mm宽度区间内,闸瓦摩擦体宽度越大,制动系统发生尖叫噪声的趋势越小.相比有缺口的闸瓦摩擦体,无缺口的闸瓦摩擦体在制动时更易发生尖叫噪声,选用梯形缺口闸瓦摩擦体的制动系统发生尖叫噪声的可能性最低.

Effect of Brake Shoe Geometric Parameters on Squeal Noise

In order to study the phenomenon of the self-excited vibration induced by the friction force between the friction body of the brake shoe and the wheel tread when the vehicle brakes, a bogie model with a pad-wheel brake system is built by using Solideworks software. In Solideworks Motion, the fluctuation of contact force between the friction body of the brake shoe and the wheel tread is respectively simulated when the pad-wheel friction coefficient is 0, 0.25 and 0.4. The effect of the width, wear degree and the shape of the brake shoe friction body on the tendency of braking squeal noise is investigated with a finite element model of a pad-wheel brake system. The stability of this system is analyzed through the complex eigenvalue method in ABAQUS software, and the distribution of frication-induced self-excited vibrations within frequency domain is obtained. The occurrence propensity of brake squeal noise is evaluated on the basis of the instability coefficient TOI (Tendency of Instability). If the TOI value is greater, the squeal noise is more likely to occur. Results show that the frication force between the friction body of the brake shoe and the wheel tread can induce unstable vibrations, which are capable of leading to the formation of squeal noise. When the friction body width increases to 90 mm from 75 mm, the TOI value drops to 2.819 form 4.226, that is, the probability of the squeal formation decreases with the increasing friction body width of the brake shoe within that range. Meanwhile, the shape of the friction body has a distinct effect on the occurrence of squeal noise, the gap-free friction body is more likely to induce squeal noise than the friction body with the gap when it is braked, and the brake system using the friction body with the trapezoidal gap is the least likely to generate squeal noise.