Abstract
This paper investigates the influence of the wheel vertical dynamics in the mechanism of squeal noise on a scaled test bench. To this purpose, sustained oscillations are first studied on a single degree of freedom oscillator, considering both a decreasing slope of the friction curve and a vertical excitation. Their relative importance to sustain the oscillations is discussed. Then, a mathematical model of a quarter scale test bench is developed in the frequency domain. Using this model, it is shown that the squeal noise resulting from the excitation of the bending modes of the wheel is sustained because these bending modes are associated with variations of the vertical contact force. Results are further confirmed by experiments conducted on a scaled test bench.
Highlights
The first squeal noise models have been developed in the seventies [18]
The motivation of this paper is to investigate the influence of the vertical dynamics of the wheel on the fluctuations mentioned above
The influence of the wheel vertical dynamics in the mechanism of squeal noise has been studied in this work
Summary
The first squeal noise models have been developed in the seventies [18]. The basic mechanism of squeal noise is a variation of the lateral creep force between the wheel and the rail, due to a frictional instability. There exists two means to get sustained oscillations with an oscillator: either by a decreasing slope of the creepage-creep force phenomenological law, or by a variation of the vertical force applied to the moving mass. In the former case, the motion of the belt is transformed into self excited vibrations of the mass. This explains why sometimes, squeal is recorded without any measurable decreasing slope of the friction law. The combination of these two mechanisms, discussed in [9,20] on single d.o.f. oscillators, is probably the most credible scenario of squeal noise in many cases
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