Prediction of wheel squeal noise under mode coupling

Abstract

Wheel squeal vibration and noise amplitude under the effects of mode coupling and rising and falling creep behavior is investigated and predicted using an efficient analytical model. Based on previous research, a simplified modal dynamics model for wheel squeal noise amplitude is enhanced to include two coupled modes. Closed form analytical solutions for the vibration and squeal noise amplitude are determined under combined squeal mechanisms of full sliding falling friction and mode coupling. The analytical predictions are then compared with numerical time domain simulations of squeal vibrations with nonlinear creep and sound pressure level amplitude over a range of angle of attacks and contact angles for the inner and outer wheels in a curve. As an example, the effect of rail dynamics on squeal amplitude is quantified by comparing results with and without the mode coupling and the conditions and occurrences of stiffness and viscous mode coupling (where the stability is determined by the coupled structural complex stiffness, due to the closeness of the uncoupled modes, and damping, respectively) are clearly identified and quantified. The viscous mode coupling from the rail is shown to significantly reduce and/or eliminate conventional wheel squeal, for the inner and outer wheels, at higher contact angles defined by the friction coefficient. It can otherwise amplify (up to approximately 5 dB) or cause squeal, under high rail damping for the leading outer wheel. Conversely, it is shown that under only a small range of contact angles and closely matched uncoupled modes, stiffness mode coupling causes very high amplitude squeal beyond the scope of the simplified creep model. Rail mass and damping only models are shown to represent the occurrences of stiffness and viscous mode coupling, respectively, where the optimum amplitudes are dependent upon the complex stiffness and rail damping, respectively. The scope of the efficient analytical model is quantified and shown to be limited by excessive non-proportional damping and very high squeal amplitudes associated with reverse full sliding. The analytical model is shown to provide insight into the effects of mode coupling dynamics on wheel squeal noise amplitude and possibly help explain the enigma that squeal occurs seemingly unreliably in the field.