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Finite element simulations are widely used for simulating disc brake squeal and the aim of this paper is to further increase the understanding of the effect of insulators. An earlier paper has presented an experimental technique for measuring the properties of the viscoelastic materials [1] and it has been shown how these data can be used in simulating brake response [2]. This paper deals with the sensitivity of a FE brake model to frequency dependent shim material properties and it is documented that with the current options for modeling shims in complex eigenvalue analysis it is only possible to accurately simulate response in a narrow frequency range. A procedure to find optimized parameters for a current damping model is discussed. The best α and β values for a Rayleigh damping model is found by obtaining a least square best fit in a frequency range of interest.

Brake squeal is a self-excited vibration caused by the dynamic instability of the brake system. Extensive research effort has been undertaken on understanding and elimination of brake squeal. However, due to the complexity of the brake system and the fugitive nature of the phenomenon, there is no systematic prevention method. Brake squeal continues to be a major warranty cost to automotive OEM and suppliers. Complex eigenvalue analysis is a widely used analytical tool to tackle brake squeal. In this paper, based on this method, a new approach combining component contribution and eigenvalue sensitivity analysis is proposed for brake squeal. The modal contribution factor is used to quantify the influence of different real system modes on the unstable mode. The real system modes are projected in component mode sub-vectors to identify the most contributing components.

Brake moan has been mostly problematic with rear drive axle assemblies. The moan phenomena exhibits itself as a low frequency chassis vibration accompanied with uncomfortable noise level both inside and outside the vehicle compartment. It is a classic example of the friction induced vibration caused by the stick-slip effect at the interface of brake rotor (or drum) and pads (or shoes). In referencing to an on-going moan investigation, this paper utilizes analytical tools, encompassing multi-body dynamics and finite element analysis, in understanding the moan mechanism and potential solutions to eliminate moan. The area of interest would be to focus on the interaction of subsystems, i.e. axle assembly subsystem and brake assembly, that are coupled by the friction. Case studies are presented in utilizing the proposed analytical tool

Noise and vibration related functional characteristics of the disc brake has, for a long time, been the nemesis of the design engineer's existence. New methods of measurement and analysis techniques are providing information which improves the practical assessment of a disc brake design and improves the basic understanding of noise and vibration operational aspects. Utilization of these new techniques make undesirable roughness prediction more feasible and potential solutions more rapidly identifiable. Development of these new measurement methods involved the measurement of in-stop torque variation and rotor thickness variation (TV), as well as rotor total indicated runout. Detailed analysis of the torque variation signature of vehicle and dynamometer data indicates significant differences. These differences are shown to be influenced by vehicle suspension resonant characteristics and (in-stop) changes to both lining and rotor mechanical characteristics.

High frequency brake squeal is often suppressed by applying an insulator to the shoe plate of the pad. This may increase the damping and change the coupling conditions in a favorable way, but detailed knowledge about which of the several effects of insulators that are most important is not at hand. A joint effort is needed to increase the understanding of the effects of insulators. This paper describes a new way of measuring the shear stiffness and damping of insulators. The method can be used to measure either the individual layers in an insulator or the complete insulator that is build up of several layers. The method does not rely on the resonant behavior of a structure and it therefore allows for measurements of the parameters over a wide frequency range. The measurement setup can be placed in a temperature chamber and this allows the parameters to be measured over a wide temperature range.

This paper applies the existing techniques used in the CAE simulation for calculation of potential high frequency (>10 kHz) squeal from disc brake system. The goal is to investigate the component interaction at the system level. A simulated dynamometer process is developed using stability analysis at different pressures and friction coefficient combinations. From the identified squealing condition, coupled with measured ODS, dynamic characteristics at system level are tracked to the components contribution based on the mode merging phenomenon as the system turns unstable due to friction coupling. The component contribution is based on the strain energy of the component in the system mode and MAC between mode components in free condition and system real modes. Special focus on rotor dynamics is discussed and its effect on system instability at high frequency range.

This two-part paper provides a systematic approach for identifying the fundamental causes of both low and high frequency brake squeal using advanced analytical and experimental methods. Also shown are methods to develop solutions to reduce or eliminate squeal by investigating effective structural countermeasures. Part I presented here is focused on low frequency squeal (2.2 & 5.5 kHz). In order to better understand the mechanism of squeal generation, this study started with the component modal alignment analysis around problem frequencies based on the component EMA (Experimental Modal Analysis) data in free-free condition. Then, the brake system EMA was conducted to gain insight into the potential system modes which caused the squeal. The last step of the brake squeal diagnosis utilized the ODS (Operational Deflection Shape) result to identify the key components involved in the squeal event.

Disc brake squeal is a very complicated phenomenon, and the influence of insulators in suppressing squeal is not fully understood. The aim of this paper is increase the understanding of the effect of insulators. A previous paper [1] presented an experimental technique for measuring the frequency- and temperature- dependent properties of viscoelastic materials currently used in insulators. The present work continues by considering the coupled vibrations of the brake pad and insulator. A comparison of natural frequencies found from experimental modal analysis and finite element modeling indicates agreement to with 5%. Experimentally determined modal loss factors of the brake pad vary dramatically with frequency, changing by a factor of 2 over the frequency range 2-11 kHz. A method for including this frequency dependence, as well as the frequency dependence of the insulator material, in state-of-the-art finite element software is proposed.