Numerical and Experimental Evaluation of Brake Squeal

Proceedings of the Institution of …, 2011

The noise and vibration generated by the braking system in passenger cars are important technical and economic problems in the automotive industry. In recent years, the finite element (FE) method has been found to be a useful tool in predicting the occurrence of noise in a particular brake system during the design stage. This paper presents a more refined FE model of the disc brake corner that includes the wheel hub and steering knuckle. The model is an extension of earlier FE disc brake models. Experimental modal analysis of the disc brake system is initially used to validate the FE model. The unstable frequencies were then predicted by applying a complex eigenvalue analysis to the FE model. Finally, a number of structural modifications are made and simulated to evaluate brake squeal at the design stage. From the predicted results, it is found that the most significant improvements in brake squeal performance could be achieved by using an aluminium metal matrix composite brake rotor, steel calliper, and steel bracket. It is also found that a stiffer friction material with a diagonal slot could reduce the propensity for brake squeal.

Abstract-- It is well-known fact that automobile brakes generate several kinds of noises like squeal, groan, chatter, judder, moan, hum and squeak. Squeal is the most prevalent, annoying and can be reduced by variations in geometry, parameters such as coefficient of friction, stiffness of material. The brake squeal generally occurs in the range of 1-16 kHz. Basically, two methods are available to study the disc brake squeal, namely complex eigenvalue analysis and dynamic transient analysis. Complex eigenvalue analysis is the standard method used for squeal analysis. Analytically it is very difficult to solve because of complex brake mechanisms. Experimental and numerical techniques have been developed by various researchers in order to study brake squeal. Experimental techniques are unable to predict brake squeal at the early stages of design process and also very costly due to associated design iterations. Therefore, finite element analysis has emerged as a viable approach for brake squeal analysis. This work presents Finite Element modelling and modal analysis of disc-pad assembly using high end software tools. Linear non-prestressed modal analysis and full nonlinear perturbed modal analysis is applied to predict frequency at which squeal occurs. Real and imaginary eigenfrequencies of unstable modes are obtained. Analysis is performed by varying the coefficient of friction and outer diameter of disc-pad assembly. Increasing friction coefficient has no desirable effect on squeal frequency while squeal propensity decreases as the outer diameter of disc is increased.

Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2003

This paper presents a method for analysing the unstable vibration of a car disc brake, and numerical results are compared with squeal frequencies from an experimental test. The stationary components of the disc brake are modelled using many thousands of solid and special nite elements, and the contacts between the stationary components and between the pads and the disc are considered. The disc is modelled as a thin plate and its modes are obtained analytically. These two parts (stationary and rotating) of the disc brake are brought together with the contact conditions at the disc/pads interface in such a way that the friction-induced vibration of the disc brake is treated as a moving load problem. Predicted unstable frequencies are seen to be close to experimental squeal frequencies.

Squeal analysis of disc brake system continues to be a challenging issue in both industrial and academia due to its complexity and frequent occurrence. Thanks to rapid development of computational device and commercial software, finite element analysis becomes much more efficient and dominates the methods of analysis. Currently, two major FEA approaches are used in general, the transient analysis and complex modal analysis. Complex modal analysis studies the stability of the steady state system under small perturbation; if the vibration amplitude blows up, squeal may occur. Transient analysis is capable to study the vibration of the system during whole braking process. Frequencies of squeal are then calculated from Fourier transform. Particularly, nonlinearity, such as thermodynamic and wear effects could be included. In our case, a disc brake system for passenger car is modelled and analysed using both approaches. We use ANSA/META as pre/postprocessor and ABAQUS as solver. Furthermore, thermal effect is included in transient analysis. Results are compared and analysed in detail.

Latin American Journal of Solids and Structures, 2015

This research paper is concerned with the disc brake squeal problem for passenger cars. The aim of the present research is developing a finite element model of the disc brake assembly in order to improve understanding of the influence of Young's modulus on squeal generation. A detailed finite element model of the whole disc brake assembly that integrates the wheel hub and steering knuckle is eveloped and validated using experimental modal analysis. Stability analysis of the disc brake assembly is accomplished to find unstable frequencies. A parametric study is carried to look into the effect of changing Young's modulus of each brake components on squeal generation. The results of simulation indicated that Young's modulus of disc brake components play a substantial role in generating the squeal noise.

Mobility and mechanics, 2018

In addition to different kinds of pollutants emitted by the vehicles, noise can also negatively effect on human health. It does not only threaten drivers, but also people living near major intersections and roads, as well as roads where traffic-flow is high. One of the biggest problems of the vehicle is the noise that occurs in the braking process. Despite the large scope of research into the development of brake systems, there are still no reliable procedures during the development phase to evaluate the robustness of these systems with respect to friction-induced vibrations. Therefore, the identification of the modal properties by using experimental methods has become even more important. Experimental and numerical modal analysis of the venting disc with radial ribs was performed in this paper. This approach enables the determination of the natural frequencies of the brake disc, as well as the verification of results obtained by the numerical methods. Changes in modal properties-resonance frequencies and modal damping values due to variation in operating conditions were also analysed.

The International Journal of Acoustics and Vibration

This paper is concerned with the disc brake squeal problem of passenger cars. The objective of this study is to develop a finite element model of the disc brake assembly in order to improve the understanding of the influence of Young's modulus on squeal generation. A detailed finite element model of the whole disc brake assembly that integrates the wheel hub and steering knuckle is developed and validated by using experimental modal analysis. Stability analysis of the disc brake assembly is conducted to find unstable frequencies. A parametric study is carried out to look into the effect of changing Young's modulus of each brake's components on squeal generation. The simulation results indicate that Young's modulus of the disc brake components plays an important role in generating the squeal noise.

Vibration induced due to friction in disc brake is a theme of major interest and related to the automotive industry. Squeal noise generated during braking action is an indication of a complicated dynamic problem which automobile industries have faced for decades. For the current study, disc brake of 150 cc is considered. Vibration and sound level for different speed are measured. Finite element and experimentation for modal analysis of different element of disc brake and assembly are carried out. In order to check that precision of the finite element with those of experimentation, two stages are used both component level and assembly level. Mesh sensitivity of the disc brake component is considered. FE updating is utilized to reduce the relative errors between the two measurements by tuning the material. Different viscoelastic materials are selected and constrained layer damping is designed. Constrained layer damping applied on the back side of friction pads and compared vibration and sound level of disc brake assembly without constrained layer damping with disc brake assembly having constrained layer. It was observed that there were reduction in vibration and sound level. Nitrile rubber is most effective material for constrained layer damping.

Disc brake squeal noise is a very complicated phenomenon, which automobile manufacturers have confronted for decades due to consistent customer complaints and high warranty costs. In recent years, the finite element method (FEM) has become the preferred method due to high hardware costs of experimental methods. In this study, a simplified model for the disc brake is presented using the ABAQUS/Standard finite element software. The analysis process uses a nonlinear static simulation sequence followed by a complex eigenvalue extraction to determine the squeal propensity. The effect of the main operational parameters (braking pressure, and friction coefficient) on the squeal propensity is performed. The influence of changing the rotor stiffness and back plates stiffness under different operation condition are investigated. The results of this analysis show that the squeal noise can be reduced by increasing the rotor stiffness and decreasing the back plate stiffness of the pads.

In this paper we consider the problem of disc brake noise, an unstable behaviour that occurs in disc brakes due to particular vibratory phenomena. The most obvious phenomenology is the product wheezing during braking. The numerous researches carried out have not yet reached satisfactory results for knowledge. There was a total of high frequency squeal, which depends only on the characteristics of the disc and not by brake complete. Finite element method is applied to achieve modal analysis; a linear model was developed noting that to eliminate or reduce brake noise it is necessary that the ranges of calliper-disc frequencies modes do not overlap. The modal analysis of the runway braking is a good starting point but is not the only approach possible because the phenomenon of brake squeal depends on many other factors that make it quite complex.