Experimental and Numerical Modal Analysis of Brake Squeal Noise

It is widely known that a typical brake system works by mitigating vehicle kinetic energy and transforming it into thermal energy, ultimately leading to energy dissipation. The main concerns related to this kind of system are: 1) low frequency vibration energy propagating throughout the vehicle structure when the system begins its unblocking action; and 2) high frequency vibration energy propagation which induces undesirable noise levels. Modal analysis of the system can provide important information about its vibration characteristics. Provided that coupling between the dynamic behavior, the pre-stress caused by the applied load, and friction characteristics will certainly occur, it is required that analyses be performed on the entire assembly. As such, this paper presents evaluation of a brake disc system regarding the brake squeal using finite element method comparing with experimental assessment.

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.

Disc brake squeal is considered as one of the major problem in NVH sector in automotive industries. The instability generated in disc brake system is mainly due to coupling of free modes of the disc rotor and brake pad. To evaluate instability, complex modal analysis is applied numerically in Ansys. A brief parametric study is done to analyze the effect of operational and material parameters in generation of instability. To validate the numerical analysis experimental modal analysis is performed. Ten different modifications were studied numerically so as to reduce the instability. A suitable modification was chosen based on numerical simulation and was modified for experimental validation. Squeal tests performed in experimental analysis also evaluate the reduction of squeal noise between unmodified disc brake system and modified disc brake system.

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.

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 …, 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.

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.

It is well-known that automobile brakes can generate several kinds of noises. Among them is squeal, a noise in the 1-15 kHz range. It is commonly accepted that brake squeal is initiated by instability due to the friction forces, leading to self excited vibrations. To predict the onset of brake instability, a modal analysis of the prestressed structure can be performed on an improved dynamic finite element model of ventilated disc brake with friction coupling. An unsymmetric stiffness matrix is a result of the friction coupling between the brake pad and disc; this may lead to complex eigenfrequencies. The complex eigenvalue method (Unsymmetric solver) used to analyse mode shapes associated with the predicted natural frequency. Creating the element of Matrix27 between the ventilated disc and pad was very important in studying the squeal of the coupled ventilated disc brake. The results demonstrated that the FEM for the coupled ventilated rotor and pad showed a good interaction between...

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.

In the last few decades, there have been extensive studies on analysis and investigation of disc brake vibrations done by many researchers around the world on the possibility of eliminating brake vibration to improve vehicle users' comfort. Despite these efforts, still no general solution exists. Therefore, it is one of the most important issues that require a detailed and in-depth study for investigation brake noise and vibration. Research on brake noise and vibration has been conducted using theoretical, experimental and numerical approaches. Experimental methods can provide real measured data and they are trustworthy. This paper aims to focus on experimental investigations and summarized recent studies on automotive disc brake noise and vibration for measuring instable frequencies and mode shapes for the system in vibration and to verify possible numerical solutions. Finally, the critical areas where further research directions are needed for reducing vibration of disc brake are suggested in the conclusions.