On the influence of contact tribology on brake squeal

Hetzler, Hartmut; Willner, Kai

doi:10.1016/j.triboint.2011.05.019

Cited by 54 publications

(27 citation statements)

References 19 publications

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“…The material of such a brake pad is a complex mixture of matrix and additives, which makes it hard to find reliable material data. Here E pad = 1.1 × 10 9 N m 2 and ν pad = 0.3 is used [5] and for the maximum shear stress τ max = σ y √ 3 = 20 × 10 6 N m 2 , where σ y = 35 × 10 6 N m 2 is the Yield strength of the graphite additives. The graphite wears off and acts as lubricant between the sliding part [6] therefore its properties are assumed to be the most relevant for the friction behavior.…”

Section: Contact and Friction Modelmentioning

confidence: 99%

“…Furthermore the plate is known to be much smoother than the pad, therefore it is modeled as a flat rigid surface [5]. For the simulation the pad with the rough surface is pressed against the flat rigid surface, see figure 2.…”

Section: Contact and Friction Modelmentioning

confidence: 99%

Section: Contact and Friction Modelmentioning

confidence: 99%

“…As an example the friction coefficient due to adhesion of a used brake pad is calculated here. The surface of a real pad has been scanned over an area of 5.556 × 5.556 mm 2 with n = 1779 × 1779 data points (for more information see [5]). The material of such a brake pad is a complex mixture of matrix and additives, which makes it hard to find reliable material data.…”

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Determination of a stochastic friction coefficient depending on a randomly rough surface

Gaus

Proppe

Hetzler

2012

Proc Appl Math and Mech

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The goal of this contribution is to calculate the the friction coefficient for a scanned surface of a worn brake pad. The data shows that the asperities can be approximated by paraboloids which allows to calculate the contact force and area with the Hertz contact model if the deformation is elastic. The friction force is calculated with the Bowden-Tabor approach which suggests that the friction force is the force to shear apart contacting asperities. This is considered to be the dominant friction cause in dry contact. To generate many surfaces with similar peak statistics the spectral decomposition is used. The friction coefficient and it's stochastic properties is calculated for these surfaces. Contact and friction modelFriction has many different reasons depending on the parameters of the involved bodies and the environment. Bowden and Tabor described in [1] that adhesion is often the dominant cause in dry contact. They suggested that the friction force is the one needed to shear apart connected contact spots. The friction force can therefore be calculated by the material's shear strength τ max times real contact area A c . To calculate the contact area A c the Hertz contact model is used within this contribution. Greenwood and Williamson used this model in [2] for their well known contact model. They suggested that a rough surface may be modelled as a set of parabolic asperities, whose peaks heights are described by a distribution function. On each of the summits, which at the peaks are considered to be spherical having the same radius of curvature, the contact area can be calculated with the Hertz contact formulation. As an example the friction coefficient due to adhesion of a used brake pad is calculated here. The surface of a real pad has been scanned over an area of 5.556 × 5.556 mm 2 with n = 1779 × 1779 data points (for more information see [5]). The material of such a brake pad is a complex mixture of matrix and additives, which makes it hard to find reliable material data. Here E pad = 1.1 × 10 9 N m 2 and ν pad = 0.3 is used [5] and for the maximum shear stress τ max = σ y √ 3 = 20 × 10 6 N m 2 , where σ y = 35 × 10 6 N m 2 is the Yield strength of the graphite additives. The graphite wears off and acts as lubricant between the sliding part [6] therefore its properties are assumed to be the most relevant for the friction behavior. The equivalent Young's modulus of the pad pressed against the plate can be calculated withFor the analytical contact analysis the surface data from [5] is used. First the summits are detected by finding the local maxima of the z-values. The curvature of the summits can be calculated by the inverse of the second derivative of the z-data on the summitsBecause the contact partner (brake disc) is known to be much stiffer the equivalent Young's modulus can be approximated as. Furthermore the plate is known to be much smoother than the pad, therefore it is modeled as a flat rigid surface [5]. For the simulation the pad with the rough surface is pressed against the flat rigid sur...

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Section: Contact and Friction Modelmentioning

confidence: 99%

Section: Contact and Friction Modelmentioning

confidence: 99%

Section: Contact and Friction Modelmentioning

confidence: 99%

mentioning

confidence: 99%

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Determination of a stochastic friction coefficient depending on a randomly rough surface

Gaus

Proppe

Hetzler

2012

Proc Appl Math and Mech

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“…However, researches focus more on the influence of mean value of friction coefficient and integral contact stiffness, and the heterogeneities of friction coefficient and contact stiffness are neglected. Some studies investigated the influence of heterogeneous contact stiffness on frictional squeal but heterogeneous friction coefficient was neglected [15]. This hinders further understanding of the mechanism of frictional squeal and reduced the prediction accuracy of frictional squeal frequency.…”

Section: Introductionmentioning

confidence: 99%

Influence of Heterogeneous Contact Stiffness and Heterogeneous Friction Coefficient on Frictional Squeal

Zhang

Meng

2018

Shock and Vibration

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Contact stiffness and friction coefficient are excitation sources and key influencing factors to frictional squeal with obvious inhomogeneous characteristic that is always neglected. In this paper, a multipoint contact flexible pin-on-disc system is established considering tangential stiffness. Then influence of contact stiffness and friction coefficient with heterogeneous distribution on frictional squeal is studied using the complex modal analysis. The research shows that contact stiffness and friction coefficient heterogeneities influence the likelihood of occurrence of the squeal, the frequency of the squeal, and the real part of the complex eigenvalue of the system. And when the contact stiffness and friction coefficient are close to the boundary of the region of modecoupling instability, flexible pin-on-disc system with homogeneous contact stiffness and friction coefficient cannot predict whether frictional squeal occurs or not. Besides, uncertain distribution of contact stiffness and friction coefficient can induce the uncertainty of brake squeal.

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Minimal model identification of drum brake squeal via SINDy

Wulff,

Gräbner,

von Wagner

2024

Arch Appl Mech

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The industrial standard in the design and development process of NVH(Noise Vibration Harshness) characteristic of brakes is the application of Finite Element(FE) models with a high number of degrees of freedom in the range of one or several millions. Nevertheless, parallel experimental investigations are still indispensable. On the other hand, minimal models with, due to the inclusion of the self-excitation process, at least two degrees of freedom are well known to be capable to explain qualitatively phenomena as instability of the desired non-vibrating solution or limit cycle oscillation but are in general very inaccurate in predicting the dynamics of a specific real brake. This is because the underlying physical assumptions are already too restrictive and model parameters (especially those referring to nonlinearities) are widely unknown. To overcome this problem, the data-driven modeling approach SINDy(Sparse Identification of Nonlinear Dynamics) is applied to identify appropriate nonlinear functions for a brake squeal minimal model. A problem thereby is the limited database. It turns out that the naive implementation of the method yielding the lowest possible residuum does not necessarily provide physically meaningful models and results, respectively. Instead, a constrained model that incorporates physical knowledge is used to robustly identify parameters and reproduce realistic dynamic behavior. Thereby, several appropriate models with coexisting limit cycles and stationary equilibrium are identified. In particular, it was found that the angular position of the brake drum has a significant influence on the model parameters and therefore must be taken into account in a model with long-term validity.

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On the influence of contact tribology on brake squeal

Cited by 54 publications

References 19 publications

Determination of a stochastic friction coefficient depending on a randomly rough surface

Determination of a stochastic friction coefficient depending on a randomly rough surface

Influence of Heterogeneous Contact Stiffness and Heterogeneous Friction Coefficient on Frictional Squeal

Minimal model identification of drum brake squeal via SINDy

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