Model Approach for a Load and Frequency Dependent Stiffness in Friction Materials

Wegmann, Enrique; Stenkamp, Axel

doi:10.4271/2011-01-2352

Cited by 4 publications

(3 citation statements)

References 5 publications

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“…The viscoelastic-plastic material behaviour leads to a stress level dependent dynamic stiffness [9]. The experimentally determined relationship between the dynamic stiffness and the stress level, as shown in Digure 4 is implemented phenomenologically in a UMAT.…”

Section: Stress-dependent Dynamic Stiffnessmentioning

confidence: 99%

“…The determined degradation of the dynamic stiffness is used to describe the stiffness degradation as shown in [8] for the meso level within the finite element (FE) simulation to analyse the stress redistribution effects for a given fibre orientation distribution through the thickness. Based on viscoelastic-plastic effects, the dynamic stiffness is dependent on the load level [9]. For the investigation of the stress redistribution mechanisms, a complete description of this non-linear material behaviour is simplified.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of local stress redistribution effects in short glass fibre-reinforced thermoplastics during fatigue using mesomechanical simulations

Schmohl,

Çelik,

Dahlmann

et al. 2023

Preprint

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Injection moulded short fibre-reinforced thermoplastics (SFRT) consist of a layer structure of different fibre orientations. As a result, the material’s stiffness and strength properties are highly anisotropic across the part and through the thickness. This study investigates the stress redistribution between layers with transverse and parallel fibre orientation caused by fatigue loading. For the analysis, fatigue data obtained from homogeneous highly oriented specimens are used to avoid layer interactions. The degradation of the dynamic stiffness of the meso plane acquired during the tests is implemented in a finite element (FE) model. Homogenisation methods for the fibre-matrix system are applied to describe the orthotropic layer stiffness. The study reveals stress redistributions from layers with transversely oriented fibres to layers with parallel fibres in relation to the load direction. The magnitude of the redistributed stresses in the simulated composite is small in relation to the quasistatic strength with a maximum amount of 0.26%.

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Section: Stress-dependent Dynamic Stiffnessmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Analysis of local stress redistribution effects in short glass fibre-reinforced thermoplastics during fatigue using mesomechanical simulations

Schmohl,

Çelik,

Dahlmann

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

“…Linking the material properties to the dynamic behaviour during braking is a complex problem, and many studies have been made to study the dependences of the loading and the frequency on the brake pads as Wegmann and Stenkamp 2 or Sanders et al 3 showed. Hornig and Von Wagner 4 analysed the stiffness dependence on the static and dynamic loading and observed that the preload has a large influence on the stiffness.…”

Section: Introductionmentioning

confidence: 99%

Stiffness distributions of brake pad friction materials using static and dynamic measurement techniques

Ramasami

Rejdych²,

Chancelier³

et al. 2015

Proceedings of the Institution of Mechanical Engineers, Part D:

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The elastic properties of a friction material play a significant role in the vibro-acoustic noise, vibration and harshness behaviour of braking systems on a structural scale. Common testing, such as pad compressibility testing and modal testing, allows identification of the global static and dynamic elastic properties respectively, which generally provide data for finite element numerical models. The present investigation presents static and dynamic testing methodology and focuses on the distribution of the elastic properties of friction materials on a pad scale. Besides trying to determine a correlation with bench testing, the added value in updating friction material models with distributed elastic properties for squeal simulation models is evaluated. For investigation of the distribution of the friction material properties of brake pads, quasi-square friction samples of friction materials were collected from several locations of the pad. The experimental meshing provides data on the inner radius and the outer radius of the brake pads as well as on the inlet and the outlet of the pad. For the purpose of this study, six different materials were tested. In addition to four known prototype friction material formulations obtained using the same production process, two commercial friction materials were investigated. The static stiffness is evaluated with a laboratory compression machine set-up whereas the dynamic stiffness is identified from laboratory ultrasonic investigations. The results and coherence of the static and dynamic stiffness distributions obtained by both approaches are compared. The trends with the noise, vibration and harshness bench testing results are also discussed for selected pads. From ultrasonic testing, it is found that the dynamic stiffness distribution can take several forms (flat, concave or convex) which can be different for the in-plane stiffness and the normal stiffness of the pad. It is mainly noticeable along the tangential direction of the pad, reaching a variation of up to 16% between middle of the pad and the edges. The stiffness can also vary by up to 8% along the radial direction of the pad. The measurements performed during this study confirm also that these stiffness distribution patterns are strongly dependent on the formulation friction of the material and on the production process itself. The above-mentioned stiffness distributions were implemented in finite element brake pad models to estimate the potential frequency shift arising from these considerations. The impact of taking into account such information was shown to be limited for the free–free pad modal properties. Nevertheless, the influence of such distributions on the complex eigenvalue analysis of complete finite element brake models was observed and is discussed. Even if the used pad models take into account to some extent the static and dynamic stiffness distributions for complex eigenvalue analysis, they still do not agree with the non-linear material models regarding the stress and the frequency, as shown experimentally. Even if an additional effort is made to determine these stiffness distributions which provide more detailed information for the brake pad finite element models, this physical degree of freedom could drive, to a certain extent, the noise, vibration and harshness responses of the brake systems. A more mature understanding of the influences of the formulations and the process on these distributions and their control at the pad design stage could add a complementary strategy for reduction in the noise, vibration and harshness issues in brake systems.

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Squeal Noise Improvement by High Damping & amp; High Stiffness under Layer Material

Nishioka¹,

Johnson²,

Rosalez³

et al. 2019

SAE Technical Paper Series

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Model Approach for a Load and Frequency Dependent Stiffness in Friction Materials

Cited by 4 publications

References 5 publications

Analysis of local stress redistribution effects in short glass fibre-reinforced thermoplastics during fatigue using mesomechanical simulations

Analysis of local stress redistribution effects in short glass fibre-reinforced thermoplastics during fatigue using mesomechanical simulations

Stiffness distributions of brake pad friction materials using static and dynamic measurement techniques

Squeal Noise Improvement by High Damping & amp; High Stiffness under Layer Material

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