Within the spectrum of noises associated with brake operation, creep groan is positioned among current high-priority NVH-issues in the automotive industry. The phenomenon belongs to the family of self-excited vibrations and originates from a continuous alternation between stick and slip states of the disc-pads contact interaction. The generated vibrations travel to the chassis, exciting bulkier elements which amplify the noise reported by consumers. Although different types of experimental setups have been applied to reproduce and analyse the onset of creep groan, state of the art product development requires the integration of numerical tools to help improve versatility and reduce related costs. On this matter, the influence of chassis components surrounding the brake system, e.g., the strut and the lower control arm, demand for broad system boundaries in the finite element (FE) environment and therefore increase the difficulty of achieving reliable results within practical time frames. Especially the complexity associated with the virtual representation of wheels and tires, which typically involves fine meshes and contact interaction between linear elastic and non-linear hyperelastic materials, either leads to the neglection or oversimplification of their real dynamical behaviour. Consequently, this paper proposes an objective condensation methodology in order to produce systems of smaller scale while maintaining the dynamical characteristics being essential for the numerical emulation of the phenomenon. The technique relies on integrating arbitrary FE representations of the wheel-tire assembly, allowing for its implementation during the build-up process of creep groan models. Additionally, the approach enables the study of the tire's impact on the generated vibrations, currently missing in literature. Depending on the frequency range of interest, the article proposes two different condensation methodologies. Firstly, for the emulation of the low-frequency creep groan signature (≈18 Hz), a replacement of the wheel-tire assembly with spring-damper elements is presented, involving the extraction of elastic properties through the deformation of the original model via an auxiliary simulation. Secondly, for the emulation of the high-frequency creep groan counterpart (≈ 80 Hz), an alternate FE substructure generation method is proposed which can retain relevant eigenmotions and their corresponding eigenfrequencies. The evaluation of both condensation methodologies relies on the calculation of key performance indicators from the results provided by steady-state dynamic analyses, yielding an objective metric for both, the impact on performance, as well as deviations from original acceleration signals.

EDAG Engineering GmbH: Ing. Tomas Bourdieu, Dr.-Ing Dominic Jekel, Mr. Christoph Schöner