Determination of the Normal Contact Stiffness and Integration Time Step for the Finite Element Modeling of Bristle-Surface Interaction
Libardo V. Vanegas-Useche, Magd M. Abdel-Wahab and Graham A. Parker
doi: 10.3970/cmc.2018.01827
Source CMC: Computers, Materials & Continua, Vol.56,No.1,pp.169-184,2018
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Keywords Brush, street sweeping, finite element modeling, contact mechanics.

In finite element modeling of impact, it is necessary to define appropriate values of the normal contact stiffness, Kn, and the Integration Time Step (ITS). Because impacts are usually of very short duration, very small ITSs are required. Moreover, the selection of a suitable value of Kn is a critical issue, as the impact behavior depends dramatically on this parameter. In this work, a number of experimental tests and finite element analyses have been performed in order to obtain an appropriate value of Kn for the interaction between a bristle of a gutter brush for road sweeping and a concrete surface. Furthermore, a suitable ITS is determined. The experiments consist of releasing a steel bristle that is placed vertically at a certain distance from a concrete surface and tracking the impact. Similarly, in the finite element analyses, a beam is modeled in free fall and impacting a surface; contact and target elements are attached to the beam and the surface, respectively. The results of the experiments and the modeling are integrated through the principle of conservation of energy, the principle of linear impulse and momentum, and Newton’s second law. The results demonstrate that, for the case studied, Kn and the impact time tend to be independent of the velocity just before impact and that Kn has a very large variation, as concrete is a composite material with a rough surface. Also, the ratio between the largest height of the bristle after impact and the initial height tends to be constant.

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