International Journal of Fracture Fatigue and Wear, Volume 3 221 Proceedings of the 4 th International Conference on Fracture Fatigue and Wear, pp. 221-226, 2015 COMPARISON OF TWO FINITE ELEMENT MODELS OF BRISTLES OF GUTTER BRUSHES FOR STREET SWEEPING M.M. Abdel-Wahab 1 , L.V. Vanegas-Useche 2 , and G.A. Parker 3 1 Ghent University, Laboratory Soete, Belgium 2 Universidad Tecnológica de Pereira, Facultad de Ingeniería Mecánica, Colombia 3 University of Surrey, Faculty of Engineering and Physical Sciences, United Kingdom Abstract: This paper models a bristle of a gutter brush for road sweeping, by means of two finite element models. In one of the models, displacement and rotation boundary conditions are applied to an end of the bristle, so that it follows a certain circular path under a given function of time. In the other model, the same end of the bristle is totally constrained, and inertia loads are applied so that they simulate the motion given by the path and function of the first model. The results of both models are validated, analysed, and compared. They indicate that their accuracy with respect to the degree of freedom results is acceptable. However, regarding force and moment results, the accuracy of the first model strongly depends on the number of straight lines used to approximate the circular path. The accuracy may be very low, mainly due to the modelling of damping. Appropriate values for the time step and integration time step are found so that both models produce reliable results. When these values are used, they provide practically the same results. It is concluded that the model that applies inertia loads may be more appropriate, because the modelling of damping may be more realistic and because much less computational resources are required. Keywords: dynamic FEM; damping; inertia loads; displacement boundary conditions; friction 1 INTRODUCTION This work is related to a research into the characteristics and performance of gutter brushes. These are cup-shaped brushes of road sweepers that sweep the debris that is located in the gutter of the road. The study of this brush is of certain interest, as about 80% of the road debris is found in the gutter [1,2]. Fig. 1 depicts a gutter brush of a street sweeper. It comprises one or more rows of clusters of bristles attached at an angle φ (bristle mount angle) relative to the mounting board normal. Fig. 1 Gutter brush of a street sweeper In particular, the research is concerned with the novel idea of analysing whether oscillations superimposed onto the rotation of the gutter brush are of any value for increasing sweeping effectiveness. Therefore, in order to study brush characteristics, a dynamic Finite Element Model (FEM) is considered. A dynamic model of a cup-like, oscillatory brush has been developed; this model entails a transient nonlinear structural 3-D analysis involving contact, and it is described in a previous work [3]. In this model, the clamped ends of the bristles are fixed (the brush mounting board is modelled as a stationary body); therefore, in order to simulate brush motion, inertia loads are applied. In conjunction to this, the road surface has to be rotated and translated to obtain the relative movement between brush and road. Mounting board Steel bristles of rectangular cross section Two rows of clusters r1 r2 φ