Dynamic finite element model of oscillatory brushes

Abstract

In this work, the concept of oscillatory brushes is studied. The main aims are to develop a generic, dynamic finite element model of oscillatory brushes and to study the effects of brush oscillations on the dynamics and performance of a cup-shaped brush, which may be used for street sweeping. The model entails a transient nonlinear analysis, involving three-dimensional large deflections and contact between bristles and surface and between bristles. An exponential friction model is assumed, and the damping generated by internal friction and bristle–bristle contact is modelled as Rayleigh damping. Existing experimental results on gutter brushes are used to validate the model and determine the coefficient of friction for bristle–surface interaction. The model is also validated through another finite element model derived by the authors. The Rayleigh damping coefficients and the normal contact stiffness for bristle–surface interaction have been obtained by means of experimental tests. The model is applied to study the behaviour of a horizontal gutter brush with a bristle mount orientation angle of 128°. In order to assess brushing performance, a number of performance criteria are proposed. It is concluded that brush oscillations significantly affect brush dynamics and tend to increase bristle tip velocities and brushing forces. According to the model and the performance criteria defined, brush oscillations may improve sweeping effectiveness for certain ranges of frequency of oscillation.