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This paper reviews investigations into the dynamics and modelling of brushes. They include brushes for surface finishing operations, removal of fouling, post-CMP brushing processes, air duct cleaning, and street sweeping. The methods that have been proposed to model brush dynamics are described, and the results of the research into brush mechanics are presented and discussed. Some conclusions of the paper are as follows: brush dynamics is very complex, as it depends on the interaction among many phenomena and variables. The bristle oscillations that occur in some brushes constitute a complexity for modelling brush behaviour and are not normally addressed. Additionally, the literature reveals that the coefficient of friction is not a constant value that depends only on the materials and surface roughness of the two contacting bodies. Frictional behaviour strongly depends on many variables, such as brush setup angles and rotational speed, which play a part in the development of stick-slip friction cycles. Finally, it is concluded that brush behaviour and the phenomena involved in brushing have not been fully studied or understood and more research into this field is needed.

A theoretical model for the free-flight behaviour of an oscillatory cutting brush of a street sweeper is developed. The bristles are modelled as cantilever beams, and the equation of motion for the transverse vibrations is derived based on the theory of vibrations and small deflection beam theory. Two angular velocity functions are studied: a sinusoidal function and a function that provides small shaft accelerations and whose exact shape depends on a parameter b. The model is applied for a range of frequencies of oscillation that contains the first and second natural frequency of the bristle. The effects of the alternating component of the rotational speed, the type of function, and the value of b are also studied. The results are compared with those obtained in a previous work for a flicking brush. The findings suggest that the bending moment and bristle deflection tend to depend fairly linearly on the alternating velocity. In contrast to the bristles of a flicking brush, in the cutting brush resonance tends to occur only near the natural frequencies of the bristle. Additionally, the behaviour of the cutting brush is similar for both functions and for different values of b.

Simulations of damage scenarios were carried out using a finite element model of a newly constructed FRP composite footbridge, the Wilcott footbridge. This footbridge represents a new generation of suspension footbridges that have lightweight decks made of pultruded glass fibre reinforced polymer (GFRP) composite elements. It offers several advantages over conventional steel or concrete footbridges, e.g. speed of installation, high resistance to corrosion and saving in weight and foundations. On the other hand, its lightness and slenderness make it more sensitive to dynamic effects, both at serviceability and ultimate limit states. A finite element model using 3-D beam elements was constructed and damage scenarios were simulated and introduced in the model. The natural frequencies, mode shapes as well as time responses due to pedestrian loading were predicted. Different size of delamination in the composite deck was simulated at various locations along the bridge. The sensitivity of natural frequencies and mode shapes due to delamination were assessed by comparing the results of the damaged deck to those of the reference intact deck. The effect of changes in the cables’ initial strains on the modal parameters was also examined, and the sensitivity of modal parameters to cable degradation was assessed.

Cutting and flicking128 brushes are two types of gutter brushes that sweep the debris that lies in the gutter towards the main sweeping mechanism of a street sweeper. As most of the debris is commonly found in the gutter, the operation of gutter brushes is important. In this work, the concept of oscillatory gutter brushes is studied. Qualitative experimental tests are carried out to determine frequencies at which enhanced vibration patterns of the bristles of cutting and flicking128 brushes are obtained. The brushes are rotated at variable angular speed, first in free rotation, and then against a concrete test bed. The findings are analyzed in the light of previous theoretical results. The results suggest that bristle vibrations may be excited at the first natural frequency of the bristles for both brush types. Notably, the trends indicate that when the frequency is a third of the first natural frequency, a resonant condition seems to occur. The results also indicate that an equivalent length for bristle vibration has to be calculated, due to the way in which the bristles are clamped into the mounting board. This equivalent length is necessary for the comparison between the experimental and analytical results. These tests are useful in the determination of frequencies that may be potentially helpful during sweeping.