Exploiting surface textures dynamics for dry friction control

We study the dynamic behavior of a lattice of bristle-like elastic elements disposed at the interface between a rigid still substrate and a rigid sliding slab, in steady conditions. Due to normal and frictional interactions with the moving slab, complex bristles dynamics occur, which may eventually alter the overall frictional response of the structured interface. Indeed, up to three main mechanisms of friction control can be identified, depending on the specific bristles dynamics: the relative velocity-dependent modulation of local friction force; the misalignment between the local relative velocity and the slab velocity, due to the emergence of transverse vibration; the local friction coefficient variation due to the normal load acting on the bristle. Results show that, depending on the interface dynamic properties (i.e., bristles stiffness, normal load, slab velocity, etc.), a significant reduction of the friction force opposing the slab motion can be achieved, also involving self-excited bristle vibration. Since the present formulation is scale independent, this result may suggest possible mechanisms of friction control in different practical application fields, ranging from bio-inspired micro-structured interfaces to macro-scale features, such as brush seals in electric motors.