Dynamic friction of nano-materials

A modified Kolsky bar method consisting in the dynamic loading in shear of a pre-compressed thin-wall sample has been developed. The technique allows the identification of the transient response from static to kinetic friction under sliding velocities of about 2–6 m/s. The normal and tangential tractions are measured independently and hence a dynamic friction coefficient identified. The sliding velocities obtained with the Kolsky bar are smaller than those obtained in pressure-shear friction experiments. Hence, the techniques are complementary and provide valuable information for the formulation of friction laws at sliding velocities, pressures and temperatures typical of manufacturing processes, dynamic shear fracture, metal forming, etc. The friction properties of two nano-ceramics sliding against metals, cermets and other ceramics are here reported.