The velocity dependence of frictional forces in point-contact friction

The velocity dependence of point-contact friction is studied by means of friction force microscopy of different carbon compounds (diamond, graphite, amorphous carbon). The measured frictional force is found to be constant over a wide range of sliding velocities [nm/s to mu m/s]. This result is substantiated by a simple mechanical model, where the frictional forces are shown to be constant at sliding velocities well below the slip velocity.