A fractal comminution approach to evaluate the drilling energy dissipation

The drilling comminution is theoretically and experimentally analysed by a fractal approach. An extension of the Third Comminution Theory is developed to evaluate the energy dissipation in the process: it occurs in a fractal domain intermediate between a surface and a volume. The theoretical assumption of a material ‘quantum’ is experimentally observed. The experimental fragment analysis evidences the characteristic size of separation between primary cutting and secondary milling. A global power balance for the drilling process is also presented and permits the prediction of drilling velocity. It shows also how the dissipation energy density (drilling strength) is not a constant parameter, but decreases considerably with the size scale. Copyright © 2002 John Wiley & Sons, Ltd.