Rotating drums are often used in industrial applications in which the main objective is reducing the particle size of the material (i.e. particle breakage). Because of the lack of understanding of the phenomena that take place in such processes, the system parameters are based on empirical laws. Experimentally, it is difficult to measure rheological and mechanical properties under such dynamic conditions. DEM simulations allow one to model the granular flow even under dynamic conditions and to track of the interactions between the particles. Moreover, by means of the Bonded Cell Method, the particle fragmentation can be also taken into account. In this work, we report on the simulations of grinding of granular materials inside rotating drums using Contact Dynamics. A parametric study of theinfluence of some operational parameters such as rotational velocity and the filling degree was performed for the grinding efficiency, indirectly characterized from the evolution of particle size and specific surface evolution.