Numerical simulations with theDiscrete Element Method are used to study agglomerate breakage under two different kinds of dynamic loading: normal impact and shear loading. Simple mechanical models based on energy balance are developed herein for each one and show good agreement with the results of the simulations. For impact, damage is found to depend on a dimensionless number Ni , which describes the ratio of the incoming kinetic energy to the internal bonding energy. For shear loading, damage is shown to depend on another dimensionless numberNf which describes the ratio of the frictional work to the internal bonding energy. The friction force is first modelled as a solid-like friction force, then the model is improved by using a granular frictional force. The two types of loading as damaging processes are then compared. These results appear to be consistent with the available experimental data on impact and abrasion wear tests.