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R. Brighenti et alii, Frattura ed Integrità Strutturale, 34 (2015) 80-89; DOI: 10.3221/IGF-ESIS.34.08 87 0 2, 4, 6 and 8 / v m s  . The force potential described above is used to quantify the particles interaction, by adopting an influence distance of the particles equal to infl 2 r d  and a time increment for the dynamic analysis equal to 5 t s    . 0.10 0.15 0.20 Figure 4 : Configuration of particles for a blade displacement equal to: (a, c) 10cm, (b, d) 20cm [25], (e, f) corresponding configurations provided by the present model. Color scale indicates the horizontal displacement of the particles expressed in m. Fig. 5 shows the configuration of the system at different time instants. In particular, the initial development of the elastic wave – propagating inside the beam – is shown in Fig. 5a, whereas the failure pattern at t=0.125 s after the first impact is represented in Fig. 5b. As can be observed, a wedge-like failure mechanism takes place producing the detachment of a wide bottom portion of the beam. Moreover, a diffused separation of the bottom layer of the beam can also be acknowledged. In Fig. 5c, the time history of the reaction force at support obtained by the discrete approach by using different discretizations is displayed and compared with the FE results provided in Ref. [27]. It can be observed that, only after a first time interval equal to about 30 ms (when the reaction is practically zero due to the time required by the elastic wave to propagate from the stricken zone to the support), such a boundary force raises very quickly. Of course, higher impact speeds correspond to higher reaction force values. The fracture pattern provided by the DEM approach roughly corresponds to the literature results, despite the other FEM approach is very different (Fig. 5d) and does not allow us to determine the detachment of material portion produced by the fracture phenomenon. C ONCLUSIONS he particulate nature of solids, naturally acknowledged at the microscale in granular or fluid materials, can also be adopted conveniently for the mechanical description of compact matter at the macroscale. Based on such an idea, a particle method can be applied to the simulation of a wide class of mechanical problems once the mechanical properties and governing equations have been established. T (a) (c) (d) (e) (f) (b)