The effect of particle shape on the dynamics of spherical projectile impacting into granular media

Abstract

To investigate the effect of particle shape on the dynamics of projectile impact into granular media, this study conducted discrete element method (DEM) numerical simulation using Particle Flow Code (PFC) software. Three particle shapes of granular materials were selected, where spherical particles represented by ball elements, ellipsoidal particles and irregular particles generated by clumps according to a certain template profile. The microscopic contact parameters were calibrated by laboratory tests and numerical simulations of standard direct shear tests. On this basis, the DEM model of a spherical projectile impact into the granular bed was established and laboratory tests were conducted. The test data matched well with the numerical results, verifying the reasonableness and accuracy of the numerical model. Analysing the results by varying the parameters shows that the impact process can be divided into three stages: impact, penetration and collapse. The particle shape does not affect the final penetration depth of the projectile as a power-law function of the initial velocity, and all follow the generalised Poncelet law. The difference in the peak impact force indicates that non-spherical particles have better cushioning capacity, and the analysis of the energy evolution during impact shows that there is significant variability in the effect of particle shape on the energy dissipation of the system. Finally, the internal response of the granular media during the impact process is elucidated by the results of porosity and coordination number. The force chains of granular materials undergo fracture and recombination during the impact process, and the particle shape significantly affects the structural distribution and evolution of the force chains.