Effect of porosity on shock propagation behaviour of single crystal aluminium: A molecular dynamics investigation

Abstract

Materials' response to shock waves is largely affected not only by their inherent atomic structure but also by their physical structure. Current study involves analysis of shock propagation behaviour of single crystal aluminium (Al) specimens with different levels of porosities at nanoscale under a compressive shock loading using three dimensional molecular dynamics (MD) simulations. Solid, two dimensional array of pores, and three dimensional array of pores in the single crystal Al specimen were considered for detailed analysis of the shock response. It is observed that the porosity causes time delay in the travel of shock wave from front end of the surface to the rear end. The computational results indicate that the porosity results into increase in time of shock wave travel and it is found that the maximum porosity (47% in this simulation) causes 4 times the time of travel taken in solid Al specimen. The shock wave causes various sequential phenomenon in the Al specimen from compression to rarefaction which further leads to spalling of the material. The study also reveals that the pore walls act as a reflecting wall to the shock wave which causes secondary rarefactions and spalling phenomenon. Analyses show that the deformation in the material during shock loading is largely dominated by Shockley partial dislocations.