Momentum transfer during the impact of granular matter with inclined sliding surfaces

Abstract

Increasing the inclination of a rigid surface that is impacted by a collimated granular flow reduces the fraction of granular matter momentum transferred. Recent studies have shown that the momentum reduction depends upon the frictional interaction between the granular flow and the impacted surface with high coefficient of friction surfaces suffering significantly more momentum transfer than predicted by resolution of the incident momentum onto the inclined plane. This discovery has raised the possibility that inclined surfaces with very low friction coefficients might reduce the impulsive transferred by the impact of ejecta from buried explosions. Here the use of a lubricated sliding plate is investigated as a means for reducing interfacial friction and impulse transfer. The study uses a combination of experimental testing and particle-based simulations to investigate impulse transfer to rigid aluminum surfaces inclined either perpendicular or at 53 o degrees to synthetic sand that had been impulsively accelerated to a velocity of 350-550 m/s. The study shows that impact of this sand with lubricated plates attached to an inclined surface, rapidly accelerates them to a velocity of about 55-70 m/s, and reduces the impulse transferred to the inclined surface. The reduction of impulse by this approach is shown to be comparable to that achieved by changing the inclination of the impact.