| dc.description.abstract | The aim of this study is to investigate the dynamics and mechanical behavior of a free-fall projectile impacting granular beds with different particle sizes, shapes, densities and high stiffnesses. A simple drop experimental device was designed. A high-speed camera was used to observe the impact process of the projectile, and the images from the two perpendicular directions were captured by means of the properly- orientated mirror. The 3D positions of the projectile were analyzed by using Improved Particle Tracking Velocimetry. The kinematical quantities, including the vertical velocity and acceleration of the projectile as well as the translational and angular velocities in the horizontal plane were further evaluated. The drag force on the projectile was determined by the acceleration of projectile. The main findings are summarized as follows: (1) The projectile in the granular bed with a larger particle size shows a larger vertical acceleration, drag force, and translational and angular velocities in the horizontal plane, which decreases with decreasing of the particle size. However, the penetration depth decreases with increasing of the particle size；(2) The penetration depth of the projectile was found to be in following sequence (from deep to shallow): ellipsoidal Ⅱ, spherical, ellipsoidalⅠ, capsule and paired. Paired and capsule particles have a greater interlocking effect so that the projectile has a larger translational velocity in the horizontal plane. On the other hand, the projectile easily penetrated through granular bed with spherical and ellipsoidal particles due to the shape effect, resulting in smaller translational velocity in the horizontal plane；(3) For granular beds with strong interlocking effects, the projectile has a larger value of acceleration, drag force, and translational and angular velocities in the horizontal plane. The penetration depth increases with smaller interlocking effect；(4) The results show that the acceleration, drag force, horizontal velocity and angular velocity of the projectile increases with increasing particle density. The penetration depth decreases with increasing particle density. | en_US |