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• Main Authors: Mu-Ho Lin, 林沐禾
• Other Authors: Y.C. Chung
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/60699910549312088081

碩士 === 國立中央大學 === 機械工程學系 === 105 === The aim of the study is to investigate the mechanical and motion behavior of a projectile vertically impacting into a cylindrical granular bed experimentally and numerically. The surface velocity distribution of granular bed was measured by particle image velocimetry technique (PIV). This study proposed a discrete element model to simulate this granular system and this DEM model was validated against the experimental data in the literature. The compared physical quantities include the penetration depth, translational and angular velocities, and translational and angular acceleration of the projectile as well as the surface velocity distribution of granular bed. The validated DEM model is then used to explore the internal physical properties of the granular system. The main research findings are as follows : (1) The solid fraction of the granular bed is partially influenced during the impacting process, especially in the region around the projectile, but the coordination number and the mobilized friction are influenced in the whole granular bed; (2) The vertical normal stress is dominated during the impacting process; (3) The contact force shows isotropic distribution in the horizontal plane, while the contact force distribution in the vertical plane was anisotropic; (4) The impact of a projectile on the granular bed greatly makes friction factor mobilized; (5) Normal and tangential contact force distributions for the inter-particle contact greatly change during the impact process, but those for particle-wall has no significant change; (6) The velocity of pressure wave depends upon the particle size and granular porosity, whereas the shear wave is related to only the particle size. The ratio of the pressure wave velocity to the shear wave velocity is found to be constant.