Effects of Particle Friction and Particle Shape on the Mechanical Response of Granular Solid under Confined Compression

• Main Authors: Han-hong Peng, 彭瀚弘
• Other Authors: Chih-kuang Lin
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/28733873117307535315

碩士 === 國立中央大學 === 機械工程學系 === 101 === The purpose of this study is to investigate the effects of particle friction and shape on the interaction between a granular assembly and an acrylic cylinder and the relevant mechanical responses at various positions under a confined compression condition. Variations of wall strains are measured through strain gages at three given axial positions and used to calculate the relevant stresses through a generalized Hooke’s law. Steel spheres of five rust levels are selected to characterize the effect of particle friction. In addition, the experimental results of five selected particle shapes, namely spherical, ellipsoidal I, ellipsoidal II, cylindrical, and paired ABS particles, are compared to characterize the effects of particle shape, aspect ratio, and particle angularity. Experimental results show that an increase in particle friction causes a greater interlocking effect between particles, resulting in a greater difficulty for particles in the granular assembly to move and press laterally under a confined compression condition. In addition, the frictional force between particles and cylindrical wall also increases as the particle friction increases. The initial assembly height increases with increasing particle friction. For spherical, ellipsoidal, and cylindrical particles, cylindrical particles have a greater interlocking effect, resulting in a greater stiffness of the granular assembly. In addition, a larger extent of decrease in the bulk wall friction is observed for the cylindrical particles indicating a smaller extent of mobilization of the particles beside the cylinder wall. Compared with spherical and cylindrical particles, ellipsoidal particles have a greater lateral pressure ratio. It indicates a greater extent of lateral movement for ellipsoidal particles under confined compression loading. An increase in the aspect ratio of ellipsoidal particles not only causes a higher packing density and a greater stiffness of the granular assembly, but also increases the extent of lateral movement of particles and induces a greater lateral pressure ratio. On the other hand, a higher particle angularity results in a greater interlocking and a greater difficulty for the particles in the granular assembly to slide and rotate. It increases the initial porosity of the assembly and lateral pressure ratio to a small extent under a confined compression condition. Due to a larger initial porosity in the particles of a greater angularity, the stiffness of the granular assembly of paired particles only increases slightly in comparison with the spherical particles