The shear behavior of binary granular mixtures was studied using the 2D discrete element method (DEM). Various specimens were prepared using different volume fractions and shapes i.e., disk and peanut, of small particles. The analyses showed that the average particle rotation of both small and large particles is equivalent to the continuum rotation field. However, when a specimen contains small disks of volume fractions in the range 5% - 15%, the average particle rotation is found to be much larger than the continuum rotation that accompanies the reduction in both shear resistance and thickness of the shear band. In such specimens, it was observed that many small particles were sandwiched by two large particles and underwent considerable rotation. In this paper, this irregul ar phenomenon is referred to as the "ball-bearing effect."
This paper studies the stability of dynamic crack growth in a homogeneous body, carrying out a numerical experiment of a plate with two anti-symmetric cracks. PDS-FEM proposed by the authors is extended to dynamic state and used in the numerical experiment. It is shown that while a common process is not found for the crack growth, there are two dominant patterns for the final crack configuration. The first pattern is anti-symmetric, indicating the stability of the homogeneous body solution, and the second pattern is not anti-symmetric, suggesting that the solution becomes unstable. It is also shown that higher loading rate tends to shift the crack configuration to the second pattern, losing the stability of the solution.