Input parameters of discrete element methods

This paper presents a sensitivity analysis of the input parameters of a program based on the discrete element method (DEM). Triaxial compression simulations were conducted on an assembly of ellipsoids with two particle shapes. We examine four input parameters including shear modulus of particles, density of particles, time step, and damping. Generally, these parameters are chosen by calibrating the result with certain known behavior of granular materials. In dynamic simulations, these input parameters are bounded by their physical attributions that should not be altered. However, in static simulations, they do not have the same physical implication. Validity of results may be questionable when input parameters are used without justification. A sensitivity analysis of the input parameters should shed light on this issue. In this paper, we will study the effect of the input values within the range of (1/10)-10 times the benchmark value. The benchmark values are commonly used by the writer. The results are presented against the benchmark simulation. The unbalanced forces in the simulations are kept below a prescribed value to enforce equilibrium. The result shows that the effect of all input parameters used in this paper is negligible as long as the small unbalanced forces in the system can be achieved. The runtimes are different. However, there are two simulations (one with low damping and the other with a large time step size) that cannot maintain the required small unbalanced force. In other words, equilibrium cannot be achieved for these simulations. CE Database subject headings: Granular materials; Discrete elements; Triaxial Compression; Micromechanics