Analysis of granular damping induced by mechanical stirring

To determine whether damping induced by stirring granular materials can be adopted as passive damping, the efficiency of damping upon stirring granular materials was investigated experimentally and numerically. In the experimental approach, a cylindrical mixer with a flat blade was used. As the rotating axis of the blade was driven by a stepping motor through a four-bar linkage mechanism, the blade rotated sinusoidally. The rotational angle of the blade and the torque exerted on the axial shaft by the blade were measured using two types of sensors. The energy dissipated per cycle was determined by calculating the area surrounded by the loop in the plot of the torque versus the rotational angle. The effects of packing ratio, particle diameter, particle material and blade frequency on the energy dissipated were examined. In the numerical approach, the torque exerted on the axial shaft was calculated by the discrete element method. The predicted relationship between the torque and the rotational angle of the blade was compared with the relationship obtained from the experimental results. Moreover, the effect of the frequency of the blade on the energy dissipated per cycle was investigated on the basis of numerical results. Graphical abstract: [Figure not available: see fulltext.]