Damping loss factor of granular material mixtures using a coupled finite element-discrete element method

Granular Materials (GM) employed within particle dampers attenuate vibration energy due to interparticle and particle-wall interactions. Estimating their kinetic energy losses is usually performed using the Discrete Element (DE) method assuming that particles of uniform size (monodisperse) are excited at anti-resonance conditions. However, the GM found in nature and industrial by-products exhibit size distributions within specific ranges. Estimating their energy losses is important in the presence of structural resonance conditions to obtain the associated damping. This study numerically investigates both monodisperse and mixtures of GM integrated within vibrating structures using a coupled Finite Element-Discrete Element approach. The model developed simulates the oscillation of a small-scale suspended panel system integrated with a 6 mm thick granular layer with a cubic packing arrangement. Various monodisperse and mixed spherical particles ranging from 1 to 6 mm occupy the packing space. Damping characteristics of various spherical particle arrangements were quantified by the panel system's damping loss factor, determined through the logarithmic decrement method. The results showed that mixtures of larger particles of 2-4 mm diameter develop higher damping compared to smaller monodisperse particles and mixtures of smaller sizes (with diameters of 3 mm or less) for the same mass. It is concluded that the damping of these particle sets (with diameters of 3 mm or less) can be assessed using a new geometric parameter developed in this study that characterizes the particles' bed. Additionally, the segregation effect in the 2-4 mm mixture with large porosity results in higher tangential velocities that increase interparticle losses. • Estimating kinetic energy losses in Granular Materials typically assumes monodispersity and excitation at anti-resonance conditions. • Monodisperse particles and mixtures sized 1–6 mm, integrated within a vibrating panel structure, are assessed based on their damping loss factor using a coupled FE-DE approach. • For unified total mass, mixtures of larger particles (2–4 mm), influenced by segregation, exhibit higher damping compared to all other particle sets. • A new geometric parameter, developed in this study characterizes the damping of particle sets with sizes of 3 mm or less.