Frequency-dependent characteristics of grain-beam system: Negative mass and jump behaviour

Abstract

We experimentally investigated the dynamic properties of a grain-beam coupling system and theoretically examined the mechanisms of new peak and jump. The dynamic mass of an excited beam buried in the grains was introduced to identify the equivalent stiffness, damping, and mass of the system. The dependence of the dynamic mass and amplitude on the excitation frequency was determined to analyse these dynamic parameters through sweeping frequency experiments under a constant force amplitude. The negative mass mainly observed in artificial metamaterials was first discovered in a grain-beam system and rationalised using a dynamic absorber model. We analysed the dynamic parameters of the system under various conditions (layer depth, force amplitude, and particle size). We found that frequency-dependent characteristics generated new peaks and jump phenomena. (I) The negative equivalent mass induced the appearance of new peaks below the first-order natural frequency of the beam. (II) The abrupt decrease in the equivalent mass, stiffness, and damping corresponded to jumps higher than the natural frequency.