Dissipation mechanisms identification of soft hollow particle-dampers in honeycomb structures for micro-vibrations environment

Particle dampers are enclosures partially filled with metallic or glass small spheres, attached to the vibrating structure. This paper deals with replacing hard classical particles by soft hollow ones to maximize damping and mass ratio. Hence, one aspect of this damping method is obtained by mixing the kinetic energy conversion of the structure into heat(frictional losses and collisions) and the elastic energy conversion into heat (visco-elastic deformation). This study is oriented toward experimental and theoretical investigations in order to distinguish the dissipation phenomena. The experimental approach first relies on identification and, then, on validation applied on composite aluminum honeycomb plates. Indeed, equivalent viscous damping is identified on small honeycomb samples; then cantilever honeycomb beams are filled with particles and studied. Theoretically, beyond the nonlinear dissipation by impact and friction, these particles add a visco-elastic behavior. The shapes of the hysteretic loops highlight that this behavior is predominant. Hence, oscillators are added in the FE model and permit to consider the effect of the particles. These kinds of particle dampers are highly nonlinear as a function of excitation frequency and amplitudes. The aim of this study is to provide a structural damping solution for space applications which require high pointing stability to enhance mission performances. In this perspective, damping of micro-vibrations was thought as a possible application; nevertheless it is shown that best efficiency is achieved in high frequency range

Identification of the non-linear hysteretic behavior of a belt tensioner

Mechanical tensioners are widely used in belt drive systems of automotive engines. They act to maintain a minimum tension in the slack span and to decrease transverse belt vibrations. They are composed of an idler pulley, an arm lever and a torsional springThe paper deals with the modeling of the dynamic behaviour of a tensioner. First an experimental investigation permits the characterisation of the tensioner: it is subjected to a force-deflection test carried out using a specific experimental set-up equipped with an electrodynamic shaker. The hysteretic loops are measured for several deflection amplitudes and forcing frequencies. Then, the experimental characterization permits identifying the parameters required by the original hysteretic model, and classical models like the Dahl’s model. The last part is devoted to the comparison of the hysteretic loops given by the tested models and the experiment