Modeling And Simulation Of Particle Damping And Its Engineering Applications

Particle Damping technology is a new damping technology, which is used to imply particles of various shape, sizes and materials in cavity of structure or auxiliary cavity in certain packing ratio. As a result of the collisions, momentum is exchanged between the structure and the particles, and kinetic energy is converted to heat. Additional energy dissipation can also occur due to particle-to-particle or particle-to-wall collisions and frictions. It offers several advantages due to its conceptual simplicity, potential effectiveness over broad frequency range, temperature and degradation insensitivity, and very low cost. Because of above, more and more researchers have payed attention to NOPD technology. In our paper, we have studied the particle damping based on requirement of engineering application though theory, simulation and experiment for expanding the range of its application and filling its gap. The dissertation is mainly focused on below sections: 1. Investigation on zero-gravity behaviour of particle dampers. The simulation study of particle damping in microgravity or zero-gravity environments is carried out using Discrete Element Method(DEM) in this paper. The results show that the damping particles in zero-gravity environments have a reasonable damping performance only when the particle container is almost fully filled with particles and at large displacement amplitude. The damper will have little effects because the particles will be getting together and forming a floating cluster in the middle of the container, if the vibration amplitude is less than half of the gap between the particle bed and the ends of the container. To break that floating cluster, a cross-shaped spoiler is introduced and fitted inside of the container, which greatly raises the damping performance in zero-gravity environments. 2. Behaviour of particle dampers beased on micromeritics modle. A micromeritics model is established to investigate the behavior of cylindrical particle dampers, and simulation is also carried out using Discrete Element Method(DEM) to study the effect of geometry and vibration level in different directions(vertical and horizontal) on the characterization of particle dampers. The research shows that when the dampers packed with the same amount of particles are vibrated vertically, the bigger inner diameter of container means particles convert from solid to fluid and gas more easily. And when the vibration level is low, the damper with a larger diameter has a better performance on the energy dissipation. The research provide a desidn criteria of particle damper, that is to say the diameter of particle damper shoud be as bigger as possible for enhancing the damping performance when the vibration of master structure is low. 3. The experiment study on dynamic properties of tuned particle dampers. Aiming at solving the ineffectiveness of conventional Particle Damper(PD) at vibration acceleration less than the acceleration of gravity(1g), we introduces a new particle damper –Tuned Particle Damper(TPD) which is literally a flexibly supported PD attached to the master structure. An experiment study on dynamic properties of a cantilever with a TPD and conventional Particle Damper(PD) is carried out to validate the TPD’s advantages over the conventional PD. From the comparison between the experimental results of TPD and PD, it can be concluded that if the vibration acceleration of the master structure is less than 1g, the TPD can reduce the vibration level of the master structure as a vibration absorber and also provide useful damping because of the damper’s acceleration is amplified as a vibration absorber. Moreover, TPD also has a better performance than the conventional PD at the vibration acceleration level greater than 1g. 4. Investigation on particle damper based on an approximate theoretical model. An equivalent method is developed to model the highly nonlinear damping of PDs, which can exhibit characteristic of PDs’ energy dissipation adequately. For the Tuned Particle Damper(TPD), a simplified theoretical model is established. And the correctness of the model has been validated by experimental results. The research also confirms that vibration acceleration has a significant effect on the three parameters of equivalent model for PD, especially for the equivalent viscous damping coefficient eqc, whose changing rule fit Gamma distribution. 5. The application of particle damping in longitudinal vibration control of hollow shaft. For longitudinal vibration of hollow shaft, a damper of longitudinal vibration was designed based the design ctiteria of TPD, which also included viscoelastic damping material. Both transfer matrix method and finite element method were used in our research, and the results show that the damper have a very good performance on controlling the first three longitudinal vibration of the hollow shaft.