Particle damping for passive vibration suppression: numerical modelling and experimental investigation

Particle damping is a technique of providing damping with granular particles embedded within small holes in a vibrating structure. The particles absorb kinetic energy through particle-to-wall and particle-to-particle frictional collisions. While the concept of particle damping seems to be simple and it has been used successfully in many fields for vibration reduction, it is difficult to predict the damping characteristics due to complex collisions in the dense particle flow. In this paper, we utilize the 3D discrete element method (DEM) for computer simulation and characterization of particle damping. With the DEM modeling tool validated with experimental results, it is shown that the particle damping can achieve a very high value of specific damping capacity. Furthermore, simulations provide information of particle motions within the container hole during three different regions and help explain their associated damping characteristics. The particle damping is a combination of the impact and the friction damping. The damping is found to be highly nonlinear as the rate of energy dissipation depends on amplitude. Particularly, the damping effect results in a linear decay in amplitude over a finite period of time. These characteristics are examined with respect to a simple single-mass impact damper and a dry-friction damper. It is concluded that the particle damping is a mix of these two damping mechanisms. It is further shown that the relative significance of these damping mechanisms depends on a particular arrangement of the damper. This study represents an effort towards a deeper understanding of particle damping to provide a comprehensive methodology for its analysis and design.

Simulation and Characterization of Particle Damping in Transient Vibrations

This paper describes an experimental investigation of a particle damping method for a beam and a plate. Tungsten carbide particles are embedded within longitudinal (and latitudinal) holes drilled in the structure, as a simple and passive means for vibration suppression. Unlike in traditional damping materials, mechanisms of energy dissipation of particle damping are highly nonlinear and primarily related to friction and impact phenomena. Experiments are conducted with a number of arrangements of the packed particles including different particle sizes and volumetric packing ratios. The results show that the particle damping is remarkably effective and that strong attenuations are achieved within a broad frequency range. The effects of the system parameters including particle size, packing ratio and particle material are studied by broadband and narrowband random excitations. The experimental results confirm a numerical prediction that shear friction in the longitudinal (and the latitudinal) directions is effective as the major contributing mechanism of damping in the case. Another unique feature of linear decay in free vibrations is also observed in this case of particle damping.

An experimental study of particle damping for beams and plates

An impact damper is a freely moving mass, constrained by stops, located on the structural system to be controlled. As the system is excited dynamically, the impact mass moves relative to the struct...

Experiments on the Effect of an Impact Damper on a Multiple-Degree-of-Freedom System:

The performance of particle dampers whose behavior under broadband excitations involves internal friction and momentum transfer is a highly complex nonlinear process that is not amenable to exact analytical solutions. While numerous analytical and experimental studies have been conducted over many years to develop strategies for modeling and controlling the behavior of this class of vibration dampers, no guidelines currently exist for determining optimum strategies for maximizing the performance of particle dampers, whether in a single unit or in arrays of dampers, under random excitation. This paper focuses on the development and evaluation of practical design strategies for maximizing the damping efficiency of multi-unit particle dampers under random excitation, both the stationary and nonstationary type. High-fidelity simulation studies are conducted with a variable number of multi-unit dampers ranging from 1 to 100, with the magnitude of the "dead-space" nonlinearity being a random variable with a prescribed probability distribution spanning a feasible range of parameters. Results of the computational studies are calibrated with carefully conducted experiments with single-unit/single-particle, single-unit/multi-particle, and multiple-unit/multi-particle dampers. It is shown that a wide latitude exists in the trade-off between high vibration attenuation over a narrow range of damper gap size versus slightly reduced attenuation over a much broader range. The optimum configuration can be achieved through the use of multiple particle dampers designed in accordance with the procedure presented in the paper. A semi-active algorithm is introduced to improve the rms level reduction, as well as the peak response reduction. The utility of the approach is demonstrated through numerical simulation studies involving broadband stationary random excitations, as well as highly nonstationary excitations resembling typical earthquake ground motions.

Studies of the Performance of Multi-Unit Impact Dampers Under Stochastic Excitation

This paper investigates the effects of mass ratio, clearance, and excitation amplitude on system dynamics and impact vibration absorber (IVA) effectiveness. The experimental studies were carried out for both free and forced vibrations. For free vibrations, the effects of system parameters on the rate of decay of vibrations were shown. Constant frequency and frequency sweep experiments were conducted to study the dynamics of the system under forced vibration. Optimum system parameters were extracted, for which the vibration absorption and absorber efficiency is greatest. It was also shown that phase plots and coherence, between the forcing function and the primary system response, offered an insight in the effectiveness of the IVA.

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I.C. Desen

Papers

Experimental study on an impact vibration absorber