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Particle damping is a kind of passive and strongly nonlinear damping for energy dissipation. Many researchers have expended huge amounts of effort and time to study internal mechanism of particle damping. However, there is not a systematic and feasible approach for estimating damping performance of non-obstructive particle damping (NOPD). In this paper, we performed studies to mathematically evaluate the damping effect of particle damping based on principles of gas-solid flows. In consideration of the structural characteristics of NOPD which granular materials should be filled into sealed cavity of vibrating structure and the damping act on lateral and bottom of holes in NOPD technology, the gross damping is divided into lateral damping and bottom damping by Janson's theory of stress change direction. And the damping coefficients are compiled into a plug-in by MATLAB and are invoked in FEM software by enterprise integration kits of COMSOL. Meanwhile the frequency domain and time domain analysis of the experiment are used to verify the prediction accuracy of dynamic vibration response of an aluminium cantilever beam which ONPD is imposed at the free end with different packing rate and granular material, the result indicate that the mathematical model has excellent performance to predict the dynamic vibration response of NOPD. Then, the relationship damping effect with the particle filling ratio, particle density and length-diameter ratio of the hole is also researched using co-simulation, it should be noted that larger packing rate and particle density, smaller length-diameter ratio of the hole can play excellent damping effects in NOPD. [ABSTRACT FROM AUTHOR]

Low-noise, energy-saving and improved sound quality has been the major concern for the eco-design of household appliance product. In this paper, taking off from vibro-acoustic coupling, a composite noise control scheme (CNCS) combined with dynamic vibration absorbing technology, the sound absorption technique, controlling noise in the outlet, and particle damping technique is developed to control the sound radiation from an outdoor unit of a split air-conditioner based on sound sources identification. With the help of developed experiment platform, application effect of each technology and CNCS are measured, experimental evaluation shows that the developed CNCS can reduce the sound pressure level (SPL) more than 10 dB. To clarify the application effect of CNCS in sound quality further, it should be evaluated subjectively by using experiments. Experimental result shows that the stability and smoothness of the unit's noise have been greatly improved in time domain signal of sound pressure, the fluctuation strength is greatly improved for the controlled unit, the value at the left ear is reduced from 0.0195 vacil to 0.0146 vacil, and the right ear value is 0.0141 vacil instead of 0.0251 vacil. In addition, the sharpness has also been significantly reduced after CNCS, the value at the left ear decreases from 2.11 acum to 1.97 acum, and 2.01 acum to 1.86 acum for the right ear. So, CNCS is a pragmatic technique to control noise, vibration and improving sound quality. [ABSTRACT FROM AUTHOR]

The particle damper as a passive means for vibration suppression, is preferred due to its simplicity and easy to implement and control, with no need for any auxiliary power equipment. The bottleneck of the design for the particle damper is that damping performance is influenced by many parameters including particle material and size, packing ratio and cavity dimensions of enclosure such as length, width and diameter. In fact, the overall damping effect of particle damper is closely related to the primary structure system parameters. However, the influences of the excitation point, dampers arrangements, excitation force amplitude, and excitation force type for overall damping effect are scarce reported in the open literatures. How to exert particle damper on the structure and how many particles filled within the cavity, which are needed to face the problem in the engineering practice. In the face of doubt above-mentioned, the above questions will be clarified in this paper. At the same time, an optimization algorithm by the application of genetic algorithms of BP neural network is carried out in order to get most excellent damping effect. These will offer significance guidance to design and conduct particle dampers implement in the specific engineering practice with reference significance. [ABSTRACT FROM AUTHOR]