The effectiveness of particle dampers under centrifugal loads

[摘要] The main research objective of this dissertation was to determine the performanceparameters of particle dampers (PDs) under centrifugal loads.A test bench was developed consisting of a rotating cantilever beam with a PD atthe tip. Equal mass containers with di erent depths, filled with a range of uniformsized steel ball bearings, were used as PDs. For all the tests, the total PD mass wasidentical. During operation the tip of the beam was displaced, and after release, thebeam could vibrate freely. The decay in the vibratory motion of the tip of the beamwas measured over a range of centrifugal loads.The experiments were duplicated numerically with a discrete element method(DEM) model, calibrated against the experimental data. This model could then beused for a more in-depth investigation of phenomena occurring when PDs are undercentrifugal loads.From the data analysis, it can be concluded that there are two zones of damping,one with a high and one with a low damping factor. These damping zones depend onthe ratio between the peak vibration acceleration and the centrifugal loading. Eachzone has a limit in terms of the centrifugal loading beyond which the PD cannotfunction if the vibration amplitude is fixed. In the high damping zone, it was foundthat the excitation state of the particles was high enough for the system vibrationfrequency to change. In the low damping zone, there is only limited motion betweenthe particles.The main parameters that influence the performance of the PDs are the frictionbetween the particles themselves and with the container, the PD length/diameteraspect ratio, and the particle size. An important finding is that a PD with less layers(increase in particle size) will still function at a higher centrifugal load compared toone with a smaller number number of layers.

[发布机构] Stellenbosch University