Damping performance of finite microperforated plates using multi-size and spatial distributions of perforations

Abstract

In the context of structural dynamics, recent works by the authors showed that microperforations can be used to mitigate vibration. Microperforated plates (MPP) have been shown to exhibit substantial added damping arising from fluid-structure interactions and visco-thermal effects in the boundary layers of the perforations during relative motion between the solid and the fluid contained in the perforations. The added damping reaches a maximum for a characteristic frequency, depending only on the diameter of the perforation. Choosing the diameter of the perforation so that the characteristic frequency coincides with a given natural frequency of the plate reduces the contribution of the associated plate mode. However, the MPP studied had a single set of perforations homogeneously distributed throughout the structure. In this work, it is proposed to extend the added damping to several modes of the plate by using MPP with multi-size perforations and an optimized spatial distribution of these perforations. As an extension of the previous vibratory model of the authors, the dynamics of MPP with perforations of multiple sizes based on a homogenization model is established. In addition, the effect of the spatial distribution of perforations on the additional damping is captured by including a spatially dependent perforation ratio in the model. Experimental measurements on MPP validate the proposed analytical models. The results show that (i) MPP with multiple-size perforations feature a wider effective damping frequency band, and (ii) the added damping is accentuated when the perforations are distributed in the zone of the antinodes of the considered modes. Thus, by combining the two effects, it is possible to achieve MPP that effectively reduce the vibratory responses on several modes.