A two-dimensional array of piezoelectric transducer (PZT) shunted on negative capacitance circuit is designed and applied to achieve broadband vibration reduction of a flexible plate over tunable frequency bands. Each surface-bonded patch is connected to a single independent negative capacitance synthetic circuit. A finite element-based design methodology is used to predict and optimize the attenuation properties of the smart structure. The predictions are then experimentally validated by measuring the harmonic response of the plate and evaluating some derived quantity such as the loss factor and the kinetic energy ratio. The validated model is finally used to explore different configurations with the aim of defining some useful design criteria.
To reduce the noise emitted by commercial aircraft turbofan engines, the inlet and aft nacelle ducts are lined with
acoustic absorbing structures called acoustic liners. Traditionally, these structures consist of a perforated facesheet
bonded on top of a honeycomb core. These traditional perforate over honeycomb core (POHC) liners create an
absorption spectra where the maximum absorption occurs at a frequency that is dictated by the depth of the honeycomb
core; which acts as a quarter-wave resonator. Recent advances in turbofan engine design have increased the need for thin
acoustic liners that are effective at low frequencies. One design that has been developed uses an acoustic metamaterial
architecture to improve the low frequency absorption. Specifically, the liner consists of an array of Helmholtz resonators
separated by quarter-wave volumes to create a dual-resonance acoustic liner. While previous work investigated the
acoustic behavior under normal incidence, this paper outlines the modeling and predicted transmission loss and
absorption of a dual-resonance acoustic metamaterial when subjected to grazing incidence sound.
Negative capacitance shunt damping is an effective broadband method for attenuating flexural vibration. However, proper selection of the location of the piezoelectric patches on a structure to maximize reduction has been an ongoing question in the field. Acoustic black holes are a recently developed concept to reduce vibrations on thin vibrating structures. By engineering the geometric or material properties of these thin structures, it is possible to minimize the reflected wave by gradually reducing the wave speed. However, the flexural wave speed cannot be reduced to zero on a realized structure. Therefore, when acoustic black holes are implemented, some of the incident wave energy is reflected because the wave speed must be truncated. Similarly due to the reduction in wave speed, the transverse velocity significantly increases within the acoustic black hole. It is therefore possible to add piezoelectric transducers to acoustic black hole regions on a structure to utilize negative capacitance shunt damping to address both of these issues. Consequently, the transducers are placed in the locations where the greatest control can be made and the reflected waves can be attenuated. The combination of negative capacitance shunt damping with acoustic black holes shows increased suppression of vibration over shunt damping alone.
The control of vibrating structures using piezoelectric elements connected to simple control circuits, known as shunts, is
a widely studied field. Many different shunts have been researched that haven been shown to obtain strong performance
in both narrow and broadband frequency ranges. Yet, the choice for the exact parameters of these shunts can be found
different ways. In this work, a new method of selecting the components of a negative capacitance shunt is presented. An
impedance model of a piezoelectric patch is developed and used to predict the control of a vibrating structure. The model
predicts the magnitude of the strain induced voltage caused by the vibrating substrate through the computation of two
voltage readings within the shunt. It is then confirmed experimentally, that it is possible to obtain experimentally the
shunt parameters that produce maximum control through measurement of the shunt response.
Shunted piezoelectric patches form an effective control mechanism for reducing vibrations of a mechanical
system. One type of shunt, a negative capacitance circuit, is capable of suppressing vibration amplitude over
a broad frequency range. Most previous work has focused on control of simple test structures such as beams
and plates. This work studies the performance of the negative capacitance shunt connected to piezoelectric
patches attached to a stiffened aircraft panel. The placement of the piezoelectric transducers is determined
using a simplified finite element model of one bay of the panel. The numerical predictions are compared to
experimental results for spatial average vibration for a point force input. The amount of control for increasing
number of patches is also investigated. These results give a more accurate representation of the achievable
performance in real world application.
The use of piezoelectric patches for actuation as a vibration control method has been widely investigated. Some of the
uses for piezoelectric actuators include velocity feedback, synthetic impedance control, and a shunted sensor-actuator.
Likewise, periodic structures have been shown to be effective in allowing the dissipation of travelling wave energy. The
combination of these control procedures, an active periodic piezoelectric array, allows for enhanced vibration control.
Presented here is the investigation of thin beam with 12 piezoelectric patch pairs. These patches will be shunted with
varying selected impedances, specifically negative capacitive impedances, to allow for comparison of control ability. This comparison includes an analysis of spatial RMS velocity and numerical propagation constant.
Periodic arrays of hybrid shunted piezoelectric actuators are used to suppress vibrations in an aluminum plate.
Commonly, piezoelectric shunted networks are used for individual mode control, through tuned, resonant RLC
circuits, and for broad-band vibration attenuation, through negative impedance converters (NIC). Periodically
placed resonant shunts allow broadband reduction resulting from the attenuation of propagating waves in frequency
bands which are defined by the spatial periodicity of the array and by the shunting parameters considered
on the circuit. Such attenuation typically occurs at high frequencies, while NICs are effective in reducing the
vibration amplitudes of the first modes of the structure. The combination of an array resonant shunts and NICs
on a two-dimensional (2<i>D</i>) panel allows combining the advantages of the two concepts, which provide broadband
attenuation in the high frequency regimes and the reduction of the amplitudes of the low frequency modes.
Numerical results are presented to illustrate the proposed approach, and frequency response measurements on a
cantilever aluminum plate demonstrate that an attenuation region of about 1000H<i>z</i> is achieved with a maximum
8 <i>dB</i> vibration reduction.
Numerical and technological tools have been developed for complete electromechanical integration of innovative
shunting damping strategies for piezoelectric composite beam stabilization to realize a new type of hybrid piezo-composite
smart structure. The approach enhances the performance of fully passive configurations to control
mechanical power flow in a beam by using negative capacitance elements. In contrast to passive shunted components
that target discrete modes, negative capacitance shunted piezoelectric transducers offer the potential for
broadband control from the low Hertz into the kilohertz range.
This paper presents an original approach to tune vibration power flow dispersion in a piezocomposite beam to
obtain total wave absorption by only optimizing the electrical circuit configuration shunting a single piezopatch.
The numerical study considers the power flow efficiency of the strategy and the stability and robustness difficulties
observed when a single device is considered.
The simplicity of the proposed electromechanical controlling device affords the possibility to define and realize
distributed configurations and also lends itself to integrated distributed smart composite structures.
Negative impedance shunts have been used with piezoelectric materials for the purposes of vibration
suppression. Details of the shunt design may be determined using different performance objectives such as
maximum dissipation or minimization of reactive input power. Experimentally optimized shunts are applied
to a composite piezoelectric aluminum beam subjected to a broadband disturbance. Performance measures of
interest include an overall power balance for the system, as well as tip vibration suppression and spatial
average vibration suppression. The resulting measures are compared to the wave-tuning and reactive power
input tuning suppression theories.