K. A. Cunefare

Broadband Vibration Control Through Periodic Arrays of Resonant Shunts: Experimental Investigation on Plates

In this work, a periodic 4 × 4 lay-out of resistive inductive (RL) shunted piezoelectric transducer (PZT) patches is designed and applied to achieve broadband vibration reduction of a flexible isotropic plate over tunable frequency bands. Each surface-bonded PZT patch is connected to a single independent RL circuit and all shunt circuits are tuned at the same frequency. A finite element-based design methodology is used to predict the attenuation properties of the unit cell that characterize the periodic assembly. The predictions are experimentally validated by measuring the spatial average harmonic response of the plate. Significant broadband attenuation is obtained over frequency bands centered at the resonance frequency of the shunting circuit.

Wave Motion Optimization in Periodically Distributed Shunted Piezocomposite Beam Structures

This article proposes a new, simple, and efficient strategy, allowing one to optimize the diffusion operator between a passive beam coupled to a like beam equipped with a periodically distributed network of shunted piezoelectric patch actuators. A multimodal wave dispersion model is used to compute the diffusion operator and analyze the stability properties of the combined system. Based on this mathematical tool, specific optimization procedures are introduced to allow maximization or minimization of the wave transmissibility between the passive and the active distributed beam. A specific example is used to demonstrate the capability of the shunted piezoelectric system to induce total reflection through the total absorption of incoming propagating flexural waves while guaranteeing the stability, robustness, and realizability of such a system.

Experimental characterization of a bi-dimensional array of negative capacitance piezo-patches for vibroacoustic control

This study presents an experimental investigation of the application of a periodic array of shunted piezoelectric patches with negative capacitance for the broadband control of waves propagating on a flexible plate. A 15 × 5 array of piezoelectric patches is bonded onto the top surface of a freely supported rectangular plate. The patch array is intended to serve as an active interface between two regions of the plate, where one region has an input disturbance force and the other does not. Each patch is shunted through a single circuit, reproducing a resistance in series with a negative capacitance. The magnitude of the reactive part of the negative shunting impedance is tuned close to the intrinsic capacitance of the piezoelectric patch. The real part is adjusted for either light damping so as to induce a reactive (reflective) response, or with heavy damping to induce greater absorption. The experimental responses of the system equipped with this active interface display a strong attenuation or reflection of vibrations, depending on the shunt resistance, over a large frequency range, including the mid-frequency regime. In an effort to control vibroacoustic phenomena, this study represents the first attempt to implement an integrated smart metacomposite active interface on a plate structure.

Generation of Lamb waves through surface mounted macro-fiber composite transducers

The paper describes a numerical approach for the analysis of Lamb wave generation in plate structures. Focus is placed on the investigation of macro-fiber composite (MFC) actuators and their directivity properties when actuated individually, or as part of rosette configurations. A local finite element model of the electro-mechanical behavior of the actuator/substrate system estimates the distribution of the interface stresses between the actuator and the substrate, which are subsequently provided as inputs to the analytical procedure that estimates the far-field response of the plate. The proposed approach allows handling of complex actuation configurations, as well as the presence of a bonding layer. The technique is first validated against the results available in the literature, and it is then applied to the analysis of macro-fiber composites. Rosette configurations show a rich directional behavior which can be tuned through the selection of phase and amplitude relations among the components of the rosette. The results suggest the potential of the approach as a tool for the optimization of the directivity of rosette actuators and for the prediction of the excitation provided by actuators of complex shapes.

Vibration control of plates featuring periodic arrays of hybrid shunted piezoelectric patches

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 (2D) 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 1000Hz is achieved with a maximum 8 dB vibration reduction.

Design variables for optimizing adaptive metacomposite made of shunted piezoelectric patches distribution

A two-dimensional array of a piezoelectric transducer shunted on a 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. The results obtained clearly show how the proposed strategy represents a robust and effective solution for the control of vibrations in complex structures.

Power performance improvements for high pressure ripple energy harvesting

A hydraulic pressure energy harvester (HPEH) device, which utilizes a housing in order to isolate a piezoelectric stack from the hydraulic fluid via a mechanical interface, generates power by converting the dynamic pressure within the system into electricity. Energy harvester prototypes were designed for generating low-power electricity from pressure ripples. These devices generate low-power electricity from off-resonance dynamic pressure excitation. The power produced per volume of piezoelectric material is analyzed to increase the power density; this is accomplished through evaluating piezoelectric stack characteristics, adding an inductor to the system circuit, and solving for optimal loading in order to achieve maximum power output. The prototype device utilizes a piezoelectric stack with high overall capacitance, which allows for inductance matching without using an active circuit. This work presents an electromechanical model and the experimental results of the HPEH devices using a parallel connection of inductive and resistive loads as the energy harvesting circuit. A non-ideal inductive load case is also considered and successfully modeled by accounting for the parasitic resistance of the inductive load. Various HPEH prototypes are fabricated, modeled, and compared in terms of their normalized power density levels, and milli-Watt level average power generation is demonstrated. The highest power density is reported for the single-crystal HPEH prototype.

Vibroacoustic Energy Diffusion Optimization in Beams and Plates by Means of Distributed Shunted Piezoelectric Patches

This chapter proposes a synthesis of different new methodologies for developing a distributed, integrated shunted piezo composite for beams and plates applications able to modify the structural vibro acoustical impedance of the passive supporting structure so as to absorb or reflect incidental power flow. This design implements tailored structural responses, through integrated passive and active features, and offers the potential for higher levels of vibration isolation as compared to current designs. Novel active and passive shunting configurations will be investigated to reduce vibrations such as distributed Resistance Inductance and Resistance with negative Capacitance circuits.

Modeling and characterization of macro-fiber composite transducers for Lamb wave excitation

The paper describes a numerical approach for the analysis of Lamb wave generation in plate structures. Focus is placed on the investigation of macro fiber composite (MFC) actuators and their directivity properties when actuated individually. A local Finite Element model of the electro-mechanical behavior of the actuator/substrate system estimates the distribution of the interface stresses between the actuator and the substrate, which are subsequently provided as inputs to the analytical procedure that estimates the far-field response of the plate. The proposed approach allows handling of complex actuation configurations, as well as the presence of a bonding layer. As an example, the technique is applied to estimate the directional Lamb wave generation of two types of macro fiber composite transducers. The numerical results are validated experimentally by using a Polytec PSV400 MS scanning laser doppler vibrometer. The results suggest the potentials of the approach as a tool for the prediction of the excitation provided by actuators of complex shapes.

Vibration control of plates through a periodic array of shunted piezoelectric patches with negative capacitance circuits

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.