Piezoelectric Research Articles

Post-buckling analysis of imperfect nonlocal piezoelectric beams under magnetic field and thermal loading

An investigation of the nonlinear thermal buckling behavior of a nano-sized beam constructed from intelligent materials called piezo-magnetic materials has been presented in this article. The nano-sized beam geometry has been considered based on two assumptions: an ideal straight beam and an imperfect beam. For incorporating nano-size impacts, the nano-sized beam formulation has been presented according to nonlocal elasticity. After establishing the governing equations based on classic beam theory and nonlocal elasticity, the nonlinear buckling path has been obtained via Galerkin's method together with an analytical trend. The dependency of buckling path to piezo-magnetic material composition, electro-magnetic fields and geometry imperfectness has been studied in detail.

Bleustein–Gulyaev wave in a nonlocal piezoelectric layered structure

Manifesting the piezoelectric and nonlocal effects on the propagation of surface waves in nanoscale smart structures can provide some new insights for the designs and applications of the nanoscale wave devices. Taking the nanoscale size effect into consideration based on the nonlocal theory, the propagation of Bleustein–Gulyaev (BG) wave in a nonlocal piezoelectric (PE) layer overlying a nonlocal piezoelectric (PE) half-space, is investigated. The dispersion relations and particular cases are derived for the open and short circuit conditions. The results show that wave propagation is highly affected by nanoscale size effects due to the nonlocality present in the media.

Local dynamic perturbation effects on the scale interactions in wall turbulence

An experimental investigation of near-wall scale interactions in the presence of a deterministic forcing input is presented in this work. The external forcing input was generated by a wall-mounted piezoelectric (PZT) actuator, which directly introduces a dynamic perturbation into the near-wall cycle of turbulent boundary layer flow. The spectra of velocity fluctuations indicated that the fundamental forcing mode can be observed in all the perturbed cases and that the occurrence of high-order harmonics is dependent on the PZT perturbation amplitude. Under the strong forcing input, the fundamental forcing mode is influenced by large-scale structures through a high-degree amplitude modulation (AM) effect. More importantly, the phase-switching process was found for the high-order harmonics and small-scale turbulence, both of which are in phase with the forcing mode in and are switched to be out of phase in . It was demonstrated that the forcing mode rearranges both the harmonics and small-scale turbulence in the near-wall region, as evidenced by the AM effect and phase relationship. In addition, the near-wall scale rearrangements were confirmed by the skewness cross-term distribution.

Review of vibration‐based electromagnetic–piezoelectric hybrid energy harvesters

SummaryThese days the health monitoring of machines and structures is performed using wireless sensor nodes (WSNs). The disadvantage of short life span of batteries in WSN is overcome by using energy harvesting techniques and the required power is extracted from the environment for operating WSNs. The energy available in environment is in the form of thermal, solar, wind, vibration, RF and acoustic energy. The Piezoelectric (PE), electromagnetic (EM), electrostatic and triboelectric transduction may be utilized to harvest power from vibration energy available on structure which otherwise may be going waste. Moreover, for enhancing power generation hybrid vibration energy harvesters are developed by combining two of such transduction mechanisms. The piezoelectric and electromagnetic based hybrid harvesters are discussed in this work for vibration energy harvesting. The hybrid vibration energy harvesters are classified here as resonant, frequency tuned, nonlinear, non‐resonant, multi‐mode and frequency up conversion harvesters. The architecture, input excitation levels and performance of the reported hybrid harvesters is discussed and compared to know the advantage of harvester's configuration. Moreover, all the reported harvesters are compared on the basis of input vibration to which these harvesters are subjected, their resonant frequencies, size, output voltage, power levels and power density. Most of the developed hybrid energy harvesters are resonant harvesters. The multi‐mode hybrid energy harvesters are generating comparatively higher power levels of up to 250.25 mW and power density 2669.3 µW/cm3 in the reported literature. The overall voltage and power generation range of the hybrid harvesters is from 0.131 mV to 26 V and 0.637 µW to 250.25 mW. Moreover, the power density for the reported energy harvesters is in the range from 1.96 µW/cm3 to 2669 µW/cm3.

Damage Identification in Plate Structures Using Sparse Regularization Based Electromechanical Impedance Technique.

This paper proposes a novel structural damage quantification approach using a sparse regularization based electromechanical impedance (EMI) technique. Minor structural damage in plate structures by using the measurement of only a single surface bonded lead zirconate titanate piezoelectric (PZT) transducer was quantified. To overcome the limitations of using model-based EMI based methods in damage detection of complex or relatively large-scale structures, a three-dimensional finite element model for simulating the PZT–structure interaction is developed and calibrated with experimental results. Based on the sensitivities of the resonance frequency shifts of the impedance responses with respect to the physical parameters of plate structures, sparse regularization was applied to conduct the undetermined inverse identification of structural damage. The difference between the measured and analytically obtained impedance responses was calculated and used for identification. In this study, only a limited number of the resonance frequency shifts were obtained from the selected frequency range for damage identification of plate structures with numerous elements. The results demonstrate a better performance than those from the conventional Tikhonov regularization based methods in conducting inverse identification for damage quantification. Experimental studies on an aluminum plate were conducted to investigate the effectiveness and accuracy of the proposed approach. To test the robustness of the proposed approach, the identification results of a plate structure under varying temperature conditions are also presented.

A novel approach for non-destructive EMI-based corrosion monitoring of concrete-embedded reinforcements using multi-orientation piezoelectric sensors

One of the major problems with the durability of concrete structures is the corrosion of embedded rebar in concrete. Early detection of corrosion can prevent catastrophic failures in structures. In this paper, the electromechanical impedance method (EMI) is used for structural health monitoring (SHM) and non-destructive corrosion diagnostics. Compared to previous methods, a new method with the highest accuracy is proposed to evaluate the electromechanical impedance curves. By using piezoelectric (PZT) sensors in concrete, the sensitivity of these sensors to compressive force is investigated through a series of experiments. Also, by bonding two PZT sensors on reinforcing bars in two different orientations, the behavior of specimens, are consistently compared with the EMI measurements. According to the results, a solution for the detection of the corrosion rate and its direction as well as the period of corrosion initiation is proposed based on the variations of the impedance curve during the corrosion.

Flexoelectric effects on dynamic response characteristics of nonlocal piezoelectric material beam

Flexoelectric effect has a major role on mechanical responses of piezoelectric materials when their dimensions become submicron. Applying differential quadrature (DQ) method, the present article studies dynamic characteristics of a small scale beam made of piezoelectric material considering flexoelectric effect. In order to capture scale-dependency of such piezoelectric beams, nonlocal elasticity theory is utilized and also surface effects are included for better structural modeling. Governing equations have been derived by utilizing Hamilton's rule with the assumption that the scale-dependent beam is subjected to thermal environment leading to uniform temperature variation across the thickness. Obtained results based on DQ method are in good agreement with previous data on pizo-flexoelectric beams. Finally, it would be indicated that dynamic response characteristics and vibration frequencies of the nano-size beam depends on the existence of flexoelectric influence and the magnitude of scale factors.

Structural Failure Detection Using Wireless Transmission Rate From Piezoelectric Energy Harvesters

This article presents a new self-powered wireless failure detection method that uses different signal transmission rates from piezoelectric energy harvesters. Reliable signal transmission from a wireless sensor network has been challenging due to the power supply issue, often covered by batteries that need regular replacement. Piezoelectric energy harvesting is an excellent option to power the sensors in a vibrational environment, but the power level is limited by input vibrational energy. In this article, we introduce a new failure detection strategy that uses multifunctional piezoelectric material for vibration sensing and energy harvesting. That is, when the vibration is stronger and the material strain is higher, piezoelectric material produces higher voltage, and power. Different power level from multiple piezoelectric sensors is used for sensing structural failure. We design a simple power management circuit that saves power proportional to the piezoelectric voltage so that the piezoelectric patch with higher strain can transmit more frequent wireless signals (higher transmission rate). To store the piezoelectric power, the circuit is composed of a full-bridge rectifier, a single pole double throw switch, a comparator with hysteresis, and a wireless transmitter (Zigbee). The failure detection performance is investigated in a case study that monitors screw joint failure in a vibrating plate. Reliability-based design optimization is conducted to determine the piezoelectric sensor network in terms of the number and sizes of multiple piezoelectric (PZT) patches. The test results show that the proposed system successfully powers the wireless transmitter using the ultra-low scale of power from the PZT sensors (microwatt) and detect the different combination of screw joint failure in the vibrating plate.

Embedded piezoelectric transducers based early-age hydration monitoring of cement concrete added with accelerator/retarder admixtures

Accelerator/retarder admixtures are often added into concrete to improve its early-age strength, which needs to be effectively monitored during its hardening process. The electromechanical impedance (EMI) technique has validated its effectiveness for concrete hydration monitoring, this study attempted to extend the EMI technique to monitor 28-day age of strength gain in concrete that added with accelerator/retarder admixtures. Two types of new piezoelectric (PZT) transducers namely cement/aluminum embedded PZT (CEP/AEP) were proposed for EMI monitoring. The feasibility of the CEP and AEP was first verified via finite element analysis, where hydration heat effect on the two types of transducers was comparatively evaluated by numerical modeling. In the experiment, CEP/AEP transducers were applied to monitor the strength gain in concrete cubes, where characteristics of EMI signature and its statistical indices including root mean square deviation (RMSD) and mean absolute percentage deviation (MAPD) were analyzed and correlated to strength development in concrete. Monitoring results demonstrated that concrete hydration triggered by retarder/accelerator were successfully captured by EMI signature. RMSD and MAPD indices further indicated that AEP had preferable performance than CEP transducer for monitoring early-age strength gain of concrete, as it could immune from hydration heat effect.

Effect of high- or low-speed fluctuations on the small-scale bursting events in an active control experiment* *Project supported by the National Natural Science Foundation of China (Grant Nos. 11972251, 11732010, 11572221, 11502066, and 11872272).

Active control of a fully developed turbulence boundary layer (TBL) over a flat plate has been investigated with a statistical view. The piezoelectric (PZT) oscillator is employed to produce periodic input into the inner region of the TBL. A wall probe is fixed upstream of the oscillator to identify the high- or low-speed fluctuations as the detecting signals. Then, the impact of the detecting signals on the small-scale bursting process is investigated based on the data acquired by the traversing probe downstream of the oscillator. The results indicate that the small-scale bursting intensity is restrained more apparently at high-speed detecting fluctuations but less impacted at low-speed detecting fluctuations. Furthermore, the perturbed-scale fluctuations arrange the small-scale bursting process in the near-wall region. The detecting signals have an obvious impact on this arrangement, especially the high-intensity regions of the small-scale bursting events: the vibration enhances the intensity at high-speed detecting signals but weakens it at low-speed detecting signals in these regions, which gives a direct evidence on how detecting signals interfering the small-scale bursting process.

Estimation of stress intensity factor reduction for a center-cracked plate integrated with piezoelectric actuator and composite patch

Active repair of a damaged structure using piezoelectric (PZT) actuators has played a significant role during the last two decades in reducing crack damage propagation in structures due to its electro-mechanical effect. Similarly, passive repair of damaged structures using composite materials has been widely used in recent years, and it has been divided into many types. In this paper, the hybrid repair of center-cracked plate using PZT actuators at the front of a plate and a composite patch at the back of the plate is analytically and numerically investigated. First, the solution is obtained from Rose's equations for the center-cracked plate integrated with a composite patch and a passive PZT actuator under uniform uniaxial load. Second, the stress intensity factor (SIF) for a center-cracked plate due to stress produced by a PZT actuator is analytically modeled using the weight functions method. The superposition principle is then used to superimpose the aforementioned solutions in order to yield the PZT actuator and composite patch's hybrid stress intensity factor for the center-cracked plate. Finally, the proposed analytical method was verified using the finite element method. The results demonstrate low relative errors between the analytical and the FE of below 5% in all the cases studied in this paper.

Pressure Waveform Estimation in Elastic Vessels Using Exciter-Detector Devices: Towards a Novel Approach for Cardiovascular Condition Assessment

Objective: This work finds its motivation in the impact that non-invasive, accurate and non-expert operable instrumentation may have on the monitoring of cardiovascular condition and proposes a new class of exciter-detector devices suited to the extraction of multiple hemodynamic parameters. Materials: The devices’ sensing unit is based on an innovative piezoelectric (PZ) sensor - MEMs accelerometer combination that enables the accelerometer to sense the vibrations produced by the PZ. The method for pressure waveform estimation relies on the amplitude modulation effect that occurs when the fluid pressure transmitted through the vessel wall attenuates the PZ oscillations sensed by the accelerometer. Methods: Two generations of devices were developed and characterized in a dedicated bench test system that was able to replicate the variability of a wide range of clinically relevant properties of the cardiovascular system. Results: The demodulation process yielded excellent results in recovering the morphology of pressure wave in bench test conditions. For the two developed prototypes, several waveforms were accurately extracted from the acceleration, current or power modulated carriers using the envelope and product detector algorithms. It was possible to reproduce the pressure waveform for successive higher applanation positions of the elastic tube at the bench test with a root mean square error of 2.4 ± 0.51%, when considering the best extracting method. Conclusion: The results obtained provide great prospects regarding the use of this group of devices as valid alternatives to currently available systems for pressure waveform assessment in physiological arteries.

Structural health monitoring of polymer-matrix composite using embedded piezoelectric ceramic transducers during several four-points bending tests

This article investigates the interest of a promising methodology, dealing with the use of an in-situ piezoelectric (PZT) disk to perform real-time Structural Health Monitoring (SHM) of glass fiber-reinforced polymer (GFRP) composites submitted to various four-points bending loadings: monotonic, load-unload and incremental load until failure. The real-time in-situ SHM is conducted acquiring the electrical signature (capacitance) variation of the embedded PZT transducer. To establish the link between the PZT capacitance response and the occurring physical phenomena, especially damage, a multi-instrumentation composed of external Non-Destructive Testing techniques (Acoustic Emission (AE) and Digital Image Correlation (DIC)) was implemented on the tested specimens, so that it was possible to make multi-physical couplings between the various obtained measurements and the PZT capacitance curves. It was shown that the PZT capacitance is very sensitive to damage initiation and progression inside the polymer-matrix composite material until its failure, mainly due to the specimens Neutral Fiber (NF) vertical offset which changes the piezoelectric coupling between the host composite and the transducer. Consequently, the SHM potential of such a PZT disk is highlighted, opening the way for its use in real technical structures submitted to bending loadings, such as aircraft wings.

Biosensors for Detecting Lymphocytes and Immunoglobulins.

Lymphocytes (B, T and natural killer cells) and immunoglobulins are essential for the adaptive immune response against external pathogens. Flow cytometry and enzyme-linked immunosorbent (ELISA) kits are the gold standards to detect immunoglobulins, B cells and T cells, whereas the impedance measurement is the most used technique for natural killer cells. For point-of-care, fast and low-cost devices, biosensors could be suitable for the reliable, stable and reproducible detection of immunoglobulins and lymphocytes. In the literature, such biosensors are commonly fabricated using antibodies, aptamers, proteins and nanomaterials, whereas electrochemical, optical and piezoelectric techniques are used for detection. This review describes how these measurement techniques and transducers can be used to fabricate biosensors for detecting lymphocytes and the total content of immunoglobulins. The various methods and configurations are reported, along with the advantages and current limitations.

An electro-optic tunable microwave delay-line using the piezoelectric-piezomagnetic superlattices with an external DC electric field

An Electro-optic tunable microwave slow-light delay-line using the piezoelectric (PZT) and piezomagnetic (CoFe2O4) superlattices (PPSs) with the external DC electric field is presented. Asymmetric coupled polaritonic band structures with respect to the forward and backward directions are induced by time-space inversion symmetry breaking due to the coexistence of ferroelectric and ferromagnetic domains. The group velocity and time-delays of electromagnetic waves in the proposed PPSs can be tuned freely by the external DC electric field via the electro-optic effect. The tunability is continuous and reversible. Thus, the proposed PPSs has a switch function that can realize the free switching between fast and slow waves by the external DC electric field. The slow-wave factors with regard to the forward and backward directions are also asymmetric. In addition, transmission spectra show that the proposed PPSs have an electro-optic tunable wavelength selection function.

Performance Evaluation of a Piezoelectric Energy Harvester Based on Flag-Flutter.

In the last few decades, piezoelectric (PZT) materials have played a vital role in the aerospace industry because of their energy harvesting capability. PZT energy harvesters (PEH) absorb the energy from an operational environment and can transform it into useful energy to drive nano/micro-electronic components. In this research work, a PEH based on the flag-flutter mechanism is presented. This mechanism is based on fluid-structure interaction (FSI). The flag is subjected to the axial airflow in the subsonic wind tunnel. The performance evaluation of the harvester and aeroelastic analysis is investigated numerically and experimentally. A novel solution is presented to extract energy from Limit Cycle Oscillations (LCOs) phenomenon by means of PZT transduction. The PZT patch absorbs the flow-induced structural vibrations and transforms it into electrical energy. Furthermore, the optimal resistance and length of the flag is predicted to maximize the energy harvesting. Different configurations of flag i.e., with Aluminium (Al) patch and PZT patch for flutter mode vibration mode are studied numerically and experimentally. The bifurcation diagram is constructed for the experimental campaign for the flutter instability of a cantilevered flag in subsonic wind-tunnel. Moreover, the flutter boundary conditions are analysed for reduced critical velocity and frequency. The designed PZT energy harvester via flag-flutter mechanism is suitable for energy harvesting in aerospace engineering applications to drive wireless sensors. The maximum output power that can be generated from the designed harvester is 6.72 mW and the optimal resistance is predicted to be 0.33 M.

Effect of Adhesive and Its Aging on the Performance of Piezoelectric Sensors in Structural Health Monitoring Systems

Adhesive and its aging can have influence on the Piezoelectric (PZT) elements in structural health monitoring (SHM) systems. However, the current research pays little attention to the effect of adhesives in SHM systems, and the mechanism of adhesive aging on monitoring signals is still unclear. In the present study, the relationship between types of adhesives, adhesive thickness, accelerated aging, and monitoring signal was analyzed in detail. The study was carried out with three kinds of epoxy resin AB adhesive (AW106, E-30CL, and E-120HP) and bonding thicknesses (0.01, 0.05, and 0.12 mm), and the elevated temperature was 100 °C for 45 days. The signal-based monitoring method was used to extract the characteristic parameters. The experimental results indicated that the standard shear strength and thickness of the adhesive may have a combined effect on the monitoring signal. Increasing the thickness may enhance the shear strength between PZT and the matrix. For the effectiveness of monitoring the signal propagation, however, increase in thickness may have a negative influence. Moreover, the elevated temperature will bring the signal amplitude to a peak in the first period of aging, and the highest point appears in 10 to 15 days. Nevertheless, with the increase of aging time, the adhesive will finally be degraded, resulting in the decrease of the signal amplitude. The experimental results may provide useful information for practical monitoring in the SHM field.

High-Precision Tracking Control of a Piezoelectric Micro-nano Platform Using Sliding Mode Control with the Fractional-Order Operator

In this paper, a sliding mode control using a fractional-order operator (SMCFO) method is presented for the hysteresis of a piezoelectric (PZT) micro-nano platform. At first, the hysteresis of the PZT micro-nano platform is described using the Duhem model. With respect to the sliding mode controller design, we introduce a fractional-order operator into the design of the sliding mode surface and enhance the performance of the proposed controller. The nonlinear switching action of the controller is eliminated through a smooth control action by applying an uncertainty and disturbance estimation technique. The stability of the proposed controller is analyzed using the Lyapunov theorem. Simulations and experimental results demonstrate that the SMCFO method achieves a no-load high precision tracking control of the PZT micro-nano platform and is also robust against load perturbations of the platform.

Study in circular auxetic structures for efficiency enhancement in piezoelectric vibration energy harvesting

Piezoelectric (PZT) components are one of the most popular elements in vibration sensing and also energy harvesting. They are very well established, cost effective and available in different geometries however there are still several challenges in their application particularly in vibration energy harvesting. They are normally narrow-band elements and work in high-frequency range. Their efficiency and power extraction density are also generally low compared with different electromagnetic techniques. Auxetic structures are proposed here to enhance efficiency of the piezoelectric circular patches in vibration energy harvesting. These kinds of patches namely PZT buzzers are inexpensive (less than 10 USD) elements and easily available. Two novel circular auxetic substrates are proposed to improve power extraction capacity of the conventional piezoelectric buzzers. Negative Poison’s ratio of the proposed meta-structure helps in efficiency enhancement. The concept is introduced, analyzed and verified through the finite element modeling and experimental testing. The idea is proved to work by comparing the harvested electrical power in the auxetic design against the conventional plain system. A parametric study is then carried out and effects of important electrical and geometrical parameters as well as the material property on the power extraction efficiency are assessed to arrive at optimum parameters. It is shown that by employing the auxetic design, a remarkable improvement in the harvested power is achievable. It is shown that for the two proposed auxetic designs, at the resonance frequency, we could reach to 10.2 and 13.3 magnification factor with respect to the plain energy harvester. Another important feature is that the resonant frequency in these new designs is very much lower than the conventional resonators. Results of this study can open a new path to application of inexpensive PZT buzzers in large-scale vibration energy harvesting.

Piezoelectric Electron-Phonon Interaction from AbInitio Dynamical Quadrupoles: Impact on Charge Transport in Wurtzite GaN.

First-principles calculations of e-ph interactions are becoming a pillar of electronic structure theory. However, the current approach is incomplete. The piezoelectric (PE) e-ph interaction, a long-range scattering mechanism due to acoustic phonons in noncentrosymmetric polar materials, is not accurately described at present. Current calculations include short-range e-ph interactions (obtained by interpolation) and the dipolelike Frölich long-range coupling in polar materials, but lack important quadrupole effects for acoustic modes and PE materials. Here we derive and compute the long-range e-ph interaction due to dynamical quadrupoles, and apply this framework to investigate e-ph interactions and the carrier mobility in the PE material wurtzite GaN. We show that the quadrupole contribution is essential to obtain accurate e-ph matrix elements for acoustic modes and to compute PE scattering. Our work resolves the outstanding problem of correctly computing e-ph interactions for acoustic modes from first principles, and enables studies of e-ph coupling and charge transport in PE materials.