Piezoelectric Smart Research Articles

Novel composite finite element model for piezoelectric energy harvesters based on 3D beam kinematics

In this study, piezoelectric smart structures are formulated using finite element method based on equivalent single layer theory for electromechanical domains, especially in energy harvesting. A model is derived where all displacement, strain, electric potential, and electric fields are decomposed into longitudinal and cross-sectional components and a finite element discretization is performed. All parameters are calculated for 3D active beam elements. Mechanical degrees of freedom are decoupled for both mechanical and electromechanical coupling matrices. Two local coordinate systems and a global one are introduced for this purpose. A method is presented and proved to transform element matrices between those systems. Natural frequencies of a cantilever harvester obtained from the theory are compared to those of ABAQUS model. Output voltage, current, RMS power, open and short circuit natural frequencies, and optimum resistive load are also calculated. Finally, the results of the present theory are compared to those presented in the literature.

Nanofibrous Smart Fabrics from Twisted Yarns of Electrospun Piezopolymer.

Smart textiles are envisioned to make a paradigm shift in wearable technologies to directly impart functionality into the fibers rather than integrating sensors and electronics onto conformal substrates or skin in wearable devices. Among smart materials, piezoelectric fabrics have not been widely reported, yet. Piezoelectric smart fabrics can be used for mechanical energy harvesting, for thermal energy harvesting through the pyroelectric effect, for ferroelectric applications, as pressure and force sensors, for motion detection, and for ultrasonic sensing. We report on mechanical and material properties of the plied nanofibrous piezoelectric yarns as a function of postprocessing conditions including thermal annealing and drawing (stretching). In addition, we used a continuous electrospinning setup to directly produce P(VDF-TrFE) nanofibers and convert them into twisted plied yarns, and demonstrated application of these plied yarns in woven piezoelectric fabrics. The results of this work can be an early step toward realization of piezoelectric smart fabrics.

Analysis of functionally graded piezoelectric Timoshenko smart beams using a multiquadric radial basis function method

In the present work, a global interpolation scheme is proposed to describe the electro-mechanical static response of piezoelectric smart beams considering applied mechanical loads and electric potential. First, bimorph and three-layered Timoshenko smart beams are investigated and the model is validated for both actuator and sensor capabilities. Lastly, a functionally graded piezoelectric (FGP) bimorph beam is studied in its actuator configuration. The governing equations of motion are derived by the application of Hamilton’s principle considering an equivalent-single-layer first-order-shear-deformation theory (ESL-FSDT) with layerwise electric potential. The equations are subsequently solved using a grid free method based on Kansa’s asymmetric collocation using multiquadric radial basis functions (RBFs). The method relies on the Euclidean distance between nodes and on a shape parameter which must be warily selected to avoid matrix ill-conditioning. Accurate results are obtained while maintaining a very low computational cost.

Application assessments of concrete piezoelectric smart module in civil engineering

Traditional structural dynamic analysis and Structural Health Monitoring (SHM) of large scale concrete civil structures rely on manufactured embedding transducers to obtain structural dynamic properties. However, the embedding of manufactured transducers is very expensive and low efficiency for sign...

A periodic piezoelectric smart structure with the integrated passive/active vibration-reduction performances

The paper proposes a new piezoelectric smart structure with the integrated passive/active vibration-reduction performances, which is made of a series of periodic structural units. Every structural unit is made of two layers, one is an array of piezoelectric bimorphs (PBs) and one is an array of metal beams (MBs), both are connected as a whole by a metal plate. Analyses show that such a periodic smart structure possesses two aspects of vibration-reduction performance: one comes from its phonon crystal characteristics which can isolate those vibrations with the driving frequency inside the band gap(s). The other one comes from the electromechanical conversion of bent PBs, which is actively aimed at those vibrations with the driving frequency outside the band gap(s). By adjusting external inductance, the equivalent circuit of the proposed structure can be forced into parallel resonance such that most of the vibration energy is converted into electrical energy for dissipation by a resistance. Thus, an external circuit under the parallel resonance state is equivalent to a strong damping to the interrelated vibrating structure, which is just the action mechanism of the active vibration reduction performance of the proposed smart structure.

Theoretical Analysis of the Dynamic Properties of a 2-2 Cement-Based Piezoelectric Dual-Layer Stacked Sensor under Impact Load.

Cement-based piezoelectric materials are widely used due to the fact that compared with common smart materials, they overcome the defects of structure-incompatibility and frequency inconsistency with a concrete structure. However, the present understanding of the mechanical behavior of cement-based piezoelectric smart materials under impact load is still limited. The dynamic characteristics under impact load are of importance, for example, for studying the anti-collision properties of engineering structures and aircraft takeoff-landing safety. Therefore, in this paper, an analytical model was proposed to investigate the dynamic properties of a 2-2 cement-based piezoelectric dual-layer stacked sensor under impact load based on the piezoelectric effect. Theoretical solutions are obtained by utilizing the variable separation and Duhamel integral method. To simulate the impact load and verify the theory, three types of loads, including atransient step load, isosceles triangle load and haversine wave load, are considered and the comparisons between the theoretical results, Li’s results and numerical results are presented by using the control variate method and good agreement is found. Furthermore, the influences of several parameters were discussed and other conclusions about this sensor are also given. This should prove very helpful for the design and optimization of the 2-2 cement-based piezoelectric dual-layer stacked sensor in engineering.

On modelling three-dimensional piezoelectric smart structures with boundary spectral element method

The computational efficiency of the boundary element method in elastodynamic analysis can be significantly improved by employing high-order spectral elements for boundary discretisation. In this work, for the first time, the so-called boundary spectral element method is utilised to formulate the piezoelectric smart structures that are widely used in structural health monitoring (SHM) applications. The resultant boundary spectral element formulation has been validated by the finite element method (FEM) and physical experiments. The new formulation has demonstrated a lower demand on computational resources and a higher numerical stability than commercial FEM packages. Comparing to the conventional boundary element formulation, a significant reduction in computational expenses has been achieved. In summary, the boundary spectral element formulation presented in this paper provides a highly efficient and stable mathematical tool for the development of SHM applications.

Optimal Piezoelectric Actuators and Sensors Configuration for Vibration Suppression of Aircraft Framework Using Particle Swarm Algorithm

Numbers and locations of sensors and actuators play an important role in cost and control performance for active vibration control system of piezoelectric smart structure. This may lead to a diverse control system if sensors and actuators were not configured properly. An optimal location method of piezoelectric actuators and sensors is proposed in this paper based on particle swarm algorithm (PSA). Due to the complexity of the frame structure, it can be taken as a combination of many piezoelectric intelligent beams and L‐type structures. Firstly, an optimal criterion of sensors and actuators is proposed with an optimal objective function. Secondly, each order natural frequency and modal strain are calculated and substituted into the optimal objective function. Preliminary optimal allocation is done using the particle swarm algorithm, based on the similar optimization method and the combination of the vibration stress and strain distribution at the lower modal frequency. Finally, the optimal location is given. An experimental platform was established and the experimental results indirectly verified the feasibility and effectiveness of the proposed method.

Damage monitoring of the RC frame shaking table test and comparison with FEM results

Piezoelectric smart aggregate (SA) is an internal stress sensor capable of full range seismic damage monitoring for concrete structures. In this study, the structure model is a one-bay-two-story RC frame, which is subjected to one direction horizontal excitation in a shaking table test. Stresses of four cross sections at the top and bottom of the two columns in the first floor which were symmetrical about the central axis along the excitation direction were monitored. Strain of rebar, acceleration, displacement of the structure was also monitored. The RC frame underwent Loma Prieta earthquake record with a peak value of 0.8g. After the simulated ground motion, only moderate damages were observed in the structure. Finite element analysis (FEA) using OpenSEES were conducted to simulate the shaking table test. By the comparison between the test and numerical results, the influence of the randomness of the material property identified by the SA-based stress monitoring on the failure pattern was discussed and the parameters of finite element model were checked.

Dynamics modeling and attitude control of a flexible space system with active stabilizers

Attitude control of rigid-flexible multi-body systems by active stabilizers is studied in this paper. During slewing maneuvers, flexible members like solar panels may be excited to vibrate. These vibrations, in turn, produce oscillatory disturbing forces on other subsystems and consequently produce error in the spacecraft motion. Also, to develop a proper model-based controller for such complicated system, the system dynamic model is derived. However, due to practical limitations and real-time control implementation, the system dynamic model should be structured such that low computations burden will be imposed on the model-based controller. In this paper, in contrast to many accumulating dynamic modeling approach, a precise compact dynamic model for an active stabilized spacecraft (ASS) system with flexible members is derived. Toward this goal, the total system is virtually partitioned into two rigid and flexible portions. Moreover, the obtained model of these complicated systems is vigorously verified using ANSYS and ADAMS programs. Finally, based on the derived dynamics and a proper virtual damping parameter, an attitude control algorithm is then developed. The suggested controller structure takes the advantage of utilizing the piezoelectric smart materials to dissipate the vibration of solar panels. The obtained results reveal the merits and effectiveness of the proposed suggested modeling and control methods for reliable attitude maneuvering of the system. In addition, it will be shown that the undesired vibrations of the flexible solar panels result in disturbing forces on the ASS system which can be significantly eliminated by the proposed attitude control algorithm.

Band gaps of the phononic piezoelectric smart materials with LCR shunting circuits

Environmental forces can produce undesired vibrations in mechanical structures that can limit the precision of mechanical equipment and cause mechanical failure. Piezoelectric-shunt damping is an attractive technique for controlling the vibrating structures, which is reliable, economical and light-weight. Phononic crystal is an internal component whose elastic constant, density and sound velocity change periodically. When the elastic wave passes through a phononic crystal, special dispersion curve is formed due to the interaction of periodic arrangement materials. In order to study the electromagnetic oscillation band gap of the piezoelectric phononic crystal with LCR shunt network at torsional and flexural vibration, we propose a new phononic piezoelectric beam, which is composed of aluminum and epoxy resin. When the piezoelectric patch is strained, the electrical energy is dissipated as current flows through an external LCR shunting circuit. By combining the piezoelectric effect with the mechanical vibration of the smart material, the equivalent additional stress of piezoelectric patches is deduced. Moreover, coupling the energy band theory of phononic crystal with the effect of electromagnetic oscillation, we calculate the band gap characteristics of torsional and flexural vibration of intelligent material. Using the transfer matrix method and Bloch theorem for periodic boundary conditions, the band gap of the phononic beam can be calculated. With the increase of resistance, the amplitude attenuation of the band gap decreases. However, it can expand the frequency range. The inherent frequency of the electromagnetic oscillation is 1/[2π√L(C + CP)]. The sum of capacitance and inherent capacitance is the total capacitance of the shunting circuit. Therefore, the frequency of the electromagnetic oscillation decreases with the increases of the capacitance and inductance. The amplitude attenuation of the band gap increases with the increase of the inductance and decreases greatly with the rise of the capacitance. Three main differences between the LCR shunt networks and traditional circuits are found. First, the band gaps of the phononic piezoelectric smart material are composed of Bragg band gaps and local resonant band gaps. The former one is due to the mismatch between aluminum and epoxy resin, which makes the elastic waves have no corresponding vibration modes at certain frequencies. The latter one is from the effect of electromagnetic oscillation in LCR shunt networks, which consume the energy by resistor. Second, by tuning the resistance, capacitance and inductance, we can change the singularity position and stress magnitude of equivalent additional force curve. The amplitude attenuations of locally resonant band gaps and electromechanical coupling coefficient will be changed. Third, both locations and widths of the band gaps can be tuned by simply varying the value of negative capacitance of the shunting networks without needing to modify the configuration of the structure. Therefore, it provides a new idea for controlling the vibration and reducing the noise of the phononic piezoelectric smart material.

A magnetic–piezoelectric smart material-structure utilizing magnetic force interaction to optimize the sensitivity of current sensing

This paper presents a magnetic–piezoelectric smart material-structure using a novel magnetic-force-interaction approach to optimize the sensitivity of conventional piezoelectric current sensing technologies. The smart material-structure comprises a CuBe-alloy cantilever beam, a piezoelectric PZT sheet clamped to the fixed end of the beam, and an NdFeB permanent magnet mounted on the free end of the beam. When the smart material-structure is placed close to an AC conductor, the magnet on the beam of the smart structure experiences an alternating magnetic attractive and repulsive force produced by the conductor. Thus, the beam vibrates and subsequently generates a strain in the PZT sheet. The strain produces a voltage output because of the piezoelectric effect. The magnetic force interaction is specifically enhanced through the optimization approach (i.e., achieved by using SQUID and machining method to reorient the magnetization to different directions to maximize the magnetic force interaction). After optimizing, the beam’s vibration amplitude is significantly enlarged and, consequently, the voltage output is substantially increased. The experimental results indicated that the smart material-structure optimized by the proposed approach produced a voltage output of 4.01 Vrms with a sensitivity of 501 m Vrms/A when it was placed close to a conductor with a current of 8 A at 60 Hz. The optimized voltage output and sensitivity of the proposed smart structure were approximately 316 % higher than those (1.27 Vrms with 159 m Vrms/A) of representative piezoelectric-based current sensing technologies presented in other studies. These improvements can significantly enable the development of more self-powered wireless current sensing applications in the future.

Investigation of cement–sand-based piezoelectric composites

A novel cement–sand-based piezoelectric smart composite was developed for conducting structural health monitoring for civil structures. To overcome the incompatibility between piezoelectric materials and reinforced concrete containing cement and sand, for the first time, sand was used to fabricate the new composite in this study. Two sets of specimens containing 30 and 50 vol% lead zirconate titanate were prepared using normal mixing and spread methods, followed by the characterization of the properties of the composites. The composite exhibited desirable piezoelectric strain and voltage coefficients. Furthermore, the dielectric constant and loss of the composite were also determined. The results indicated that the piezoelectric effect and dielectric constant were enhanced with increasing lead zirconate titanate content. Compressive tests were conducted to study the sensing effect of the composite. The investigation demonstrated the feasibility of using the new composite as sensors in structural health monitoring systems to prevent possible failure of civil structures.

A locking-free coupled polynomial Timoshenko piezoelectric beam finite element

Purpose – Piezoelectric extension mode smart beams are vital part of modern control technology and their numerical analysis is an important step in the design process. Finite elements based on First-order Shear Deformation Theory (FSDT) are widely used for their structural analysis. The performance of the conventional FSDT-based two-noded piezoelectric beam formulations with assumed independent linear field interpolations is not impressive due to shear and material locking phenomena. The purpose of this paper is to develop an efficient locking-free FSDT piezoelectric beam element, while maintaining the same number of nodal degrees of freedom. Design/methodology/approach – The governing equations are derived using a variational formulation to establish coupled polynomial field representation for the field variables. Shape functions based on these coupled polynomials are employed here. The proposed formulation eliminates all locking effects by accommodating strain and material couplings into the field interpolation, in a variationally consistent manner. Findings – The present formulation shows improved convergence characteristics over the conventional formulations and proves to be the most efficient way to model extension mode piezoelectric smart beams, as demonstrated by the results obtained for numerical test problems. Originality/value – To the best of the authors’ knowledge, no such FSDT-based finite element with coupled polynomial shape function exists in the literature, which incorporates electromechanical coupling along with bending-extension and bending-shear couplings at the field interpolation level itself. The proposed formulation proves to be the fastest converging FSDT-based extension mode smart beam formulation.

A consistently efficient and accurate higher order shear deformation theory based finite element to model extension mode piezoelectric smart beams

The accuracy and efficiency of the conventional higher order shear deformation theory based piezoelectric beam finite elements are shown to be affected by the geometric and material parameters of piezoelectric smart beams. The accuracy is affected by the induced potential effects and the efficiency is affected by asymmetric distribution of material over the beam cross-section. In this work, a novel higher order shear deformation theory based extension mode piezoelectric beam finite element is proposed, which consistently maintains the same level of accuracy and efficiency over a wide range of applicable material properties and geometric configurations of the beam. A consistent higher order through-thickness electric potential distribution, obtained from the electrostatic equilibrium equation is used in the variational formulation to derive the governing equations. These equations are solved to establish relationships between the field variables. Starting with assumed polynomials for the transverse displacement and a layerwise electric potential, coupled polynomial expressions for axial displacement and section rotation are derived using these relations. The set of coupled shape functions obtained using these polynomials accommodates the bending–extension, bending–shear and induced potential couplings in a variationally consistent manner, at the field interpolation level itself, and is shown to improve the performance of the proposed element. Moreover, the number of mechanical degrees of freedom per node is reduced from four (for the conventional higher order shear deformation theory beam elements) to three for the present higher order shear deformation theory beam element, without affecting the applicability.

An accurate modeling of piezoelectric smart beams with first-order shear deformation theory

A finite element model for piezoelectric smart beam in extension mode based on First-order Shear Deformation Theory (FSDT) with an appropriate through-thickness distribution of electric potential is presented. Accuracy of piezoelectric finite element formulations depends on the selection of assumed mechanical and electrical fields. Most of the conventional FSDT-based piezoelectric beam formulations available in the literature use linear through-thickness distribution of electric potential which is actually nonlinear. Here, a novel quadratic profile of the through-thickness electric potential is proposed to include the nonlinear effects. The results obtained show that the accuracy of conventional formulations with linear through-thickness potential approximation is affected by the material configuration, especially when the piezoelectric material dominates the beam cross section. It is shown that the present formulation gives the same level of accuracy for all regimes of material configurations in the beam cross section. Also, a modified form of the FSDT displacements is employed, which utilizes the shear angle as a degree of freedom instead of section rotation. Such a FSDT displacement field shows improved performance compared to the conventional field. The present formulation is validated by comparing the results with ANSYS 2D simulation. The comparison of results proves the improved efficiency and accuracy of the present formulation over the conventional formulations.

Experimental study on obtaining hydraulic concrete strength by use of concrete piezoelectric ceramic smart module pairs

The concrete strength has the strong influence on service safety of mass hydraulic concrete structures. The real-time identification of concrete strength is very important to ensure the pouring quality during the construction and find timely the hidden troubles in service. Based on the analysis for the mapping relationship between concrete strength and stress wave amplitude, the method is proposed to obtain indirectly the concrete strength with self-made concrete piezoelectric ceramic smart module pairs. First, according to the service condition of hydraulic concrete structure, the concrete piezoelectric ceramic smart module is designed and the process manufacturing concrete piezoelectric ceramic smart module is presented. The protecting measures of piezoelectric ceramic piece, the peripheral material constituent, and the pouring links are introduced. Second, an integrated system, which is composed of self-made concrete piezoelectric ceramic smart modules in pair as sensor and actuator, fuzzy inference system, and other auxiliary equipments, is developed to monitor indirectly concrete strength. Its working principle is studied. Finally, an experiment of hydraulic concrete strength is implemented to demonstrate the feasibility and validity of the proposed method and developed system. The concrete piezoelectric ceramic smart modules in pair are taken as sensor and actuator embedded in hydraulic concrete specimens. The wave-based analysis method is adopted to collect the stress wave amplitude data during the pouring process of concrete specimens. The fuzzy inference approach is utilized to build the mathematical model describing the relationship between concrete strength and stress wave amplitude. Based on the above mathematical model, the concrete strength can be identified indirectly.

Numerical modeling of damage detection in concrete beams using piezoelectric patches

Research and development of active monitoring systems for reinforced concrete structures should lead to improved structural safety and reliability. Numerical models of active monitoring and damage detection systems can help in the development and implementation of these systems. Modeling of damage detection process in a concrete beam with piezoelectric sensors/actuators based on wave propagation is investigated in this paper. Numerical modeling process is divided into two parts: (1) piezoelectric smart aggregates (SA), and (2) wave propagation models. Displacement obtained in the SA model is used as an input parameter for the modeling of wave propagation. Wavelet analysis is used as a signal processing tool and the damage index is calculated based on the wave energy. In this paper root-mean-square deviation (RMSD) damage index is used. Damage indices obtained by this numerical analysis are compared with experimental results. Very good fit between the finite element (FE) results and experimental results confirm a good FE approach of this problem.

Embedded Electromechanical Impedance and Strain Sensors for Health Monitoring of a Concrete Bridge

Piezoelectric lead zirconate titanate (PZT) is one of the piezoelectric smart materials, which has direct and converse piezoelectric effects and can serve as an active electromechanical impedance (EMI) sensor. The design and fabrication processes of EMI sensors embedded into concrete structures are presented briefly. Subsequently, finite element modeling and modal analysis of a continuous rigid frame bridge are implemented by using ANSYS and MIDAS and validated by the field test results. Uppermost, a health monitoring technique by employing the embedded EMI and strain sensors is proposed in this paper. The technique is not based on any physical model and is sensitive to incipient structural changes for its high frequency characteristics. A practical study on health monitoring of the continuous rigid frame bridge is implemented based on the EMI and strain signatures. In this study, some EMI and strain sensors are embedded into the box-sectional girders. The electrical admittances of distributed EMI active sensors and the strains of concrete are measured when the bridge is under construction or in operation. Based on the electrical admittance and strain measurements, the health statuses of the continuous rigid frame bridge are monitored and evaluated successfully in the construction and operation stages using a root-mean-square deviation (RMSD) index.

Electromechanical Impedance Analysis on Piezoelectric Smart Beam with a Crack Based on Spectral Element Method

An electromechanical impedance (EMI) analysis of a piezoelectric smart beam with a crack is implemented in this paper. Spectral element method (SEM) is used to analyze the EMI response of the piezoelectric smart beam. In this analysis, the spectral element stiffness matrices of different beam segments are derived in this paper. The crack is simulated using spring models, and the EMI signatures of piezoelectric smart beam with and without crack are calculated using SEM, respectively. From the analysis results, it is found that the peak position and amplitude of the EMI signatures have significant changes with the change in crack depth, especially in higher frequency ranges. Different vibration modes of the piezoelectric smart beam are analyzed, and the effect of thickness of the adhesive layer on the admittance is also researched. An experimental study is also implemented to verify the validity of the analysis results using SEM.