Piezoceramic Transducers Research Articles

FORCED ELECTRO-ELASTIC VIBRATIONS OF THE PIEZOCERAMIC PLATES AND RODS WITH DIVIDED ELECTRODES. PART I: ANALYTICAL RELATIONS FOR COUPLING COEFFICIENTS AND ADMITTANCE’S COMPONENTS

This article analyses the forced vibrations of the non-uniform loaded piezoceramic transducers, such as plates-rods with thickness polarization and one or two bilateral electrode coating divisions, thin disks and circular rings with full or concentric and diameter divided electrodes, as well as partly electroded plates. The analytical relations for thin piezoceramic discs’ with partial electrodes radial vibrations and for rods’ with no uniform electric loading longitudinal vibrations are represented in a first part. The experimental data for rods with divided or partial electrodes are represented in a second part.Ref. 74, fig. 1.

Impedance based bolt pre-load monitoring using piezoceramic smart washer

Bolted connection is widely used in mechanical and civil engineering; however, in some cases, bolt looseness may cause catastrophic consequences. Bolt pre-load monitoring in real time can help to ensure the safety of component connections and durability of the entire steel structure. Previous research has demonstrated that a ‘smart washer (SW)’ fabricated by embedding a piezoceramic transducer into two flat metal rings could effectively detect the pre-load looseness of a bolted connection. The active sensing method, in which two SWs are necessary, was used in the previous research. In this research, an electro-mechanical impedance (EMI) method enabled by one ‘SW’ was developed to investigate the pre-load condition of a bolted connection. Since the installed SW is directly subjected to the same axial pre-load as that on the bolt, the piezoceramic SW with the EMI technique is uniquely suited for pre-load monitoring of a bolted connection. The pre-load reduction is directly reflected by the EMI of the piezoceramic SW. In particular, a decrease of the pre-load on a bolt connect results in the reduced of its resonant frequency, which can be revealed by the real part of the impedance. In addition, the root mean square deviation (RMSD) of the impedance signals was employed as an index to evaluate the bolt looseness degree. For the experimental study, a bolted connectional specimen with a piezoceramic SW was fabricated and investigated. In the experiment, eleven cases of different pre-loads on the bolt were studied. Experimental results clearly show that with the decrease of the bolt pre-load, the resonant frequency of the bolt joint also decreased, as reflected by the impedance of piezoceramic SW. In addition, experimental results demonstrated that the SW with the EMI based RMSD index can monitor bolt pre-load.

SIMULATION AND ANALYSIS OF MICRO ELECTRO MECHANICAL SYSTEMS PIEZO CERAMIC TUBE FOR ULTRASONIC FLOW MEASUREMENT

Tube piezoceramic used for the laying of a variety of sensors with a relatively small diameter to the size of a few micrometer to a few milli meters. Materials used in Piezoceramic Tube specially formulated standards for cylinders, so many different kinds of sensors which has a cylindrical shape for use as a place Piezoceramic. Use of Piezoceramic Tube one to measure ultrasonic flow. In the ultrasonic flow rate measurement distinction is made between two different measurement principles, namely the Doppler effect and timing analysis wave. In both cases Piezoceramic transducer placed on the walls of the tube produces ultrasonic waves, which are then transmitted into the liquid diagonal to the direction of flow.

Detection of Debonding Between Fiber Reinforced Polymer Bar and Concrete Structure Using Piezoceramic Transducers and Wavelet Packet Analysis

Fiber reinforced polymer (FRP), a composite material with high corrosion resistance and high strength-to-weight ratio, has been increasingly used in reinforced concrete structures. The effectiveness of the structures depends on the bonding behavior between FRP composites and concrete structures. Therefore, detection of the debonding between the FRP materials and the hosting concrete structure is of great importance to ensure the structural safety. This paper proposes a stress wave-based active sensing approach to monitor the debonding process of FRP bar with the hosting concrete structure. One shear-type lead zirconate titanate (PZT) patch bonded on the outer surface of the FRP bar was used as an actuator to generate stress wave. Two smart aggregates (SAs), which were fabricated by sandwiching a shear type PZT patch between two protection marble pieces, were embedded in the hosting concrete structure to detect the wave response. The occurrence of debonding between the FRP bar and the hosting concrete structure attenuates the wave propagation. An FRP bar reinforced concrete specimen was designed and fabricated in laboratory. A pullout test was conducted to simulate different degrees of debonding damage. The attenuation of the stress wave due to debonding was clearly observed from the signal received by SAs in both time and frequency domain. Furthermore, a damage index based on wavelet packet analysis was developed to evaluate the debonding status. Experimental results demonstrate that the proposed method has potentials to detect different degrees of debonding damage of FRP bar reinforced concrete composite structures.

Thermodynamically consistent derivation and computation of electro-thermo-mechanical systems for solid bodies

For electro-thermo-mechanical systems such as a piezoceramic transducer, pyroelectric energy harvester, or a magnetic sensor using a magnetoelectric coupling, there are various formulations in continuum mechanics. The consensus of a well-established formulation is still missing. In this work we try to shed light to varying formulations and develop a thermodynamically consistent derivation of field equations for electro-thermo-mechanical systems. In order to justify their feasibility and verify their strength of modeling a physical system, we present simulations of engineering applications by exploiting open-source packages and solving problems monolithically with finite difference method in time and finite element method in space.

Chatter reduction in boring process by using piezoelectric shunt damping with experimental verification

Chatter is a self-excited type of vibration that develops during machining due to process-structure dynamic interactions resulting in modulated chip thickness. Chatter is an important problem as it results in poor surface quality, reduced productivity and tool life. The stability of a cutting process is strongly influenced by the frequency response function (FRF) at the cutting point.In this study, the effect of piezoelectric shunt damping on chatter vibrations in a boring process is studied. In piezoelectric shunt damping method, an electrical impedance is connected to a piezoelectric transducer which is bonded on cutting tool. Electrical impedance of the circuit consisting of piezoceramic transducer and passive shunt is tuned to the desired natural frequency of the cutting tool in order to maximize damping. The optimum damping is achieved in analytical and finite element models (FEM) by using a genetic algorithm focusing on the real part of the tool point FRF rather than the amplitude. Later, a practical boring bar is considered where the optimum circuit parameters are obtained by the FEM. Afterwards, the effect of the optimized piezoelectric shunt damping on the dynamic rigidity and absolute stability limit of the cutting process are investigated experimentally by modal analysis and cutting tests. It is both theoretically and experimentally shown that application of piezoelectric shunt damping results in a significant increase in the absolute stability limit in boring operations.

The study of mechanical effect on the characteristics of the PZT-system piezoelectric elements

The paper examines the characteristics of the piezoengine by the method of glancing collisions under the conditions of the moving scheme with mobile connections. The research results of the values’ changes of the PZT materials’ electrophysical parameters and their structural composition are represented. In the course of the research, the voltage boundary values, occurring during glancing collision of the inclined piezoceramic transducer, have been obtained.

A PZT Actuated Triple-Finger Gripper for Multi-Target Micromanipulation

This paper presents a triple-finger gripper driven by a piezoceramic (PZT) transducer for multi-target micromanipulation. The gripper consists of three fingers assembled on adjustable pedestals with flexible hinges for a large adjustable range. Each finger has a PZT actuator, an amplifying structure, and a changeable end effector. The moving trajectories of single and double fingers were calculated and finite element analyses were performed to verify the reliability of the structures. In the gripping experiment, various end effectors of the fingers such as tungsten probes and fibers were tested, and different micro-objects such as glass hollow spheres and iron spheres with diameters ranging from 10 to 800 μm were picked and released. The output resolution is 145 nm/V, and the driven displacement range of the gripper is 43.4 μm. The PZT actuated triple-finger gripper has superior adaptability, high efficiency, and a low cost.

Inspection of Piezoceramic Transducers Used for Structural Health Monitoring.

The use of piezoelectric wafer active sensors (PWAS) for structural health monitoring (SHM) purposes is state of the art for acousto-ultrasonic-based methods. For system reliability, detailed information about the PWAS itself is necessary. This paper gives an overview on frequent PWAS faults and presents the effects of these faults on the wave propagation, used for active acousto-ultrasonics-based SHM. The analysis of the wave field is based on velocity measurements using a laser Doppler vibrometer (LDV). New and established methods of PWAS inspection are explained in detail, listing advantages and disadvantages. The electro-mechanical impedance spectrum as basis for these methods is discussed for different sensor faults. This way this contribution focuses on a detailed analysis of PWAS and the need of their inspection for an increased reliability of SHM systems.

Damage detection in composite panels based on mode-converted Lamb waves sensed using 3D laser scanning vibrometer

This paper introduces damage identification approach based on guided ultrasonic waves and 3D laser Doppler vibrometry. The method is based on the fact that the symmetric and antisymmetric Lamb wave modes differ in amplitude of the in-plane and out-of-plane vibrations. Moreover, the modes differ also in group velocities and normally they are well separated in time. For a given time window both modes can occur simultaneously only close to the wave source or to a defect that leads to mode conversion. By making the comparison between the in-plane and out-of-plane wave vector components the detection of mode conversion is possible, allowing for superior and reliable damage detection. Experimental verification of the proposed damage identification procedure is performed on fuel tank elements of Reusable Launch Vehicles designed for space exploration. Lamb waves are excited using low-profile, surface-bonded piezoceramic transducers and 3D scanning laser Doppler vibrometer is used to characterize the Lamb wave propagation field. The paper presents theoretical background of the proposed damage identification technique as well as experimental arrangements and results.

ДИНАМИЧЕСКАЯ ОСЕСИММЕТРИЧНАЯ ЗАДАЧА ПРЯМОГО ПЬЕЗОЭФФЕКТА ДЛЯ КРУГЛОЙ БИМОРФНОЙ ПЛАСТИНЫ

The dynamic axisymmetric problem for a round bimorph structure consisting of the metal substrate and the axially polarized piezoceramic plate is considered. Its bending modes are caused by the action of the mechanical loading (normal tension) on the side surface; the loading is a function of the radial coordinate and time. The rigid and hinge supports of the plate are considered. The initial design relations are formulated for the piezoceramic material with the hexagonal crystal lattice of the 6 mm class. In order to solve the problem of the theory of electrodynamics in a three-dimensional formulation, the finite integral Hankel transformations along the axial coordinate and a generalized transformation (FIT) over the radial variable is used. At each stage, the standardization is carried out which allows implementing an appropriate transformation algorithm. In the first case the boundary conditions are presented in a mixed form; and in the second case they are homogeneous by introducing auxiliary functions. This approach allows gaining precise (within the used models) calculated ratios in a most general form. The built closed solution allows defining the frequency range of the axisymmetric oscillations, the stress-strain state and the nature of the changing induced electric field of the bimorph plate. This makes it possible to establish the conventional solutions of the designed devices, determine a way of fixing the electrical signal, pick up all the geometrical and physical characteristics of the typical elements of the piezoceramic transducers Also, the developed solution allows solving the problems of the elasticity and electroelasticity theory for circular thick and thin plates with an arbitrary number of layers under most general loading conditions without the use of kinematic hypotheses.

Experimental study of the polymer powder film thickness uniformity produced by the corona discharge

The results of an experimental study of the polymer powder film thickness uniformity are presented. Polymer powder films are produced by the electrostatic field of corona discharge. Epoxy and epoxy-polyester powder films with thickness in the range of 30-120 microns are studied. Experimentally confirmed possibility of using these coatings as protective matching layer of piezoceramic transducers at frequencies of 0.5-15 MHz.

An imaging algorithm for damage detection with dispersion compensation using piezoceramic induced lamb waves

Piezoceramic induced Lamb waves are often used for imaging based damage detection, especially for plate like structures. The dispersion effect of the Lamb waves deteriorates the performance of most of imaging methods, since the waveform of the dispersion signals will spread out. In this paper, an imaging method which can compensate the dispersion is developed. In the proposed method, the phase induced by the propagation distance is compensated firstly. After that, the phase deviation generated by the dispersion effect is compensated. Via the two compensations, the proposed method can derive an accurate location of the target with a clean imaging map. An experiment using a plate like structure with four piezoceramic transducer was conducted. In the experiment, the four piezoceramic sensors were used to obtain the signals of the scatterer that simulated the damage on an aluminum plate. The experimental results show that since the dispersion effect is compensated, the target’s image based on the proposed method is about 10 cm × 14 cm, which is about a quarter of that of using the back-projection imaging method.

Comparison of model-based damage imaging techniques for transversely isotropic composites

In order to reduce operation and maintenance costs of aircraft, in situ structural health monitoring techniques are implemented on critical parts and assemblies. Many of these techniques rely on models considering, with various levels of complexity, the generation, propagation and interaction of ultrasonic guided waves with potential damages, in order to detect, localize and estimate damage severity. Although their potential has been extensively demonstrated on isotropic substrates, their implementation still poses a challenge for composite assemblies for which only quasi-isotropic and cross-ply composites have been considered. This is mainly due to the limitations of the models to properly predict the complex behaviour of guided waves on composites, where the assumptions behind the models actually used for damage imaging do not fully consider the impact of the anisotropy on guided wave generation and propagation. This article presents a comparative analysis of the performances of three model-based damage imaging techniques for composites previously validated on isotropic substrates. The main objective of the study is to address the interest in using more complex analytical formulations to improve the performance of imaging techniques. This is obtained by comparing three imaging techniques, each presenting different levels of complexity in their numerical formulations. Performance of (a) delay-and-sum, (b) dispersion compensation and (c) correlation-based techniques are addressed numerically and experimentally. The analysis is conducted on a unidirectional transversely isotropic laminate instrumented with four circular piezoceramic transducers. A robustness analysis of the models is performed numerically, where the effect of varying stiffness parameters and velocity is addressed. The correlation-based technique is adapted for the first time to composite laminates where the generation is considered using the pin-force model and the propagation is modelled via the use of the global matrix model. Experimental validation is carried out and the results obtained show the benefit of considering the steering effect for well-resolved multi modal damage imaging.

UV-induced acoustooptics of matrices containing BaHf(BO3)2 microcrystallites embedded into olygoetheracrylate photopolymer

UV-induced acoustooptics was explored for BaHf(BO3)2 microcrystallites with sizes varying within 5–30 μm range. The titled microcrystallites were embedded into the polymer matrices. The results were analyzed using both experimental optical as well as theoretical DFT approach. The measurements were done for principal acoustical frequencies: 0.5 MHz, 1 MHz, 2 MHz, and 3 MHz. The acoustical waves were excited by an electromechanical LiNbO3 piezoceramics transducers from acoustical generator. We explored dependence of the acoustooptical efficiency versus the photoinducing laser beam power, angle between the beams, acoustical power light polarization and temperature. We explored variation of the acoustooptical efficiency at 1150 nm probing cw He-Ne laser wavelength under influence of pulsed nitrogen laser at wavelength 371 nm working in the 7 ns regime with frequency repetition 6 Hz at power densities up to 900 MW/cm2. Existence of some optimal conditions at about 1 MHz and UV photoinduced power equal to about 0.8 MW/cm2 was found. The spatial acousooptical gratings formation was observed. The DFT simulations of the charge density in main structural fragments under photoinducing UV beams is presented and principal role of the BO3 structural fragments is established. This is confirmed by crystallochemistry analysis. The phenomenological description is also presented.

Load Monitoring of the Pin-Connected Structure Using Time Reversal Technique and Piezoceramic Transducers—A Feasibility Study

An effective approach using time reversal technique and lead zirconate titanate (PZT) transducer was described in this paper to monitor the loading status of pin-connected structures, which are widely used in the construction industry. A tension-controllable structure with a pin connection was fabricated and used for experimentation. Two PZT patch sensors were mounted on the pin and on the connected structural surface. In the experiment, the time reversal process was performed by varying the tension on the pin joint, and the experimental results demonstrate that the peak value of the focused signal, detected by the PZT sensor, increases with the load on the pin connection. In addition, the entire experimental process was repeated seven times to verify the repeatability and consistency of the proposed method. Subsequently, the reliability of the experimental results was verified in an environment with high disturbances. All the test results show that the proposed method using PZT sensors along with the time reversal technique has potential to be employed in practical applications, especially monitoring the load of a cable-deck connection in a cable-strut bridge in an environment with severe disturbances.

Active monitoring of pipeline tapered thread connection based on time reversal using piezoceramic transducers

The monitoring of structural integrity of pipeline tapered thread connections is of great significance in terms of safe operation in the industry. In order to detect effectively the loosening degree of tapered thread connection, an active sensing method using piezoceramic transducers was developed based on time reversal technique in this paper. As the piezoeramic transducers can be either as actuators or sensors to generate or detect stress waves, the energy transmission for tapered thread connection was analyzed. Subsequently, the detection principle for tapered thread connection based on time reversal was introduced. Finally, the inherent relationship between the contact area and tightness degree of tapered thread connection for the pipe structural model was investigated. Seven different contact area scenarios were tested. Each scenario was created by loosening connectors ranging from 3 turns to 4.5 turns in the right tapered threads when the contact area in the left tapered threads were 4.5 turns. The experiments were separately conducted with a highly noisy environment and various excitation signal amplitudes. The results show the focused peaks based on time reversal have the monotonously rising trend with the increase of the contact areas of tapered threads within an acceptable monitoring resolution for metal pipes. Compared with the energy method, the proposed time reversal based method to monitor tapered threads loosening demonstrates to be more robust in rejecting noise in Structural Health Monitoring (SHM) applications.

Feasibility study of using smart aggregates as embedded acoustic emission sensors for health monitoring of concrete structures

Acoustic emission (AE) is a nondestructive evaluation technique that is capable of monitoring the damage evolution of concrete structures in real time. Conventionally, AE sensors are surface mounted on the host structures, however, the AE signals attenuate quickly due to the high attenuation properties of concrete structures. This study conducts a feasibility study of using smart aggregates (SAs), which are a type of embedded piezoceramic transducers, as embedded AE sensors for the health monitoring of concrete structures. A plain concrete beam with two surface mounted AE sensors and two embedded SAs was fabricated in laboratory and loaded under a designed three-point-bending test. The performance of embedded SAs were compared with the traditional surface mounted AE sensors in their ability to detect and evaluate the damage to the concrete structure. The results verified the feasibility of using smart aggregates as embedded AE sensors for monitoring structural damage in concrete. Potentially, the low cost smart aggregates could function as embedded AE sensors, providing great sensitivity and high reliability in applications for the structural health monitoring of concrete structures.

Design and analysis of radially polarized screen-printed piezoelectric transducers

Piezoelectric transducers have applications from ultrasonic structural health monitoring to micro-electromechanical systems. Small physical size coupled with large actuation is desirable in many applications, requiring unique transducer designs to take advantage of the material properties. Screen-printed piezoceramics were developed as a means of mass producing mezzo-scale transducers that are geometrically small and light weight, but large enough to generate significant actuation. Screen-printed piezoceramic transducers display significantly different properties than chemically identical bulk ceramic elements, largely attributed to high void fraction of screen-printed piezoceramic materials and detrimental to the functionality of traditional transducer designs. This article presents analysis, simulation, and initial testing of new designs for screen-printed piezoceramic transducers with concentric through-thickness electrodes. Analytical models were developed enabling analysis across material properties and design parameters. Analytical results were verified against finite element models for some designs. Prototypes were created and underwent initial testing to assess the properties of the design.

Dissimilar trend of nonlinearity in ultrasound transducers and systems at resonance and non-resonance frequencies

Several factors can affect performance of an ultrasound system such as quality of excitation signal and ultrasound transducer behaviour. Nonlinearity of piezoelectric ultrasound transducers is a key determinant in designing a proper driving power supply. Although, the nonlinearity of piezoelectric transducer impedance has been discussed in different literatures, the trend of the nonlinearity at different frequencies with respect to excitation voltage variations has not been clearly investigated in practice. In this paper, to demonstrate how the nonlinearity behaves, a sandwich piezoceramic transducer was excited at different frequencies. Different excitation signals were generated using a linear power amplifier and a multilevel converter within a range of 30–200V. Empirical relation was developed to express the resistance of the piezoelectric transducer as a nonlinear function of both excitation voltage and resonance frequency. The impedance measurements revealed that at higher voltage ranges, the piezoelectric transducer can be easily saturated. Also, it was shown that for the developed ultrasound system composed of two transducers (one transmitter and one receiver), the output voltage measured across receiver is a function of a voltage across the resistor in the RLC branches and is related to the resonance frequencies of the ultrasound transducer.