Search Results (39)

This study explores the vibrational behavior of Thermoformed Magneto-Piezoelectrets (TMPs), multifunctional materials consisting of thermoformed piezoelectrets with open tubular channels integrated with an additional magnetic layer. The inverse piezoelectric effect was characterized using laser vibrometry analysis, measuring the mechanical response of TMPs subjected to electrical excitation over a frequency range of 0–20 kHz. Vibrational analysis was conducted at 144 spatial points, enabling the construction of detailed three-dimensional (3D) maps of the vibration operational modes and the spatial distribution of the piezoelectric coefficient ($d_{33}$). The results demonstrated significant frequency-dependent behavior, with open channels exhibiting pronounced resonance peaks, whereas valleys displayed smoother and more uniform responses due to enhanced damping effects. The observed heterogeneity in vibrational behavior is attributed to structural variations, material composition, and anisotropic coupling between the piezoelectric and magnetic properties. The findings presented in this research provide a comprehensive understanding of the development and utilization of TMPs, offering parameters for enhancing their application and supporting new discoveries in studies related to the fabrication of novel thermoformed piezoelectric sensors. Full article

To explore the nonlinear dynamics of a piezoelectric energy harvesting device, we consider the simultaneous parametric and external excitations. Based on Bernoulli–Euler beam theory, a new dynamic model is proposed taking into account the curvature of the beam, geometric and electro-mechanical coupling nonlinearities, and damping nonlinearity, with inextensible deformation. The system is discretized by using the Galerkin–Bubnov procedure and then is investigated by the optimal auxiliary functions method. Explicit analytical expressions of the approximate solutions are presented for a complex problem near the primary resonance. The main novelty of our approach relies on the presence of different auxiliary functions, the involvement of a few convergence-control parameters, the construction of the initial and first iteration, and much freedom in selecting the procedure for obtaining the optimal values of the convergence-control parameters. Our procedure proves to be very efficient, simple, easy to implement, and very accurate to solve a complicated nonlinear dynamical system. To study the stability of equilibrium points, the Routh–Hurwitz criterion is adopted. The Hopf and saddle node bifurcations are studied. Global stability is analyzed by the Lyapunov function, La Salle’s invariance principle, and Pontryagin’s principle with respect to the control variables. Full article

The paper presents results of experimental investigations of the influence of temperature on the effectiveness of passive vibration isolation. Two types of viscoelastic materials (butyl rubber and bituminous material) were tested. In the performed vibration analysis, the Oberst beam made out of aluminum alloy with a damping material in a Free Layer Damping (FLD) configuration was used. The experimental modal analysis was performed using the Unholtz-Dickie UDCO TA-250 vibration system. To investigate the influence of temperature on the effectiveness of passive vibration isolation, an isothermal cooling chamber (using Peltier cells) was designed and constructed. The tests were carried out in a wide frequency range from 40 Hz to 4000 Hz, at a constant sweep rate, in a temperature range from −2 °C to 22 °C. Miniature piezoelectric acceleration sensors were used to determine the acceleration of the beam and the exciter head. The analysis of accelerations of both the object and the shaker head allowed for the determination of a Frequency Response Function (FRF) for the beam. The course of FRF was used to determine the resonance frequencies and the vibration amplitudes of the beam damped with bituminous material and butyl rubber at various temperatures. The loss factor η, calculated for each resonance using the generalized half-power method (n-dB method), was used as an indicator of damping intensity. The research results presented in this work (important from scientific point of view) also have utilitarian significance and can be used in the design of more quiet and comfortable motor vehicles, railway wagons and aircraft structures. Full article

In order to solve the hysteresis nonlinearity and resonance problems of piezoelectric stages, this paper takes a three-degree-of-freedom tip-tilt-piston piezoelectric stage as the object, compensates for the hysteresis nonlinearity through inverse hysteresis model feedforward control, and then combines the composite control method of positive acceleration velocity position feedback damping control and high-gain integral feedback controller to suppress the resonance of the system and improve the tracking speed and positioning accuracy. Firstly, the three-degree-of-freedom motion of the end-pose is converted into the output of three sets of piezoelectric actuators and single-axis control is performed. Then, the rate-dependent Prandtl–Ishlinskii model is established and the parameters of the inverse model are identified. The accuracy and effectiveness of parameter identification are verified through open-loop and closed-loop compensation experiments. After that, for the third-order system, the parameters of positive acceleration velocity position feedback damping control and high-gain integral feedback controller are designed as a whole based on the pattern of the Butterworth filter. The effectiveness of the design method is proved by step signal and triangle wave signal trajectory tracking experiments, which suppresses the resonance of the system and improves the bandwidth of the system and the tracking speed of the stage. Full article

For several decades, Moore’s law has driven the semiconductor industry, with computational power and production costs as the main drivers. Such drivers have enabled several technological innovations in the mechatronics and dynamics architecture of photolithography machines, used for semiconductor circuits manufacturing. Among current investigations, the use of superconductive magnets would enable higher accelerating stages and, thus, higher throughput and lower manufacturing costs. However, this involves a complex magnet structure that needs to operate at cryogenic temperatures and mechanical resonances at relatively low frequencies as a result of the thermal architecture of the system. The damping options are also limited due to the very low temperature. This paper explores the use of shunted piezoelectric transducers for damping the internal modes of the magnet mass. A classical resistive and inductive RL shunt is considered. The study was conducted both numerically and experimentally on a demonstrator of a superconductive magnet plate concept, where piezoelectric transducers are incorporated to support the superconducting coils. The study demonstrates the effectiveness of piezoelectric shunts as a damping solution at very low temperatures, with limited impact of the temperature variation on the performance. Full article

Focusing on the bending wave characteristic of plate–shell structures, this paper derives the complex band curve of piezoelectric phononic crystal based on the equilibrium differential equation in the plane stress state using COMSOL PDE 6.2. To ascertain the computational model’s accuracy, the computed complex band curve is then cross-validated against real band curves obtained through coupling simulations. Utilizing this model, this paper investigates the impact of structural and electrical parameters on the bandgap range and the attenuation coefficient in the bandgap. Results indicate that the larger surface areas of the piezoelectric sheet correspond to lower center bands in the bandgap, while increased thickness widens the attenuation coefficient range with increased peak values. Furthermore, the influence of inductance on the bandgap conforms to the variation law of the electrical LC resonance frequency, and increased resistance widens the attenuation coefficient range albeit with decreased peak values. The incorporation of negative capacitance significantly expands the low-frequency bandgap range. Visualized through vibration transfer simulations, the vibration-damping ability of the piezoelectric phononic crystal is demonstrated. Experimentally, this paper finds that two propagation modes of bending waves (symmetric and anti-symmetric) result in variable voltage amplitudes, and the average vibration of the system decreases by 4–5 dB within the range of 1710–1990 Hz. The comparison between experimental and model-generated data confirms the accuracy of the attenuation coefficient calculation model. This convergence between experimental and computational results emphasizes the validity and usefulness of the proposed model, and this paper provides theoretical support for the application of piezoelectric phononic crystals in the field of plate–shell vibration reduction. Full article

A new axially vibrating sensor based on an audio voice coil transducer and a lead zirconate titanate (PZT) piezoelectric disc microphone was developed as a probe for the measurement of in vitro rheological fluid properties, including curing progress for polymethylmethacrylate (PMMA) mixtures with important uses as bone cement in the field of orthopedics. The measurement of the vibrating axial sensor’s acoustic spectra in PMMA undergoing curing can be described by a damped harmonic oscillator formalism and resonant frequency (ca. 180 Hz) shift can be used as an indicator of curing progress, with shifts to the blue by as much as 14 Hz. The resonant frequency peak was measured in 19 different 4.0 g PMMA samples to have a rate of shift of 0.0462 ± 0.00624 Hz·s⁻¹ over a period of 400 s while the PMMA was in a dough state and before the PMMA transitioned to a hard-setting phase. This transition is unambiguously indicated by this sensor technology through the generation of a distinct circa 5 kHz high-Q under-damped ring-down response. Full article

In applications of piezoelectric actuators and sensors, the dependability and particularly the reliability throughout their lifetime are vital to manufacturers and end-users and are enabled through condition-monitoring approaches. Existing approaches often utilize impedance measurements over a range of frequencies or velocity measurements and require additional equipment or sensors, such as a laser Doppler vibrometer. Furthermore, the non-negligible effects of varying operating conditions are often unconsidered. To minimize the need for additional sensors while maintaining the dependability of piezoelectric bending actuators irrespective of varying operating conditions, an online diagnostics approach is proposed. To this end, time- and frequency-domain features are extracted from monitored current signals to reflect hairline crack development in bending actuators. For validation of applicability, the presented analysis method was evaluated on piezoelectric bending actuators subjected to accelerated lifetime tests at varying voltage amplitudes and under external damping conditions. In the presence of a crack and due to a diminished stiffness, the resonance frequency decreases and the root-mean-square amplitude of the current signal simultaneously abruptly drops during the lifetime tests. Furthermore, the piezoelectric crack surfaces clapping is reflected in higher harmonics of the current signal. Thus, time-domain features and harmonics of the current signals are sufficient to diagnose hairline cracks in the actuators. Full article

Civil engineering structures need to be protected from earthquakes, representing a new area of research that is growing continuously and very rapidly. Design engineers are always searching for lightweight, stronger, and stiffer materials to be applied as vibration-damping materials. Stability in dynamics necessitates an active, robust, and convenient mechanism that can absorb the kinetic energy of vibration to prevent the structural system from resonance. Recently, many researchers have successfully used nanomaterials to develop energy-absorbing materials that are lightweight and cost-effective. Traditional damping treatments are based on combinations of viscoelastic, elastomeric, magnetic, and piezoelectric materials. In this paper, a review of various damping techniques for composites made of cement modified by various nanomaterials like Nano Al2O₃ (Aluminum Dioxide), Nano SiO₂ (Silicon Dioxide), Nano TiO₂ (Titanium Dioxide), Graphene, and CNTs (Carbon Nanotubes) is presented. The designs of various nano-composite dampers are presented to strengthen the information progress in this field. The current study’s goal is to discover how nanoparticles impact the cement-based material’s damping properties. The study examined several nanomaterials in cement composites at differing concentrations. With the help of the Dynamic Mechanical Analysis (DMA) method and the Logarithmic Decrement approach, the damping properties of these composites were examined. Scanning Electron Microscopy (SEM) was used to examine the effects of nanomaterials on the microstructure and pore size distribution of the composite. Increasing the quantity of nanoparticles in cement paste may improve its capacity to lessen vibration. The experiments also showed that certain nanomaterials may improve load transmission inside the cement matrix and connect neighboring hydration products, helping to reduce energy loss during the loading process. These nanoparticles will eventually replace the large machinery employed to dampen vibrations in buildings due to their small weight, increased mechanical strength, and effective damping properties. Full article

The literature confirms that fine recycled concrete aggregate (fRCA) can be used as a replacement for natural soil in new concrete, offering many advantages. Despite these advantages, there are also critical barriers to the development of fRCA in new mixes. Among these, the first challenge is the variability of fRCA properties, in both physical, chemical, and mechanical terms. Many individual studies have been carried out on different RCA or fRCA properties, but little investigative work has been performed to analyze their dynamic properties. Therefore, the influence of the non-cohesive fine fraction content of RCA on the dynamic properties of this waste material, when used as a specific anthropogenic soil, has been studied in laboratory conditions, employing a standard resonant column apparatus, as well as piezoelectric elements. In the present research, special emphasis has been placed on the dynamic shear modulus, dynamic damping ratio, small-strain shear modulus, and small-strain damping ratio, as well as shear modulus degradation G(γ)/G_max, the damping ratio increase D(γ)/D_min, and the threshold shear strain amplitudes γ_tl and γ_tv. Artificially prepared fRCAs with varying fine fraction contents (0% ≤ FF ≤ 30%, within increments of 5%) have been tested at different pressures (p′ = 90, 180, and 270 kPa) and relative densities of D_r > 65%. This study also examined the effect of two tamping-based sample preparation methods, i.e., dry and wet tamping. The results presented herein indicate that the analyzed anthropogenic material, although derived from concrete and produced by human activities, behaves very similarly to natural aggregate when subjected to dynamic loading. The introduction of a fine fraction content to fRCA leads to changes in the dynamic properties of the tested mixture. Concrete material with lower stiffness but, at the same time, with stronger damping properties can be obtained. A fine fraction content of at least 30% is sufficient to cause a significant loss of stiffness and, at the same time, a significant increase in the damping properties of the mixture. This study can serve as a reference for designing fRCA mixtures in engineering applications. Full article

Active and passive vibration control systems are of paramount importance in many engineering applications. If an external load excites a structure’s resonance and the damping is too low, detrimental events, such as crack initiation, growth and, in the worst case, fatigue failure, can be entailed. Damping systems can be commonly found in applications such as industrial machines, vehicles, buildings, turbomachinery blades, and so forth. Active control systems usually achieve higher damping effectiveness than passive ones, but they need a sensor to detect the working conditions that require damping system activation. Recently, the development of such systems in rotating structures has received considerable interest among designers. As a result, the development of vibration monitoring equipment in rotating structures is also a topic of particular interest. In this respect, a reliable, inexpensive and wireless monitoring system is of utmost importance. Typically, optical systems are used to measure vibrations, but they are expensive and require rather complex processing algorithms. In this paper, a wireless system based on a commercial MEMS accelerometer is developed for rotating blade vibration monitoring. The proposed system measurement accuracy was assessed by means of comparison with a reference wired measurement setup based on a mini integrated circuit piezoelectric (ICP) accelerometer adapted for data acquisition in a rotating frame. Both the accelerometers were mounted on the tip of the blade and, in order to test the structure under different conditions, the first four blade resonances were excited by means of piezoelectric actuators, embedded in a novel experimental setup. The frequency and amplitude of acceleration, simultaneously measured by the reference and MEMS sensors, were compared with each other in order to investigate the viability and accuracy of the proposed wireless monitoring system. The rotor angular speed was varied from 0 to 300 rpm, and the data acquisitions were repeated six times for each considered condition. The outcomes reveal that the wireless measurement system may be successfully used for vibration monitoring in rotating blades. Full article

This paper proposes a bi-directional acoustic micropump driven by two groups of oscillating sharp-edge structures: one group of sharp-edge structures with inclined angles of 60° and a width of 40 μm, and another group with inclined angles of 45° and a width of 25 μm. One of the groups of sharp-edge structures will vibrate under the excitation of the acoustic wave generated with a piezoelectric transducer at its corresponding resonant frequency. When one group of sharp-edge structures vibrates, the microfluid flows from left to right. When the other group of sharp-edge structures vibrates, the microfluid flows in the opposite direction. Some gaps are designed between the sharp-edge structures and the upper surface and the bottom surface of the microchannels, which can reduce the damping between the sharp-edge structures and the microchannels. Actuated with an acoustic wave of a different frequency, the microfluid in the microchannel can be driven bidirectionally by the inclined sharp-edge structures. The experiments show that the acoustic micropump, driven by oscillating sharp-edge structures, can produce a stable flow rate of up to 125 μm/s from left to right, when the transducer was activated at 20.0 kHz. When the transducer was activated at 12.8 kHz, the acoustic micropump can produce a stable flow rate of up to 85 μm/s from right to left. This bi-directional acoustic micropump, driven by oscillating sharp-edge structures, is easy to operate and shows great potential in various applications. Full article

In recent decades, many studies have been conducted on the use of smart materials in order to dampen and control vibrations. Lead zirconate titanate piezoceramics (PZT) are very attractive for such applications due to their ability of delivering high energy strain in the structure. A pair of piezoelectric actuators can actively dampen the resonances of the structure, but the damping effectiveness strongly relies on its location. Damping effectiveness can be substantially increased if the structure is fully covered with PZT actuator pairs and the voltage distribution on each pair is optimized. In this way, each actuator pair contributes to the vibration attenuation and only the driving voltage’s sign, distributed on each actuator pair, needs to be identified for each resonance. This approach is here applied to the case of Euler–Bernoulli beams with constant cross-section and the optimal voltage distribution is investigated for several boundary conditions. The theoretical model results were corroborated with finite element simulations, which were carried out considering beams covered by ten PZT actuator pairs. The numerical results agree remarkably well with the theoretical predictions for each examined case (i.e., free-free, pinned-pinned, and fixed-fixed). Full article

Vibration mitigation is a prominent matter in several engineering fields. Several adverse phenomena are related to vibrations, such as fatigue, noise, etc. The availability of smart materials increases the solutions for both vibration damping and energy harvesting applications. Piezoelectric materials seem to be the most promising for these applications. However, their positioning significantly affects their efficiency. Several studies were performed on the positioning of piezoelectric actuators to dampen a target resonance in cantilever beams with constant cross-sections. Here, an analytical model for the optimal voltage distribution on an array of piezoceramic (PZT) actuator pairs is proposed in the case of tapered beams. The effect of tapering on the optimal voltage distribution was investigated for several eigenmode excitations and tapering ratios. The model outcomes were corroborated via FEM simulations and a fair agreement was found for each considered case. Full article

Piezoelectric energy harvesters have traditionally taken the form of base excited cantilevers. However, there is a growing body of research into the use of curved piezoelectric transducers for energy harvesting. The novel contribution of this paper is an analytical model of a piezoelectric energy harvesting curved beam based on the dynamic stiffness method (DSM) and its application to predict the measured output of a novel design of energy harvester that uses commercial curved transducers (THUNDER TH-7R). The DSM predictions are also verified against results from commercial finite element (FE) software. The validated results illustrate the resonance shift and shunt damping arising from the electrical effect. The magnitude, phase, Nyquist plots, and resonance frequency shift estimates from DSM and FE are all in satisfactory agreement. However, DSM has the advantage of having significantly fewer elements and is sufficiently accurate for commercial curved transducers used in applications where beam-like vibration is the predominant mode of vibration. Full article