Piezoelectric Accelerometer Research Articles

Design and simulation of micro piezoelectric fiber triaxial acceleration sensor

Aiming at the demand for passive sonar systems for medium and low-frequency detection, low cost, and small working platform working sensor, a three-axis pressure piezoelectric accelerometer based on piezoelectric ceramic fiber is designed. Firstly, based on the acoustic vibration pick-up principle and extended Hamilton, the action mode of the accelerometer is analyzed theoretically to determine the accelerometer structure size. The accelerometer with a special mass structure is designed by using axially polarized piezoelectric ceramic fiber. The characteristic frequency and frequency domain analysis of the accelerometer are simulated by the FEM method. The results show that the overall size of the piezoelectric accelerometer is 20 mm ×20 mm×35 mm, the first-order natural frequency is 410 Hz, the external field directivity is standard “8” type, and the acceleration sensitivity reaches 112.2 mV/g, which verifies the great potential of the three-axis accelerometer designed by piezoelectric ceramic fiber material in the field of medium and low frequency.

Accuracy Characterization of a MEMS Accelerometer for Vibration Monitoring in a Rotating Framework

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.

Evaluation of Vibration Detection Using Smartphones in a Two-Story Masonry-Infilled RC Frame Building

For measuring the structural health of buildings, high-performance vibration detection devices are used in a structural health monitoring (SHM) system, which consists of a sensor and a data logger. Those devices are seismographs or devices with high-performance sensors which are expensive. Recently, smartphones are being used as seismographs to accumulate big data of earthquake wave detection because they have accelerometers of microelectromechanical systems. Since a smartphone has the functions of a detection sensor and a data logger, a low-cost SHM system can be developed by using a low-cost smartphone. In this paper, smartphones were used to confirm the possibility of the development of a low-cost SHM system. To evaluate the vibration detection performance from small displacement and large displacement, smartphones were installed in a specimen of a large shaking table test. The specimen is a scale model of a two-story non-reinforced masonry-filled reinforce concrete (RC) frame building. The natural period and interstory drift ratio were used as the evaluation criteria. The natural period estimated by the smartphone data agreed with that found by the piezoelectric accelerometer data. For estimating the building deformation, which is related to building stability, the measurement performance for large deformation using smartphones was evaluated. The smartphones have 90% or higher accuracies for the estimation of the maximum acceleration and displacement.

Dynamic Compensation of a Piezoelectric Accelerometer Obtained through a General Probabilistic Approach.

Dynamic compensation is the (partial) correction of the measurement signals for the effects due to bandwidth limitations of measurement systems and constitutes a research topic in dynamic measurement. The dynamic compensation of an accelerometer is here considered, as obtained by a method that directly comes from a general probabilistic model of the measurement process. Although the application of the method is simple, the analytical development of the corresponding compensation filter is quite complex and had been previously developed only for first-order systems, whilst here a second-order system is considered, thus moving from a scalar to a vector problem. The effectiveness of the method has been tested both through simulation and by a dedicated experiment. Both tests have shown the capability of the method of significantly improve the performance of the measurement system when dynamic effects are more prevalent than additive observation noise.

A Study on Frequency Response Functions in Pavement Engineering

Mechanical impedance (MI) defines the ability of a system to vibrate as a consequence of force application. In the recent years, the correlation of this parameter with tire-road noise and other characteristics has gained certain attention. Nevertheless, the information about this topic is still insufficient. Usually, the force is set through an impulse hammer as a master and the acceleration is measured through an accelerometer as a response in order to measure the corresponding Frequency Response Function (FRF). The objectives of the study presented in this paper are i) to analyse the differences between the axial mechanical impedance (complex ratio of force and velocity referred to the same point, named driving-point impedance) and the non-axial mechanical impedance (complex ratio of the force at the point i and velocity at the point j, named transfer impedance); ii) to analyse the effect of adding crumb rubber (2% by mixture weight) and of the percentage of bitumen on the mechanical impedance for the bituminous samples. Therefore, laboratory tests on asphalt concrete specimens have been performed, using an instrumentation system composed of i) an impact hammer reporting the impact force value; ii) an impedance head measuring the direct impact force and the direct acceleration at the hitting point location; iii) a piezoelectric accelerometer measuring the transfer acceleration at a certain distance from the hitting point location. Results demonstrate that the ratio between the repeatability and the average is quite constant, while for heights higher than 10 cm, also MI tends to be independent on the height. A number of recommendations have been made based on the results of the present research.

Simulative study of vertical cavity with distributed feedback optical sources coupling to fiber systems evaluation

Abstract This paper has demonstrated the simulative study of vertical cavity with distributed feedback light sources coupling to the fiber systems. The simulative study of piezoresistive, capacitive and piezoelectric sensing for micro electro mechanical system has been clarified. The span against the diaphragm thickness for the square diaphragm, round diaphragm, a round bossed diaphragm and rectangular diaphragm is clarified. Acceleration against displacement for a capacitive accelerometer for step signal based on signal sided and double sided is reported. Besides, acceleration against max pulse time for a capacitive accelerometer is outlined. The frequency response plot for a piezoelectric accelerometer under longitudinal load and for thin film based piezoelectric accelerometer is demonstrated based on MEMSolver simulation software version 3.3.

Multi-Disciplinary Monitoring Networks for Mesoscale Underground Experiments: Advances in the Bedretto Reservoir Project.

The Bedretto Underground Laboratory for Geosciences and Geoenergies (BULGG) allows the implementation of hectometer (>100 m) scale in situ experiments to study ambitious research questions. The first experiment on hectometer scale is the Bedretto Reservoir Project (BRP), which studies geothermal exploration. Compared with decameter scale experiments, the financial and organizational costs are significantly increased in hectometer scale experiments and the implementation of high-resolution monitoring comes with considerable risks. We discuss in detail risks for monitoring equipment in hectometer scale experiments and introduce the BRP monitoring network, a multi-component monitoring system combining sensors from seismology, applied geophysics, hydrology, and geomechanics. The multi-sensor network is installed inside long boreholes (up to 300 m length), drilled from the Bedretto tunnel. Boreholes are sealed with a purpose-made cementing system to reach (as far as possible) rock integrity within the experiment volume. The approach incorporates different sensor types, namely, piezoelectric accelerometers, in situ acoustic emission (AE) sensors, fiber-optic cables for distributed acoustic sensing (DAS), distributed strain sensing (DSS) and distributed temperature sensing (DTS), fiber Bragg grating (FBG) sensors, geophones, ultrasonic transmitters, and pore pressure sensors. The network was realized after intense technical development, including the development of the following key elements: rotatable centralizer with integrated cable clamp, multi-sensor in situ AE sensor chain, and cementable tube pore pressure sensor.

An aerosol deposition based MEMS piezoelectric accelerometer for low noise measurement

Potentially applied in low-noise applications such as structural health monitoring (SHM), a 1-axis piezoelectric MEMS accelerometer based on aerosol deposition is designed, fabricated, simulated, and measured in this study. It is a cantilever beam structure with a tip proof mass and PZT sensing layer. To figure out whether the design is suitable for SHM, working bandwidth and noise level are obtained via simulation. For the first time, we use aerosol deposition method to deposit thick PZT film during the fabrication process to achieve high sensitivity. In performance measurement, we obtain the charge sensitivity, natural frequency, working bandwidth and noise equivalent acceleration of 22.74 pC/g, 867.4 Hz, 10–200 Hz (within ±5% deviation) and 5.6 mu {{{rm{g}}}}/sqrt{{{{rm{Hz}}}}} (at 20 Hz). To demonstrate its feasibility for real applications, vibrations of a fan are measured by our designed sensor and a commercial piezoelectric accelerometer, and the results match well with each other. Moreover, shaker vibration measurement with ADXL1001 indicates that the fabricated sensor has a much lower noise level. In the end, we show that our designed accelerometer has good performance compared to piezoelectric MEMS accelerometers in relevant studies and great potential for low-noise applications compared to low-noise capacitive MEMS accelerometers.

Fabrication and testing of FBG sensor-based one-dimensional shock accelerometer attached to novel 3D printed structure

This study presents an FBG-based one-dimensional shock accelerometer fabricated by Fused Deposition Modelling (FDM) technology. The bare fiber Bragg grating (FBG) sensor is fixed to the 3D-printed elastomer structure. The dimension of the sensor was simulated by the finite element method to explore the customizability of the acceleration sensor. The deformation in the elastic material structure leads to a change in the wavelength of the FBG sensor, and it is observed that the total Bragg wavelength shift over the acceleration range was recorded as 2.53 nm, corresponding to an acceleration sensitivity of 1.16 pm/g with a randomly generated acceleration between 655 g and 2635 g (1 g = 9.81 m/s2). A linear analysis showed that the linear values of the data obtained in the experiments reached above 96%. A comparison of the accelerometer signal obtained from the piezoelectric accelerometer data with the FBG accelerometer shows an excellent match in pulse amplitudes with pulse durations of only about 100 μs each time the acceleration occurs and the proposed sensor operating frequency is from 200 to 3000 Hz. The proposed FBG acceleration sensor is based on 3D printing technology, so it also inherits the outstanding advantages of this technology such as fast manufacturing time, saving production costs, and especially the ability to easily customize based on the size change of the structure, weight of mass block or the printed material.

High-Resolution Sensors for Mass Deposition and Low-Frequency Vibration Based on Phase-Shifted Bragg Gratings

This work presents high-resolution sensors based on phase-shifted Bragg gratings (PSBGs) for low-frequency vibrations monitoring and mass deposition sensing. We analyzed the reflected spectrum using a commercial interrogator for six values of deposited mass: 0, 0.22, 0.27, 0.32, 0.40, and 0.47 g. For the experimental data, a linear regression was calculated for PSBG 1 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}^{{2}} = {0.9379}$ </tex-math></inline-formula> with a sensitivity of 0.0491 nm/g) and for uniform fiber Bragg grating (FBG) ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}^{{2}} = {0.909}$ </tex-math></inline-formula> with a sensitivity of 0.05182 nm/g). Machinery fault simulator (MFS) was used for the vibration monitoring setup for engine rotation frequency of 4–14 Hz in steps of 2 Hz. We used an alternative noncommercial interrogation system that consisted of a tunable laser, an optical circulator, an optical power acquisition board, and a prefixed phase-shifted Bragg. The proposed alternative interrogation system has the ability to center the tunable laser in the narrow valley region of the PSBG reflected spectrum, increasing the resolution for monitoring vibration at low frequencies. As a reference, the PSBG measurement results were compared with those of a piezoelectric accelerometer (PZT) fixed at the same bearing. For 4, 6, 8, 10, and 14 Hz, the relative error was 15%, 10%, 0%, 0%, and 1.43%, respectively. According to these results, PSBGs are a suitable option for monitoring low-frequency vibrations and for mass deposition sensing.

Pressure-induced damage monitoring in prestressed concrete of nuclear containment wall segments using acoustic emission technique – Application to VeRCoRs containment building

This paper reports benchmark findings of an experimental study of pressure-induced damage monitoring in a nuclear containment building (NCB) reproducing realistic conditions of internal pressure increase accidents. The leak-tightness of NCBs is assessed every 10 years during integrated leak-rate tests (IRLT). For double-wall containments, which have no metallic liners, the leak-tightness is strongly influenced by the degree of cracking of concrete and opening of the cracks. This paper is focused on assessing the effectiveness of the Acoustic Emission (AE) technique to evaluate the damage evolution of a reinforced concrete containment wall under pressure loading test. Piezoelectric accelerometers were mounted on the internal containment wall of the VeRCoRs mockup, which constitutes the containment building of a Nuclear Power Plant in a 1:3 scale. The Akaike criterion (AIC) as an AE hit picking method and the adaptive meshing algorithm (AMA) as an AE events localization algorithm have been applied for damage and cracking monitoring. A benchmark analysis based on the distribution of AE events and energy is presented for the detection of damages and the monitoring of crack propagation in correlation with the known locations of main cracks. The potential and limitations of the AE technique for in situ damage sources estimation are discussed upon two experimental campaigns (2017 and 2019), and the main conclusions of the benchmark survey are given. The results show that the AE technique is adequate for damage evaluation in large-scale concrete structures. It provides important information about the integrity of the structure and the assessment of damage evolution with time.

Experimental detection of train wheel defects using wayside vibration signal processing

While many studies have been used onboard monitoring methods to detect train wheel defects, this paper aims to extract damage features from vibrational signals obtained by the wayside monitoring system. To provide an appropriate tool for the decomposition of experimental nonstationary vibration signals containing impacts, an analytical amplitude-based signal decomposition method is provided. A two-axle motor car with a flat wheel defect is studied at different operating conditions. Vibrational signals arising from wheel-rail interactions are gathered by the Wayside Data Collection Setup (WDCS) with five piezoelectric accelerometers. The tests are performed at the constant speeds of 10, 20, 30, and 40 km/h. The acquired signals are decomposed by the Multi-channel Singular Spectrum Analysis (MSSA) into the contributing components. Based on the results, increases in the amplitudes of the second reconstructed components (RCs) of the vibrational signals sensed by all the accelerometers can be observed at a specific time instance as a repeating pattern. Similar patterns are obtained at different motor car positions relative to the measurement area, as well as different motor car speeds. To verify the consistency of the second RCs, the crest factors are obtained for all the angular positions. The results show sudden increases in the crest factor at a fixed angular position that indicate the existence of a defect at that specific angular position of the wheel.

Lead-Free Piezoelectric Acceleration Sensor Built Using a (K,Na)NbO3 Bulk Ceramic Modified by Bi-Based Perovskites

Piezoelectric accelerometers using a lead-free (K,Na)NbO3 (KNN) piezoceramic modified by a mixture of two Bi-based perovskites, Bi(Na,K,Li)ZrO3 (BNKLZ) and BiScO3 (BS), were designed, fabricated and characterized. Ring-shaped ceramics were prepared using a conventional solid-state reaction method for integration into a compression-mode accelerometer. A beneficial rhombohedral-tetragonal (R-T) phase boundary structure, especially enriched with T phase, was produced by modifying intrinsic phase transition temperatures, yielding a large piezoelectric charge coefficient d33 (310 pC/N) and a high Curie temperature Tc (331 °C). Using finite element analyses with metamodeling techniques, four optimum accelerometer designs were obtained with high magnitudes of charge sensitivity Sq and resonant frequency fr, as evidenced by two key performance indicators having a trade-off relation. Finally, accelerometer sensor prototypes based on the proposed designs were fabricated using the KNN-BNKLZ-BS ceramic rings, which exhibited high levels of Sq (55.1 to 223.8 pC/g) and mounted fr (14.1 to 28.4 kHz). Perfect charge-to-acceleration linearity as well as broad flat frequency ranges were achieved with excellent reliability. These outstanding sensing performances confirm the potential application of the modified-KNN ceramic in piezoelectric sensors.

Experimental studies on compaction of soil with HAMM 3411 vibrating roller

Introduction. Mathematical modelling is used to assess the influence of various factors on the result of soil compaction by a vibratory roller. The verification of the mathematical model is carried out by comparing it with the results of the experimental studies. Expanding the list of the roller models in the experimental studies allows expanding the range of conditions for verification of the mathematical model. The article presents the results of field experimental studies of soil compaction by HAMM 3411 vibrating roller. The data on the change in the value of the dynamic soil deformation modulus Evd depending on the number of passes of the roller during compaction of sandgravel mixture with a layer thickness of 0.5 m have been obtained. The peculiarities that are reasonable to take into account when carrying out further experimental research are revealed.Materials and methods. The experimental studies of the scope of vertical movements of the roller, as well as vertical accelerations of the roller and its frame were carried out on a HAMM 3411 vibrating roller during compaction of a sand-gravel mixture. The result of compaction of the soil after each pass was estimated by the value of the dynamic deformation modulus Evd, measured using the ZORN ZFG 3.0 dynamic loading unit. In the experiment, vertical movements of the vibrating roller were recorded using a BAUMER OADM 13U6480/S35A laser sensor. Accelerations of vibrations of the vibrating roller and the roller frame were recorded by piezoelectric accelerometers of the AR2099-100 and AR99-100 models. When processing sensor readings, digital signal processing technology was used – low-pass filters with a limit frequency of 200 Hz.Results. The studies were carried out on two sites with different soil moisture. On a site with waterlogged soil in the range of Evd values = 10 ...13 MPa, the amplitude values of the vertical accelerations of the roller were in the range from +20 ... +45 to -25 ...-43 m/s2, and the frames in the range from +2.5 ...+5 to -2 ...-5 m/s2. The range of vibrations of the vibrating roller in the area with waterlogged soil was 3.3...4.8 mm. On a site with soil with close to optimal importance, in the range of values Evd= 18...28 MPa, the amplitude values of vertical accelerations of the roller were in the range from +36 ... +48 to -35 ... -40 m/s2, and frames in the range from +3.5 ... +6 to -2...-4.5 m/s2.Discussion and conclusion. The results show that the range of oscillations of the drum, as well as the amplitude values of vertical accelerations of the drum and the drum frame slightly increase with increasing soil deformation modulus Evd. The results of the experiment correlate with the studies conducted on the models of rollers DM-DM-617. When measuring values of Evd in one cross-section, the difference between measured values along the axis of roller’s movement and on the pneumatic wheel track reached 30%. When analyzing obtained results, it is necessary to take into account that in the experiment the actual frequency of oscillation of the roller was 18 Hz, instead of 27 Hz as stated in the technical specifications. With such reduction of frequency, the forced force of oscillations will decrease approximately 2.25 times. Results of the experiment will help in further verification of mathematical model of the roller and in carrying out experimental researches of similar character.

Design and Development of a Low-Power Wireless MEMS Lead-Free Piezoelectric Accelerometer System

In this paper, a complete 3-D integrated sensing system intended for practical applications was presented on a PCB board, starting with lead-free piezoelectric films deposited using an RF sputtering system, a MEMS structure design/simulation, device fabrication, and a signal processing chip design including charge-to-voltage transformation, signal amplification, 60-Hz noise rejection, and low-power RF wireless transmission chip for remote monitoring. Both the signal processing chips and the RF wireless transmitter chips were manufactured using the TSMC CMOS process. The piezoelectric coefficient d33 was measured as 27.21pm/V of the proposed MLZO (ZnO: Li doped Mg) films. To meet the frequency specifications of industrial applications, the ring-structure devices with a 7730-Hz resonance frequency were designed using ANSYS simulation software. There was only a 0.39% deviation as compared to the simulation results with the actual experimental data. The measurement results of the proposed system showed that the acceleration detection range was approximately 137 mV/g(p-p). The voltage-controlled oscillator adopted in the wireless transmitter chip had a four-leaf clover structure inductor with two symmetrical axes resulting in better suppression of magnetic field radiation. Finally, this system was applied to industrial spindles, and the normal and abnormal operation information of spindles was successfully and wirelessly monitored.

深松机振动特性试验与分析

In this paper, the vibration characteristics of the 1ST-460 vibration subsoiler was analyzed. In order to solve the problem of vibration imbalance caused by the vibration component under the action of multiple groups of vibration shovels, the optimal combination mode of the vibration component under the interaction of multiple groups of shovels was obtained. Piezoelectric accelerometers are fixed symmetrically on the frame of the subsoiler to measure the vibration at different positions. TST5910 dynamic signal test and analysis system is used to collect and process the acceleration data. Non-load tests were carried out with different initial eccentric phase angle combination. Results showed that the combination of [0°, 180°, 180°, 0°] (symmetrically up and down staggered vibration) for the eccentric vibration component of four shovels is the optimal initial phase combination, which can lead to the minimum adverse vibration on the frame. Further tests were conducted under different vibrating frequency and amplitude/eccentric with optimal phase combination. The results showed that, when amplitude/eccentricity ratio was 2.0 and 2.5, frequency of vibration was 6.7 and 8.3 Hz, the required traction force of the subsoiler was stable and significantly reduced, which can improve the soil loosening performance and reduce the harmful vibration on the tractor.

Fabrication and Underwater Testing of a Vector Hydrophone Comprising a Triaxial Piezoelectric Accelerometer and Spherical Hydrophone.

A vector hydrophone is an underwater acoustic sensor that can detect the direction of a sound source. Wide-band characteristics and high sensitivity enhance the performance of underwater surveillance systems in complex environments. A vector hydrophone comprising a triaxial piezoelectric accelerometer and spherical hydrophone was fabricated and tested in the air and underwater. The vector hydrophone was designed to exceed the quantitative figures of merit (i.e., receiving voltage sensitivity and bandwidth) of commercially available hydrophones. Accelerometer performance was enhanced by placing a pair of piezoelectric single crystals on each axis and modifying the seismic mass material. The receiving voltage sensitivity of the omnidirectional hydrophone was approximately -160 dB relative to 1&amp;nbsp;V/μPa with the amplifier in water; the sensitivity of the accelerometer exceeded 300 mV/g in air and -215 dB relative to 1&amp;nbsp;V/μPa underwater over the frequency range of interest. The receiving directivity of the vector hydrophone was validated underwater, which confirmed that it could detect the direction of a sound source.

High temperature piezoelectric accelerometer fabricated by 0.75BiFeO3–0.25BaTiO3 ceramics with operating temperature over 450 °C

Owing to the high Curie temperature and good piezoelectric thermal stability, BiFeO3–BaTiO3 ceramics show great potentials for high-temperature piezoelectric sensor applications. In this paper, a compression-mode piezoelectric sensor was fabricated by the lead-free and high-temperature 0.75BiFeO3–0.25BaTiO3–MnO2 (BFBT25–Mn) ceramic and its sensitivity was characterized from room temperature to 550 °C over a frequency range of 200–1000 Hz. The output charge of the BFBT25–Mn piezoelectric sensor is independent of the measuring frequency at different temperatures. The maximum working temperature of the BFBT25–Mn piezoelectric sensor is 450 °C, about 250, 150, and 100 °C higher than those of these piezoelectric sensors fabricated by PZT-5A, BSPT64–Mn, and BSPT66–Mn ceramics, respectively. The temperature sensitivity coefficient from room temperature to 350 °C of the BFBT25–Mn piezoelectric sensor is 30% of that for the BSPT66–Mn sensor. Furthermore, the sensitivity of the BFBT25–Mn piezoelectric sensor is stable with the dwelling time at 400 °C. These results indicate that the BFBT25–Mn ceramic is a strong competitor for high temperature sensing applications.

Development of an embedded piezoelectric transducer for bearing fault detection

The trend toward intelligent monitoring and industry 4.0 has attracted more attention to the performance of intelligent bearings with integrated sensors. Compared with the standard technique of mounting a sensor on the housing of machines, embedding the sensor inside the bearing housing can benefit several aspects. The short transmission path between the fault and sensor provides more efficient condition monitoring and fault detection, especially in a noisy setting or at low rotational speeds where fault symptoms have low energy. Therefore, this paper presents the design and implementation of an embedded piezoelectric transducer for fault detection in a cylindrical roller bearing. Experimental tests and simulations using ANSYS are employed to investigate the transducer performance in three different tests. The first test analyzes experimental voltage signals and a simulated transducer for a faulty outer ring and roller. Experimental tests and simulations have demonstrated that the proposed transducer can successfully detect the local fault in the bearing through obvious fault symptoms in the voltage signal. The piezoelectric transducer and accelerometer signals are analyzed in the second test by artificially exciting the bearing apparatus structure and creating noise using an air motor. In the noisy condition, the piezoelectric transducer performed better in time and frequency domain analysis than the reference accelerometer. Contrary to the accelerometer, the signal statistical indicators of the transducer remained constant during the impact, and the air motor frequency did not mask the fault symptoms. In the third test, a preliminary analysis of the transducer's durability was performed, and according to the results, the transducer was not significantly stressed under high radial loads from the shaft, which is promising for real applications.

Lead-Free BF-BT Ceramics With Ultrahigh Curie Temperature for Piezoelectric Accelerometer.

Piezoelectric ceramics have been widely used in high precision sensors such as vibration detection, but piezoelectric accelerometers in high-temperature applications are very rare. We prepared ( 1- x ) BiFeO3- x BaTiO3-0.0035MnO2-0.001Li2CO3(BF- x BT) ceramics by a solid state approach, and investigated the effect of BT content( x ) on the phase structure, microstructure, dielectric properties, ferroelectric properties, piezoelectric properties, temperature stability, and especially the sensitivity of the piezoelectric accelerometer. The crystal structure of the sample is pure perovskite structure with the MPB (R and P phases) locating in a composition range of 0.28 ≤ x ≤ 0.32 for BF-xBT ceramics, and the single R phase exist at . When x = 0.30, the ceramic presents both high Curie temperature and d₃₃ . Notably, the sensitivity of BF-0.30BT piezoelectric accelerometer reaches the highest value of about 40 pC/g and shows an excellent stability until 400 °C, indicating that this material is a promising candidate for high-temperature piezoelectric accelerometer applications.