Inner damage identification and residual strength assessment of a 3D printed tunnel with marble-like cementitious materials using piezoelectric transducers

Quantitative damage identification of surrounding rock is important to assess the current condition and residual strength of underground tunnels.In this work,an underground tunnel model with marble-like cementitious materials was first fabricated using the three-dimensional(3D)printing technique and then loaded to simulate its failure mode in the laboratory.Lead zirconate titanate piezoelectric(PZT)transducers were embedded in the surrounding rock around the tunnel in the process of 3D printing.A 3D monitoring network was formed to locate damage areas and evaluate damage extent during loading.Results show that as the load increased,main cracks firstly appeared above the tunnel roof and below the floor,and then they coalesced into the tunnel boundary.Finally,the tunnel model was broken into several parts.The resonant frequency and the peak of the conductance signature firstly shifted rightwards with loading due to the sealing of microcracks,and then shifted backwards after new cracks appeared.An overall increase in the root-mean-square deviation(RMSD)calculated from conductance signatures of all the PZT transducers was observed as the load(damage)increased.Damage-dependent equivalent stiffness parameters(ESPs)were calculated from the real and imaginary signatures of each PZT at different damage states.Satisfactory agreement between equivalent and experimental ESP values was achieved.Also,the relationship between the change of the ESP and the residual strength was obtained.The method paves the way for damage identification and residual strength estimation of other 3D printed structures in civil engineering.

Novel Traveling Wave Sandwich Piezoelectric Transducer with Single Phase Drive:Theoretical Modeling,Experimental Validation,and Application Investigation

Most of traditional traveling wave piezoelectric transducers are driven by two phase different excitation signals,leading to a complex control system and seriously limiting their applications in industry.To overcome these issues,a novel traveling wave sandwich piezoelectric transducer with a single-phase drive is proposed in this study.Traveling waves are produced in two driving rings of the transducer while the longitudinal vibration is excited in its sandwich composite beam,due to the coupling property of the combined structure.This results in the production of elliptical motions in the two driving rings to achieve the drive function.An analytical model is firstly developed using the transfer matrix method to analyze the dynamic behavior of the proposed transducer.Its vibration characteristics are measured and compared with computational results to validate the effectiveness of the proposed analytical model.Besides,the driving concept of the transducer is investigated by computing the motion trajectory of surface points of the driving ring and the quality of traveling wave of the driving ring.Additionally,application example investigations on the driving effect of the proposed transducer are carried out by constructing and assembling a tracked mobile system.Experimental results indicated that 1)the assembled tracked mobile system moved in the driving frequency of 19410 Hz corresponding to its maximum mean velocity through frequency sensitivity experiments;2)motion characteristic and traction performance measurements of the system prototype presented its maximum mean velocity with 59 mm/s and its maximum stalling traction force with 1.65 N,at the excitation voltage of 500 V_(RMS).These experimental results demonstrate the feasibility of the proposed traveling wave sandwich piezoelectric transducer.

Fluid Pump Using a Bar-shaped Piezoelectric Transducer

There are two kinds of piezoelectric pumps:check valve pumps and valve-less pumps.Whether to use a check valve or not depends upon the application occasion.To achieve large backpressure for higher flow rates,the pump with check valve is desirable.However,adding check valves implies more complex structure and higher probability of valve blocking,etc.In order to solve the problem,effective driving and transport mechanics with compact construction and reliable service are being sought.In this paper,using the second-order longitudinal vibration mode of a bar-shaped piezoelectric vibrator for driving fluid,a piezoelectric pump is successfully made.The proposed piezoelectric pump consists of coaxial cylindrical shells and a bar-shaped piezoelectric vibrator,which has a disk part and a cone part.The lead zirconium titanate ceramic rings fixed in the vibrator are polarized along the thickness direction.When the second-order longitudinal vibration of the vibrator along its axis is excited,the disk part of the vibrator changes periodically the volume of the chamber and the cone part acts as a pin valve,driving the fluid from the inlet port to the outlet port.Finite elements analysis on the proposed pump model is carried out to verify its operation principle and design by the commercial FEM software ANSYS.Components of the piezoelectric pump were manufactured,assembled,and tested for flow rate and backpressure to validate the concepts of the proposed pump and confirm the simulation results of modal and harmonic analyses.The test results show that the performance of the proposed piezoelectric pump is about 910 mL/min in flow rate with a highest pressure level of 1.5 kPa under 400 V peak-to-peak voltage and 51.7 kHz operating frequency.It is confirmed that this bar-shaped piezoelectric transducer can be effectively applied in fluid transferring mechanism of pump through this research.

Study on Enhancement Effect of Cavitation Caused by HIFU Piezoelectricity Transducer

An orthogonal ultrasonic irradiation system consisting of HIFU with frequency at 1.05 MHz combined with ultrasound with frequency at 28 kHz was applied in this paper.Effect of cavitation was detected by pH-value measurement and conductance measurement.The result shows that the effect of cavitation caused by ultrasound with frequency at 28 kHz is greatly enhanced by HIFU piezoelectricity transducer with frequency at 1.05 MHz.

DYNAMIC CHARACTERISTICS OF AXIALLY-SYMMETRICAL ANNULAR CORRUGATED SHELL PIEZOELECTRIC TRANSDUCERS

The coupled extensional and flexural vibrations of an annular corrugated shell piezoelectric transducer consisting of multiple circularly-annular surfaces smoothly connected along the interfaces were investigated in the paper. Only a time-harmonic voltage is applied across two electrodes of the piezoelectric shell as the external loading. A theoretical solution was obtained using the classical shell theory. Based on the solution, basic vibration characteristics of resonant frequencies, mode shapes were calculated and examined.

Analysis of Vibration Frequencies of Piezoelectric Ceramic Rings as Ultrasonic Transducers in Welding of Facial Mask Production

The explosive demands for facial masks as vital personal protection equipment(PPE)in the wake of Covid-19 have challenged many industries and enterprises in technology and capacity,and the piezoelectric ceramic(PZT)transducers for the production of facial masks in the welding process are in heavy demand.In the earlier days of the epidemic,the supply of ceramic transducers cannot meet its increasing demands,and efforts in materials,development,and production are mobilized to provide the transducers to mask producers for quick production.The simplest solution is presented with the employment of Rayleigh-Ritz method for the vibration analysis,then different materials can be selected to achieve the required frequency and energy standards.The fully tailored method and results can be utilized by the engineers for quick development of the PZT transducers to perform precise function in welding.

A unidirectional SH wave transducer based on phase-controlled antiparallel thickness-shear(d15)piezoelectric strips

In recent years,shear horizontal(SH)waves are being paid more and more attention to in structural health monitoring as it has only one displacement component.In this paper,a unidirectional SH wave transducer based on phase-controlled antiparallel thickness-shear(d15)piezoelectric strips(APS)is proposed.Here two pairs of identical APS were used each of which is a bidirectional SH wave transducer.By setting the interval between the two pairs of APS as 1/4 wavelength and the excitation delay between them as 1/4 period of the central operating frequency,unidirectional SH waves can be excited.Both finite element simulations and experiments were performed to validate the proposed design.Results show that SH0 waves were successfully excited only along one direction and those along the unwanted directions were suppressed very well.The proposed unidirectional SH wave transducer is very helpful to study the fundamentals and applications of SH waves.

Voltage Generated Characteristics of Piezoelectric Ceramics Cymbal Transducer

In this study the relation between the generated open circuit output voltages of the piezoelectric ceramics Cymbal transducers with applied impact mechanical energy is studied. The output voltages of piezoelectric ceramics Cymbal transducers are increased with the increasing of the applied mechanical energy. Under the same impact mechanical energy, the generated open circuit output voltages of the piezoelectric ceramics Cymbal transducer is much higher than that of uncapped piezoelectric ceramics disk alone. The generated open circuit output voltages of the piezoelectric ceramics Cymbal transducer depend on the geometry parameters and the metal thickness of end-cap. The generated open circuit voltage of piezoelectric ceramics Cymbal transducer with thick metal thickness is small than that with thin metal thickness.

New Three Dimension Piezoelectric Transducer

Abstract: A new type of piezoelectric transducer with compression/shear sense is developed and was successfully tested for measuring three dimension accelerations in shock and vibration experiment.

一种基于高压静电纺丝工艺制备的P(VDF-TrFE)/PZT压电传感器及其在睡眠监测中的应用

针对日常睡眠监测的需求,提出一种基于高压静电纺丝工艺制备的P(VDF-TrFE)/锆钛酸铅(PZT)压电传感器并对其性能进行了研究。首先,介绍了P(VDF-TrFE)/PZT压电传感器的制作及封装流程。其次对其灵敏度,频率响应特性,瞬时响应和稳定性等进行了测试。结果表明,该传感器不仅具有良好的微观外貌形态,且相比于纯P(VDF-TrFE)压电传感器0.73 V/N的灵敏度,制备的含30%PZT的P(VDF-TrFE)/PZT压电传感器灵敏度是纯P(VDF-TrFE)压电传感器的2.5倍,达到了1.78 V/N。此外在低频下能够保持稳定压电输出且具备2 ms较快的响应时间。最后采用自制的P(VDF-TrFE)/PZT压电传感器测量人体心冲击信号,并通过支持向量机(SVM)训练睡眠分期模型实现了对睡眠质量的监测,四分类模型平均准确率达到72.5%,为可穿戴睡眠监测传感器的选择提供了参考。

高于居里温度极化的硬性PZT压电陶瓷的制备及叠层驱动器性能研究

压电叠层驱动器具有低驱动电压、大位移的特点,被广泛应用于诸多领域。作为目前压电叠层驱动器中最常使用的材料,软性锆钛酸铅(PZT)陶瓷较大的介电常数和损耗往往会导致较高的功耗和发热量,进而影响驱动器的疲劳特性和稳定性。为了制备出低发热量、适用于压电叠层驱动器的压电陶瓷,本工作选取Mn掺杂(摩尔分数)的Pb(Sb_(1/2)Nb_(1/2))_(0.02)Zr_(0.51)Ti_(0.47)O_(3)-0.6%MnCO_(3)(PSN-PZT)硬性压电陶瓷作为基体材料,通过掺入一定含量的Li_(2)CO_(3)烧结助剂来降低陶瓷的烧结温度,并采用高于居里温度极化工艺进一步提升陶瓷的电学性能。最后采用该材料,利用流延工艺制备出压电叠层驱动器,并与相同工艺制备的Pb(Mg_(1/3)Nb_(2/3))_(0.25)(Ti_(0.48)Zr_(0.52))_(0.75)O_(3)(PMN-PZT)驱动器进行比较。结果显示,Li_(2)CO_(3)通过引入液相烧结的方式将PSN-PZT陶瓷烧结温度降低至1050℃。当Li_(2)CO_(3)含量为0.1%(质量分数)时,高于居里温度极化的PSN-PZT陶瓷电学性能最优,其压电系数(d33)和2 kV/mm电场下的单极应变分别为388 pC/N和0.13%。在200 Hz下,PSN-PZT驱动器温升比PMN-PZT驱动器低大约20℃,且经过5×10^(6)次循环后应变仅降低6%。这表明Li_(2)CO_(3)低温烧结的PSN-PZT陶瓷不仅具备不错的压电性能,而且在发热和疲劳特性方面有较大优势,在大功率、高频等苛刻工况中有潜在的应用前景。

Design and analysis of longitudinal–flexural hybrid transducer for ultrasonic peen forming

Ultrasonic peen forming(UPF)is an emerging technology that exhibits great superiority in both its flexible operating modes and the deep residual stress that it produces compared with conventional plastic forming methods.Although ultrasonic transducers with longitudinal vibration have been widely studied,they have seldom been incorporated into UPF devices for machining in confined spaces.To meet the requirements of this type of machining,a sandwich-type piezoelectric transducer with coupled longitudinal-flexural vibrational modes is proposed.The basic structure of the transducer is designed to obtain large vibrational amplitudes in both modes.Experimental results obtained with a prototype device demonstrate the feasibility of the proposed transducer.The measured vibrational amplitude for the working face in the longitudinal vibrational mode is 1.0μm,and electrical matching increases this amplitude by 40%.The flexural vibration characteristics of the same prototype transducer are also tested and are found to be slightly smaller than those of longitudinal mode.The resultant working strokes of the UPF impact pins reach 1.7 mm and 1.2 mm in the longitudinal and flexural modes,respectively.The forming capability of the prototype has been evaluated via 15-min machining on standard 2024-T351 aluminum plates.After UPF,an improved surface morphology with lower surface roughness is obtained.The aluminum plate test piece has an apparent upper deformation with an arc height of 0.64 mm.The measured peak value of the compressive residual stress is around 250 MPa,appearing at a depth of 100μm.The proposed longitudinal-flexural hybrid transducer thus provides a high-performance tool for plate peen forming in confined spaces.

Structure of Pb(Zr,Ti)O3(PZT)for Power Ultrasonic Transducer

To improve the performance of ultrasonic transducer, the samples of PZT were improved by doping. The doped PZT was observed and analyzed from the following aspects： the crystal phase structures, the surface morphologies and the dielectric constant. According to the transducer parameter requirements for ultrasonic machining, there are also requirements for the parameters of piezoelectric ceramics. The high performance PZT was prepared by doping the elements of Ga, Ba, Nb, Sn, and Sr in PZT. The doped PZT is suitable for power ultrasonic machining at 20 kHz through analysis using X-ray diffraction（XPD）, a scanning electron microscope（SEM） and LCR meter. Therefore, the excellent performance of transducer for power ultrasonic machining is guaranteed.

用于能量收集器的PMnN-PZT压电陶瓷

试验采用固相合成法,通过Li_(2)CO_(3)掺杂,制得高能量密度的Pb_(0.95)Sr_(0.05)[(Mn_(1/3)Nb_(2/3))_(0.04)(Zr_(0.52)Ti_(0.48))0.96]O_(3)+0.25wt%CeO_(2)+0.50wt%Yb_(2)O_(3)+0.15wt%Fe_(2)O_(3)三元系压电陶瓷材料。研究分析了掺杂不同质量分数的Li_(2)CO_(3)对PMnNPZT压电陶瓷材料的压电性能、介电性能、相组成及其微观结构的影响。结果显示:当掺杂量为0.1 wt%,烧成温度为1050℃时,材料结构致密,晶粒均匀,材料的压电和介电性能:d 33=340 pC/N,K_(p)=0.60,ε_(r)=725,tanδ=0.23%,Q_(m)=670,g_(33)=53.0×10^(-3)V·(m·N)^(-1),机电转化效率d_(33)·g_(33)为18016.8×10^(-15)m^(2)/N,满足能量收集器用压电陶瓷元件需要。

Piezoelectric and dielectric properties of Cr-doped PSN-PZN-PZT qua-ternary piezoelectric ceramics

PSN-PZN-PZT + x wt. %Cr2O3, X = 0.0-0-9, were prepared by conventional mixed oxide techniques at sintering temperatures of 1220 degrees C-1300 degrees C for 2 h. The effect of sintering temperature on the microstructure and the piezoelectric properties was investigated by XRD, SEM, and other conventional measurement. The result indicated that with temperature increasing, the valence of Cr ion from Cr5+ or Cr6+ changes into C3+, and the piezoelectric properties turn hard. With increasing Cr2O3 content, the amount of rhombohedral phases increases and the morphotropic boundary phase is correspondingly shifts to rhombohedral phase. A uniform microstructure and excellent comprehensive properties were obtained at 1240 degrees C as the amount of Cr2O3 is 0.5 wt.%.

Synthesis of piezoelectric nanocrystalline PZT powder by stearic acid gel method

PZT nanocrystalline powder was prepared by a stearic acid gel method. Thecrystallization process from the precursor was monitored by infrared spectroscopy, differentialthermal analysis, and thermogravimetric analysis. The nano-sized PZT powder was characterized byX-ray diffraction and transmission electron microscopy. It shows that pure single-phase PZT powdercould be obtained at 450 deg C for 1 h, and the particle size is about 20 nm. With an increase inthe calcination temperature, the PZT crystallite size increased.

The Effect of Deposition Temperature of Pb(Zr,Ti)O₃(PZT)Thin Films with Thicknesses of around 100 nm on the Piezoelectric Response for Nano Storage Applications

We investigated the effect of the deposition temperature of PZT thin films with thicknesses of around 100 nm on the piezoelectric response using an atomic force microscope (AFM). The preferred orientation of the PZT thin film was changed from (001) to (110) as the deposition temperature increased. The surface roughness of PZT thin films decreased with the increase of deposition temperature. The maximum amplitude of the piezoelectric response of PZT thin films decreased till the deposition temperature increased to 350°C. This tendency seems to be due to the change of the preferred orientation form (001) to (110). At over 450°C, this maximum value decreased due to both the increase of the surface roughness and the degradation of the crystallinity.

Analysis on Output Power for Multi-direction Piezoelectric Vibration Energy Harvester

To predict the performance of multi-direction piezoelectric vibration energy harvester,an equation for calculating its output power is obtained based on elastic mechanics theory and piezoelectricity theory.Experiments are performed to verify theoretical analysis.When the excitation direction is along Y direction,a maximal output power about 0.139 mW can be harvested at a resistive load of 65kΩ and an excitation frequency of 136 Hz.Theoretical analysis agrees well with experimental results.Furthermore,the performance of multi-direction vibration energy harvester is experimentally tested.The results show that the multi-direction vibration energy harvester can harvest perfect energy as the excitation direction changes in XY plane,YZ plane,XZ plane and body diagonal plane of the harvester.

HIGH-FREQUENCY VIBRATIONS OF CORRUGATED CYLINDRICAL PIEZOELECTRIC SHELLS

Coupled extensional and flexural cylindrical vibrations of a corrugated cylindrical piezoelectric shell consisting of multiple pieces of circular cylindrical surfaces smoothly connected along their generatrix are studied. To validate the results for the case of relatively thick shells or equivalently high-frequency modes with short wavelengths, existing analysis is extended by considering shear deformation and rotatory inertia. An analytical solution is obtained. Based on the solution, resonant frequencies and mode shapes are calculated.

Sr取代硬性PMS-PZT压电陶瓷研究

采用常规固相反应法合成了Pb_(1-x)Sr_(x)(Mn_(1/3)Sb_(2/3))_(0.05)Zr_(0.48)Ti_(0.47)O_(3+)0.25%CeO_(2)+0.50%Yb_(2)O_(3)+0.15%Fe_(2)O_(3)(PMS-PZT,x=0,0.02,0.04,0.06)的三元系硬性压电陶瓷。采用X线衍射仪、准静态压电常数测试仪和铁电测试仪系统地研究了Sr取代对PMS-PZT陶瓷的相结构及电学性能的影响。实验结果表明,无Sr取代和有Sr取代的PMS-PZT压电陶瓷均具有单一的四方相晶体结构。当x=0.02时,PMS-PZT的性能最佳:d_(33)=415 pC/N,Q_(m)=522,T_(C)=291℃,k_(p)=0.64,ε_(r)=1304,P_(r)=11.32μC/cm^(2),E c=9.05 kV/cm.