Transducer Excitation Research Articles

Research on acoustic logging while drilling transmitting technologies

Abstract Acoustic logging while drilling (LWD) technology plays an important role in oil and gas exploration and development. Compared to traditional wireline logging, LWD must address more additional crucial problems, such as great noise confusions. This paper studies a series of technologies to improve the transmitting performances of LWD tools. First, we verified that the shear wave remote detection technology successfully adopted in wireline logging was also suitable for LWD, which could significantly expand its detection range. In addition, we calculated its dominant excitation frequency bands, which were different with wireline logging. Second, a class AB push–pull excitation circuit was designed. The results demonstrated that this circuit could obtain ideal excitation signals for LWD transmitting transducers. Furthermore, the signal shapes, excitation frequencies and cycle amounts are easily to adjust. In this study, we proposed a broadband impedance matching technology to solve the impedance mismatching problem between the excitation circuits and the excitation transducer. Acoustic experiments showed that this technology improved emitting powers of LWD transducers significantly.

Insight into excitation and acquisition mechanism and mode control of Lamb waves with piezopolymer coating-based array transducers: Analytical and experimental analysis

In-situ fabricated piezopolymer coating-based transducers have been developed to build large-area, lightweight and flexible networks for wave-based structural health monitoring (SHM). Meanwhile, their tunability can be realized by array electrodes for mode control with proper tuning methods. However, conventional standard tuning by phase matching seems not always effective. In this study, the excitation and acquisition mechanism of Piezopolymer Coating-based Array Transducers (PCATs) were first studied for Lamb waves. Distinctly different coupling mechanisms of PCAT actuators and sensors were discussed by analytical models and experimental verification, respectively. Then comprehensive parameter studies were performed to understand the filtering effect with finite temporal pulse duration of PCAT actuators, and finite spatial electrode span of PCAT actuators and sensors. Corresponding bias tuning methods were proposed with analytical solutions to improve mode control in Lamb-wave excitation and acquisition. This new guideline of designing array electrodes for PCAT actuators and sensors has been proven effective by successfully tuning the poor mode-controlled wavefield originated by the standard tuning method. Such tunability has great potential to be applied for detecting various damages in Lamb wave-based SHM, where sensitivity, accuracy, and signal interpretation can be improved with good control of particular frequency-mode selections.

A passive radio frequency excited acoustic transducer

The physical processes that govern the operation of a passive acoustic transducer driven into operation by a broadcast radio-frequency electromagnetic wave are presented. The transducer is comprised of a re-entrant cavity resonator operating in its resonant TEM mode and a sensing membrane. By displacing the membrane using the acoustic pressure, one can generate an amplitude modulated radio frequency signal proportional to the product of the displacement and the excitation signal. One may use the backscattered electromagnetic signal to recover the audio signal. The results for power generation, sound transduction, and radio-frequency backscatter transmission of the audio signal are presented.

An omnidirectional piezoelectric transducer for selective excitation and reception of high-order shear horizontal waves

Guided wave tomography, as an advanced structural health monitoring (SHM) method, has offered a feasible solution to wall thickness quantification which is essential in petrochemical industries. However, previously used low-frequency Lamb waves (A0 and S0) limit the resolution of tomography. Recently, the first-order shear horizontal guided wave (SH1) was found very promising in tomography for its capability in resolution improvement. However, the SHM-required omnidirectional piezoelectric transducers for selectively generating and receiving the SH1 wave, namely OSH1-PT, are not available yet. In this work, a general method was developed to design an OSH1-PT based on the thickness-poled PZT half-ring configuration. Firstly, the excitation function of the OSH1-PT was explicitly derived and validated through finite element simulations. Secondly, a design formula was obtained and used to determine the size of the OSH1-PT. Then, the designed OSH1-PT was fabricated and tested by using a 2D laser Doppler vibrometer. Significant mode selectivity was observed in all directions (0 ∼ 90°) with the excited SH1 to SH0 ratio higher than 15 dB. Pitch-catch tests were conducted from 400 ∼ 520 kHz and the received SH1 to SH0 ratio was found higher than 19 dB at all frequencies and reached its maxima of 30.7 dB at 490 kHz, which is very close to the designed working frequency of 500 kHz. Finally, an OSH2-PT was theoretically designed and validated by FE simulations. Due to its simplicity and effectiveness in designing the OSHn-PT, the proposed method is expected to pave the road to wide applications of high-order SH wave tomography.

Focusing of Micrometer-Sized Metal Particles Enabled by Reduced Acoustic Streaming via Acoustic Forces in a Round Glass Capillary

Two-dimensional (2D) metal-particle focusing is an essential task for various fabrication processes. While acoustofluidic devices can manipulate particles in two-dimensions, the production of these devices often demands a cleanroom environment. Therefore, acoustically excited glass capillaries present a cheap alternative to labor-intensive cleanroom production. Here, we present 2D metal microparticle focusing in a round glass capillary using bulk acoustic waves. Excitation of the piezoelectric transducer at specific frequencies leads to mode shapes in the round capillary, concentrating particles toward the capillary center. We experimentally investigate the particle line width for different particle materials and concentrations. We demonstrate the focus of copper particles approximately $1\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{m}$ in diameter down to a line of width $60.8\ifmmode\pm\else\textpm\fi{}7.0\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{m}$ and height $45.2\ifmmode\pm\else\textpm\fi{}9.3\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{m}$, corresponding to a local concentration of 4.5% v/v, which is $90$ times higher than the concentration of the initial solution. Further, we achieve the focusing of 1-$\ensuremath{\mu}\mathrm{m}$ polystyrene particles, which is usually prevented due to acoustic streaming. Through numerical analysis, we reveal the mechanism enabling the manipulation of particles in the low-micrometer range. Due to a transition of the acoustic streaming patterns from two dominant vortices in the lower half to two dominant vortices in the upper half, the streaming velocity exhibits a local minimum while the overall acoustic energy density stays at a sufficiently high level for particle focusing, leading to a lower critical particle radius than in conventional rectangular microchannels. Finally, we use our method to eject copper particles through a tapered round capillary with an opening of $25\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{m}$ in diameter, which would not be possible without particle focusing. Our setup can be utilized for various applications that otherwise might suffer from abrasion, clogging, and limited resolution.

Transmission rules of ultrasonic at the contact interface between soil medium in farmland and ultrasonic excitation transducer

To analyze the phenomenon of distortion and frequency dispersion in the ultrasonic pressure curve at the excitation transducer-soil contact interface (incident interface), a new method to study the ultrasonic propagation in farmland soil media based on DEM (discrete element method) was proposed in this paper. And its feasibility was verified through simulation and actual measurement equivalent experiments. The excitation amplitude, excitation frequency and soil compression ratio were used as influencing factors to carry out single-factor experiments. The analysis was carried out from three aspects: the time domain and the frequency domain curve of the ultrasonic, and the microscopic characteristics of the soil particles near the interface. The experimental results show that the reduction of soil compression ratio, the increase of excitation frequency and amplitude can trigger the non-linear response of the soil, which will lead to the distortion of the ultrasonic waveform. Among them, the compression rate has the most significant influence on the distortion of the sound wave. When the compression ratio is 0%, the trough and the second peak disappear. When the compression ratio reaches 12%, the amplitude of the trough and the second peak are 424% and 749% of the compression ratio of 6%, which is far greater than the influence of other factors. As the excitation frequency increases from 20 kHz to 60 kHz, the ultrasonic frequency domain range increases from 0 to 40 kHz to 0–150 kHz, the dispersion phenomenon is enhanced, which leads to a more serious waveform distortion, while other factors have less influence on the dispersion phenomenon. Under the ultrasound, it is found that the soil particles have a hysteresis phenomenon, that is, the direction of the force and the velocity of the soil particles is inconsistent. And as the soil compression ratio decreases, the excitation frequency increases, the greater the excitation amplitude, the more serious the hysteresis phenomenon, and then causes more serious ultrasonic distortion. The research of ultrasonic waves at the transducer-soil interface is helpful to reveal the propagation law of ultrasonic waves in soil, which provides a theoretical reference for the improvement of the accuracy of ultrasonic testing instruments.

Transfer matrix modeling on a longitudinal-bending coupled piezoelectric transducer with single-phase excitation: Analysis and verification.

Surface-bonded type piezoelectric transducers have the advantages of simple structure, easy miniaturization, and flexible designand have been widely employed as the stator of ultrasonic motors. In order to simplify the control system, a surface-bonded type single-phase excited piezoelectric transducer operating in the longitudinal-bending coupling vibration is proposed, modeled, and validated in this study. Using the asymmetrical excitation effect, the longitudinal-bending coupled vibration is generated in the proposed piezoelectric transducer only applied with a single-phase electrical signal, leading to the production of the elliptical motion at its driving tip. The proposed transducer holds the advantages of compact structure, simple control system, and low manufacturing costs. The transfer matrix method, which is an efficient and fast semi-analytic computation solution, is employed to develop a dynamic model for the proposed transducer in this study in order to provide a general modeling method for surface-bonded type piezoelectric transducers operating with the longitudinal-bending coupled vibration. A novel longitudinal-bending coupled vibration transfer matrix is created first for surface-bonded type piezoelectric composite element. Then, a general semi-analytical electromechanical coupling model is developed to analyze dynamic behaviors of the proposed piezoelectric transducer. Finally, experimental validation is carried out on the prototype of the proposed piezoelectric transducer and compared with the calculation results using the developed transfer matrix model. Experimental results matched well with the calculation results, which confirmed the correctness of the transducer designand verified the feasibility of the developed transfer matrix model. The proposed piezoelectric transducer presents the potential application for linear ultrasonic motors.

Reflection-mode acousto-optic imaging using plane wave ultrasound pulses.

.Significance: Performance of an acousto-optic imaging system is limited by light fluence rate and acoustic pressure field distributions characteristics. In optically scattering media, the former determines the achievable contrast, whereas the latter the imaging resolution. The system parameters can be shaped by changing relative positions of ultrasound (US) transducer array and optodes. However, in the case of many potential clinical applications, optimization possibilities in this regard are limited, as a sample is accessible from one side only and using a water tank for coupling is not feasible.Aim: We investigate the possibilities of improving performance of an acousto-optic imaging system operating in reflection mode geometry with linear US array in direct contact with a sample using plane wave instead of focused US pulses.Approach: Differences in acoustic pressure field distributions for various transducer excitation patterns were determined numerically and experimentally. Acousto-optic images of phantoms with and without optically absorbing inclusions were acquired by measuring laser speckle contrast decrease due to the light modulation by plane wave and focused US pulses with different apodization patterns.Results: The residual acoustic pressure field components occupy relatively large volume and contribute to light modulation. Using nonsteered plane wave US pulses instead of focused ones allows one to mitigate their influence. It also allows one to obtain clear two-dimensional reconstructions of light fluence rate maps by shifting transducer apodization along the lateral direction.Conclusions: Using nonsteered plane wave US pulses allows one to achieve better imaging performance than with focused pulses in the assumed system geometry.

Direct-write piezoelectric coating transducers in combination with discrete ceramic transducer and laser pulse excitation for ultrasonic impact damage detection on composite plates

In this work, direct-write piezoelectric transducers (DWTs) were made by spraying piezoelectric poly(vinylidene fluoride-co-trifluoroethylene) coating with comb-shaped electrodes on carbon fibre reinforced polymer (CFRP) plates for drop weight impact damage detection. Their ability and performance were investigated and compared to discrete piezoelectric lead zirconate titanate (PZT) ceramic transducers that were adhesively bonded on the same CFRP plate. Guided wave signals were acquired with different combinations of actuator-sensor involving DWT, PZT and laser ultrasonic excitation, in pitch-catch configuration. DWTs allowed consistency and simplified signal interpretation due to an effective mode selection (A0 or S0 mode) with wavelengths of 10 and 12 mm. PZTs generated stronger but much more complex signals and mode selection with a larger wavelength (20 mm). The configuration with PZT as actuator and DWT as receiver showed the highest signal amplitude changes of A0 or S0 mode, allowing efficient detection of damage introduced by a 31 J impact. Further ultrasonic B- and C-scans revealed a 27 mm long crack on the plate’s backside developed in addition to internal cracks and delaminations of about 34 mm in length. For realizing contactless ultrasound excitation, a neodymium-doped yttrium aluminium garnet laser (wavelength of 1064 nm, 5.4 ns pulses) was used to replace the surface-mounted brittle PZT. The combination of the broadband laser excitation with the DWTs as sensors achieved more reliable damage detection than equivalent PZTs, attributed to DWT’s effective single mode selection. In addition to reduced weight, the polymeric coated DWTs allow large area implementation (scaling up), even on curved surfaces due to their flexibility and conformability, in contrast to adhesively bonded discrete transducers.

Analysis of a passive radio frequency excited acoustic transducer.

In this work, the physical processes that govern the operation of a passive acoustic transducer are analyzed and modeled. The wireless battery-free transducer derives its power from an externally applied electromagnetic field generated by a radio transmitter. The audio signal is encoded in the backscattered electromagnetic field. Electro-mechano-acoustical analogies are developed and presented. Power generation, sound transduction, and radio frequency backscatter transmission of the audio signal are analyzed. The resonant frequency of the passive acoustic transducer derived from this analysis is comparable to those reported in the literature.

Experiments and finite element analysis for detecting the embedded defects in concrete using PZT transducers

Deficiencies inside concrete may reduce the load-bearing capacity and bring potential safety and durability problems to infrastructures. Detection of concrete deficiencies at the earliest time poses a great importance on structure safety. While there is still a lack of accurate and efficient method for quantitative evaluation of defects in concrete structures. In this study, the damage index was introduced to quantitatively evaluate the defects in concrete using piezoelectric (PZT) transducers. Meanwhile, the simulations of transducer excitation, the wave propagation in concrete, and the transducer receiving were established by Abaqus software. The results indicate that the localization and quantitative evaluation of defects in concrete could be achieved by using the damage index. The relative deviation of wave velocity and amplitude between the numerical and experimental results was within 15% and 20% respectively. The change of damage index obtained from experiments could be reasonably explained by the changing of normal stress distribution of finite element analysis. Numerical modeling could also help to understand and analyze the ultrasonic signal attenuation of the experimental results by using the normal stress distribution along propagation path.

2-D Ultrasonic Array-Based Optical Coherence Elastography.

Acoustic radiation force optical coherence elastography (ARF-OCE) has been successfully implemented to characterize the biomechanical properties of soft tissues, such as the cornea and the retina, with high resolution using single-element ultrasonic transducers for ARF excitation. Most currently proposed OCE techniques, such as air puff and ARF, have less capability to control the spatiotemporal information of the induced region of deformation, resulting in limited accuracy and low temporal resolution of the shear wave elasticity imaging. In this study, we propose a new method called 2-D ultrasonic array-based OCE imaging, which combines the advantages of 3-D dynamic electronic steering of the 2-D ultrasonic array and high-resolution optical coherence tomography (OCT). The 3-D steering capability of the 2-D array was first validated using a hydrophone. Then, the combined 2-D ultrasonic array OCE system was calibrated using a homogenous phantom, followed by an experiment on ex vivo rabbit corneal tissue. The results demonstrate that our newly developed 2-D ultrasonic array-based OCE system has the capability to map tissue biomechanical properties accurately, and therefore, has the potential to be a vital diagnostic tool in ophthalmology.

Mode excitability and selectivity for enhancing scanning guided wave-based characterization of subwavelength defect

The scanning guided ultrasonic waves (GUWs) have been exploited intensively for characterizing defects or material anomalies at their early stage. Yet, the evaluation of defects in a subwavelength scale, which induces indiscernible disturbance to the linear and nonlinear features of GUWs, remains a daunting task for methods using the scanning GUWs owning to their limitation in terms of sensitivity and applicability. Based on the investigation of effect of defect on the excitability of GUW modes, we establish a framework to distinguish the optimal GUW mode with which the characterization of the small defect with subwavelength size using scanning GUWs can be enhanced. In this framework, the excitation transducer is scanned across the specimen surface to generate probing GUWs. The excitability of each GUW mode is investigated analytically, and the theoretical interpretation of effect of defect on excitation of each GUW mode is interrogated using a reciprocity theorem and Born approximation. In conjunction with the analysis of group velocity of GUW modes, the candidate GUW mode, i.e. mode S1 at a frequency-thickness product of 3.58 MHz⋅mm, which features an excitability with optimal sensitivity to defect and high practical applicability is selected. A damage index that calibrates the extent of defect-induced variation in the waveform of the selected GUW mode is proposed, with which the subwavelength defects can be characterized accurately and reliably. Numerical and experimental validations are performed, in which the surface and subsurface defects of subwavelength scales are identified and visualized using the selected mode and an imaging algorithm. The results corroborate the effectiveness of the proposed framework for enhancing the characterization of subwavelength defects using modally selective scanning GUWs.

Нелинейное возбуждение гиперзвуковых колебаний в ферритовой пластине в условиях комбинированного воздействия на двух частотах. Часть 2. Вариация постоянного поля

Нелинейное возбуждение гиперзвуковых колебаний в ферритовой пластине в условиях комбинированного воздействия на двух частотах. Часть 2. Вариация постоянного поля

Fluid Independent Flow Determination by Surface Acoustic Wave Driven Ultrasonic Techniques

A fluid-independent ultrasonic approach for flow determination in microchannels in the harsh environment of an ultra high pressure liquid chromatography (UHPLC) system is presented. Ultrasonic waves in the fluid are excited by separate media surface acoustic waves (SAW) of Rayleigh-Wave type. The LiNbO3 SAW chip being equipped with interdigitated transducers for SAW excitation also marks the bottom of the fluid channel and thus allows for very effective SAW coupling to the fluid. The channel ceiling acts as an acoustical mirror for longitudinal ultrasonic waves propagating through the fluid. To deduce the fluid flow from the ultrasonic transmission after reflection, we employ a combination of time differential phase and time of flight measurements with a two port vector network analyzer. To verify and assign our experimental results, we use an adapted time explicit finite element method. In the simulation, both the piezoelectric single crystal and the fluid are included and we solve the linear Navier-Stokes equation to evaluate the background flow. By changing the ultrasonic propagation direction, we are able to deduce the fluid volume flow over time with very high accuracy, independent of the actual liquid in the channel.

Numerical assessment of induced damages of RC frames using PZT patch in embedded configurations with and without bond layer

Abstract In the present times, health monitoring is playing a key role in assessing the damages occurred in the civil structures. The current study deals with estimating damages induced to a reinforced concrete (RC) frame using ceramic piezoelectric Lead zirconate titanate (PZT) patches in embedded forms. Coupled field analysis on finite element models have been performed for acquiring the electro-mechanical impedance (EMI) response of structure in transducer excitation frequency range of 100–200 kHz. Two-fold study have been carried out to numerically analyze the performance of damage monitoring system with increasing crack depths that are induced at critical locations in the presence and absence of adhesive bond layer between PZT patch and surrounding concrete. Regression models based on root mean square deviation of EMI signatures have been proposed to estimate the severity of damages in RC frames.

Monitoring corrosion-induced thickness loss of stainless steel plates using the electromechanical impedance technique

Stainless steel plates are widely used in steel structures. Corrosion damage of a stainless steel plate can induce the thickness and mass loss of the stainless steel plate. The corrosion-induced thickness loss (CITL) is one of the main reasons for the degradation of the stiffness and bearing capacity of the stainless steel plate, which endangers the safety of the structure and causes economic losses. Therefore, effective monitoring of the CITL of the stainless steel plate can help to ensure the safety of steel structures. In this study, a novel monitoring method for the CITL of the stainless steel plate based on the electromechanical impedance (EMI) technique is presented. The effective mechanical admittance (EMA) of a simply supported thin stainless steel plate under the excitation of a single surface-bonded piezoelectric transducer is derived theoretically; the resonance frequency shift () of the bending vibration mode in the admittance signature is extracted as the CITL-sensitive feature to identify the CITL of the stainless steel plate. The quantitative relationship between and CITL, based on the EMA, is established theoretically for monitoring the CITL of the stainless steel plate. The effectiveness of the proposed method is verified by experiments. The experimental results demonstrate that the proposed method can sensitively identify, accurately quantify and predict the CITL of the stainless steel plate, and has excellent stability and reliability. This method can not only overcome the limitation of the existing statistics-based EMI methods that cannot quantify the CITL, but also compensate for the weakness of commonly-used non-destructive testing methods that cannot quantitatively predict CITL in an on-line monitoring manner. The proposed method provides an effective monitoring and tracking tool for the CITL of the stainless steel plate.

The Mechanical Impedance of the Human Skull via Direct Bone Conduction Implants.

PurposeThe mechanical skull impedance is used in the design of direct bone drive hearing systems. This impedance is also important for the design of skull simulators used in manufacturing, service, and fitting procedures of such devices.Patients and MethodsThe skull impedance was measured in 45 patients (25 female and 20 male) who were using percutaneous bone conduction implants (Ponto system or Baha system). Patients were recruited as a consecutive prospective case series and having an average age of 55.4 years (range 18–80 years). Seven patients were treated in Gothenburg, Sweden, and 38 patients in Edmonton, Canada. An impedance head (B&K 8001), driven by an excitation transducer with emphasized low-frequency response, was used to measure the mechanical point impedance with a swept sine from 100 to 10k Hz.Results and DiscussionThe skull impedance was found to have an anti-resonance of approximately 150 Hz, with a median maximum magnitude of 4500 mechanical ohms. Below this anti-resonance, the mechanical impedance was mainly mass-controlled corresponding to an effective skull mass of 2.5 kg at 100 Hz with substantial damping from neck and shoulder. Above the anti-resonance and up to 4 kHz, the impedance was stiffness-controlled, with a total compliance of approximately 450n m/N with a small amount of damping. At frequencies above 4 kHz, the skull impedance becomes gradually mass-controlled originating from the mass of the osseointegrated implant and adjacent bone. No significant differences related to gender or skull abnormalities were seen, just a slight dependence on age and major ear surgeries. The variability of the mechanical impedance among patients was not found to have any clinical importance.ConclusionThe mechanical skull impedance of percutaneous implants was found to confirm previous studies and can be used for optimizing the design and test procedures of direct bone drive hearing implants.

Design and development of ultrasonic bipolar square-wave pulser for non-destructive testing of concrete structures.

This paper provides design and development details of the generation of bipolar High Voltage (HV) square wave pulses for the excitation of low frequency ultrasonic transducers. Such a circuit is required for the purpose of ultrasonic inspection of components, particularly where high energy is required to insonify the attenuative medium, such as concrete. A HV (±350 V) square wave pulse has been generated by an ultrafast complementary Metal Oxide Semiconductor Field-Effect Transistor (MOSFET) pair, which is driven by high speed MOSFET drivers. The generated bipolar square wave pulse has been utilized to energize a 108 kHz ultrasonic transducer to operate in the pulse-echo mode for the evaluation of a concrete test block. The receiver amplifier filters the received low-amplitude echo signals, which are reflected back from a discontinuity, and amplifies further for signal to noise ratio enhancement. The pulser board designed has been tested and evaluated for its functionality to measure ultrasonic velocity in the highly attenuative concrete medium up to a depth of 1 m. The measured value of acoustic velocity was compared with the value obtained from the commercially available ultrasonic pulse velocity instrument, and the values obtained are within ±5%.

Application of Ultrasonic Guided Waves for Inspection of High Density Polyethylene Pipe Systems

The structural integrity assessment of thermoplastic pipes has become an interesting area of research due to its elevated usage in the liquid/gas transportation industry. Ultrasonic guided wave testing has gained higher attention from industry for the inspection of elongated structures due to the reduced inspection time and cost associated with conventional non-destructive testing techniques, e.g., ultrasonic testing, radiography, and visual inspection. Current research addresses the inspection of thermoplastic pipes using ultrasonic guided waves as a low cost and permanently installed structural health-monitoring tool. Laboratory and numerical investigations were conducted to study the potential of using ultrasonic guided waves to assess the structural health of thermoplastic pipe structures in order to define optimum frequency range for inspection, array design, and length of inspection. In order to achieve a better surface contact, flexible Macro-Fiber Composite transducers were used in this investigation, and the Teletest® Focus+ system was used as the pulser/receiver. Optimum frequency range of inspection was at 15−25 kHz due to the level of attenuation at higher frequencies and the larger dead zone at lower frequencies due to the pulse length. A minimum of 14 transducers around the circumference of a 3 inch pipe were required to suppress higher order flexural modes at 16 kHz. According to the studied condition, 1.84 m of inspection coverage could be achieved at a single direction for pulse-echo, which could be improved by using a higher number of transducers for excitation and using pitch-catch configuration.