Type Of Piezoelectric Transducer Research Articles

Damage detection and localization based on different types of actuators using the electromechanical impedance method in 3D-printed material

Electromechanical impedance (EMI) measurement, using piezoelectric transducers (PZTs) in the high-frequency range is a potential method for assessing the health of lightweight structures. The major objective of this work is to comprehend how different actuators react to damage in additively manufactured (AM) polymer structures. A novel frequency-range selection technique was suggested based on the maxima of the standard deviation of the impedance frequency spectra gathered for the referential and damage cases. A 3D-printed acrylonitrile butadiene styrene (ABS) plate was used for the investigation, where two PZT and one macro fiber composite (MFC) actuator were glued to the surface. Small magnets were used to simulate damage and were positioned at increasing distances from each transducer as EMI measurements were made using the MFC and 1 PZT. This served both in studying the transducers’ sensitivity to damage and selecting the proper frequency range for damage detection utilizing the standard-deviation approach. The EMI-acquired data from the MFC actuator displays damage-sensitive peaks in a low-frequency band (0–58 ), while the PZT shows a good sensitivity in a higher frequency range (94–304 ). In order to evaluate the PZT and MFC actuators’ sensitivity to damage in the 3D-printed ABS plate, impact damage is also generated in the plate’s center. The impedance-based damage indices obtained from different types of PZTs (2 PZTs and 1 MFC) were projected to the same base level and then fused—for the first time—for impact-damage localization and further added magnetic mass damage localization. The obtained damage index values of impedance are encouraging for the evaluation of AM polymer structures with a 4.48 mm positional error from a real location by fusing data in the different frequency ranges for PZTs and MFC. The damage localization error increases significantly to the new location beyond the damage sensitivity range of the PZT2 and MFC for the added magnetic mass on the 3D printed structure.

Acoustic Field of an Ultrasound Device for Differential Diagnosis of Human Hearing

In this paper analyzes the relevance and novelty of using a multielement array in an electroacoustic transducer for differential diagnosis of human inner ear coagulation by changing the pulse duration and direction of radiation. Today the clinical applications of ultrasound are numerous and diverse, and ultrasound diagnostics is one of the most rapidly developing methods in medicine. In recent years the effect of focused ultrasound on the human auditory system has been actively studied. The structure of the human inner ear is in the middle of a system of spaces and channels of bony labyrinths. It is known that the most successful way to the auricular labyrinth is the one with the shortest distance and with the least tissue loss. In order for the width of the scanning ultrasound beam to remain constant throughout the entire length of probing, the mode of dynamic focusing of the ultrasound beam was considered. The ultrasonic beam in the scanners is formed using a linear multielement array with individual element dimensions of several wavelengths by introducing between the electrical signals sent or received from the elements such delays that ensure that the fields are focused at a given point on the beam axis, and additionally by using acoustic lenses. In practice, the problem is solved by successive focusing of the beam at several fixed distances from the working surface. Calculations of the geometric dimensions and the study of the acoustic field for the cylindrical wave front created by a linear multielement array of piezoelements are performed. Calculations of the acoustic field distribution in depth at varying pulse duration and at changing the angle of deflection from the axis, with the focal distance unchanged. It is concluded that it is reasonable to use this type of electroacoustic transducer for differential diagnosis of human hearing. From the obtained graphs it was found that an increase in the pulse attenuation coefficient leads to a decrease in the values of the diffraction maximum. It is also shown that the relative amplitude of the diffraction maximum can be reduced by reducing the pulse duration and increasing the number of piezoelectric elements in the working group. This type of piezoelectric transducer will allow, by changing the angle, to affect all parts of the cochlea of a person, as it is known that each part of the cochlea is responsible for a certain frequency of perception, pick up a certain duration for safe exposure. And it will also be possible to perform acoustic influence on the cochlea to confirm the functioning of the auditory nerves before cochlear implantation.

АВТОМАТИЗОВАНИЙ ДВОКАНАЛЬНИЙ П’ЄЗОЕЛЕКТРИЧНИЙ ГРАВІМЕТР АГС

The purpose of the article is to obtain the basic working equation of motion of a dual-channel piezoelectric gravimeter of the aviation gravimetric system; to prove that a new dual-channel piezoelectric gravimeter has greater accuracy than the known ones. Today, piezoelectric transducers are used to determine the internal defects of solids with the help of ultrasonic waves, to measure the speed of ultrasound, as well as in medicine, mechanical engineering, geophysics, etc. Intensive development of new types of piezoelectric transducers is also carried out in Ukraine. The scientific works of Ukrainian scientists consider the use of piezoelectric transducers only as accelerometers but do not indicate the possibility of their use as dual-channel aviation gravimeters for measuring the acceleration of gravity. From the above review of prominent scientific works, it is clear that there is no information as to the use of the physical phenomenon of the direct piezoelectric effect to create a dual-channel gravity AGS more accurate than a known one. Improving the measurement accuracy in the automated dual-channel piezogravimeter is provided by the fact that the second measurement channel is created. To do this, the sensing element is made with two channels. The output electrical signals of the piezoelectric plates of both channels are summed in the adder. The output signal from the adder is fed to the device for calculating the output signal of the gravimeter (on-board computer), where it is calculated for a certain time interval. As a result, we get the output that contains a double signal of gravity acceleration. It is completely free of such measurement errors, which are caused by the influence of vertical acceleration, instrumental errors and errors from the non-identity of the two channels. The principle of operation of the new dual-channel piezogravimeter is described, its structural scheme is shown. It is shown that it is realistic to achieve greater accuracy of the piezogravimeter AGS (0.5 mGal) by compensating for errors from the influence of vertical acceleration (103 times the useful signal) and instrumental errors and errors from the residual non-identity of the two channels.

A Comparative Study of Wave Excitation in Plates Using Piezoelectric Transducers Operating at Different Modes

Structural health monitoring (SHM) and damage detection techniques have recently gained attention in various fields of engineering for preventing catastrophic failures. Among different SHM techniques, Lamb wave propagation methods are widely used as these waves can propagate large distance from a single source. Piezoelectric (PZT) transducers are used here as actuators and sensors to generate and receive wave signals. Most of the studies conducted on wave propagation in plates are by use of conventional d31 mode piezoelectric transducer. However, so far very few studies have been done using other types of PZT transducers. The primary objective of this paper is to determine and study the wave responses in a thin plate using different types of PZT transducers. The results indicate that the d31 and d33 type transducers generate Lamb waves, whereas d24 and d15 type transducers generate shear horizontal waves in two orthogonal directions. The study indicates that each of the transducers has its own directional property. The present study will be helpful for the application of Lamb waves and shear horizontal waves in plate structures

Experimental Study of the Focused Ultrasonic System for Differential Diagnostics of the Human Hearing

In this paper the analysis of relevance and novelty of application of piezoelectric transducer for noninvasive diagnostics of a cochlea of the human by means of the focused ultrasound is carried out. To date, clinical use of ultrasound is numerous and diverse, and ultrasound diagnosis is one of the fastest growing methods in medicine. Revealed a previously unknown effect of spatial notch filtering quarter wavelength layers diffuse heat radiation. It is shown that the effect, together with a focused acoustic thermometer, allows for greater accuracy and allows measurement of the body's deep body temperature in real time.The design of the converter consists of a piezoceramic, an acoustic lens with the help of which the transformation of a flat wave front into an acoustic system with a flat piezoelement. The flat, concave lens is made of solid material, the rate of ultrasonic diffusion in which exceeds its value in water (biological tissue) for the studied acoustic system, organic glass was chosen. It is provided the theory, calculation and a design of measuring means: a high-frequency wattmeter for measurement of the electric power consumed by a piezoelectric transducer; the radiometer for measurement of acoustic power of the focused ultrasonic bunches. With their help detailed pilot study of the acoustic system is conducted, namely, parameters of her acoustic field and efficiency are determined. The theory, calculation and design are given: free float radiometer for measuring acoustic power of both focused and unfocused ultrashort beams; high-frequency wattmeter without active elements for measuring the power consumption of a piezus emitter.The experimental study of the layout of the acoustic focusing system is to measure the emitted acoustic and consumed electrical power of the piezoelectric element with the lens. The task of measuring acoustic power is solved using a radiometer. The measurement of the consumed electric power is made by means of a high-frequency wattmeter, which contains a multiplication scheme in the form of a circular scheme on four diodes and a current transformer. The received frequency dependences of radiated acoustic power, electric power consumed and the efficiency factor are obtained.The conclusion about expediency of use of this type of the electro-acoustic transducer for differential diagnostics of hearing of the human is drawn. The calculated intensity is sufficient for both diagnostic and therapeutic use of the developed acoustic system. This type of piezoelectric transducer will make it possible to distinguish between diseases of the middle ear of a person from internal diseases, and therefore to carry out differential diagnostics of the auditory system. This is especially important in clinical practice for choosing a further recovery strategy: if the loss occurs in the middle ear - the hearing aid is used, if in the inner one - is performed surgically by implantation of the cochlear implant.Ref. 10, fig. 6, tabl. 2.

Impact Damage Prediction for Wave Energy Converters

Marine and hydrokinetic energy is of growing interest across the globe because it has the potential to provide a large source of renewable energy from the world’s oceans and rivers. These marine and hydrokinetic devices, such as wave energy converters, must operate remotely in all weather conditions, including severe storms. Thus, these devices can suffer from structural damage affecting their performance and lifespan. Therefore, there is interest in developing structural health monitoring systems that can identify new damage, estimate its severity, and then make a decision to provide crews with a maintenance or control recommendation. In this study, we investigate using the electromechanical impedance response of piezoelectric transducers to actively monitor the structural health of composite materials similar to those used in several marine and hydrokinetic devices. Recurring impact damage experiments were completed on five plates using a test drop stand, consisting of five consecutive impacts at the same location for each plate. Classification and regression methods were evaluated in an attempt to predict impact damage on a new plate. Machine learning algorithms were used on data collected over a frequency range of 10 kHz to 100 kHz for two types of piezoelectric transducers.

Circular sensing networks for guided waves based structural health monitoring

In this paper, results of damage localization performed for four sensing network configurations are compared. Process of damage localization is based on guided waves propagation phenomenon. Guided waves are excited using piezoelectric transducer and received by scanning laser vibrometer. Different excitation frequencies are also investigated. In experimental investigations two types of piezoelectric transducers are used as guided waves exciters. Frequency–magnitude characteristics of symmetric and antisymmetric modes are created for both types of transducers. These characteristics allow a choice of an excitation frequency for efficient generation of selected wave mode. The amplitude of second mode in this case has negligibly small value. Finally, sensing networks in the form of circle with three different diameters are realized based on piezoelectric transducers. Damage localization algorithm is prepared in MATLAB® environment as well as in C++.

Piezoelectric film transducer for recording of oculography in electro-encephalogram-polygraphy.

Oculography is important during clinical electroencephalography (EEG). Routinely, silver-silver plate/cup electrodes have been used. However, the electrical activity of the anterior parts of the brain can be mixed with the effect of eye/eyelid movements. This can result in artifacts disturbing or making it impossible to differentiate the frontal activity of the brain from eye movement artifacts. Therefore, crystal piezoelectric materials have been used for oculography, but they are relatively fragile in practice. In this study we present a new type of piezoelectric transducer for the recording of oculography, a piezoelectric polyvinylidenefluoride (PVDF) film transducer. Our preliminary material consists of routine EEG recordings of 15 subjects performed by means of this method. All recordings were of good quality and corresponded well with the routine electro-oculography recordings.