Experimental researching of biological objects noninvasive passive acoustothermometry features

The energy method of calculating the properties of piezoelectric electroacoustic transducers is considered. The Lagrangian of an electroacoustic transducer as a system performing multiple energy conversions is introduced. The Euler equations describing operation of a transducer with many mechanical degrees of freedom are derived from the least action principle. The corresponding multicontour equivalent circuit of the transducer is introduced. For the particular case of a transducer having one mechanical degree of freedom the governing equations are obtained by applying the Energy Conservation Law, and equivalent circuit with one mechanical branch also introduced. Application of the energy method is illustrated with examples of the pulsating spherical transducer as the one degree of freedom system and the multimode cylindrical transducer comprised of circular rings as the system with multiple degrees of freedom. Advantages of the method for application with electroacoustic transducers are summarized.

In the article highlights the infusion of additional structural elements into the characteristics of a piezoelectric electroacoustic transducer, leading to the breakdown of the structure, as well as their straightness diagrams. The major tasks of ultrasonic measuring systems are sound waves concentrated sending to the controlled object and reflected waves receiving. Electro-acoustic transducer is an oscillating system with a sufficiently high quality factor and contains an asymmetric bimorph element. The considered butts of improving the sensitivity of the central beam of the electroacoustic transducer added to the design volumetric resonator. Directional effect of concentration can be obtained using the irradiator as Helmholtz resonator consisting of bimorph piezoelectric resonator and tube of required length and diameter, which orients sound beam on the acoustic axis of the electroacoustic transducer. An example of improving the selectivity of the central lobe electroacoustic transducer is adding additional cavity resonator to the construction of the piezoelectric transducer. Further research can be carried out directly based on mathematical models for various design circuits of piezoelectric transformers. Important tasks in the design and development of the main components of ultrasonic vibrating devices are considered. The main advantages and shortcomings of the ultrasonic signal-receiving path have analyzed, in which electroacoustic converters combined with additional structural elements for ultrasonic vibrating systems to ensure autonomous vicination specification of the design parameters and military technology in open areas and intersections.

Pulsed electroacoustic (PEA) method is a very popular method for measurement of charge in dielectrics. In this method, an acoustic wave proportional to charge is generated by a pulsed HV. The acoustic wave traverses several material layers before being sensed and converted to electrical signal by a piezoelectric transducer. Due to multiple reflections in its path, a direct analysis of traveling acoustic wave would be complex. In this paper, we have proposed simulation of the physical model of the PEA method consisting of electrical and acoustic circuits. Using PSpice model of the method, authors have tried to address some design-related issues, which appear to have not been reported in earlier works. The acoustic circuit has been realized using analogy between acoustic wave and wave propagation in electric transmission line. The piezoelectric transducer is also modeled as a transmission line as in modified Leach's transducer model, except that, in the present case the transducer absorbs acoustic signal instead of generating. Approximate theoretical equations have been used to compare with simulations, wherever a comparison is possible, and found to match well in those cases.

Large scale acoustophoretic separation of particles in a flow field can be accomplished by trapping the particles, i.e., remain in a stationary position, in ultrasonic standing waves. The particles are collected in a column pattern, separated by half a wavelength. Within each nodal plane, the particles are trapped in the minima of the acoustic radiation potential. The axial component of the acoustic radiation force drives the particles to their stable axial position. The radial or lateral component of the acoustic radiation force is the force that traps the particle. It must be larger than the combined effect of fluid drag force, i.e., Stokes drag, and gravitational force. There is a need for a better understanding of the lateral acoustic radiation force in realistic acoustophoretic separation devices. COMSOL Multiphysics® software was used to predict the acoustic field in two and three dimensional models of acoustophoretic separation devices driven by piezoelectric transducers. The resulting acoustic field was then used to calculate the acoustic radiation force acting on a suspended particle in two and three dimensions by applying Gor’kov’s equation. Measurements of trapped particles in standing waves indicate accurate calculations of acoustic field and radiation force. [Work supported by NSF PFI:BIC 1237723.]

The study of piezoceramic and piezoelectric transducers behavior by finite element method (FEM) shows an important influence of viscous damping. Damping values for piezoceramic materials are not provided by manufacturers. In addition, damping values for non-piezoelectrics materials, such as, resins, steel, aluminum, etc, which are usually applied to assemble these transducers are not appropriately given for FEM simulations. Therefore, the objective of this work is to determine damping values of these materials so they can be used in a FEM software, such as, the ANSYS, which has four different ways for damping input. Damping values are determined by combining experimental and numerical techniques. For piezoceramics the damping is determined through the quality factor (Qm) by measuring the admittance curve which are influenced by damping. By using these damping values, harmonic and transient FEM simulations of piezoceramics and piezoelectric transducers are performed and the simulated admittance curve is compared with the measured one, as well as, displacement results are compared with laser interferometer measurements. Damping determination for non-piezoelectric materials are done by comparing experimental and simulated results. By using the obtained damping values, experimental measurements and simulated results for different piezoelectric transducers show a very good agreement.

Design and fabrication of an ultrasonic speaker with thickness mode piezoceramic transducers

This chapter presents development of a novel structural health monitoring methodology used for incipient damage detection in moving structures. This method is built upon implementation of low-cost deposition of piezoceramic transducers on crucial substrates together with electromechanical impedance (EMI) to provide a practical solution to damage/fault detection of moving structures that suffer from mechanical fatigue, thermal fatigue or corrosion, before any catastrophic failure. Important steps towards application of such technology are: i) Chemo-physical fabrication of piezoceramic transducers, i.e., deposition of precursor solutions or piezoelectric materials, on geometrically irregular structures; ii) Development of a portable impedance-based transceiver and signal processing algorithm capable of transmitting actuating signals as well as receiving and analyzing response signals to/from piezoelectric transducers, respectively; iii) Development of a monitoring algorithm, and iv) Methodology verification through bunch of semi-filed tests by building the prototype of a moving structure. Multiple characterizations are performed to assure the micro and macro-structural functionality, accuracy, and precision of fabricated transducers. To verify the functionality of the custom-built system, electromechanical response of the transducers and the results obtained from the transceiver are compared with commercially available piezoelectric wafers and standard impedance analyzers. Frequency response of transducers measured in a wide bandwidth shows obvious frequency shift and change in the admittance/ impedance amplitude corresponding to the resonance/anti-resonance peaks at pristine vs. damaged conditions. Furthermore, for rotary structures, rotational speed and temperature play important role in this method. Application of this method could be extended to moving structures such as airplane engine blades, fuselage frames, wing ribs, helicopter main rotor assembly, critical parts of the exploration rovers, satellite loaded modules and thrusters, moving links/joints on the international space station, rotors in hydroelectric or nuclear power plants, autonomous underwater vehicles, submarine propellers, hydro/diving planes, wind turbines, hot/cold rollers in steel production lines, drones, mobile robots, etc.

Aircraft smart skin technology requires the integration of large-scale, lightweight, and integrative sensor networks with aircraft structural skin, but it is difficult to directly manufacture such sensor networks in a large-scale, low-cost, reliable, and simple way. To study this issue, a design and manufacturing method of a stretchable and large-scale guided wave sensor network is proposed in this article. The key principle of the method is to design and manufacture the guided wave sensor network in a limited scale and expand it in a large-scale for aircraft smart skin of structural health monitoring. To ensure the excellent stretchability of the network, the design method of a serpentine-based fractal island-interconnect structure combined with the flexible printed circuit manufacturing process is proposed. The whole manufacturing process of the guided wave sensor network is realized by the mature flexible printed circuit process and the piezoelectric transducers (referred to as PZTs) are integrated with the network by reflow soldering which is compatible with the flexible printed circuit process, which greatly reduce manufacturing costs, simplify manufacturing process, and improve the yield and stability of the network. The guided wave sensor network can be uniaxially stretched to 500% of its original size and work well when fully expanded to cover 2500% of its original area. The test results of guided wave response show that the PZTs on the network can excite and receive guided wave signal normally. In addition, the network is placed on the surface of a carbon fiber composite laminate with stiffeners and the validation results show that the network can be applied to both active and passive guided wave–based structural health monitoring of composite structures, including damage imaging and impact imaging.

In this work, a new design method is proposed to intensify the focused acoustic field generated inside a circular cylindrical piezoelectric transducer. The proposed design incorporates a stepped-thickness piezoelectric transducer which has thickness variations along the length. The location of these steps are identified based on the mode shape analysis of a uniform-thickness tube. Once the step locations are identified, two cases are considered with internal and external steps. Acoustic radiation characteristics and mode shapes are compared with the uniform-thickness shell. All the investigations are performed using ANSYS. An increase in the sound pressure level is obtained utilizing the stepped-thickness tube at the same input power.

The quality factor of a passive, linear, small acoustic radiator is fundamentally limited by its volume normalized to the emitted wavelength, imposing severe constraints on the bandwidth and efficiency of compact acoustic sources and of metamaterials composed of arrangements of small acoustic resonators. We demonstrate that these bounds can be overcome by loading a piezoelectric transducer with a non-Foster active circuit, showing that its radiation bandwidth and efficiency can be largely extended beyond what is possible in passive radiators, fundamentally limited only by stability considerations. Based on these principles, we experimentally observe a threefold bandwidth enhancement compared to its passive counterpart, paving the way toward non-Foster acoustic radiation and more broadly active metamaterials that overcome the bandwidth constraints hindering passive systems.

Composite materials are widely used in aerospace industries due to their light weight, strength, and various other desired properties. However, they are susceptible to various defects occurring during the manufacturing process or in service. Typical defects include porosity, wrinkles, and delamination. Nondestructive means of detection of the defects at any stage are of great importance to ensure quality and safety of composite structures. A nonintrusive removable Lamb wave system and accompanied methodology that is not material dependent are presented in this paper to detect various types of typical defects in laminated composite plates, flat or curved. Through multidimensional data acquisition and processing, abnormality in waves caused by defects is captured and presented in inspection images. The methodologies are demonstrated in two cases: delamination in a curved plate and wrinkles in a flat plate. Overall, the results show that Lamb waves using the piezoelectric transducer and laser vibrometer system can be used for various types of defects inspection in flat or curved composite plates.

Lead zirconate-titanate containing 1 wt % niobium with different Zr/Ti ratios compositions were studied. A pronounced increase in densification during sintering process occurred near tetragonal-rhombohedral phase. Dielectric constant of polarized and unpolarized samples was studied. The rotation of all 90° domains to their original positions caused the more looseness of Ti4+ and Zr4+ in the octahedral configuration 1eading to greater polarization in the tetragonal structure, thus 1eading to , higher dielectric constant. Near the phase change, the minimum resonance frequency caused the minimum values of ultrasonic waves, which were emitted from the edge of the polarized ceramic transducers.

This paper presents a compliance and positioning control characteristics of additive manufactured-nanopositioning system consisted of the flexure mechanism and voice coil motor (VCM). The double compound notch type flexure stage was designed to utilize the elastic deformation of two symmetrical four-bar mechanisms to provide a millimeter-level working range. Additive manufacturing (AM) process, stereolithography, was used to fabricate the flexure stage. The AM stage was inspected by using 3D X-ray computerized tomography scanner: air-voids and shape irregularity. The compliance, open-loop resonance peak, and damping ratio of the AM stage were measured 0.317 mm/N, 80 Hz, and 0.19, respectively. The AM stage was proportional-integral-derivative positioning feedback-controlled and the capacitive type sensor was used to measure the displacement. As a result, the AM flexure mechanism was successfully 25 nm positioning controlled within 500 μm range. The resonance peak was found approximately at 280 Hz in closed-loop. This research showed that the AM flexure mechanism and the VCM can provide millimeter range with high precision and can be a good alternative to an expensive metal-based flexure mechanism and piezoelectric transducer.

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This paper presents a parameter based form of a wave absorbing controller (WAC) in the time domain. The controller is applied to a flexible structure with the piezoceramic transducers bonded onto it. A distributed piezosensor gives the moment rate of the wave absorbing region as an output current. This current is then fed back to a piezoceramic actuator, resulting in a wave absorbing controller. The controller is originally designed in the frequency domain by minimization of the ratio of total output to total input wave amplitudes. Although the controller performance appears satisfactory in the frequency domain, its time domain behavior is of interest for overall performance evaluation. However, the wave absorbing method usually produces controllers which are difficult to realize in practice. In order to study the behavior of the controller and closed loop system in the time domain, and also to address these realization issues, we introduce a method of approximation of the controller enabling it to be represented in a simple form. Frequency domain comparison of system performance under the original controller and this approximation demonstrates the accuracy of the latter. The system is then studied in the time domain, showing that this novel wave absorbing controller is effective and can be easily implemented in practice. The main contribution of this paper is the introduction of a new controller for flexible structures, based on the wave absorbing method (WAM), which depends on only system parameters, i.e., E, I, (rho) , and natural frequencies. Therefore, rather than the usual controller design based on dynamic model (such as LQR) for obtaining control gains, these gains can be easily calculated from a simple formula based only on the mechanical parameters of the flexible structure.