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Justina Sestoke
Ultrasound Institute, Kaunas University of Technology, LT-51423 Kaunas, Lithuania.

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Journal article
Published: 09 May 2020 in Applied Sciences
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Air-coupled ultrasonic guided A0 mode is already used for material characterization. By measuring the phase velocity of the A0 mode the elastic properties, such as the Young’s modulus, can be determined. The objective of this work was the development of measurement methods and corresponding signal processing procedures enabling the acquisition of spatial distributions of non-uniform elastic properties of thin films and plates. Those methods are based on the excitation of a slow sub-sonic A0 Lamb wave mode in a plate, the measurement of normal displacements at different distances from the source, the formation of the B-scan, and processing the collected signals. Two different signal processing methods were proposed and investigated. In the first method the all zero-crossing instants of the ultrasonic signals at different distances are found and from them spatial distributions of the A0 mode velocity are determined. According to the second method 2D spatial-temporal spectrum of the B-scan is calculated and propagating A0 modes with different velocities are identified. Efficiency of the proposed methods was evaluated theoretically and experimentally using thin mineral MICA paper samples, which is used in the electrical and aerospace industries as an insulating material. The zones with different A0 mode phase velocities (95 ± ∆3 m/s and (106 ± ∆6 m/s) at the frequency 47 kHz were identified.

ACS Style

Rymantas Jonas Kazys; Liudas Mazeika; Justina Sestoke. Development of Ultrasonic Techniques for Measurement of Spatially Non-Uniform Elastic Properties of Thin Plates by Means of a Guided Sub-Sonic A0 Mode. Applied Sciences 2020, 10, 3299 .

AMA Style

Rymantas Jonas Kazys, Liudas Mazeika, Justina Sestoke. Development of Ultrasonic Techniques for Measurement of Spatially Non-Uniform Elastic Properties of Thin Plates by Means of a Guided Sub-Sonic A0 Mode. Applied Sciences. 2020; 10 (9):3299.

Chicago/Turabian Style

Rymantas Jonas Kazys; Liudas Mazeika; Justina Sestoke. 2020. "Development of Ultrasonic Techniques for Measurement of Spatially Non-Uniform Elastic Properties of Thin Plates by Means of a Guided Sub-Sonic A0 Mode." Applied Sciences 10, no. 9: 3299.

Journal article
Published: 19 September 2018 in Sensors
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Ultrasonic non-destructive testing techniques (NDT) based on the application of guided waves are already used for inspection of plate-type structures made of various materials, including composite materials. Air-coupled ultrasonic techniques are used to test such structures by means of guided waves. The objective of this research was development and investigation of air-coupled excitation of a slow A0 Lamb wave mode in thin plastic films by a PMN-32%PT ultrasonic array. It is known that when the velocity of the A0 mode in the film is less than the ultrasound velocity in air no leaky wave is observed in a surrounding air. It opens new possibilities for NDT of composite structures. The influence of the airborne wave may be eliminated by 3D filtering in a wavenumbers-frequency domain. A special filter and corresponding signals processing technique were developed in order to obtain directivity patterns and velocity maps of the waves propagating in all directions. The measured ultrasound velocity values prove that, with the proposed method, it is possible to excite a slow A0 Lamb wave mode and to separate it from other parasitic waves propagating in air. Measurements of the parameters of the slow A0 mode, such as the propagation velocity in the plastic film, may be applied for the material characterization.

ACS Style

Rymantas J. Kazys; Liudas Mazeika; Reimondas Sliteris; Justina Sestoke. Air-Coupled Excitation of a Slow A0 Mode Wave in Thin Plastic Films by an Ultrasonic PMN-32%PT Array. Sensors 2018, 18, 3156 .

AMA Style

Rymantas J. Kazys, Liudas Mazeika, Reimondas Sliteris, Justina Sestoke. Air-Coupled Excitation of a Slow A0 Mode Wave in Thin Plastic Films by an Ultrasonic PMN-32%PT Array. Sensors. 2018; 18 (9):3156.

Chicago/Turabian Style

Rymantas J. Kazys; Liudas Mazeika; Reimondas Sliteris; Justina Sestoke. 2018. "Air-Coupled Excitation of a Slow A0 Mode Wave in Thin Plastic Films by an Ultrasonic PMN-32%PT Array." Sensors 18, no. 9: 3156.

Journal article
Published: 11 August 2018 in Sensors
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Air-coupled excitation and reception of ultrasonic guided waves is already used for non-destructive testing and evaluation (NDT & E). Usually for air-coupled NDT & E purposes the lowest zero-order antisymmetric Lamb wave mode A0 is used, because it is most sensitive to internal defects and thickness variations. The velocity of the A0 mode is reduced with a reducing frequency and at low frequencies may become slower than the ultrasound velocity in air. Such a wave is named a slow Lamb wave. The objective of this research was the development and investigation of an air-coupled excitation method of the slow zero-order antisymmetric Lamb wave based on application of a piezoceramic ultrasonic array. We have proposed to excite the A0 mode by a planar air-coupled phased array with rectangular elements. The array is matched to the wavelength of the A0 mode in the film. Performance of such an excitation method was investigated both theoretically and experimentally. Two excitation methods of the array were analysed: when all array elements were excited simultaneously or one by one with a proper delay. In order to reduce crosstalk between array elements via the air gap, we have proposed an optimization procedure based on additional shifts of electric excitation impulses of the array elements. For experimental verification of the proposed approach a prototype of the air-coupled eight element array made of Pz-29 piezoceramic strips was manufactured. Experimental validation confirmed the possibility of exciting the slow A0 Lamb wave mode through the air gap in thin plates and films.

ACS Style

Rymantas J. Kazys; Almantas Vilpisauskas; Justina Sestoke. Application of Air-Coupled Ultrasonic Arrays for Excitation of a Slow Antisymmetric Lamb Wave. Sensors 2018, 18, 2636 .

AMA Style

Rymantas J. Kazys, Almantas Vilpisauskas, Justina Sestoke. Application of Air-Coupled Ultrasonic Arrays for Excitation of a Slow Antisymmetric Lamb Wave. Sensors. 2018; 18 (8):2636.

Chicago/Turabian Style

Rymantas J. Kazys; Almantas Vilpisauskas; Justina Sestoke. 2018. "Application of Air-Coupled Ultrasonic Arrays for Excitation of a Slow Antisymmetric Lamb Wave." Sensors 18, no. 8: 2636.

Journal article
Published: 16 October 2017 in Sensors
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For improvement of the efficiency of air-coupled ultrasonic transducers PMN-32%PT piezoelectric crystals which possess very high piezoelectric properties may be used. The electromechanical coupling factor of such crystals for all main vibration modes such as the thickness extension and transverse extension modes is more than 0.9. Operation of ultrasonic transducers with such piezoelectric elements in transmitting and receiving modes is rather different. Therefore, for transmission and reception of ultrasonic signals, separate piezoelectric elements with different dimensions must be used. The objective of this research was development of novel air-coupled ultrasonic receivers with PMN-32%PT strip-like piezoelectric elements vibrating in a transverse-extension mode with electromechanically controlled operation and suitable for applications in ultrasonic arrays. Performance of piezoelectric receivers made of the PMN-32%PT strip-like elements vibrating in this mode may be efficiently controlled by selecting geometry of the electrodes covering side surfaces of the piezoelectric element. It is equivalent to introduction of electromechanical damping which does not require any additional backing element. For this purpose; we have proposed the continuous electrodes to divide into two pairs of electrodes. The one pair is used to pick up the electric signal; another one is exploited for electromechanical damping. Two types of electrodes may be used—rectangular or non-rectangular—with a gap between them directed at some angle, usually 45°. The frequency bandwidth is wider (up to 9 kHz) in the case of non-rectangular electrodes. The strip-like acoustic matching element bonded to the tip of the PMN-32%PT crystal may significantly enhance the performance of the ultrasonic receiver. It was proposed to use for this purpose AIREX T10.110 rigid polymer foam, the acoustic impedance of which is close to the optimal value necessary for matching with air. It was found that in order to get a wide bandwidth the length of the matching strip should be selected not a quarter wavelength λ/4 at the antiresonance frequency but at lower frequency. It allowed achieving the frequency bandwidth (14–18)% with respect to the central frequency at −3 dB level.

ACS Style

Rymantas J. Kazys; Reimondas Sliteris; Justina Sestoke. Air-Coupled Ultrasonic Receivers with High Electromechanical Coupling PMN-32%PT Strip-Like Piezoelectric Elements. Sensors 2017, 17, 2365 .

AMA Style

Rymantas J. Kazys, Reimondas Sliteris, Justina Sestoke. Air-Coupled Ultrasonic Receivers with High Electromechanical Coupling PMN-32%PT Strip-Like Piezoelectric Elements. Sensors. 2017; 17 (10):2365.

Chicago/Turabian Style

Rymantas J. Kazys; Reimondas Sliteris; Justina Sestoke. 2017. "Air-Coupled Ultrasonic Receivers with High Electromechanical Coupling PMN-32%PT Strip-Like Piezoelectric Elements." Sensors 17, no. 10: 2365.

Journal article
Published: 06 January 2017 in Sensors
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Air-coupled ultrasonic techniques are being increasingly used for material characterization, non-destructive evaluation of composite materials using guided waves as well as for distance measurements. Application of those techniques is mainly limited by the big losses of ultrasonic signals due to attenuation and mismatch of the acoustic impedances of ultrasonic transducers and air. One of the ways to solve this problem is by application of novel more efficient piezoelectric materials like lead magnesium niobate-lead titanate (PMN-PT) type crystals. The objective of this research was the development and investigation of low frequency (<50 kHz) wide band air-coupled ultrasonic transducers and arrays with an improved performance using PMN-32%PT crystals. Results of finite element modelling and experimental investigations of the developed transducers and arrays are presented. For improvement of the performance strip-like matching elements made of low acoustic impedance, materials such as polystyrene foams were applied. It allowed to achieve transduction losses for one single element transducer −11.4 dB, what is better than of commercially available air-coupled ultrasonic transducers. Theoretical and experimental investigations of the acoustic fields radiated by the eight element ultrasonic array demonstrated not only a good performance of the array in a pulse mode, but also very good possibilities to electronically focus and steer the ultrasonic beam in space.

ACS Style

Rymantas J. Kazys; Reimondas Sliteris; Justina Sestoke. Air-Coupled Low Frequency Ultrasonic Transducers and Arrays with PMN-32%PT Piezoelectric Crystals. Sensors 2017, 17, 95 .

AMA Style

Rymantas J. Kazys, Reimondas Sliteris, Justina Sestoke. Air-Coupled Low Frequency Ultrasonic Transducers and Arrays with PMN-32%PT Piezoelectric Crystals. Sensors. 2017; 17 (1):95.

Chicago/Turabian Style

Rymantas J. Kazys; Reimondas Sliteris; Justina Sestoke. 2017. "Air-Coupled Low Frequency Ultrasonic Transducers and Arrays with PMN-32%PT Piezoelectric Crystals." Sensors 17, no. 1: 95.

Journal article
Published: 01 July 2016 in Solid State Phenomena
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Lead magnesium niobate-lead titanate (PMN-PT) single crystal has first been successfully grown in 1990 by the Bridgman method using PbO as a flux. These single crystals have excellent piezoelectric properties. The PMN-PT crystals with different vibration modes may be used for development of novel high efficiency ultrasonic transducers due to high piezoelectric properties.

ACS Style

Rymantas Jonas Kazys; Reimondas Sliteris; Justina Sestoke; Marius Zienius. Investigation of High Frequency Mechanical Vibrations in PMN-32%PT Crystals by Laser Interferometry. Solid State Phenomena 2016, 251, 83 -88.

AMA Style

Rymantas Jonas Kazys, Reimondas Sliteris, Justina Sestoke, Marius Zienius. Investigation of High Frequency Mechanical Vibrations in PMN-32%PT Crystals by Laser Interferometry. Solid State Phenomena. 2016; 251 ():83-88.

Chicago/Turabian Style

Rymantas Jonas Kazys; Reimondas Sliteris; Justina Sestoke; Marius Zienius. 2016. "Investigation of High Frequency Mechanical Vibrations in PMN-32%PT Crystals by Laser Interferometry." Solid State Phenomena 251, no. : 83-88.

Journal article
Published: 19 September 2015 in Physics Procedia
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Due to very high piezoelectric properties of PMN-PT crystals they may significantly improve performance of air-coupled ultrasonic transducers. For these purpose vibrations of PMN-PT rectangular plates and strips were investigated. An air-coupled ultrasonic transducer and array consisting of 8 single piezoelectric strips were designed. Operation of the transducer was simulated by the finite element method using ANSYS Mechanical APDL Product Launcher software. Spatial distributions of displacements inside piezoelectric elements and matching strip were obtained. Experimental investigations were carried out by the laser Doppler vibrometer Polytec OFV-5000 and the Bruel&Kjaer microphone 4138 with the measurement amplifier NEXUS WH 3219. It was found that performance of the ultrasonic transducer with PMN–32PT crystals was a few times better than of a PZT based ultrasonic transducer.

ACS Style

Rymantas Jonas Kažys; Reimondas Sliteris; Justina Sestoke. Application of PMN-32PT Piezoelectric Crystals for Novel Air-coupled Ultrasonic Transducers. Physics Procedia 2015, 70, 896 -900.

AMA Style

Rymantas Jonas Kažys, Reimondas Sliteris, Justina Sestoke. Application of PMN-32PT Piezoelectric Crystals for Novel Air-coupled Ultrasonic Transducers. Physics Procedia. 2015; 70 ():896-900.

Chicago/Turabian Style

Rymantas Jonas Kažys; Reimondas Sliteris; Justina Sestoke. 2015. "Application of PMN-32PT Piezoelectric Crystals for Novel Air-coupled Ultrasonic Transducers." Physics Procedia 70, no. : 896-900.

Journal article
Published: 19 May 2015 in Ferroelectrics
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The discovery of high piezoelectric properties for lead magnesium niobate–lead titanate (PMN–32%PT) enables to develop ultrasonic transducers with significantly improved performance. The domain engineering technologies could be improved by employing techniques enabling continuous monitoring of the piezoelectric properties during poling process of the single crystals at different times.

ACS Style

Rymantas Kazys; R. Šliteris; J. Sestoke. Simultaneous Monitoring of the Electromechanical Coupling Coefficients and Domain Structural Changes of the PMN–32%PT Crystals during Poling Process. Ferroelectrics 2015, 480, 24 -31.

AMA Style

Rymantas Kazys, R. Šliteris, J. Sestoke. Simultaneous Monitoring of the Electromechanical Coupling Coefficients and Domain Structural Changes of the PMN–32%PT Crystals during Poling Process. Ferroelectrics. 2015; 480 (1):24-31.

Chicago/Turabian Style

Rymantas Kazys; R. Šliteris; J. Sestoke. 2015. "Simultaneous Monitoring of the Electromechanical Coupling Coefficients and Domain Structural Changes of the PMN–32%PT Crystals during Poling Process." Ferroelectrics 480, no. 1: 24-31.