This page has only limited features, please log in for full access.

Unclaimed
Rymantas Kažys
Ultrasound Research Institute, Kaunas University of Technology, Barsausko st. 59, LT-51368 Kaunas, Lithuania

Basic Info

Basic Info is private.

Honors and Awards

The user has no records in this section


Career Timeline

The user has no records in this section.


Short Biography

The user biography is not available.
Following
Followers
Co Authors
The list of users this user is following is empty.
Following: 0 users

Feed

Review
Published: 05 May 2021 in Sensors
Reads 0
Downloads 0

There are many fields such as online monitoring of manufacturing processes, non-destructive testing in nuclear plants, or corrosion rate monitoring techniques of steel pipes in which measurements must be performed at elevated temperatures. For that high temperature ultrasonic transducers are necessary. In the presented paper, a literature review on the main types of such transducers, piezoelectric materials, backings, and the bonding techniques of transducers elements suitable for high temperatures, is presented. In this review, the main focus is on ultrasonic transducers with piezoelectric elements suitable for operation at temperatures higher than of the most commercially available transducers, i.e., 150 °C. The main types of the ultrasonic transducers that are discussed are the transducers with thin protectors, which may serve as matching layers, transducers with high temperature delay lines, wedges, and waveguide type transducers. The piezoelectric materials suitable for high temperature applications such as aluminum nitride, lithium niobate, gallium orthophosphate, bismuth titanate, oxyborate crystals, lead metaniobate, and other piezoceramics are analyzed. Bonding techniques used for joining of the transducer elements such as joining with glue, soldering, brazing, dry contact, and diffusion bonding are discussed. Special attention is paid to efficient diffusion and thermo-sonic diffusion bonding techniques. Various types of backings necessary for improving a bandwidth and to obtain a short pulse response are described.

ACS Style

Rymantas Kazys; Vaida Vaskeliene. High Temperature Ultrasonic Transducers: A Review. Sensors 2021, 21, 3200 .

AMA Style

Rymantas Kazys, Vaida Vaskeliene. High Temperature Ultrasonic Transducers: A Review. Sensors. 2021; 21 (9):3200.

Chicago/Turabian Style

Rymantas Kazys; Vaida Vaskeliene. 2021. "High Temperature Ultrasonic Transducers: A Review." Sensors 21, no. 9: 3200.

Journal article
Published: 24 February 2021 in Materials
Reads 0
Downloads 0

This article compares different air-coupled ultrasonic testing methods to characterize impact-type defects in a pultruded quasi-isotropic glass fiber-reinforced plastic (GFRP) composite plate. Using the air-coupled transducers, comparisons among three methods were performed, namely, bulk-wave through transmission, single-side access using guided waves, and ultrasonic-guided wave tomography. The air coupled through transmission technique can determine the size and shape of impact-type defects with a higher resolution, but with the consequence of time consumption and, more importantly, the necessity of access to both sides of the sample. The guided wave technique on the other hand, allows a single-side inspection and is relatively fast. It can be used to determine the size of the defect using ultrasonic B-scan, but the exact shape of the defect will be compromised. Thus, in this article, to determine the shape of the defect, application of the parallel beam tomographic reconstruction technique using guided Lamb waves is demonstrated. Furthermore, a numerical finite element simulation was performed to study the effects of guided wave propagation in the composite sample and interaction with the internal defect. Lastly, the results from the experiments of different techniques were compared according to possibilities of defect sizing and determination of its shape.

ACS Style

Aadhik Asokkumar; Elena Jasiūnienė; Renaldas Raišutis; Rymantas Kažys. Comparison of Ultrasonic Non-Contact Air-Coupled Techniques for Characterization of Impact-Type Defects in Pultruded GFRP Composites. Materials 2021, 14, 1058 .

AMA Style

Aadhik Asokkumar, Elena Jasiūnienė, Renaldas Raišutis, Rymantas Kažys. Comparison of Ultrasonic Non-Contact Air-Coupled Techniques for Characterization of Impact-Type Defects in Pultruded GFRP Composites. Materials. 2021; 14 (5):1058.

Chicago/Turabian Style

Aadhik Asokkumar; Elena Jasiūnienė; Renaldas Raišutis; Rymantas Kažys. 2021. "Comparison of Ultrasonic Non-Contact Air-Coupled Techniques for Characterization of Impact-Type Defects in Pultruded GFRP Composites." Materials 14, no. 5: 1058.

Journal article
Published: 27 September 2020 in Applied Sciences
Reads 0
Downloads 0

The objective of this study is to compare the performance of different ultrasonic non-destructive testing (NDT) techniques for bonding quality evaluation. Aluminium-epoxy-aluminium single lap joints containing debonding in the form of release film inclusions have been investigated using three types of ultrasonic NDT methods: contact testing, immersion testing, and air-coupled testing. Apart from the traditional bulk wave ultrasound, guided wave testing was also performed using air coupled and contact transducers for the excitation of guided waves. Guided wave propagation within adhesive bond was numerically simulated. A wide range of inspection frequencies causing different ultrasonic wavelengths has been investigated. Average errors in defect sizing per ultrasonic wavelength have been used as a feature to determine the performance of each ultrasonic NDT technique. The best performance is observed with bulk wave investigations. Particularly, the higher frequencies (10–50 MHz) in the immersion testing performed significantly better than air-coupled testing (300 kHz); however, air coupled investigations have other advantages as contactless inspection. Whereas guided wave inspections show relatively lower accuracy in defect sizing, they are good enough to detect the presence of the debonding and enable to inspect long range. Even though each technique has its advantages and limitations, guided wave techniques can be practical for the preliminary in-situ inspection of adhesively bonded specimens.

ACS Style

Bengisu Yilmaz; Aadhik Asokkumar; Elena Jasiūnienė; Rymantas Jonas Kažys. Air-Coupled, Contact, and Immersion Ultrasonic Non-Destructive Testing: Comparison for Bonding Quality Evaluation. Applied Sciences 2020, 10, 6757 .

AMA Style

Bengisu Yilmaz, Aadhik Asokkumar, Elena Jasiūnienė, Rymantas Jonas Kažys. Air-Coupled, Contact, and Immersion Ultrasonic Non-Destructive Testing: Comparison for Bonding Quality Evaluation. Applied Sciences. 2020; 10 (19):6757.

Chicago/Turabian Style

Bengisu Yilmaz; Aadhik Asokkumar; Elena Jasiūnienė; Rymantas Jonas Kažys. 2020. "Air-Coupled, Contact, and Immersion Ultrasonic Non-Destructive Testing: Comparison for Bonding Quality Evaluation." Applied Sciences 10, no. 19: 6757.

Journal article
Published: 09 May 2020 in Applied Sciences
Reads 0
Downloads 0

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: 16 January 2020 in Sensors
Reads 0
Downloads 0

At low frequencies, in thin plates the phase velocity of the guided A0 mode can become slower than that of the ultrasound velocity in air. Such waves do not excite leaky waves in the surrounding air, and therefore, it is impossible to excite and receive them by conventional air-coupled methods. The objective of this research was the development of an air-coupled technique for the reception of slow A0 mode in thin plastic films. This study demonstrates the feasibility of picking up a subsonic A0 mode in plastic films by air-coupled ultrasonic arrays. The air-coupled reception was based on an evanescent wave in air accompanying the propagating A0 mode in a film. The efficiency of the reception was enhanced by using a virtual array which was arranged from the data collected by a single air-coupled receiver. The signals measured at the points corresponding to the positions of the phase-matched array were recorded and processed. The transmitting array excited not only the A0 mode in the film, but also a direct wave in air. This wave propagated at ultrasound velocity in air and was faster than the evanescent wave. For efficient reception of the A0 mode, the additional signal-processing procedure based on the application of the 2D Fourier transform in a spatial–temporal domain. The obtained results can be useful for the development of novel air-coupled ultrasonic non-destructive testing techniques.

ACS Style

Rymantas J. Kazys; Almantas Vilpisauskas. Air-Coupled Reception of a Slow Ultrasonic A0 Mode Wave Propagating in Thin Plastic Film. Sensors 2020, 20, 516 .

AMA Style

Rymantas J. Kazys, Almantas Vilpisauskas. Air-Coupled Reception of a Slow Ultrasonic A0 Mode Wave Propagating in Thin Plastic Film. Sensors. 2020; 20 (2):516.

Chicago/Turabian Style

Rymantas J. Kazys; Almantas Vilpisauskas. 2020. "Air-Coupled Reception of a Slow Ultrasonic A0 Mode Wave Propagating in Thin Plastic Film." Sensors 20, no. 2: 516.

Journal article
Published: 21 May 2019 in Materials
Reads 0
Downloads 0

The ultrasonic testing technique using Lamb waves is widely used for the non-destructive testing and evaluation of various structures. For air-coupled excitation and the reception of A0 mode Lamb waves, leaky guided waves are usually exploited. However, at low frequencies (

ACS Style

Rymantas Kažys; Reimondas Šliteris; Liudas Mažeika; Olgirdas Tumšys; Egidijus Žukauskas. Attenuation of a Slow Subsonic A0 Mode Ultrasonic Guided Wave in Thin Plastic Films. Materials 2019, 12, 1648 .

AMA Style

Rymantas Kažys, Reimondas Šliteris, Liudas Mažeika, Olgirdas Tumšys, Egidijus Žukauskas. Attenuation of a Slow Subsonic A0 Mode Ultrasonic Guided Wave in Thin Plastic Films. Materials. 2019; 12 (10):1648.

Chicago/Turabian Style

Rymantas Kažys; Reimondas Šliteris; Liudas Mažeika; Olgirdas Tumšys; Egidijus Žukauskas. 2019. "Attenuation of a Slow Subsonic A0 Mode Ultrasonic Guided Wave in Thin Plastic Films." Materials 12, no. 10: 1648.

Review
Published: 21 November 2018 in MATEC Web of Conferences
Reads 0
Downloads 0

In the aerospace industry contactless measurement has been a very versatile and adaptable in recent years, mainly because of its diverse applications. Usually ultrasonic measurement requires acoustic contact media which may disserve the sample and varies for different materials. In the operational hand, acoustic contact media like water is also not preferred for on-aircraft inspection. The air coupled inspection technique among other nondestructive testing techniques is often not enticing due to acoustic mismatch and wave propagation. Though, acoustical mismatch of the transducers can be reduced by application of a matching layer and also by using different corresponding transducers. Air-coupled transducers are the captivating alternatives for the inspection. This paper comprises different air coupled inspection techniques i.e. through transmission and guided wave generation as well as its working modes. Various transducer arrangements, the advantages of air-coupled ultrasonic guided wave inspection over other NDT techniques and their specifications are discussed revolving around the materials. Composite materials have superior properties like tensile strength, better heat resistance which cannot be materialized in single. The utilization of composite materials like CFRP, GFRP, other polymers and ceramic composites seeks the improvement in lift to weight ratio. An overall review deals with air coupled techniques and scrutiny of different materials concerning this technique, which includes characteristics of various composite materials used in aerospace industry.

ACS Style

Jaishree Vyas; Rymantas Jonas Kažys. A Review on Nondestructive Techniques and Characteristics of Composite Materials for the Aerospace System. MATEC Web of Conferences 2018, 233, 00003 .

AMA Style

Jaishree Vyas, Rymantas Jonas Kažys. A Review on Nondestructive Techniques and Characteristics of Composite Materials for the Aerospace System. MATEC Web of Conferences. 2018; 233 ():00003.

Chicago/Turabian Style

Jaishree Vyas; Rymantas Jonas Kažys. 2018. "A Review on Nondestructive Techniques and Characteristics of Composite Materials for the Aerospace System." MATEC Web of Conferences 233, no. : 00003.

Journal article
Published: 19 September 2018 in Sensors
Reads 0
Downloads 0

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
Reads 0
Downloads 0

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.

Original article
Published: 13 March 2018 in Journal of Medical Ultrasonics
Reads 0
Downloads 0

For long time, blood clot retraction was measured only by thromboelastographic or platelet contractile force measurement techniques. The purpose of the present study was development of a novel ultrasonic method based on simultaneous monitoring of variations in the ultrasound velocity and the frequency spectrum of the signal propagating in clotting blood and its application for automatic evaluation of blood clotting parameters. Simultaneous measurement of ultrasound velocity and variations in the frequency spectrum of wideband ultrasonic signals in clotting blood samples was performed. All measurements were performed in pulse-echo mode. Standard clinical data were obtained using routine clinical laboratory methods. The amplitudes of ultrasonic signals during native blood coagulation varied up to ten times for different frequencies. The measurement results of the start and duration of blood clot retraction differed between patient samples: different components of the blood coagulation system had significant impact on the blood clot retraction process. Our results showed that during blood clotting, the ultrasound velocity and variations in frequency spectrum should be used simultaneously to determine the beginning and duration of blood clot retraction. Our results also showed that blood clot retraction is controlled by the activity of factor XIII.

ACS Style

Vacis Tatarunas; Algirdas Voleisis; Reimondas Sliteris; Rymantas Kazys; Liudas Mazeika; Vaiva Lesauskaitė. A novel ultrasonic method for evaluation of blood clotting parameters. Journal of Medical Ultrasonics 2018, 45, 545 -553.

AMA Style

Vacis Tatarunas, Algirdas Voleisis, Reimondas Sliteris, Rymantas Kazys, Liudas Mazeika, Vaiva Lesauskaitė. A novel ultrasonic method for evaluation of blood clotting parameters. Journal of Medical Ultrasonics. 2018; 45 (4):545-553.

Chicago/Turabian Style

Vacis Tatarunas; Algirdas Voleisis; Reimondas Sliteris; Rymantas Kazys; Liudas Mazeika; Vaiva Lesauskaitė. 2018. "A novel ultrasonic method for evaluation of blood clotting parameters." Journal of Medical Ultrasonics 45, no. 4: 545-553.

Article
Published: 26 November 2017 in Polymer Composites
Reads 0
Downloads 0

In the present study, the relationships between poly(methyl methacrylate) (PMMA) structure modified by nanoparticles and the impact behavior of carbon fiber (CF) reinforced PMMA (CF/PMMA) thermoplastic nanocomposite were explored. CF/PMMA composite was prepared by nanofiller-containing methyl methacrylate monomer impregnation of fibers followed by in-situ polymerization in the mould. Composite matrix PMMA was modified by halloysite, multiwalled carbon nanotubes, and organically modified and unmodified layered silicate clays. The structure of modified PMMA was investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. SEM results show that nanotubes are uniformly distributed in the PMMA matrix without formation of aggregates. XRD studies of PMMA with layered silicates indicate poor unmodified clay exfoliation in polymer monomer. A low-velocity impact test was performed and an air-coupled ultrasonic non-destructive testing technique was used to size delamination type defects in the composite samples after impact. The impact damage behavior was explained by microstructural parameters of composites obtained by optical microscopy. It was obtained that CF/PMMA composite modified by nanotubes both multiwalled carbon and halloysite absorbs 10 % more energy at the low velocity impact compared to that of unmodified one, due to high interaction of the nanotubes and PMMA. Layered silicate clays adversely affected the composite impact properties compared with unmodified CF/PMMA. Organic modifications of clays slightly improve their dispersion into the monomer, but does not have an observed effect on the impact properties of the composite. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

ACS Style

Kristina Žukienė; Egidijus Žukauskas; Rymantas Kazys; Daiva Zeleniakienė; Virginija Jankauskaite. Structure – Impact properties relationships of carbon fiber reinforced poly(methyl methacrylate) composite. Polymer Composites 2017, 40, 1 .

AMA Style

Kristina Žukienė, Egidijus Žukauskas, Rymantas Kazys, Daiva Zeleniakienė, Virginija Jankauskaite. Structure – Impact properties relationships of carbon fiber reinforced poly(methyl methacrylate) composite. Polymer Composites. 2017; 40 (S1):1.

Chicago/Turabian Style

Kristina Žukienė; Egidijus Žukauskas; Rymantas Kazys; Daiva Zeleniakienė; Virginija Jankauskaite. 2017. "Structure – Impact properties relationships of carbon fiber reinforced poly(methyl methacrylate) composite." Polymer Composites 40, no. S1: 1.

Journal article
Published: 21 October 2017 in Vibroengineering PROCEDIA
Reads 0
Downloads 0
ACS Style

Renaldas Raišutis; Rymantas Kažys; Liudas Mažeika; Egidijus Žukauskas; Reimondas Šliteris; Alfonsas Vladišauskas. Application of ultrasonic guided waves for non-destructive testing of large and complex geometry engineering structures. Vibroengineering PROCEDIA 2017, 14, 87 -90.

AMA Style

Renaldas Raišutis, Rymantas Kažys, Liudas Mažeika, Egidijus Žukauskas, Reimondas Šliteris, Alfonsas Vladišauskas. Application of ultrasonic guided waves for non-destructive testing of large and complex geometry engineering structures. Vibroengineering PROCEDIA. 2017; 14 ():87-90.

Chicago/Turabian Style

Renaldas Raišutis; Rymantas Kažys; Liudas Mažeika; Egidijus Žukauskas; Reimondas Šliteris; Alfonsas Vladišauskas. 2017. "Application of ultrasonic guided waves for non-destructive testing of large and complex geometry engineering structures." Vibroengineering PROCEDIA 14, no. : 87-90.

Journal article
Published: 16 October 2017 in Sensors
Reads 0
Downloads 0

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: 01 July 2017 in Ultrasonics
Reads 0
Downloads 0

The purpose of this work was to develop a multichannel ultrasonic measurement method for monitoring a spatially non-uniform blood clotting process. This novel method is based on simultaneous multi-channel measurements of ultrasound propagation velocities in different horizontal cross-sections of clotting blood. The most common method used for determining blood-clotting time is the capillary tube method. For this purpose ultrasonic methods based on measurements of the velocities of ultrasound waves in clotting blood are also used. Measurement results essentially depend on the propagation path of the ultrasonic wave in a blood sample. The ultrasound velocity changes as fresh blood transforms into clot plus serum. The objective of this work was to develop a measurement method that allows one to measure ultrasound velocity and its evolution in time and space in an evolving clot while avoiding the influence of serum. To achieve this objective, a novel method has been proposed that is based on ultrasound propagation velocity measurements in different horizontal cross-sections of clotting blood using a pulse-echo mode. Such a technique enables researchers to monitor the clotting process and a clot's spatial structure, which are different in different layers due to the influence of gravity. The four-channel measurement chamber utilizing this method has been designed and manufactured. For the generation and reception of ultrasonic waves of high frequency, wide band (3-20MHz at -6dB) ultrasonic transducers were developed. To verify that the multi-channel measurement system was operational, a special procedure based on monitoring of a polymerisation process in the acrylamide solution was proposed. Performance of the developed method was investigated by measuring clotting blood (sample volumes of less than 0.6ml) at the frequency of 12MHz. The results revealed that a clot structure indeed varies within a blood sample due to the influence of gravity; clotting times are different in different horizontal layers of the clot and range from 9 to 15min, defined by the standard capillary method. Clotting times are determined precisely from abrupt increases in ultrasound velocity. Uncertainty of the ultrasound velocity measurements was less than ±0.05m/s. The experiments were performed at 36.90±0.01°C. The proposed method may be exploited for monitoring polymerisation reactions in the chemistry field, as well.

ACS Style

A. Voleisis; R. Kazys; B. Voleisiene; R. Sliteris; L. Mazeika. Ultrasonic method for monitoring the clotting process during whole blood coagulation. Ultrasonics 2017, 78, 146 -151.

AMA Style

A. Voleisis, R. Kazys, B. Voleisiene, R. Sliteris, L. Mazeika. Ultrasonic method for monitoring the clotting process during whole blood coagulation. Ultrasonics. 2017; 78 ():146-151.

Chicago/Turabian Style

A. Voleisis; R. Kazys; B. Voleisiene; R. Sliteris; L. Mazeika. 2017. "Ultrasonic method for monitoring the clotting process during whole blood coagulation." Ultrasonics 78, no. : 146-151.

Journal article
Published: 01 June 2017 in NDT & E International
Reads 0
Downloads 0
ACS Style

Renaldas Raišutis; Olgirdas Tumšys; Rymantas Kažys. Development of the technique for independent dual focusing of contact type ultrasonic phased array transducer in two orthogonal planes. NDT & E International 2017, 88, 71 -80.

AMA Style

Renaldas Raišutis, Olgirdas Tumšys, Rymantas Kažys. Development of the technique for independent dual focusing of contact type ultrasonic phased array transducer in two orthogonal planes. NDT & E International. 2017; 88 ():71-80.

Chicago/Turabian Style

Renaldas Raišutis; Olgirdas Tumšys; Rymantas Kažys. 2017. "Development of the technique for independent dual focusing of contact type ultrasonic phased array transducer in two orthogonal planes." NDT & E International 88, no. : 71-80.

Journal article
Published: 06 January 2017 in Sensors
Reads 0
Downloads 0

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: 25 August 2016 in International Journal of Structural Stability and Dynamics
Reads 0
Downloads 0

The aim of this paper is to investigate the propagation of ultrasonic shear horizontal guided waves along waveguides with a rectangular cross-section and with a finite constant and variable width and to determine the peculiarities of propagation of those waves. The dispersion curves of guided waves in finite-width waveguides were modeled by using a semi-analytical finite element (SAFE) technique. The propagation of pulsed shear horizontal ultrasonic guided waves was investigated numerically by using 3D finite element modeling. It was found that in the case of finite-width waveguides, the SH0 shear horizontal wave splits into a family of SH-type dispersive modes propagating with different phase velocities. It was also found that the number of propagating modes depends on the width-to-thickness ratio. The first time spatial distributions of pulsed displacements across the waveguide were determined for waveguides of different widths. Investigation of the waveguides with a rectangular cross-section and varying lateral dimensions was performed. It was found that by properly selecting the geometry of the transient zone of waveguides with a rectangular cross-section, it is possible to improve the performance of such waveguides, e.g. to increase the amplitude of the transmitted pulse type signal without significant distortions of the waveforms.

ACS Style

Rymantas Kazys; Egidijus Žukauskas; Liudas Mažeika; Renaldas Raisutis. Propagation of Ultrasonic Shear Horizontal Waves in Rectangular Waveguides. International Journal of Structural Stability and Dynamics 2016, 16, 1 .

AMA Style

Rymantas Kazys, Egidijus Žukauskas, Liudas Mažeika, Renaldas Raisutis. Propagation of Ultrasonic Shear Horizontal Waves in Rectangular Waveguides. International Journal of Structural Stability and Dynamics. 2016; 16 (8):1.

Chicago/Turabian Style

Rymantas Kazys; Egidijus Žukauskas; Liudas Mažeika; Renaldas Raisutis. 2016. "Propagation of Ultrasonic Shear Horizontal Waves in Rectangular Waveguides." International Journal of Structural Stability and Dynamics 16, no. 8: 1.

Journal article
Published: 01 July 2016 in Solid State Phenomena
Reads 0
Downloads 0

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: 06 June 2016 in Materials
Reads 0
Downloads 0

Multi-wire ropes are widely used as load-carrying constructional elements in bridges, cranes, elevators, etc. Structural integrity of such ropes can be inspected by using non-destructive ultrasonic techniques. The objective of this work was to investigate propagation of ultrasonic guided waves (UGW) along composite multi-wire ropes in the cases of various types of acoustic contacts between neighboring wires and the plastic core. The modes of UGW propagating along the multi-wire ropes were identified using modelling, the dispersion curves were calculated using analytical and semi-analytical finite element (SAFE) techniques. In order to investigate the effects of UGW propagation, the two types of the acoustic contact between neighboring wires were simulated using the 3D finite element method (FE) as well. The key question of investigation was estimation of the actual boundary conditions between neighboring wires (solid or slip) and the real depth of penetration of UGW into the overall cross-section of the rope. Therefore, in order to verify the results of FE modelling, the guided wave penetration into strands of multi-wire rope was investigated experimentally. The performed modelling and experimental investigation enabled us to select optimal parameters of UGW to be used for non-destructive testing.

ACS Style

Renaldas Raisutis; Rymantas Kazys; Liudas Mazeika; Vykintas Samaitis; Egidijus Zukauskas. Propagation of Ultrasonic Guided Waves in Composite Multi-Wire Ropes. Materials 2016, 9, 451 .

AMA Style

Renaldas Raisutis, Rymantas Kazys, Liudas Mazeika, Vykintas Samaitis, Egidijus Zukauskas. Propagation of Ultrasonic Guided Waves in Composite Multi-Wire Ropes. Materials. 2016; 9 (6):451.

Chicago/Turabian Style

Renaldas Raisutis; Rymantas Kazys; Liudas Mazeika; Vykintas Samaitis; Egidijus Zukauskas. 2016. "Propagation of Ultrasonic Guided Waves in Composite Multi-Wire Ropes." Materials 9, no. 6: 451.

Journal article
Published: 01 March 2016 in Archives of Acoustics
Reads 0
Downloads 0

Longitudinal and shear ultrasonic wave velocities were measured versus temperature in the viscosity standards of Paragon S8000S, N30000S and Cannon N2700000. The measurements were performed by the through-transmission method at the frequency of 2 MHz. Ultrasonic pulses were sent via polymethyl methacrylate (PMMA) waveguides between the tips of which a small amount of the particular standard liquid was placed. The velocities of longitudinal and shear waves were determined to depend on the viscosity of the liquid and increase with the viscosity.

ACS Style

Rymantas Kazys; Algirdas Voleisis; Reimondas Sliteris. Investigation of the Acoustic Properties of Viscosity Standards. Archives of Acoustics 2016, 41, 55 -58.

AMA Style

Rymantas Kazys, Algirdas Voleisis, Reimondas Sliteris. Investigation of the Acoustic Properties of Viscosity Standards. Archives of Acoustics. 2016; 41 (1):55-58.

Chicago/Turabian Style

Rymantas Kazys; Algirdas Voleisis; Reimondas Sliteris. 2016. "Investigation of the Acoustic Properties of Viscosity Standards." Archives of Acoustics 41, no. 1: 55-58.