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

Prof. Dr. Steve Dixon
Department of Physics and School of Engineering, University of Warwick, Coventry, CV4 7AL, UK

Basic Info

Basic Info is private.

Research Keywords & Expertise

0 Ultrasonic transduction-experimental and modelling
0 Ultrasonic measurements of material properties
0 Non-contact ultrasound, particularly EMATs and laser based ultrasound
0 Eddy current and electromagentic methods for NDE
0 Thermographic methods, particularly laser spot thermography

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

Journal article
Published: 02 August 2021 in Ultrasonics
Reads 0
Downloads 0

The interaction of guided waves with wall thinning can be complex, depending on the thinning geometry and the frequency. At a high frequency–thickness, when a shear-horizontal (SH) guided wave mode impinges upon a tapered wall thinning region, there is mode conversion to other propagating SH modes, either in reflection or transmission, which heavily depends on the shape of the taper. In this paper, we have combined the reciprocity theorem of elastodynamics and the theory of multiple reflections, in order to analytically calculate the scattered SH wavefield in plates, due to the interaction with an arbitrary tapered thinning. The taper is discretized into several sections and the formulation is addressed in matrix notation, in order to tackle several modes which arise due to mode interconversion distributed within the taper. The method was validated with experimental and numerical data at linear tapered thinning, in the high-frequency–thickness regime. It was also applied to provide understanding of the reflection behaviour within smoother taper profiles, namely, raised-cosine and Blackman window tapers, and to visualize the propagating field of each mode. It is shown that for a linear taper profile, the reflection within the taper is virtually constant, which produces an interference pattern in the overall reflection from the whole taper. Such a mechanism is broken with smoother tapers, since they impose lower reflection close to the taper ends. The method proves itself useful for analytically investigating the scattering from arbitrary wall thinning when mode-conversion arises.

ACS Style

Alan C. Kubrusly; Steve Dixon. Application of the reciprocity principle to evaluation of mode-converted scattered shear horizontal (SH) wavefields in tapered thinning plates. Ultrasonics 2021, 117, 106544 .

AMA Style

Alan C. Kubrusly, Steve Dixon. Application of the reciprocity principle to evaluation of mode-converted scattered shear horizontal (SH) wavefields in tapered thinning plates. Ultrasonics. 2021; 117 ():106544.

Chicago/Turabian Style

Alan C. Kubrusly; Steve Dixon. 2021. "Application of the reciprocity principle to evaluation of mode-converted scattered shear horizontal (SH) wavefields in tapered thinning plates." Ultrasonics 117, no. : 106544.

Journal article
Published: 19 May 2021 in IEEE Sensors Letters
Reads 0
Downloads 0

Clamp-on ultrasonic transit-time difference measurements of liquid flowrate are widely used in industry for both flow metering and heat metering applications. However, the sensors used tend to be relatively large, hindering their use on small diameter pipes, and using more material in the transducer wedge than is strictly necessary. The accuracy of the technique depends on a number of factors, and particularly on the accuracy of the compression wave speed in the liquid that is used in the calculations to obtain flowrate or heat transfer rate from the liquid in the pipe. Many flow meters either assume a value for the wave speed or obtain it using thermocouple measurements of the pipe exterior with a lookup table or simple equation. An error in the liquid ultrasonic velocity relates directly to errors in the calculated flowrate. It is highly beneficial if the ultrasonic wave speed in the liquid can be accurately measured in real time for flowrate calculations, especially for temperature and pressure varying conditions. A new type of small clamp-on ultrasonic transducer is reported, using a 6-mm-wide PEEK wedge that contains two piezoelectric elements, one of which generates sound normal to the flow direction, yielding the measurement of ultrasonic wave speed in the liquid. The new transducers were tested on a small rig with a 15-mm diameter copper pipe and a 70-mm diameter stainless steel pipe, yielding accurate measurements of liquid ultrasonic velocity and flowrates.

ACS Style

Zhichao Li; Luke Smith; Steve Dixon. Design of Miniature Clamp-On Ultrasonic Flow Measurement Transducers. IEEE Sensors Letters 2021, 5, 1 -4.

AMA Style

Zhichao Li, Luke Smith, Steve Dixon. Design of Miniature Clamp-On Ultrasonic Flow Measurement Transducers. IEEE Sensors Letters. 2021; 5 (6):1-4.

Chicago/Turabian Style

Zhichao Li; Luke Smith; Steve Dixon. 2021. "Design of Miniature Clamp-On Ultrasonic Flow Measurement Transducers." IEEE Sensors Letters 5, no. 6: 1-4.

Journal article
Published: 04 March 2021 in IEEE Access
Reads 0
Downloads 0

Shear Horizontal (SH) guided waves have been extensively used to estimate and detect defects in structures like plates and pipes. Depending on the frequency and plate thickness, more than one guided-wave mode propagates, which renders signal interpretation complicated due to mode mixing and complex behavior of each individual mode interacting with defects. This paper investigates the use of machine learning models to analyse the two lowest order SH guided modes, for quantitative size estimation and detection of corrosion-like defects in aluminium plates. The main contribution of the present work is to show that mode separation through machine learning improves the effectiveness of predictive models. Numerical simulations have been performed to generate time series for creating the estimators, while experimental data have been used to validate them. We show that a full mode separation scheme decreased the error rate of the final model by 30% and 67% in defect size estimation and detection respectively.

ACS Style

Mateus Gheorghe De Castro Ribeiro; Alan Conci Kubrusly; Helon Vicente Hultmann Ayala; Steve Dixon. Machine Learning-Based Corrosion-Like Defect Estimation With Shear-Horizontal Guided Waves Improved by Mode Separation. IEEE Access 2021, 9, 40836 -40849.

AMA Style

Mateus Gheorghe De Castro Ribeiro, Alan Conci Kubrusly, Helon Vicente Hultmann Ayala, Steve Dixon. Machine Learning-Based Corrosion-Like Defect Estimation With Shear-Horizontal Guided Waves Improved by Mode Separation. IEEE Access. 2021; 9 ():40836-40849.

Chicago/Turabian Style

Mateus Gheorghe De Castro Ribeiro; Alan Conci Kubrusly; Helon Vicente Hultmann Ayala; Steve Dixon. 2021. "Machine Learning-Based Corrosion-Like Defect Estimation With Shear-Horizontal Guided Waves Improved by Mode Separation." IEEE Access 9, no. : 40836-40849.

Letter
Published: 21 January 2021 in Journal of Physics D: Applied Physics
Reads 0
Downloads 0

Transducers for ultrasonic sensing and measurement are often operated with a short burst signal, for example a few cycles at a specific excitation voltage and frequency on the generating transducer. The vibration response of a narrowband transducer in detection is usually dominated by resonant ringing, severely affecting its ability to detect two or more signals arriving at the receiver at similar times. Prior researchers have focused on strategies to damp the ringing of a transducer in transmission, to create a temporally short output pressure wave. However, if the receiving transducer is narrowband, the incident pressure waves can create significant ringing of this receiving transducer, irrespective of how temporally short the incident pressure waves are on the receiving transducer. This can reduce the accuracy of common measurement processes, as signals are temporally long and multiple wave arrivals can be difficult to distinguish from each other. In this research, a method of damping transducers in reception is demonstrated using a flexural ultrasonic transducer (FUT). This narrowband transducer can operate effectively as a transmitter or receiver of ultrasound, and due to its use in automotive applications, is the most common ultrasonic transducer in existence. An existing mathematical analog for the transducers is used to guide the design of an engineered pressure wave to actively damp the receiving FUT. Experimental measurements on transducers show that ultrasonic receiver resonant ringing can be reduced by 80%, without significantly compromising sensitivity and only by using a suitable driving voltage waveform on the generating transducer.

ACS Style

Steve Dixon; Lei Kang; Andrew Feeney; William E Somerset. Active damping of ultrasonic receiving sensors through engineered pressure waves. Journal of Physics D: Applied Physics 2021, 54, 13LT01 .

AMA Style

Steve Dixon, Lei Kang, Andrew Feeney, William E Somerset. Active damping of ultrasonic receiving sensors through engineered pressure waves. Journal of Physics D: Applied Physics. 2021; 54 (13):13LT01.

Chicago/Turabian Style

Steve Dixon; Lei Kang; Andrew Feeney; William E Somerset. 2021. "Active damping of ultrasonic receiving sensors through engineered pressure waves." Journal of Physics D: Applied Physics 54, no. 13: 13LT01.

Journal article
Published: 24 December 2020 in Ultrasonics
Reads 0
Downloads 0

When shear horizontal ultrasonic guided waves interact with thickness discontinuities in plates, the reflected and transmitted wavefields can be composed of several modes due to mode conversion. It is known that in a plate with a symmetric discontinuity, with respect to the plate’s mid-plane, mode conversion is restricted to modes that share the same symmetry as the incident mode. In this paper, we use an analytical model based on the reciprocity principle and finite element analysis to investigate mode conversion due to the interaction with different types of discontinuity, namely, non-symmetric, symmetric and geometrically symmetric but with opposite boundary conditions, that is one side of the discontinuity free and the other rigidly fixed. We show that the reflected field due to interaction with the latter is virtually restricted to modes with the opposite symmetry of the incident one, acting as a symmetry inverter discontinuity. Unlike fully symmetric discontinuities, the effectiveness of a symmetry inverter discontinuity depends on the frequency. This was proved with aid of the analytical model for a full-depth discontinuity and verified for partial depth discontinuities. Finally, symmetry inversion of SH waves was experimentally verified in acrylic plates which were symmetrically machined and filled with steel in one side to mimic a fixed boundary condition.

ACS Style

Alan C. Kubrusly; Pedro Tovar; Jean Pierre von der Weid; Steve Dixon. Mode conversion of SH guided waves with symmetry inversion in plates. Ultrasonics 2020, 112, 106334 .

AMA Style

Alan C. Kubrusly, Pedro Tovar, Jean Pierre von der Weid, Steve Dixon. Mode conversion of SH guided waves with symmetry inversion in plates. Ultrasonics. 2020; 112 ():106334.

Chicago/Turabian Style

Alan C. Kubrusly; Pedro Tovar; Jean Pierre von der Weid; Steve Dixon. 2020. "Mode conversion of SH guided waves with symmetry inversion in plates." Ultrasonics 112, no. : 106334.

Journal article
Published: 15 December 2020 in Sensors
Reads 0
Downloads 0

The characteristics of removable magnetostrictive thin patches are investigated for the generation of guided waves in plates. The directivity patterns of SH, S0 and A0 modes have been measured in a thin metallic plate for different combinations of static and dynamic magnetic field directions. This used different coil geometries such as racetrack and spiral coils to generate the dynamic magnetic field, as well as separate biasing static magnetic fields from permanent magnets. This arrangement generated signals via both Lorentz and magnetostrictive forces, and the resultant emitted guided waves were studied for different dynamic and static magnetic field directions and magnitudes. It is demonstrated that different guided wave modes can be produced by controlling these parameters.

ACS Style

Akram Zitoun; Steven Dixon; Graham Edwards; David Hutchins. Experimental Study of the Guided Wave Directivity Patterns of Thin Removable Magnetostrictive Patches. Sensors 2020, 20, 7189 .

AMA Style

Akram Zitoun, Steven Dixon, Graham Edwards, David Hutchins. Experimental Study of the Guided Wave Directivity Patterns of Thin Removable Magnetostrictive Patches. Sensors. 2020; 20 (24):7189.

Chicago/Turabian Style

Akram Zitoun; Steven Dixon; Graham Edwards; David Hutchins. 2020. "Experimental Study of the Guided Wave Directivity Patterns of Thin Removable Magnetostrictive Patches." Sensors 20, no. 24: 7189.

Journal article
Published: 28 September 2020 in IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control
Reads 0
Downloads 0

Periodic permanent magnet (PPM) array electromagnetic acoustic transducers (EMATs) can efficiently generate and receive shear horizontal (SH) ultrasonic waves. Conventional PPM EMATs typically generate waves which simultaneously propagate both forwards and backwards. This can complicate the received signals and make it difficult to locate the position of scatterers. Unidirectional generation of ultrasounds can be achieved if two ultrasonic sources are separated by a predefined distance and are excited with the proper delay. Relying on this principle, EMATs have been previously designed aiming to generate other modes of ultrasonic waves. The main challenge when extending this conception to an SH-wave EMAT is how to restrict each coil to its specific magnet array. We present the concept of a unidirectional SH EMAT consisting of two racetrack coils and two interlaced PPM arrays, that are slightly shifted sideways, in such a way that the generated wavefronts still properly interfere. The design was fabricated and experimentally evaluated in an aluminum plate generating the SH0 guided wave mode. The forward to backward generated wave ratio is above 20 dB and well agrees with finite element simulations.

ACS Style

Alan C. Kubrusly; Lei Kang; Steve Dixon. Unidirectional Shear Horizontal Wave Generation With Side-Shifted Periodic Permanent Magnets Electromagnetic Acoustic Transducer. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 2020, 67, 2757 -2760.

AMA Style

Alan C. Kubrusly, Lei Kang, Steve Dixon. Unidirectional Shear Horizontal Wave Generation With Side-Shifted Periodic Permanent Magnets Electromagnetic Acoustic Transducer. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. 2020; 67 (12):2757-2760.

Chicago/Turabian Style

Alan C. Kubrusly; Lei Kang; Steve Dixon. 2020. "Unidirectional Shear Horizontal Wave Generation With Side-Shifted Periodic Permanent Magnets Electromagnetic Acoustic Transducer." IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 67, no. 12: 2757-2760.

Journal article
Published: 03 September 2020 in IEEE Sensors Journal
Reads 0
Downloads 0

Electromagnetic acoustic transducers (EMATs) are well suited to generating and detecting a variety of different ultrasonic wavemodes, without the need for couplant, and they can be operated through some coatings. EMATs can be used to generate shear horizontal (SH) waves, which show promise for fast screening of wall thinning and other defects. However, commercial SH-wave EMATs are not suitable for robotic implementation on ferritic steel due to the large magnetic drag force from the magnets. This paper describes the design and characterisation of miniaturised SH guided wave EMATs, which significantly reduce the magnetic drag and enable mounting onto a small crawler robot for sample scanning. The performance of the miniaturised EMATs is characterised and compared to a commercial EMAT. It is shown that signal to noise ratio is reduced, but remains within an acceptable range to use on steel. The bandwidth and directivity are increased, depending on the exact design used. Their ability to detect flat bottomed holes mimicking wall thinning is also tested.

ACS Style

Oksana Trushkevych; Morteza Tabatabaeipour; Steve Dixon; Mark D. G. Potter; Gordon Dobie; Charles Macleod; Rachel S. Edwards. Miniaturised SH EMATs for Fast Robotic Screening of Wall Thinning in Steel Plates. IEEE Sensors Journal 2020, 21, 1386 -1394.

AMA Style

Oksana Trushkevych, Morteza Tabatabaeipour, Steve Dixon, Mark D. G. Potter, Gordon Dobie, Charles Macleod, Rachel S. Edwards. Miniaturised SH EMATs for Fast Robotic Screening of Wall Thinning in Steel Plates. IEEE Sensors Journal. 2020; 21 (2):1386-1394.

Chicago/Turabian Style

Oksana Trushkevych; Morteza Tabatabaeipour; Steve Dixon; Mark D. G. Potter; Gordon Dobie; Charles Macleod; Rachel S. Edwards. 2020. "Miniaturised SH EMATs for Fast Robotic Screening of Wall Thinning in Steel Plates." IEEE Sensors Journal 21, no. 2: 1386-1394.

Journal article
Published: 01 June 2020 in IEEE Sensors Journal
Reads 0
Downloads 0
ACS Style

Andrew Feeney; Lei Kang; William E. Somerset; Steve Dixon. Venting in the Comparative Study of Flexural Ultrasonic Transducers to Improve Resilience at Elevated Environmental Pressure Levels. IEEE Sensors Journal 2020, 20, 5776 -5784.

AMA Style

Andrew Feeney, Lei Kang, William E. Somerset, Steve Dixon. Venting in the Comparative Study of Flexural Ultrasonic Transducers to Improve Resilience at Elevated Environmental Pressure Levels. IEEE Sensors Journal. 2020; 20 (11):5776-5784.

Chicago/Turabian Style

Andrew Feeney; Lei Kang; William E. Somerset; Steve Dixon. 2020. "Venting in the Comparative Study of Flexural Ultrasonic Transducers to Improve Resilience at Elevated Environmental Pressure Levels." IEEE Sensors Journal 20, no. 11: 5776-5784.

Journal article
Published: 20 March 2020 in IEEE Sensors Journal
Reads 0
Downloads 0

Flexural ultrasonic transducers are robust and low cost sensors that are typically used in industry for distance ranging, proximity sensing and flow measurement. The operating frequencies of currently available commercial flexural ultrasonic transducers are usually below 50 kHz. Higher operating frequencies would be particularly beneficial for measurement accuracy and detection sensitivity. In this paper, design principles of High Frequency Flexural Ultrasonic Transducers (HiFFUTs), guided by the classical plate theory and finite element analysis, are reported. The results show that the diameter of the piezoelectric disc element attached to the flexing plate of the HiFFUT has a significant influence on the transducer’s resonant frequency, and that an optimal diameter for a HiFFUT transmitter alone is different from that for a pitch-catch ultrasonic system consisting of both a HiFFUT transmitter and a receiver. By adopting an optimal piezoelectric diameter, the HiFFUT pitch-catch system can produce an ultrasonic signal amplitude greater than that of a non-optimised system by an order of magnitude. The performance of a prototype HiFFUT is characterised through electrical impedance analysis, laser Doppler vibrometry, and pressure-field microphone measurement, before the performance of two new HiFFUTs in a pitch-catch configuration is compared with that of commercial transducers. The prototype HiFFUT can operate efficiently at a frequency of 102.1 kHz as either a transmitter or a receiver, with comparable output amplitude, wider bandwidth, and higher directivity than commercially available transducers of similar construction.

ACS Style

Lei Kang; Andrew Feeney; Steve Dixon. The High Frequency Flexural Ultrasonic Transducer for Transmitting and Receiving Ultrasound in Air. IEEE Sensors Journal 2020, 20, 7653 -7660.

AMA Style

Lei Kang, Andrew Feeney, Steve Dixon. The High Frequency Flexural Ultrasonic Transducer for Transmitting and Receiving Ultrasound in Air. IEEE Sensors Journal. 2020; 20 (14):7653-7660.

Chicago/Turabian Style

Lei Kang; Andrew Feeney; Steve Dixon. 2020. "The High Frequency Flexural Ultrasonic Transducer for Transmitting and Receiving Ultrasound in Air." IEEE Sensors Journal 20, no. 14: 7653-7660.

Journal article
Published: 20 January 2020 in IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Reads 0
Downloads 0

A phased electromagnetic acoustic transducer (EMAT) array system has been developed for detection and characterisation of surface breaking defects. An array of four linear coils which are individually controlled are used to generate a Rayleigh wave. The high current electronics combined with the coil designs enables the array to generate either narrowband or broadband signals, and controlling the phase delay between the channels makes it possible to change the ultrasound wavelength without requiring the physical separation of the coils to be changed. Experimental results show that the four-coil phased array is able to generate a wavelength range from 3.0 mm to 11.7 mm. Surface breaking defects were characterised using a transmit-receive set-up with a broadband EMAT detector being used to detect the Rayleigh wave. Machined surface slots with different depths were used for technique validation. The results show that the array is sensitive to surface defects and that a wide depth sensitivity range for defect sizing can be easily achieved by applying phasing to tune the wavelength of operation. A large increase in detection flexibility is immediately shown.

ACS Style

Lunci Xiang; David Greenshields; Steve Dixon; Rachel S. Edwards. Phased Electromagnetic Acoustic Transducer Array for Rayleigh Wave Surface Defect Detection. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 2020, 67, 1403 -1411.

AMA Style

Lunci Xiang, David Greenshields, Steve Dixon, Rachel S. Edwards. Phased Electromagnetic Acoustic Transducer Array for Rayleigh Wave Surface Defect Detection. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control. 2020; 67 (7):1403-1411.

Chicago/Turabian Style

Lunci Xiang; David Greenshields; Steve Dixon; Rachel S. Edwards. 2020. "Phased Electromagnetic Acoustic Transducer Array for Rayleigh Wave Surface Defect Detection." IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 67, no. 7: 1403-1411.

Journal article
Published: 19 November 2019 in IEEE Transactions on Instrumentation and Measurement
Reads 0
Downloads 0
ACS Style

Zhichao Li; Foz Hughes; Noel C. Kerr; Richard Wilson; Steve Dixon. Liquid Flow Measurement Using Silicone Polymer Wedge Clamp-On Ultrasonic Transducers. IEEE Transactions on Instrumentation and Measurement 2019, 69, 5157 -5165.

AMA Style

Zhichao Li, Foz Hughes, Noel C. Kerr, Richard Wilson, Steve Dixon. Liquid Flow Measurement Using Silicone Polymer Wedge Clamp-On Ultrasonic Transducers. IEEE Transactions on Instrumentation and Measurement. 2019; 69 (7):5157-5165.

Chicago/Turabian Style

Zhichao Li; Foz Hughes; Noel C. Kerr; Richard Wilson; Steve Dixon. 2019. "Liquid Flow Measurement Using Silicone Polymer Wedge Clamp-On Ultrasonic Transducers." IEEE Transactions on Instrumentation and Measurement 69, no. 7: 5157-5165.

Journal article
Published: 04 November 2019 in Sensors
Reads 0
Downloads 0

Accurate average flow velocity determination is essential for flow measurement in many industries, including automotive, chemical, and oil and gas. The ultrasonic transit-time method is common for average flow velocity measurement, but current limitations restrict measurement accuracy, including fluid dynamic effects from unavoidable phenomena such as turbulence, swirls or vortices, and systematic flow meter errors in calibration or configuration. A new spatial averaging method is proposed, based on flexural ultrasonic array transducer technology, to improve measurement accuracy and reduce the uncertainty of the measurement results. A novel two-dimensional flexural ultrasonic array transducer is developed to validate this measurement method, comprising eight individual elements, each forming distinct paths to a single ultrasonic transducer. These paths are distributed in two chordal planes, symmetric and adjacent to a diametral plane. It is demonstrated that the root-mean-square deviation of the average flow velocity, computed using the spatial averaging method with the array transducer is 2.94%, which is lower compared to that of the individual paths ranging from 3.65% to 8.87% with an average of 6.90%. This is advantageous for improving the accuracy and reducing the uncertainty of classical single-path ultrasonic flow meters, and also for conventional multi-path ultrasonic flow meters through the measurement via each flow plane with reduced uncertainty. This research will drive new developments in ultrasonic flow measurement in a wide range of industrial applications.

ACS Style

Lei Kang; Andrew Feeney; Riliang Su; David Lines; Sivaram Nishal Ramadas; George Rowlands; Steve Dixon. Flow Velocity Measurement Using a Spatial Averaging Method with Two-Dimensional Flexural Ultrasonic Array Technology. Sensors 2019, 19, 4786 .

AMA Style

Lei Kang, Andrew Feeney, Riliang Su, David Lines, Sivaram Nishal Ramadas, George Rowlands, Steve Dixon. Flow Velocity Measurement Using a Spatial Averaging Method with Two-Dimensional Flexural Ultrasonic Array Technology. Sensors. 2019; 19 (21):4786.

Chicago/Turabian Style

Lei Kang; Andrew Feeney; Riliang Su; David Lines; Sivaram Nishal Ramadas; George Rowlands; Steve Dixon. 2019. "Flow Velocity Measurement Using a Spatial Averaging Method with Two-Dimensional Flexural Ultrasonic Array Technology." Sensors 19, no. 21: 4786.

Journal article
Published: 30 October 2019 in Sensors
Reads 0
Downloads 0

The flexural ultrasonic transducer comprises a piezoelectric ceramic disc bonded to a membrane. The vibrations of the piezoelectric ceramic disc induce flexural modes in the membrane, producing ultrasound waves. The transducer is principally utilized for proximity or flow measurement, designed for operation at atmospheric pressure conditions. However, there is rapidly growing industrial demand for the flexural ultrasonic transducer in applications including water metering or in petrochemical plants where the pressure levels of the gas or liquid environment can approach 100 bar. In this study, characterization methods including electrical impedance analysis and pitch-catch ultrasound measurement are employed to demonstrate the dynamic performance of flexural ultrasonic transducers in air at elevated pressures approaching 100 bar. Measurement principles are discussed, in addition to modifications to the transducer design for ensuring resilience at increasing air pressure levels. The results highlight the importance of controlling the parameters of the measurement environment and show that although the conventional design of flexural ultrasonic transducer can exhibit functionality towards 100 bar, its dynamic performance is unsuitable for accurate ultrasound measurement. It is anticipated that this research will initiate new developments in ultrasound measurement systems for fluid environments at elevated pressures.

ACS Style

Andrew Feeney; Lei Kang; William E. Somerset; Steve Dixon. The Influence of Air Pressure on the Dynamics of Flexural Ultrasonic Transducers. Sensors 2019, 19, 4710 .

AMA Style

Andrew Feeney, Lei Kang, William E. Somerset, Steve Dixon. The Influence of Air Pressure on the Dynamics of Flexural Ultrasonic Transducers. Sensors. 2019; 19 (21):4710.

Chicago/Turabian Style

Andrew Feeney; Lei Kang; William E. Somerset; Steve Dixon. 2019. "The Influence of Air Pressure on the Dynamics of Flexural Ultrasonic Transducers." Sensors 19, no. 21: 4710.

Journal article
Published: 08 October 2019 in NDT & E International
Reads 0
Downloads 0

The interaction of the SH0, SH1, SH2 and SH3 guided wave modes on a metal plate with a thickness discontinuity is numerically and experimentally investigated. Two different geometries were evaluated, namely symmetric and non-symmetric discontinuities, relative to the plate longitudinal mid-plane. Experiments were performed with periodic permanent magnet array EMATs as transmitters and receivers. Mode separation in transmission and reception was experimentally and numerically performed by dual transduction and by modal decomposition post-processing techniques, respectively. The reflection and transmission coefficients at the discontinuity for each of the investigated SH modes was calculated. It has been experimentally confirmed that when interacting with symmetric discontinuities, only modes that share the same symmetry as the incident mode are created by mode conversion, whereas mode conversion to modes of different symmetry can occur with non-symmetric discontinuities. Experimental and numerical data show good agreement, revealing that the higher the order of the incident mode, the more complex the behaviour of the reflection coefficient is, as a function of the discontinuity depth. For the same incident mode, symmetric discontinuities impose less complexity than non-symmetric ones.

ACS Style

Alan C. Kubrusly; Jean Pierre von der Weid; Steve Dixon. Experimental and numerical investigation of the interaction of the first four SH guided wave modes with symmetric and non-symmetric discontinuities in plates. NDT & E International 2019, 108, 102175 .

AMA Style

Alan C. Kubrusly, Jean Pierre von der Weid, Steve Dixon. Experimental and numerical investigation of the interaction of the first four SH guided wave modes with symmetric and non-symmetric discontinuities in plates. NDT & E International. 2019; 108 ():102175.

Chicago/Turabian Style

Alan C. Kubrusly; Jean Pierre von der Weid; Steve Dixon. 2019. "Experimental and numerical investigation of the interaction of the first four SH guided wave modes with symmetric and non-symmetric discontinuities in plates." NDT & E International 108, no. : 102175.

Journal article
Published: 25 April 2019 in IEEE Sensors Journal
Reads 0
Downloads 0

The flexural ultrasonic transducer is a unimorph device which typically comprises a piezoelectric ceramic bonded to a metallic membrane. It is widely applied in industrial applications for metrology and proximity sensing. However, the electromechanical and dynamic characteristics of this class of transducer have only recently been reported, and the influence of different excitation levels on dynamic nonlinearity remain unclear. Dynamic nonlinearity in high-power piezoelectric ultrasonic transducers is familiar, where the performance or dynamic stability of the transducer can significantly reduce under high amplitudes of excitation. Nonlinearity can manifest as measurable phenomena such as resonance frequency drift, influenced by thermomechanical phenomena or structural constraints. There is relatively little reported science of the dynamic nonlinearity in the vibration response of flexural ultrasonic transducers. This study examines the vibration responses of four flexural ultrasonic transducers, showing the existence of dynamic nonlinearity for increases in excitation voltage. An analytical solution of the governing equations of motion for the flexural ultrasonic transducer is presented which complements the experimental investigation, and suggests a close relationship between material properties and nonlinearity. This research demonstrates a detailed dynamic characterisation of the flexural ultrasonic transducer, showing the potential for the optimisation of dynamic performance in industrial measurement applications.

ACS Style

Andrew Feeney; Lei Kang; George Rowlands; Leiqing Zhou; Steve Dixon. Dynamic Nonlinearity in Piezoelectric Flexural Ultrasonic Transducers. IEEE Sensors Journal 2019, 19, 6056 -6066.

AMA Style

Andrew Feeney, Lei Kang, George Rowlands, Leiqing Zhou, Steve Dixon. Dynamic Nonlinearity in Piezoelectric Flexural Ultrasonic Transducers. IEEE Sensors Journal. 2019; 19 (15):6056-6066.

Chicago/Turabian Style

Andrew Feeney; Lei Kang; George Rowlands; Leiqing Zhou; Steve Dixon. 2019. "Dynamic Nonlinearity in Piezoelectric Flexural Ultrasonic Transducers." IEEE Sensors Journal 19, no. 15: 6056-6066.

Journal article
Published: 05 October 2018 in NDT & E International
Reads 0
Downloads 0

The Electromagnetic acoustic transducer (EMAT) is used in a number of non-destructive testing applications [1–5]. The EMAT's operation is principally based on one of two mechanisms; the Lorenz force and magnetostriction mechanism [6–9]. The magnetostriction mechanism of an EMAT at elevated temperatures is reported in this paper. An optimized model is developed to describe the magnetostriction of polycrystalline iron, which is based on Brown's magnetic domain wall movement model [10] and Lee's magnetic domain rotation model [11]. The magnetostriction curves of polycrystalline iron for the temperature range 300 K–900 K are predicted, which reveal that the saturated magnetostriction coefficient changes from −4×10−6 to approximately 12×10−6. A non-linear, isotropic magnetostriction, finite element model is developed to simulate the Lamb waves generated in 4 mm thick steel plate by an EMAT, and the results show that the amplitude of S0 Lamb wave is greatly enhanced with an increase of temperature. In the experiments, a magnetostriction-based EMAT is used to generate Lamb waves in 4 mm thick steel plate. Experimental measurements verify that the contribution of the magnetostriction mechanism on steel rises as temperature increases in the range 298 K–873 K, while the contribution to ultrasonic generation from the Lorenz force mechanism decreases, as expected.

ACS Style

Weiping Ren; Ke Xu; Steve Dixon; Chu Zhang. A study of magnetostriction mechanism of EMAT on low-carbon steel at high temperature. NDT & E International 2018, 101, 34 -43.

AMA Style

Weiping Ren, Ke Xu, Steve Dixon, Chu Zhang. A study of magnetostriction mechanism of EMAT on low-carbon steel at high temperature. NDT & E International. 2018; 101 ():34-43.

Chicago/Turabian Style

Weiping Ren; Ke Xu; Steve Dixon; Chu Zhang. 2018. "A study of magnetostriction mechanism of EMAT on low-carbon steel at high temperature." NDT & E International 101, no. : 34-43.

Journal article
Published: 28 May 2018 in IEEE Sensors Journal
Reads 0
Downloads 0

Resonating inductive sensors are increasingly popular for numerous measurement techniques, not least in non-destructive testing (NDT), due to the increased sensitivity obtained at frequencies approaching electrical resonance. The highly unstable nature of resonance limits the practical application of such methods while no comprehensive understanding exists of the resonance distorting behaviour in relation to typical measurements and environmental factors. In this paper, a study into the frequency spectrum behaviour of electrical resonance is carried out exploring the effect of key factors. These factors, known to distort the electrical resonance of inductive sensors, include proximity to (or lift-off from) a material surface, and the presence of discontinuities in the material surface. Critical features of resonance are used as metrics to evaluate the behaviour of resonance with lift-off and defects. Experimental results are compared to results from a 2D finite element analysis (FEA) model that geometrically mimics the inductive sensor used in the experiments, and to results predicted by an equivalent circuit transformer model. The findings conclusively define the physical phenomenon behind measurement techniques such as near electrical resonance signal enhancement (NERSE), and show that lift-off and defect resonance distortions are unique, measurable and can be equated to exclusive variations in the induced variables in the equivalence circuit model. The resulting understanding found from this investigation is critical to the future development and understanding of a complete model of electrical resonance behaviour, integral for the design of novel sensors, techniques and inversion models.

ACS Style

Robert R. Hughes; Steve Dixon. Analysis of Electrical Resonance Distortion for Inductive Sensing Applications. IEEE Sensors Journal 2018, 18, 5818 -5825.

AMA Style

Robert R. Hughes, Steve Dixon. Analysis of Electrical Resonance Distortion for Inductive Sensing Applications. IEEE Sensors Journal. 2018; 18 (14):5818-5825.

Chicago/Turabian Style

Robert R. Hughes; Steve Dixon. 2018. "Analysis of Electrical Resonance Distortion for Inductive Sensing Applications." IEEE Sensors Journal 18, no. 14: 5818-5825.

Journal article
Published: 10 May 2018 in IEEE Sensors Journal
Reads 0
Downloads 0

Flexural ultrasonic transducers are a widely available type of ultrasonic sensor used for flow measurement, proximity, and industrial metrology applications. The flexural ultrasonic transducer is commonly operated in one of the axisymmetric modes of vibration in the low-kilohertz range, under 50 kHz, but there is an increasing demand for higher frequency operation, towards 300 kHz. At present, there are no reports of the measurement of high-frequency vibrations using flexural ultrasonic transducers. This research reports on the measurement of high-frequency vibration in flexural ultrasonic transducers, utilizing electrical impedance and phase measurement, laser Doppler vibrometry, and response spectrum analysis through the adoption of two flexural ultrasonic transducers in a transmit-receive configuration. The outcomes of this research demonstrate the ability of flexural ultrasonic transducers to measure high-frequency ultrasound in air, vital for industrial metrology.

ACS Style

Andrew Feeney; Lei Kang; Steve Dixon. High-Frequency Measurement of Ultrasound Using Flexural Ultrasonic Transducers. IEEE Sensors Journal 2018, 18, 5238 -5244.

AMA Style

Andrew Feeney, Lei Kang, Steve Dixon. High-Frequency Measurement of Ultrasound Using Flexural Ultrasonic Transducers. IEEE Sensors Journal. 2018; 18 (13):5238-5244.

Chicago/Turabian Style

Andrew Feeney; Lei Kang; Steve Dixon. 2018. "High-Frequency Measurement of Ultrasound Using Flexural Ultrasonic Transducers." IEEE Sensors Journal 18, no. 13: 5238-5244.

Journal article
Published: 10 May 2018 in IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Reads 0
Downloads 0

Shear horizontally (SH) guided waves, generated by periodic permanent magnet arrays, have been used previously in nondestructive evaluation of metal plates and pipes. When an SH guided wave interacts with a defect or a change in sample thickness, the incident SH wave may undergo mode conversion. Analysis of mode conversion is complicated, due to the interference of several propagating modes in the received signal that can often temporally overlap. This paper proposes a mode selection technique to help understand the interaction of SH guided waves with changes in sample thickness. Using an understanding of the propagation characteristics of the guided waves, SH guided waves are sequentially generated and detected on both surfaces of the plate, capturing four distinct waveforms. By superposition of the detected signals, symmetric modes can be clearly separated from antisymmetric modes in the processed received signals. For this method to work well, the transducers used should have very similar responses and be precisely positioned on exactly opposite positions either side of the plate. Finite element simulations are also performed, mirroring the experimental measurements, and the results correlate well with the experimental observations made on an 8-mm-thick plate with a region of simulated wall thinning machined into the sample.

ACS Style

Alan C. Kubrusly; Miguel A. Freitas; Jean Pierre Von Der Weid; Steve Dixon. Mode Selectivity of SH Guided Waves by Dual Excitation and Reception Applied to Mode Conversion Analysis. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 2018, 65, 1239 -1249.

AMA Style

Alan C. Kubrusly, Miguel A. Freitas, Jean Pierre Von Der Weid, Steve Dixon. Mode Selectivity of SH Guided Waves by Dual Excitation and Reception Applied to Mode Conversion Analysis. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control. 2018; 65 (7):1239-1249.

Chicago/Turabian Style

Alan C. Kubrusly; Miguel A. Freitas; Jean Pierre Von Der Weid; Steve Dixon. 2018. "Mode Selectivity of SH Guided Waves by Dual Excitation and Reception Applied to Mode Conversion Analysis." IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 65, no. 7: 1239-1249.