Dr. Philip Wayne Loveday Profile

Dr. Philip Wayne Loveday

Associate Professor at Univ of the Witwatersrand Johannesburg

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Author

Publications (14)

Proceedings Article | 9 April 2010 Paper

Guided wave propagation as a measure of axial loads in rails

Philip Loveday, Paul Wilcox

Proceedings Volume 7650, 765023 (2010) https://doi.org/10.1117/12.847531

KEYWORDS: Waveguides, Wave propagation, Temperature metrology, Phase velocity, Dispersion, Finite element methods, 3D modeling, Phase shifts, Phase measurement, Biological research

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Proceedings Article | 18 September 2008 Paper

Intracavity mode competition between classes of flat-top beams

Igor Litvin, Philip Loveday, Craig Long, Nikolai Kazak, Vladimir Belyi, Andrew Forbes

Proceedings Volume 7062, 706210 (2008) https://doi.org/10.1117/12.793686

KEYWORDS: Mirrors, Diffractive optical elements, Resonators, Output couplers, Optical resonators, Wavefronts, Gaussian beams, Chemical elements, Deformable mirrors, Laser resonators

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Proceedings Article | 12 September 2008 Paper

Variable flattened Gaussian beam order selection by dynamic control of an intracavity diffractive mirror

Andrew Forbes, Craig Long, Igor Litvin, Philip Loveday, Vladimir Belyi, Nikolai Kazak

Proceedings Volume 7062, 706219 (2008) https://doi.org/10.1117/12.793698

KEYWORDS: Mirrors, Diffractive optical elements, Electrodes, Resonators, Gaussian beams, Deformable mirrors, Output couplers, Optical resonators, Chemical elements, Beam propagation method

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Proceedings Article | 10 April 2008 Paper

Measurement of modal amplitudes of guided waves in rails

Philip Loveday

Proceedings Volume 6935, 69351J (2008) https://doi.org/10.1117/12.776163

KEYWORDS: Wave propagation, Waveguides, Transducers, Time metrology, Distance measurement, Chemical elements, Finite element methods, Superposition, Analytical research, Sensors

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One important application of guided wave ultrasound is that of rail condition monitoring where long lengths of rail can be monitored from permanently attached transducer locations. During the development of transducers for such a system it is advantageous to be able to measure the amplitude of the individual modes of propagation on a short length of rail in the laboratory. This paper describes a method of extracting modal amplitudes from measured time domain signals performed at a limited set of points on the waveguide. The method uses the wave propagation characteristics of the waveguide, predicted by a semi-analytical finite element model, to extract the modal amplitudes from experimental measurements. The frequency response at a set of measurement locations is described by a superposition (with unknown amplitude coefficients) of the frequency response of the modes that propagate in the frequency range of interest. Experimental time domain responses are measured and transformed to frequency responses. The amplitude of each mode is estimated using the pseudo-inverse to provide a minimum norm least-squares estimate. The technique is demonstrated on a rail excited by a piezoelectric patch transducer. A laser vibrometer was used to measure displacements at five points around the rail circumference at three distances giving a total of 15 measurements. Eight propagating modes were extracted from these measurements. The extracted modes were then used to predict the response at points further along the waveguide and these predictions were verified by further measurements indicating that the modes of propagation were accurately estimated. The technique requires that the distance between the measurement points be known but does not require that the distance from the transducer be known. This feature and the fact that only a few measurements are required make the method suitable for measuring the propagation of individual modes over long distances in the field.

Proceedings Article | 19 March 2008 Paper

A piezoelectric deformable mirror for intra-cavity laser adaptive optics

Craig Long, Philip Loveday, Andrew Forbes

Proceedings Volume 6930, 69300Y (2008) https://doi.org/10.1117/12.776178

KEYWORDS: Mirrors, Zernike polynomials, Deformable mirrors, Electrodes, Diffractive optical elements, Finite element methods, Prototyping, Adaptive optics, Laser resonators, Output couplers

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Proceedings Article | 11 April 2007 Paper

A thermo-hydraulic wax actuation system for high force and large displacement applications

Craig Long, Philip Loveday

Proceedings Volume 6527, 652707 (2007) https://doi.org/10.1117/12.714737

KEYWORDS: Actuators, Silicon, Smart materials, Temperature metrology, Solids, Liquids, Contamination, Shape memory alloys, Solid state electronics, Microelectromechanical systems

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Proceedings Article | 10 April 2007 Paper

Time domain simulation of piezoelectric excitation of guided waves in rails using waveguide finite elements

Philip Loveday, Craig Long

Proceedings Volume 6529, 65290V (2007) https://doi.org/10.1117/12.714744

KEYWORDS: Waveguides, Wave propagation, Transducers, Finite element methods, 3D modeling, Waveguide modes, Fourier transforms, Dispersion, Matrices, Sensors

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Piezoelectric transducers are commonly used to excite waves in elastic waveguides such as pipes, rock bolts and rails. While it is possible to simulate the operation of these transducers attached to the waveguide, in the time domain, using conventional finite element methods available in commercial software, these models tend to be very large. An alternative method is to use specially formulated waveguide finite elements (sometimes called Semi-Analytical Finite Elements). Models using these elements require only a two-dimensional finite element mesh of the cross-section of the waveguide. The waveguide finite element model was combined with a conventional 3-D finite element model of the piezoelectric transducer to compute the frequency response of the waveguide. However, it is difficult to experimentally verify such a frequency domain model. Experiments are usually conducted by exciting a transducer, attached to the waveguide, with a short time signal such as a tone-burst and measuring the response at a position along the waveguide before reflections from the ends of the waveguide are encountered. The measured signals are a combination of all the modes that are excited in the waveguide and separating the individual modes of wave propagation is difficult if there are numerous modes present. Instead of converting the measured signals to the frequency domain we transform the modeled frequency responses to time domain signals in order to verify the models against experiment. The frequency response was computed at many frequency points and multiplied by the frequency spectrum of the excitation signal, before an inverse Fourier transform was used to transform from the frequency domain to the time domain. The time response of a rail, excited by a rectangular piezoelectric ceramic patch, was computed and found to compare favorably with measurements performed using a laser vibrometer. By using this approach it is possible to determine which modes of propagation dominate the response and to predict the signals that would be obtained at large distances, which cannot be measured in the lab, and would be computationally infeasible using conventional finite element modeling.

Proceedings Article | 27 March 2006 Paper

Numerical comparison of patch and sandwich piezoelectric transducers for transmitting ultrasonic waves

Philip Loveday

Proceedings Volume 6166, 616612 (2006) https://doi.org/10.1117/12.658451

KEYWORDS: Waveguides, Transducers, Wave propagation, Inspection, Waveguide modes, Finite element methods, Ultrasonics, Numerical modeling, Actuators, Ceramics

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Proceedings Article | 19 May 2005 Paper

Finite element computation of dispersion in piezoelectric waveguides

Philip Loveday, Michael Shatalov

Proceedings Volume 5757, (2005) https://doi.org/10.1117/12.599561

KEYWORDS: Waveguides, 3D modeling, Chemical elements, Wave propagation, Dispersion, Finite element methods, Composites, Polymers, Matrices, Ferroelectric polymers

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Proceedings Article | 29 July 2004 Paper

Development of a variable stiffness spring for adaptive vibration isolators

Johan Cronje, P. Heyns, Nico Theron, Philip Loveday

Proceedings Volume 5386, (2004) https://doi.org/10.1117/12.539738

KEYWORDS: Actuators, Optical isolators, Vibration isolation, Copper, Chemical elements, Liquids, Feedback control, Shape memory alloys, Solids, Finite element methods

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Proceedings Article | 26 July 2004 Paper

Ultrasonic motor resonator design using shape and topology optimization

Philip Loveday, Craig Long, Albert Groenwold

Proceedings Volume 5390, (2004) https://doi.org/10.1117/12.539791

KEYWORDS: Resonators, 3D modeling, Ultrasonics, Solids, Prototyping, Optimization (mathematics), Chemical elements, Manufacturing, Optical amplifiers, Finite element methods

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Proceedings Article | 5 August 2003 Paper

Practical optimization of amplification mechanisms for piezoelectric actuators

Philip Loveday

Proceedings Volume 5056, (2003) https://doi.org/10.1117/12.483455

KEYWORDS: Actuators, Optimization (mathematics), Manufacturing, Ceramics, Kinematics, Finite element methods, Amplifiers, Matrices, Measurement devices, Homogenization

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Proceedings Article | 15 July 2002 Paper

Comparison of amplified piezoelectric actuators based on topological optimization

Philip Loveday

Proceedings Volume 4701, (2002) https://doi.org/10.1117/12.474679

KEYWORDS: Actuators, Amplifiers, Systems modeling, Optimization (mathematics), Chemical elements, Solid state electronics, Ceramics, Data modeling, Sensing systems, Active vibration control

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Proceedings Article | 20 April 2000 Paper

Development of piezoelectric transducers for a railway integrity monitoring system

Philip Loveday

Proceedings Volume 3988, (2000) https://doi.org/10.1117/12.383154

KEYWORDS: Transducers, Finite element methods, Wave propagation, 3D modeling, Telecommunications, Signal detection, Head, Receivers, Transmitters, Signal to noise ratio

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Showing 5 of 14 publications

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