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Browsing by Author "Loveday, Philip W"

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Accuracy of semi-analytical finite elements for modelling wave propagation in rails

Author: Andhavarapu, EV ; Loveday, Philip W ; Long, Craig S ; Heyns, PS Date: Jan 2010 The semi-analytical finite element method (SAFE) is a popular method for analysing guided wave propagation in elastic waveguides of complex cross-section such as rails. The convergence of these models has previously been studied for linear ... Read more
Adaptive SAFE model of a rail for parameter estimation

Author: Setshedi, Itumeleng ; Long, Craig S ; Loveday, Philip W ; Wilke, Daniel N Date: Sep 2018 Permanently installed monitoring systems, which make use of guided wave ultrasound, can monitor long distances of rail track from a single transducer location. Read more
Axisymmetric solid-of-revolution finite elements with rotational degrees of freedom

Author: Long, Craig S ; Loveday, Philip W ; Groenwold, AA Date: Jan 2009 Two new solid-of-revolution axisymmetric finite elements, which account for hoop fibre rotations, are introduced. The first is based on an irreducible formulation, with only displacement and rotation fields assumed independently. The second ... Read more
Comparison between SAFE forced response and Abaqus/Explicit solutions of a rail excited at a cut-frequency

Author: Long, Craig S ; Ramatlo, Dineo AM ; Loveday, Philip W Date: Sep 2018 In this paper, we present a comparison between two different methods for modelling the response of an elastic waveguide to a point force excitation. Read more
Coupled electromechanical model of an imperfect piezoelectric vibrating cylinder gyroscope

Author: Loveday, Philip W Date: Jan 1996 Coupled electromechanical equations of motion, describing the dynamics of a vibrating cylinder gyroscope, are derived using Hamilton's principle and the Rayleigh-Ritz method. The vibrating cylinder gyroscope comprises a thin walled steel ... Read more
Development of a novel ultrasonic motor resonator using topology optimization

Author: M'Boungui, G ; Loveday, Philip W ; Long, Craig S Date: Jan 2011 The use of topology optimization in the design of a novel stator for an ultrasonic motor (USM) is investigated. The design challenge is to produce a stator, with two resonant modes whose frequencies are in a ratio of 1:2. When driven together, ... Read more
Development of a Piezoelectric Adaptive Mirror for Laser Beam Control

Author: Long, Craig S ; Loveday, Philip W ; Forbes, A Date: Jun 2008 An intra-cavity adaptive mirror is developed for compensation of time-dependent phase aberrations to a laser beam, such as those caused by thermal lensing. The unimorph-type device consists of a metallic disc, with a mirror finish, bonded to ... Read more
Development of a variable stiffness and damping tunable vibration isolator

Author: Cronje, JM ; Heyns, PS ; Theron, NJ ; Loveday, Philip W Date: Mar 2005 In this paper we report on the development of a variable stiffness and damping Liquid Inertia Vibration Eliminator (LIVE) vibration isolator. The result is the ability to shift the isolation frequency of the isolator and also to change the ... Read more
Development of an optimal piezoelectric transducer to excite guided waves in a rail web

Author: Ramatlo, Dineo AM ; Wilke, DN ; Loveday, Philip W Date: Apr 2018 Ultrasonic transducers have demonstrated the ability to effectively excite guided waves that can propagate over long distances and are thus employed in monitoring systems. An ultrasonic piezoelectric transducer that strongly excites a mode ... Read more
Effects of finite element formulation on optimal plate and shell structural topologies

Author: Long, Craig S ; Loveday, Philip W ; Groenwold, AA Date: Sep 2009 The effects of selected membrane, plate and flat shell finite element formulations on optimal topologies are numerically investigated. Two different membrane components are considered. The first is a standard 4-node bilinear quadrilateral, ... Read more
Effects of planar element formulation and numerical integration order on checkerboard material layouts

Author: Long, Craig S ; Loveday, Philip W ; Groenwold, AA Date: Jan 2009 The effects of selected planar finite element formulations, and their associated integration schemes, on the stiffness of a checkerboard material layout are investigated. Standard 4-node bilinear elements, 8- and 9-node quadratic elements, ... Read more
Estimation of probability of defect detection by combining simulated defect signatures with measured ultrasonic guided wave signals

Author: Ramatlo, Dineo AM ; Loveday, Philip W ; Long, Craig S ; Wilke, DN Date: Sep 2018 Continuously welded heavy haul railway lines experience very large stresses due to high axle loads and varying environmental conditions. Read more
Estimation of rail properties using semi-analytical finite element models and guided wave ultrasound measurements

Author: Setshedi, Isaac I ; Loveday, Philip W ; Long, Craig S ; Wilke, Daniel N Date: Jul 2019 Guided wave based monitoring systems require accurate knowledge of mode propagation characteristics such as wavenumber and group velocity dispersion curves. These characteristics may be computed numerically for a rail provided that the material ... Read more
Excitation of waves in elastic waveguides by piezoelectric patch actuators

Author: Loveday, Philip W Date: Jan 2006 Piezoelectric patch actuators are employed for monitoring the health of structures and for performing active control of vibration. When the structure is long, slender and has constant cross-section, such as a pipe, rail or rod, it can be ... Read more
Experimental development of an ultrasonic linear motor

Author: M'Boungui, G ; Loveday, Philip W ; Long, Craig S Date: Jan 2010 The authors investigate a novel ultrasonic motor which generates a stator trajectory in the form of a figure-of-eight by superimposing two resonant modes, with one double the frequency of the other. Topology optimization was used to design ... Read more
Experimental development of electromagnetic acoustic transducers for measuring ultraguided waves

Author: Loveday, Philip W ; Dhuness, Kahesh ; Long, Craig S Date: Sep 2018 Guided wave ultrasoud offers the potential to monitor long sections of structures such as pipes and rails from a single transducer location and is used in a system for monitoring continuouosly welded rail track which was developed in South Africa Read more
Feasibility of detecting cracks in rail track at long range using guided wave ultrasound

Author: Loveday, Philip W ; Long, Craig S Date: Jan 2014 A transducer array comprising four transducers was developed and used to perform pulse – echo measurements on a heavy duty welded rail track. A signal processing algorithm, which uses properties of the propagating modes computed using ... Read more
Free vibration of elastically supported thin cylinders including gyroscopic effects

Author: Loveday, Philip W ; Rogers, CA Date: 29 Oct 1998 The free vibration of thin cylinders with elastic boundary conditions was analysed by application of the exact solution of the Flugge shell theory equations of motion. The elastic boundaries were represented by distributed linear springs. By ... Read more
Guided wave inspection and monitoring of railway track

Author: Loveday, Philip W Date: Jul 2012 Cost-effective NDE of the vast length of aging railway track around the world remains a challenge for the community. Continuously welded rail is installed in tension but temperature changes can result in rail buckling if the initial tension ... Read more
Guided wave inspection and monitoring of railway track

Author: Loveday, Philip W Date: Apr 2012 Cost-effective NDE of the vast length of ageing railway track around the world remains challenge for the community. Since continuously welded railway lines may be thought of as one-dimensional elastic waveguides, they are natural candidates ... Read more

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