Neil Popplewell

• University of Manitoba

An exhaustive study is carried out on the mechanics of waves travelling through a coupled elasto-acoustic system of a fluid-filled, thick-walled spherical shell embedded in an elastic formation. Important but previously untouched aspects of this classical problem are addressed rigorously. An exact local theory of linear elasticity is applied to the...

In this paper, the effects of transverse acoustic waves in characterizing a bone-like, porous medium filled with a viscous fluid are analyzed for the first time. Scattering operators along with stress fields are derived by using the standard Biot-JKD model. A short duration acoustical pulse is applied to one side of a bone-like, porous medium so th...

Acquiring detailed information about the state of the pavement structures is an important element in rehabilitation planning of sections showing significant damage. The Falling Weight Deflectometer Test (FWD) is a popular Non-Destructive Testing (NDT) technique used to characterize the mechanical properties of a pavement structure. This paper aims...

The paper addresses the problem of transient elastodynamics analysis of a thick-walled, fluid-filled spherical shell embedded in an elastic medium with an analytical approach. This configuration is investigated at first step for a full-space case. Different constitutive relations for the elastic medium, shell material and filling fluid can be consi...

A Control-Volume Finite-Element Method (CVFEM) is newly formulated within Eulerian and spatial averaging frameworks for effective simulation of disperse transport, deposit distribution and interface tracking. Their algorithms are implemented alongside an existing continuous phase algorithm. Flow terms are newly implemented for a control volume (CV)...

The use of a single, non-dispersive ultrasonic guided wave mode is one important approach to monitoring a structure's health. It is advantageously non-destructive with the ability of propagating over tens of metres to detect a hidden defect. The dimensional assessment of a defect, on the other hand, requires reflection coefficients for two or more...

A closed form solution was derived previously for the response of a submerged spherical shell when the shell was excited by a spatially distributed, transient load at its inner surface [Zakout (2001). J. Acoust. Soc. Am. 109(6), 2789-2796]. Numerical results were presented for the modal and total acoustic pressures outside the empty sphere when the...

A hybrid Semi-Analytical Finite Element (SAFE) and standard finite element procedure is adopted to simulate ultrasonically generated waves traveling in an infinitely long steel pipe having an open, rectangular notch. Numerical illustrations indicate that dispersive guided waves can be used to locally detect and characterize such a notch. A frequenc...

A hybrid Semi-Analytical Finite Element (SAFE) and standard finite element procedure is adopted to locally detect and characterize an outer surface breaking, axisymmetric notch in an otherwise infinitely long steel pipe. Numerical simulations demonstrate that interactions between incident, dispersive ultrasonic guided waves and the notch change a...

A hybrid Semi-Analytical Finite Element (SAFE) and standard finite element procedure is adopted to ultrasonically but locally detect and characterize an axisymmetric open notch in an infinitely long steel pipe. Interactions between incident, dispersive guided waves and the notch are shown numerically to change a radial displacement's temporal histo...

Three principal challenges are described that hamper non-destructively assessing the health of a structure by using ultrasonic guided waves. They relate to computer run times, transducer coupling and its characterization, as well as accurate signal processing. Although more universally applicable, comments are illustrated by using the 3-dimensional...

The effect of a nozzle's internal geometry on a water jet issuing into a subsonic cross air flow was studied experimentally to determine the jet's breakup length and trajectory. The geometrical parameters considered were the nozzle's diameter, nominal surface roughness, length-to-diameter ratio and contraction angle. Although the nozzles employed w...

A non-destructive inverse procedure to determine a homogeneous, isotropic pipe's elastic properties and wall thickness is first described in principle. The procedure uses the cut-off frequencies of three ultrasonic guided wave modes that are employed with a semi-analytical finite element (SAFE) forward solver and the pipe's known density and outer...

The ability to simultaneously measure a homogeneous, isotropic pipe’s elastic properties and wall thickness from its known mass density, outer diameter and the cut-off frequencies of three ultrasonic guided wave modes is demonstrated for a typical steel pipe. This inverse procedure is based upon simulated results computed by using an efficient Semi...

The aerodynamics involved in the galloping of lightly-iced transmission lines were studied in a series of wind tunnel experiments. A representative section of a lightly-iced conductor produced in an outdoor freezing rain simulator was used throughout. In the first set of experiments aerodynamic loads were measured on a static model at different win...

A computer model-based inversion procedure is used to simultaneously determine the elastic constants and wall thickness of a typical steel pipe from the experimentally determined cut-off frequencies of three guided wave modes as well as the pipe’s mass density and outer diameter. Nominal values for the unknown parameters agree well with those found...

Loaded cylinders are ubiquitous in industrial applications (e.g., pipes carrying pressurized fluids). Defects in a cylinder reduce the load that can be carried safely; catastrophic failure of a cylinder can be costly in terms of both economics and loss of life. An apparent dichotomy exists presently in the literature. To date, analyses are performe...

A new, cooperative job dispatching approach is presented to minimize the mean flowtime in dynamic flowshops. A dispatching decision taken at any machine is reached collectively through consultation with other machines, and conflicting priorities are resolved by employing a penalty-based procedure. Computer results indicate that the proposed coopera...

A novel add-on device, called a hybrid nutation damper (HND), is proposed to control galloping on both single and bundled conductors of overhead power lines. An HND employs a nutation damper (also called a tuned liquid damper) as an energy dissipator, and a tuned mass damper as the mechanism to transfer a conductor's plunge motion into a nutation d...

The effect of liquid viscosity on the penetration and trajectory of a jet in a low subsonic cross-airflow was investigated experimentally. An open-loop wind tunnel was used to generate an airstream in a square cross-sectional test section. Liquid was injected downward through a nozzle that was flush with the top inner surface of the test section. A...

This paper deals with the problem of cutting multiple sized, rectangular stock sheets into smaller rectangular order pieces to satisfy a given bill of material with minimum him loss. A new heuristic procedure is devised that finds; an effective stock sheet selection sequence, given that the layout procedure used for individual sheets is known. Resu...

A water jet exposed to a low subsonic air cross-flow was studied experimentally to determine the jet/spray trajectory based on the jet's zipper boundary. The nozzle diameter as well as the flow and water jet speeds were varied to provide a wide range of experimental conditions. Although this study is not entirely novel, the results of previous rese...

This paper considers the n-job, m-machine permutation flowshop with the objective of minimizing the mean flowtime. Initial sequences that are structured to enhance the performance of local search techniques are constructed from job rankings delivered by a trained neural network. The network's training is done by using data collected from optimal se...

It is estimated that the rehabilitation of deteriorating engineering infrastructure in the harsh North American environment could cost billions of dollars. Bridges are key infrastructure components for surface transportation. Steel-free and fibre-reinforced concrete is used increasingly nowadays to circumvent the vulnerability of steel rebar to cor...

A parallel computational algorithm that models three-dimensional elastic wave scattering in an infinite pipe is introduced. The algorithm combines two procedures: a Wave Function Expansion (WFE) and a Finite Element Discretization (FED). The WFE represents a flawless unbounded region while the FED idealizes a bounded region containing the defects....

A novel numerical model is proposed to simulate liquid sloshing in a rectangular nutation damper (i.e. a tuned liquid damper) undergoing a coupled horizontal and rotational motion. Shallow water theory is used consistently to derive the governing equations of motion so that the model is applicable to large sloshing involving a hydraulic jump. It ca...

In the present study, a 3D hybrid method, which couples the finite element region with guided elastic wave modes, is formulated to investigate the scattering by a non-axisymmetric crack in a welded steel pipe. The algorithm is implemented on a parallel computing platform. Implementation is facilitated by the dynamic memory allocation capabilities o...

A somewhat generalized numerical procedure is used in this paper to study the problem of wave scattering by circumferential cracks in composite pipes. The study is motivated by the need to develop a model for the quantitative, ultrasonic non-destructive evaluation of cracks in pipes. For this purpose, a stiffness-based Rayleigh–Ritz type approach i...

A new type of wind tunnel for multiphase flows with droplets and icing is presented. Under the current design, testing of flows under high speed (small droplet) and low speed (large droplet) conditions can be performed. Spraying of droplets can be adjusted for each case so that the droplets reach thermal equilibrium with the air stream, while follo...

Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

A novel numerical procedure is presented in this paper to study wave scattering by circumferential cracks in steel pipes. The study is motivated by the need to develop a quantitative ultrasonic technique to characterize properties of cracks in pipes. By employing wave function expansion in axial direction and decomposing the problem into a symmetry...

The present paper reports on extensive experiments performed on short, fixed, unheated conductor samples in an outdoor freezing rain simulator. Their purpose is to relate the weight of ice (or, alternatively, the equivalent radial ice thickness) accreted on the samples with the associated weather conditions. Over 50 specimens have been obtained und...

It is normal when programming a robotic manipulator to provide the end effector's orientation and position at the pick up and drop off locations. Additional sensory information and intelligence is needed, however, to detect the presence of a part as well as its location if the assembly site cannot be controlled precisely by employing expensive jigs...

This paper presents an approach for single machine job sequencing problems that is based on artificial neural networks. A problem is classified first by one type of neural network into one of a number of categories. The categorization is based on the problem’s characteristics. Then another neural network, which is specialized for a particular categ...

A useful design tool is developed for a bundle conductor of an electrical transmission line by using a three-degree-of-freedom hybrid model. The model is adaptable because it incorporates numerical mode shapes determined by numerically employing the finite element technique to form relevant matrices. On the other hand, it is quite computationally e...

Numerical simulations of a single-degree-of-freedom (SDOF) structure, rigidly supporting a tuned liquid damper (TLD) and subjected to both real and artificially generated earthquake ground motions, show that a properly designed TLD can significantly reduce the structure's response to these motions. The TLD is a rigid, rectangular tank with shallow...

Infrastructures are deteriorating and billions of dollars are spent to rehabilitate them. Civil structures usually comprise of pavements and bridge decks (plates), pipelines (cylinders), and structural members having, say, I, L, etc. cross sections. The deterioration of these structures causes flaws arising from factors such as the severity of the...

An analytical model is developed for the prediction of glaze ice accretion with runback water for electric power lines including the Joule heating effect. In this model, the external air flow is coupled with the liquid film flow by slip (non-zero velocity) boundary conditions a the liquid-air interface. In this way, corrections to previous rime ice...

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An operator-based formulation is used to show the completeness of the eigenfunctions of a non-uniform, axially-loaded, transversely-vibrating Euler-Bernoulli beam having eccentric masses and supported by offset linear springs. This result generalizes the classical expansion theorem for a beam having conventional end conditions. Furthermore, the eff...

The objective of this paper is to consider the dynamic motions of second order, weakly non-linear, discrete systems. The main attention is focused on a comparison, for such systems, of the method of Krylov-Bogoliubov (KB) and an enhanced Galerkin (EG) method which produce seemingly different solutions. Despite the apparent differences, the two meth...

Efficient perturbation schemes are developed to compute the large amplitude, low frequency, galloping vibrations of a multi-span, overhead transmission line. Systematic procedures are formulated to assess the stability of a conductor's wind and ice loaded static profile by employing a multiple-degree-of-freedom finite element model. The use of the...

A new approach is proposed for the on-line measurement of the maximum peak-to-valley roughness,R max, of a finished-turned surface in the feed direction. The method is based on solving the inverse problem of light scattering by using a linear least-square estimate of the angular scattered light pattern reflected from a surface. A laser system has b...

A laser system which incorporates a charge-coupled-device (CCD) sensor is developed to measure, in real lime, the maximum peak-to-valley surface roughness, R max. produced during finish turning. A three-layer neural network is used in conjunction with a back-propagation learning algorithm to predict R max, by quickly recognizing the angular scatter...

A computationally efficient, finite element idealization is presented to analyse galloping, which is characterized by large amplitude vibrations of iced, multi-span, electrical transmission lines. A three-node, isoparametric cable element having three translational and a torsional degree-of-freedom at each node is developed to model a conductor. Su...

A unique technique is developed for on-line prediction of the tool flank wear in turning using the spindle speed change. A mathematical model is presented for the approach. The speed sensing element is an optical encoder mounted on the spindle shaft and interfaced to an IBM compatible microcomputer employing custom designed electronics. The changes...

The non-resonant dynamic galloping of an iced, electrical transmission line is studied. Conditions and trends for the initiation of galloping have been given previously. Boundaries are presented here at which a periodic plunge or torsional motion loses stability and bifurcates into a quasi-periodic (mixed-mode) motion. Specific attention is given t...

The objective of this paper is to investigate the trends of the dynamic behavior of a single iced conductor. Attention is focused not only on the initiation of galloping but also on boundaries where a periodic plunge or torsional motion emerge. Trends with respect to the iced conductor's eccentricity and its inertia to mass ratio are particularly s...

A heuristic algorithm combining priority rules with a restricted search procedure is presented for solving the two-dimensional, bin-packing problem. The method of solution is one of problem reduction, where the initial problem is decomposed into subproblems that are solved separately. The search procedure acts to minimize the number of subproblems...

It is common practice in power transmission to use bundled overhead electrical conductors because the lower rate of corona discharge, compared with single conductors, makes the bundle attractive for high voltages. However, secondary problems may arise from the vibrations induced by the aerodynamic forces which act on the leeward conductors as a res...

A neural network is employed to select earthquake waves in a time history approach for structural dynamics. The neural network is a preferable alternative to an expert system because knowledge can easily be renewed. It involves a back propagation model having three layers (one input, one hidden and one output layer) and is used to avoid inappropria...

Illustrative comparisons are given of several numerical procedures for finding the contact forces and their peak values when an elastic beam collides repeatedly with a resilient stop. Computational efficiency is shown to depend upon the variable of interest.

The results of an investigation into the desing of an adaptive force control system for machine tool turning operations are examined. The control system modifies the feedrate in real time in order to keep the cutting force constant, while maintaining the accuracy of the tool path. The approach is unique in that a computer simulation is used offline...

A three-degree-of-freedom model is developed to comprehensively describe and predict different galloping behavior observed on a single iced, electrical transmission line. Interactions arc accommodated between a line's plunge, twist, and swing in the along-wind direction. Eccentricity of the cross section is also considered and the longitudinal stat...

Internal nonresonant and resonant galloping of an iced electrical transmission line is studied by employing a three-degree-of-freedom (3DOF) model formulated in part I where the conditions for the initiation of galloping and the governing bifurcation equations were derived for dynamic motions. Perturbation techniques are employed so that the govern...

An electronic-optical method of determining surface roughness in real time during finish turning is presented. The electronic design makes it possible to store pixel information from a CCD video image device at selective rather than continuous intervals. Selective triggering allows a direct correlation between electronically and mechanically acquir...

Lateral energy fractions, LF, and inter‐aural cross correlations, IACC, have both been proposed as correlates of spaciousness in concert halls. Although, theoretically, related previous measurements have not shown a strong relationship between the two quantities. New measurement results from 80 locations in 10 different halls indicate varying relat...

This paper is concerned with the galloping of iced conductors modeled as a two-degrees-of-freedom system. It is assumed that a realistic cross-section of a conductor has eccentricity; that is, its center of mass and elastic axis do not coincide. Bifurcation theory leads to explicit asymptotic solutions not only for the periodic solutions but also f...

The problem of solder joint inspection is viewed as a two-step process of pattern recognition and classification. A modified intelligent histogram regrading technique is used which divides the histogram of the captured image into different modes. Each distinct mode is identified, and the corresponding range of grey levels is separated and regraded...

Although the galloping of an iced electrical conductor has been considered by many researchers, no special attention has been given to the galloping's sensitivity to alternations in the system's parameters. A geometrical method is presented in this paper to describe these instability trends and to provide compromises for controlling an instability....

Students can be motivated by ‘hands-on’ computer laboratories that complement standard mathematical vibration theory. Such laboratories encourage students' questions and, in subsequent discussions with staff, expose some of the limitations of classicial classroom theory.

A new parameter called the critical offset distance is introduced to evaluate the stability of an artificial knee. This parameter is used in conjunction with a finite element analysis to successfully redesign a commercially popular safety knee. Stability is improved for this particular knee by increasing the flexibility and reducing the machined cl...

A high resolution tachometer device is described which can monitor transient speed changes of the order of 0.1% centred around a steady-state, nominal speed in the range 12 · 56 to 209 · 44 rads−1. Unlike existing designs, the unit employs electronically adjusted pulse counting to maintain a constant percentage error over a wide speed range. The de...

A comprehensive analysis is presented for the galloping of an oscillator that may vibrate both transversely and torsionally. Explicit solutions are given for the conditions needed to initiate galloping and also for the ensuing nonlinear periodic responses. Internal resonance as well as previously considered nonresonance responses are treated consis...

An experiment, similar to the one devised by Lochner and Burger to find the integration characteristics of the ear, was performed in an anechoic chamber. The experiment was conducted in the absence of any disturbing background noise at a speech level approaching the threshold of hearing (22 dB(A) re 20 μPa). It is concluded that, under these condit...

The performance of a resilient bean bag and a conventional rigid impact damper are compared for sinusoidal external forces. The bean bag damper is not only a better attenuator of the resonant displacement of a lightly damped oscillator but the contact forces and the noise generated by collisions are also reduced. Two semi-empirical approaches are d...

Not Available Now at Department of Mechanical Engineering, McMaster University, Hamilton, Ontario, Canada.

The design and development of a microcomputer-based servo motor controller is presented. The control procedure is implemented within the microcomputer so that it can be modified easily. Indeed, the flexibility introduced by the software rather than the usual emphasis on hardware makes the control package extremely attractive for machine retrofits o...

Impact damping utilizes the principle of momentum exchange and the energy dissipation usually arising from the collisions of a lightly damped, resonant primary system with a smaller secondary mass. It has been used to successfully attenuate the excessive vibrations of turbine blades, antennae and aircraft wings. Various forms have been considered t...

A numerically efficient procedure is presented for generating the stiffness of a parabolic, three-node finite element for the static, nonlinear analysis of three-dimensional cable-supported structures. Numerical computations are minimized by explicitly evaluating the large deformation stiffness matrix with respect to global coordinates while avoidi...

A free vibration analysis is presented for a transmission line. The guyed supporting towers are somewhat novel, consisting of a Y-shaped frame made of hollow steel sections. Transverse vibrations in both the conductors and the guy-wires were modelled by using special parabolic cable elements. The lowest frequency modes primarily involve conductor m...

Several important vibroimpact systems are shown similar under certain specified limits or constraints. Such relationships enable a non-linear dynamic behaviour to be corroborated economically or applied easily elsewhere.

The use of Dunkerley's first-order method for estimating the fundamental natural frequencies of tower structures is discussed. An asymmetric geometry may be considered, even though this leads to coupling between bending and torsion. The analysis of an asymmetric high-voltage transmission tower is considered as a practical example.

The traditional simplification for one commonly used example of repeated collisions is shown to be frequently erroneous for a wide range of coefficients of restitution. Bounded errors arise from an artificial speed constraint whose circumvention is largely but not exclusively unpredictable. Therefore exact equations, whose periodic solutions are de...

A relatively easy procedure for hand-calculating reasonably accurate fundamental natural frequencies of free-standing, latticed transmission towers is demonstrated. The procedure is based upon a first-order Dunkerley approximation and is illustrated by using three different yet fairly typical transmission towers. It may be employed straightforwardl...

This article describes the behavior of transmission towers, insulator strings, conductors, and foundations as determined from theoretical analyses, model testing, and full-scale tests. Line vibration is also briefly reviewed.

The asymptotically stable vibrations of a loaded oscillator colliding periodically with a rigid mass are described. Comparison of the numerical results with the few existing examples is encouraging but inconclusive. Better overall agreement is demonstrated with fairly comprehensive measurements from a specially built experimental rig. Impact motion...

The asymptotically stable motion of two rigid masses separated by a clearance is formulated most generally when the masses collide periodically. Predictions are shown to agree satisfactorily with comprehensive experimental results. Difficulties encountered in the practical application of this and similar stability theories are discussed with the he...

Two previously established methods of predicting the largest displacement modulus of discretized structures under incompletely described loads are extended logically to continuous structures. The general procedure is illustrated by using the particular example of a simply supported, homogeneous beam whose free flexural vibrations can be characteriz...

Estimates of the maximax displacements of multi-, rather than single-, degree-of-freedom systems to incompletely described loads are shown to be reasonable. The conventional approach to designing a constant tuned vibration neutralizer appears justifiable even though it does not produce a truly optimum solution.

Formulae for estimating the maximax response of linear, stable structures to incompletely described loads are reviewed. The accuracies of these formulae are evaluated for fairly comprehensive but ideal circumstances where the loads and, hence, the exact solutions are known fully. One of the formulae is least accurate but the ranking of the others a...

The effect of neighbouring, smooth obstacles on the sound generated by statistically stationary traffic movements is analysed for simple but realistic practical situations. Dimensions of obstacles like buildings are assumed much larger than the predominant, A-weighted wavelength of traffic noise so that diffraction may be neglected. The sound at an...

A general theory is developed to estimate the greatest maximum response of linear structures subjected to deterministic or random excitations. The analysis utilizes the prolate spheroidal wave functions and the uncertainty principle. Such a technique is useful in checking the results of different methods, which may involve tedious calculations, for...

The time-averaged overall mean-square sound pressure created by statistically stationary traffic travelling a finite, straight road segment is determined explicitly. This result is extended to a system of roads by using digital simulation. Theoretical predictions for a typical urban conurbation show encouraging agreement with measured values. There...

The effect of conserving computer effort by reducing the impact of the normally high frequency motion associated with in-plane movements is investigated for rectangular structures with a range of shallow sloping roofs. In-plane motions are found experimentally to be insignificant for predominantly bending modes and, from the standpoint of economy,...

The finite element displacement method is used to predict the vibrations of box-like buildings induced by weak blast waves. The theory is the first to incorporate experimental data to describe comprehensively the complex distortions of the blast waves by flexible structures. Numerical computations performed for three typical medium-low buildings in...