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The performance of smart structures depends on the dynamic electromechanical behavior of piezoelectric sensors/actuators and the bonding condition along the interface. This thesis contents a theoretical study of the coupled electromechanical characteristics of a surface-bonded piezoelectric sensor with interfacial debonding, which is subjected to high frequency mechanical loads. A one dimensional sensor model is proposed. Analytical solutions based on the integral equation method are provided. Numerical simulation is conducted to evaluate the effects of different parameters upon the dynamic load transfer between the sensor and the host medium. The results indicate that, the material combination, the sensor geometry, and the loading frequency, affect the load transfer significantly. The analytical solution of the elastic wave field in the host medium is obtained and used to evaluate the effects of different parameters upon the resulting wave field. The theoretical solution demonstrates the basic properties of wave propagation under current loading conditions.

<p> Multiple impact tests were performed on mild steel. The pulse durations ranged from 15 to 250 milliseconds. Peak stresses extending to 135,000 p.s.i. were attained. </p> <p> A dynamic model, based on dislocation dynamics, was derived for polycrystalline metals and made specific to mild steel. The model provided a means of indirectly determining the dislocation velocity-stress exponent 𝑛 by experiment. </p> <p> An empirical flow function was evaluated which related dynamic load conditions to plastic deformation. This function is a further extension of the dynamic model. Several dislocation parameters are grouped together to pennit experimental evaluation of the strain rate effect on crystalline material. </p> <p> Experimental studies indicated that a given strain: </p> <p> 1) if produced by a single pulse, can be estimated by evaluation of the flow function for that load-time trace, or, </p> <p> 2) if produced by multiple impacts, can be estimated by the cumulative flow function, a summation of the flow functions for all impact traces. </p> <p> The multiple impact tests established the flow function as an equation of state. The plastic deformation could then be determined for a given dynamic load as long as the strain history is known. </p> <p> The theoretical model was used to support the experimental findings. </p> / Thesis / Master of Engineering (ME)

This study, carried out in cooperation with ESSAIM, Ecole Supérieure des Sciences Appliquées pour l'Ingénieur, Mulhouse in France, was aimed at developing accurate mathematical models of some types of tyre, in order to analyze their influence on vehicle dynamics. The complete vehicle was studied under dynamic conditions, to quantify the influence of all factors, such as rolling forces, aerodynamic forces and many others, acting on their components on torque distribution and vehicle dynamics. Mathematical models for two common types of vehicle, namely front and rear wheel drive, each ones equipped with the different types of tyre, were developed. Both models were used to simulate the behaviour of a real vehicle, developing complete simulation software, developed in Matlab-Simulink environment at MIPS, Modélisation Intelligence Processus Systèmes. Therefore, this car model, running on a straight and curve track, was also developed, to get a qualitative insight of the influence of these kinds of interactions on traction capabilities. The software, used to simulate some dynamics manoeuvres, shows up the basic behaviour of vehicle dynamics.

In order to establish the rules and criteria· to be satisfied in order to develop a scale model, which may be employed to predict the dynamic behaviour of a fullscale rope-guide mineshaft installation, the theory of the dynamic behaviour of rope-guides is considered. In order to establish to what degree a scale model rope-guide system may be expected to simulate the dynamic behaviour of its fullscale prototype a series of correlation test on an existing rope-guide installation and its dynamic scale model are described. A further series of model investigations into the aerodynamic scale effects which may occur in rope-guide installations, are also described. These investigations demonstrate certain limitations in the use of dynamic scale models of rope-guides and also explain the mechanism of air flow in shaftscontaining bluff bodies. On the strength of the experience gained in this research recommendations are made for the execution of efficient experimental investigations into the dynamic behaviour of various rope-guide mineshaft installations. 6ome information is also provided on the actual design of fullscale rope-guide systems. / Thesis (PhD)--University of Pretoria, 1965. / gm2014 / Mechanical and Aeronautical Engineering / unrestricted

The fundamental requirement of the research reported within this thesis is the provision of physical models to enable model based simulation of mainstream printed circuit assembly (PCA) process discrete events for use within to-be-developed (or under development) software tools which codify cause & effects knowledge for use in product and process design optimisation. To support a national competitive advantage in high reliability electronics UK based producers of aircraft electronic subsystems require advanced simulation tools which offer model based guidance. In turn, maximization of manufacturability and minimization of uncontrolled rework must therefore enhance inservice sustainability for 'power-by-the-hour' commercial aircraft operation business models.

Multi-pantograph operation allows several short electric multiple unit (EMU) trainsets to be coupled or decoupled to adapt to daily or seasonal passenger-flow variation. Although this is a convenient and efficient way to operate rolling stock and use railway infrastructure, pantographs significantly influence each other and even significantly change the dynamic behaviour of the system compared to single-pantograph operation in the same condition. The multi-pantograph system is more sensitive and vulnerable than the single-pantograph system, especially at high operational speeds or with pantographs spaced at short distances. Heavy oscillation in the system can result in low quality of current collection, electromagnetic interference, severe wear on the contact surfaces or even structural damage. The mechanical interaction between the pantograph and the catenary is one of the key issues which limits the maximum operational speed and decides the maintenance cost.     Many researchers have paid a lot of attention to the single-pantograph operation and have made great progress on system modelling, optimizing, parameter studies and active control. However, how the pantographs in a train configuration affect each other in multi-pantograph operation and which factors limit the number of pantographs is not fully investigated. Nowadays, to avoid risking operational safety, there are strict regulations to limit the maximum operational speed, the maximum number of pantographs in use, and the minimum spacing distance between pantographs. With the trend of high-speed railways, there are huge demands on increasing operational speed and shortening spacing distance between pantographs. Furthermore, it is desirable to explore more practical and budget-saving methods to achieve higher speed on existing lines without significant technical modification.     In addition to a literature survey of the dynamics of pantograph-catenary systems, this thesis carries out a numerical study on multi-pantograph operation based on a three-dimensional pantograph-catenary finite element (FE) model. In this study, the relationship between dynamic performance and other parameters, i.e. the number of pantographs in use, running speed and the position of the pantographs, are investigated. The results show that the spacing distance between pantographs is the most critical factor and the trailing pantograph does not always suffer from deterioration of the dynamic performance. By discussing the two-pantograph operation at short spacing distances, it is found that a properly excited catenary caused by the leading pantograph and the wave interference between pantographs can contribute to an improvement on the trailing pantograph performance. To avoid the additional wear caused by poor dynamic performance on the leading pantograph and achieve further improvement at high speeds, it is suggested to use the leading pantograph as an auxiliary pantograph, which does not conduct any electric current and optimize the uplift force on the leading pantograph. After a brief discussion on some system parameter deviations, it is shown that a 30% of speed increase should be possible to achieve while still sustaining a good dynamic performance without large modifications on the existing catenary system. / <p>QC 20150928</p>

<p>This thesis studies the effect of-floor slabs on the static and dynamic behaviour of the shear wall structure. A single component has been analysed using the 'Matrix Transfer' technique along with Vlaspv's thin walled elastic beam theory. Experimental verification was done on a small scale plexiglas eight storey model in the form of a channel section for both static and dynamic loading. The thesis also deals with the ·analysis of the nonplanar shear walls coupled through floor beams subjected to static loading. The continuum approach along with Vlasov's theory h&s been used in the analysis. Experimental verification was done on a small scale plexiglas model in the form of two equal angles connected by eight floor beams at equal spacing.</p> / Thesis / Master of Engineering (ME)

In partnership with iMonSys - an emerging company in the passive care field - a new system, 'Verity', is being developed to fulfil the role of a passive behaviour monitoring and alert detection device, providing an unobtrusive level of care and assessing an individual's changing behaviour and health status whilst still allowing for independence of its elderly user. In this research, a Hidden Markov Model incorporating Fuzzy Logic-based sensor fusion is created for the behaviour detection within Verity, with a method of Fuzzy-Rule induction designed for the system's adaptation to a user during operation. A dimension reduction and classification scheme utilising Curvilinear Distance Analysis is further developed to deal with the recognition task presented by increasingly nonlinear and high dimension sensor readings, and anomaly detection methods situated within the Hidden Markov Model provide possible solutions to identification of health concerns arising from independent living. Real-time implementation is proposed through development of an Instance Based Learning approach in combination with a Bloom Filter, speeding up the classification operation and reducing the storage requirements for the considerable amount of observation data obtained during operation. Finally, evaluation of all algorithms is completed using a simulation of the Verity system with which the behaviour monitoring task is to be achieved.