This work investigates the use of shape memory alloys (SMAs) for vibration isolation and damping of mechanical systems. The first part of this work evaluates the nonlinear dynamics of a passive vibration isolation and damping (PVID) device through numerical simulations and experimental correlations. The device, a mass connected to a frame through two SMA wires, is subjected to a series of continuous acceleration functions in the form of a sine sweep. Frequency responses and transmissibility of the device as well as temperature variations of the SMA wires are analyzed for the case where the SMA wires are pre-strained at 4.0% of their original length. Numerical simulations of a one-degree of freedom (1-DOF) SMA oscillator are also conducted to corroborate the experimental results. The configuration of the SMA oscillator is based on the PVID device. A modified version of the constitutive model proposed by Boyd and Lagoudas, which considers the thermomechanical coupling, is used to predict the behavior of the SMA elements of the oscillator. The second part of this work numerically investigates chaotic responses of a 1- DOF SMA oscillator composed of a mass and a SMA element. The restitution force of the oscillator is provided by an SMA element described by a rate-independent, hysteretic, thermomechanical constitutive model. This model, which is a new version of the model presented in the first part of this work, allows smooth transitions between the austenitic and the martensitic phases. Chaotic responses of the SMA oscillator are evaluated through the estimation of the Lyapunov exponents. The Lyapunov exponent estimation of the SMA system is done by adapting the algorithm by Wolf and co-workers. The main issue of using this algorithm for nonlinear, rateindependent, hysteretic systems is related to the procedure of linearization of the equations of motion. The present work establishes a procedure of linearization that allows the use of the classical algorithm. Two different modeling cases are considered for isothermal and non-isothermal heat transfer conditions. The evaluation of the Lyapunov exponents shows that the proposed procedure is capable of quantifying chaos in rate-independent, hysteretic dynamical systems.

Voltage flicker limitation of electric utilities has been discussed in the past three decades. Arc furnace is one of the most disturbing loads that cause flicker problems in the power network. If displeasing flicker levels are predictable, then corrective solution such as static var compensation or furnace controls could be developed in cooperation between the utility and the customer. In the past, the electric fluctuations in the arc furnace voltage have been proven to be chaotic in nature. This thesis proposes a phase space approach based on nonlinearity chaotic techniques to analyze and predict voltage flicker. The determination of the phase space dimension and the application of Lyapunov exponent for flicker prediction are described. Test results have shown that accurate prediction results are obtainable for short term flicker prediction based on chaos theory.

This dissertation provides the conceptual development, modeling and simulation, physical implementation, and measured hardware results for a practicable digital coherent chaotic communication system. Such systems are highly desirable for robust communications due to the maximal entropy signal characteristics that satisfy Shannon's ideal noise-like waveform and provide optimal data transmission across a flat communications channel. At the core of the coherent chaotic communications system is a fully digital chaotic circuit, providing an efficiently controllable mechanism that overcomes the traditional bottleneck of chaotic circuit state synchronization. The analytical, simulation, and hardware results yield a generalization of direct sequence spread spectrum waveforms, that can be further extended to create a new class of maximal entropy waveforms suitable for optimized channel performance, maximal entropy transmission of chaotically spread amplitude modulated data constellations, and permission-based multiple access systems.

Die vorliegende Arbeit kombiniert Aspekte der nichtlinearen Dynamik mit denen der Unordnungsphysik. Die bekannte Standardabbildung wird mit einem räumlich ungeordneten aber periodischen Potential modifiziert. Transportexponenten sowohl für den Impuls als auch die kanonisch konjugierte Koordinate für das Standard- und das Zufallsmodell werden gegenübergestellt. Für das Zufallspotential ergibt sich verstärkter Transport. Gemittelte Transportexponenten des Zufallspotentials werden präsentiert und für verschiedene Systemausdehnungen verglichen. / The thesis at hand combines aspects of nonlinear dynamics with the physics of disorder. The standard map potential is replaced by a spatially quenched random periodic potential. Transport exponents for the standard and the random model are determined for the momentum as well as the canonically conjugate coordinate. Transport for the disordered potential is increased in comparison to the standard map. For the random case, quenched average transport exponents are presented. Finite-size effects are examined.

Reproduction de : Thèse de doctorat : Génie électrique : Reims : 2005. / Titre provenant de l'écran titre. Bibliogr. f. 143-152.

Thèse de doctorat : Sciences physiques : Lille 1 : 2000. / Résumé en français et en anglais. Textes en français et en anglais (publications). Bibliogr. p. 127-131. Notes bibliogr.

Thèse doctorat : Lasers, molécules, rayonnement atmosphérique : Lille 1 : 2003. / N° d'ordre (Lille 1) : 3343. Publications en anglais et en français reproduites dans le texte. Résumé en français et en anglais. Bibliogr. p. 229-234.

Thèse de doctorat : Automatique et traitement du signal : INPL : 2006. / Titre provenant de l'écran-titre. Bibliogr.

Thèse de doctorat : Electronique.Electrotechnique.Automatique : Strasbourg 1 : 2007. / Titre provenant de l'écran-titre. Bibliogr. p. 131-138.

<p>The dynamics of impacting components is of particular interest to engineers due to concerns about noise and wear, but is particularly difficult to study due to impact's non-linear nature. To begin transferring concepts studied purely analytically to the world of physical mechanisms, four experiments are outlined, and important non-linear concepts highlighted with these systems. A linear oscillator with a kicked impact, an impacting forced pendulum, two impacting forced pendulums, and a cam follower pair are studied experimentally, with complementary numerical results.</p><p>Some important ideas highlighted are limit cycles, basins of attraction with many wells, grazing, various forms of coexistence, super-persistent chaotic transients, and liftoff. These concepts are explored using a variety of non-linear tools such as time lag embedding and stochastic interrogation, and discussions of their intricacies when used in non-smooth systems yield important observations for the experimentalist studying impacting systems. </p><p>The focus is on experimental results with numerical validation, and spends much time discussing identification of these concepts from an experiment-first mindset, rather than the more traditional analytical-first approach. As such a large volume of experimentally important information on topics such as transducers and forcing mechanism construction are included in the appendices.</p> / Dissertation