Reduction of power consumption in ultrasonic linear motor for linear translation by partially laminated actuators

Doctor of Philosophy (Mechanical Engineering), 201

Modeling and optimization of ultrasonic linear motors

Ultrasonic motors have received much attention these last years, in particular with regard to their modeling and their design principle. Their operating principle is based on piezoelectric ceramics that convert electrical energy into mechanical energy in the form of vibrations of an elastic body whose surface points perform an elliptic motion with a frequency in the ultrasonic range (≥ 20 kHz). The moving part, which is pressed against the vibrating body by a prestressing force, can move thanks to the friction forces presented at the interface between the stator (resonator) and the rotor (slider). Their specific properties make ultrasonic motors a very attractive solution for a direct transmission for different applications like precise positioning devices. Indeed, they present the possibility to obtain unlimited motions, high resolution and excellent dynamics of positioning. Then, it is obvious that ultrasonic motors could be used in new application fields, in particular to replace conventional electromagnetic motors. However, they have to overcome two principal difficulties: their efficiency is rather poor and they are often too expensive. Moreover, their use in the car industry or for the positioning of axes in machine tools for example requires driving forces and velocities higher than those which they currently present. Analytical modeling of such motors is not obvious and assumptions that are made are often too restrictive. This is why the use of a numerical modeling (3-D) is necessary to model the behavior of this type of motors. Thus, finite element simulations are used but they often require high computing times. To avoid it, the number of simulations can be decreased by choosing the input parameters (dimensions, materials, boundary conditions,...) more judiciously according to their influence on the output parameters. Thus, one can obtain the sensitivity of an input parameter on the value of the output parameter. With this intention, the application of design of experiments has been adopted in this thesis work. This methodology, applied to finite element simulations, is an innovative technique in the field of theoretical modeling of such motors. This methodology is particularly interesting in sight of predicting the results but also to find out an optimal set of input parameters for the motor. According to the results obtained and presented in this thesis work, the use of design of experiments in the field of ultrasonic motors modeling proves to be very promising and demonstrates to be a powerful tool. The application of the proposed methodology for the optimization of an ultrasonic linear motor used for the auto-focus function of the lens of an optical system also made it possible to show the validity and the potential of this optimization method

Advances in Vibration Analysis Research

Vibrations are extremely important in all areas of human activities, for all sciences, technologies and industrial applications. Sometimes these Vibrations are useful but other times they are undesirable. In any case, understanding and analysis of vibrations are crucial. This book reports on the state of the art research and development findings on this very broad matter through 22 original and innovative research studies exhibiting various investigation directions. The present book is a result of contributions of experts from international scientific community working in different aspects of vibration analysis. The text is addressed not only to researchers, but also to professional engineers, students and other experts in a variety of disciplines, both academic and industrial seeking to gain a better understanding of what has been done in the field recently, and what kind of open problems are in this area

Low velocity impact energy absorption of fibrous metal-matrix composites using smart materials.

Thesis (Ph.D.)-University of Natal,Durban,2003.In general, the basic concept of an intelligent material is defined as the multifunctional material that has a sensor, a processor and an actuator function in the material that allows it to maintain optimum conditions in response to environmental changes. Despite the fact that these materials have demonstrated varying degrees of success in shape and position control, active and passive control of vibration and acoustic transmission of materials subjected to dynamic loads, impact damage and creep resistance in structures and have been applied in industries from aerospace to biomechanics to civil engineering structures, very little literature is available on the subject. Thus, the objective of this dissertation is to add to the fundamental understanding of the behaviour of these special materials by investigating the possibility of a magnetostrictive SMA hybrid metalmatrix composite beam with piezoelectric actuator, to enhance the materials load attenuation and energy absorption characteristics under low velocity impact loading. The methodology employed in this investigation is driven by two primary factors. The first is the unique approach that the author puts forward to attempt to simplify the characterisation of damage in not just metal matrix composites, but in materials in general. The second factor is the lack of available literature on smart material energy absorption as well as a lack of precise theory for short fibre composites. The methodology includes an extensive literature review, the development of an analytical model, based on the new damage modulus approach, verification of the model using experimental results presented by Agag et. aI., adjustment of the model to include smart material effects and finally numerical simulation using the MATLAB® software to predict the effect of smart materials on the energy absorption capacity of the material under impact. The results show that the damage modulus (ED) is a material characteristic and can be derived from the stress strain diagram. Further, it takes into account degradation of the material through the plastic region, up to the point just before ultimate failure. Thus, ED lends itself to the simplification of many damage models in terms of a reducing sustainable load and energy absorption capacity. Only the energy consumed through material rupture remains to be characterised. The results also show that smart fibres diminish the capacity of the beam to sustain a load, but increase the displacement to failure. Thus, for a compatible substrate material, this increased displacement translates to a significant enhancement of energy absorption characteristics. The effect of prestrain on energy absorption is also considered and there appears to be a definite turning point where the dissertation thus achieves its objective in investigating the ability of smart materials to enhance the energy absorption characteristics of regular fibre reinforced metal-matrix composite materials subject to low velocity impact loading. Of equal importance to the achievement of this objective is the introduction in the dissertation of the unique damage modulus that goes to the foundation of material characterisation for mechanical engineering design and has profound implications in damage theory and future design methodologies. Significant learning has taken place in the execution of this PhD endeavour and this dissertation will no doubt contribute to other investigations in the field of smart materials

Cumulative index to NASA Tech Briefs, 1963-1967

Cumulative index to NASA survey on technology utilization of aerospace research outpu

Microfluidics and Nanofluidics Handbook

The Microfluidics and Nanofluidics Handbook: Two-Volume Set comprehensively captures the cross-disciplinary breadth of the fields of micro- and nanofluidics, which encompass the biological sciences, chemistry, physics and engineering applications. To fill the knowledge gap between engineering and the basic sciences, the editors pulled together key individuals, well known in their respective areas, to author chapters that help graduate students, scientists, and practicing engineers understand the overall area of microfluidics and nanofluidics. Topics covered include Finite Volume Method for Numerical Simulation Lattice Boltzmann Method and Its Applications in Microfluidics Microparticle and Nanoparticle Manipulation Methane Solubility Enhancement in Water Confined to Nanoscale Pores Volume Two: Fabrication, Implementation, and Applications focuses on topics related to experimental and numerical methods. It also covers fabrication and applications in a variety of areas, from aerospace to biological systems. Reflecting the inherent nature of microfluidics and nanofluidics, the book includes as much interdisciplinary knowledge as possible. It provides the fundamental science background for newcomers and advanced techniques and concepts for experienced researchers and professionals