Application of mechanical micromachining for fabricating complex three-dimensional (3D) micro-scale features and small parts on a broad range of materials has increased significantly in the recent years. In particular, mechanical micromachining finds applications in manufacturing of biomedical devices, tribological surfaces, energy storage/conversion systems, and aerospace components. Effectively addressing the dual requirements for high accuracy and high throughput for micromachining applications necessitates understanding and controlling of dynamic behavior of micromachining system, including positioning stage, spindle, and the (micro-) tool, as well as their coupling with the mechanics of the material removal process. The dynamic behavior of the tool-collet-spindle-machine assembly, as reflected at the cutting edges of a micro-tool, often determines the achievable process productivity and quality. However, the common modeling techniques (such as beam based approaches) used in macro-scale to model the dynamics of cutting tools, cannot be used to accurately and efficiently in micro-scale case. Furthermore, classical modal testing techniques poses significant challenges in terms of excitation and measurement requirements, and thus, new experimental techniques are needed to determine the speed-dependent modal characteristics of miniature ultra-high-speed (UHS) spindles that are used during micromachining. The overarching objective of this thesis is to address the aforementioned issues by developing new modeling and experimental techniques to accurately predict and analyze the dynamics of micro-scale cutting tools and miniature ultra-high-speed spindles, including rotational effects arising from the ultra high rotational speeds utilized during micromachining, which are central to understanding the process stability. Accurate prediction of the dynamics of micromachining requires (1) accurate and numerically-efficient analytical approach to model the rotational dynamics of realistic micro-tool geometries that will capture non-symmetric bending and coupled torsional/axial dynamics including the rotational/ gyroscopic effects; and (2) new experimental approaches to accurately determine the speed-dependent dynamics of ultra-high-speed spindles. The dynamic models of cutting tools and ultra-high-speed spindles developed in this work can be coupled together with a mechanistic micromachining model to investigate the process stability of mechanical micromachining. To achieve the overarching research objective,first, a new three-dimensional spectral- Tchebychev approach is developed to accurately and efficiently predict the dynamics of (micro) cutting tools. In modeling the cutting tools, considering the efficiently and accuracy of the solution, a unified modeling approach is used. In this approach, the shank/taper/extension sections, vibrational behavior of which exhibit no coupling between different textural motion, of the cutting tools are modeled using one-dimensional (1D) spectral-Tchebychev (ST) approach; whereas the fluted section (that exhibits coupled vibrational behavior) is modeled using the developed 3D-ST approach. To obtain the dynamic model for the entire cutting tool, a component mode synthesis approach is used to `assemble' the dynamic models. Due to the high rotational speeds needed to attain high material removal rate while using micro tools, the gyroscopic/rotational effects should be included in predicting the dynamic response at any position along the cutting edges of a micro-tool during its operation. Thus, as a second step, the developed solution approach is improved to include the effects arising from the high rotational speeds. The convergence, accuracy, and efficiency of the presented solution technique is investigated through several case studies. It is shown that the presented modeling approach enables high-fidelity dynamic models for (micro-scale) cutting-tools. Third, to accurately model the dynamics of miniature UHS spindles, that critically affect the tool-tip motions, a new experimental (modal testing) methodology is developed. To address the deficiency of traditional dynamic excitation techniques in providing the required bandwidth, repeatability, and impact force magnitudes for accurately capturing the dynamics of rotating UHS spindles, a new impact excitation system (IES) is designed and constructed. The developed system enables repeatable and high-bandwidth modal testing of (miniature and compliant) structures, while controlling the applied impact forces on the structure. Having developed the IES, and established the experimental methodology, the speed-dependent dynamics of an air bearing miniature spindle is characterized. Finally, to show the broad impact of the develop modeling approach, a macro-scale endmill is modeled using the presented modeling technique and coupled to the dynamics of a (macro-scale) spindle, that is obtained experimentally, to predict the tool-point dynamics. Specific contributions of this thesis research include: (1) a new 3D modeling approach that can accurately and efficiently capture the dynamics of pretwisted structures including gyroscopic effects, (2) a novel IES for repeatable, high-bandwidth modal testing of miniature and compliant structures, (3) an experimental methodology to characterize and understand the (speed-dependent) dynamics of miniature UHS spindles.

In 1967 the US Air Force solicited proposals for ``low-disc-loading [Vertical Takeoff and Landing] configurations suitable for high speed flight.' Bell Helicopter elected to respond with a proposal after initial analysis on configurations including a stopped edgewise disc and a trail rotor. They concluded that a folding proprotor design would best meet the requirements laid forth. Initial analysis work began on this folding proprotor (stop-fold) design in the same year and concluded in 1972 with a full scale 25 foot diameter pylon and rotor assembly wind tunnel test at the NASA-Ames Large Scale Wind Tunnel. The project was concluded at this point and never resulted in a production or research aircraft. The original proposed stop-fold tiltrotor design by Bell Helicopter allowed for vertical takeoff and landing, a transition sequence rotating the pylon rotor assembly from helicopter to airplane mode, a conversion sequence during which the rotor stopped and blades folded along the pylon, and a transition from prop thrust to auxiliary jet engine power while the rotor was being stopped. This configuration effectively removes the high-speed restraints typical of a prop-driven aircraft and instead opens a flight envelope comparable to a fixed-wing jet. This project entails both the simulation and basic analysis of the stop-fold concept with special attention to frequency responses and potential coupling between modes.

Excessive vibrations continue to be a major hurdle in improving machining efficiency and achieving stable high speed cutting. To overcome detrimental vibrations, an enhanced understanding of the underlying nonlinear dynamics is required. Cutting instability is commonly studied through modeling and analysis which incorporates linearization that obscures the true nonlinear characteristics of the system which are prominent at high speeds. Thus to enhance cutting dynamics knowledge, a comprehensive nonlinear turning model that includes tool-workpiece interaction is experimentally validated using a commercial laser vibrometer to capture tool and workpiece vibrations. A procedure is developed to use instantaneous frequency for experimental time-frequency analysis and is shown to thoroughly characterize the underlying dynamics and identify chatter. For the tests performed, chatter is associated with changing spectral components and bifurcations which provides a view of the underlying dynamics not experimentally observed before. Validation of the turning model revealed that the underlying dynamics observed experimentally are accurately captured, and the coupled tool-workpiece chatter vibrations are simulated. The stability diagram shows an increase in the chatter-free limit as the spindle speed increases until 1500rpm where it begins to level out. At high speeds the workpiece dominates the dynamics, and excessive workpiece vibrations create another stability limit to consider. Thus, workpiece dynamics should not be neglected in analyses for the design of machine tools and robust control laws. The chip formation mechanisms and high speeds make micro-milling highly non-linear and capable of producing broadband frequencies that negatively affect the tool. A nonlinear dynamic micro-milling model is developed to study the effect of parameters on tool performance through spectral analysis using instantaneous frequency. A lumped mass-spring-damper system is assumed for modeling the tool, and a slip-line force mechanism is adopted. The effective rake angle, helical angle, and instantaneous chip thickness are accounted for. The model produced the high frequency force components seen experimentally in literature. It is found that increasing the helical angle decreased the forces, and an increase in system stiffness improved the dynamic response. Also, dynamic instability had the largest effect on tool performance with the spindle speed being the most critical parameter.

A comprehensive understanding of high-speed liquid jets is required for their introduction into engine and combustion applications. Their transient nature, short lifetime, unique characteristics and the inability to take many experimental readings, has inhibited this need. This study investigates the outflow of a high-speed liquid jet into quiescent atmospheric air. The key characteristics present are, a bow shock wave preceding the jet head, an enhanced mixing layer and the transient deformation of the liquid jet core. The outflow regime is studied in an experimental and numerical manner. In the experimental investigation, a high-speed liquid water jet is generated using the momentum exchange by impact method. The jet velocity is supersonic with respect to the impinged gaseous medium. The resulting jet speed is Mach 1.8. The jet is visualised with the use of shadowgraph apparatus. Visualisation takes place over a variety of time steps in the liquid jet???s life span and illustrates the four major development stages. The stages progress from initial rapid core jet expansion to jet stabilisation and characteristic uniform gradient formation. The visualisation shows that at all stages of the jet???s life it is axi-symmetric. One dimensional nozzle analysis and a clean bow shock wave indicate that the pulsing jet phenomenon can be ignored. In the numerical investigation, a time marching finite volume scheme is employed. The bow shock wave characteristics are studied with the use of a blunt body analogy. The jet at a specific time frame is considered a solid body. The jet shape is found to have an important influence on the shock position and shape. Analysis of the results indicates a shock stand-off similar to that seen in experimental observations and the prediction of shock data. The jet life span is modelled using a species dependent density model. The transient calculations reproduce the key jet shape characteristics shown in experimental visualisation. The mushrooming effect and large mixing layer are shown to develop. These effects are strongest when the shock wave transience has yet to stabilise. Quantitative analysis of the mixing layer at varying time steps is presented.

Thesis (Ph.D.) -- McMaster University, 1997. / Includes bibliographical references (leaves 196-205). Also available via World Wide Web.

Thesis (Ph.D.) - Carleton University, 2002. / Includes bibliographical references (p. 159-172). Also available in electronic format on the Internet.

Thesis (M.App.Sc.) - Carleton University, 2003. / Includes bibliographical references (p. 121-128). Also available in electronic format on the Internet.

Thesis (M. App. Sc.)--Carleton University, 2003. / Includes bibliographical references (p. 113-122). Also available in electronic format on the Internet.

Thesis (M.App.Sc.) - Carleton University, 2005. / Includes bibliographical references. Also available in electronic format on the Internet.

Thesis (M.App.Sc.) - Carleton University, 2005. / Includes bibliographical references (p. 126-132). Also available in electronic format on the Internet.