The aim of the thesis is to propose active damping as a potential control strategy for chatter instability in machine tools. The regenerative process theory explains chatter as a closed loop interaction between the structural dynamics and the cutting process. This is considered to be the most dominant reason behind machine tool chatter although other instability causing mechanisms exist. The stability lobe diagram provides a quantitative idea of the limits of stable machining in terms of two physical parameters: the width of contact between tool and the workpiece, called the width of cut and the speed of rotation of the spindle. It is found that the minimum value of the stability limit is proportional to the structural damping ratio for turning operations. This important finding provides the motivation of influencing the structural dynamics by active damping to enhance stability limits of a machining operation. A direct implementation of active damping in an industrial environment may be difficult. So an intermediate step of testing the strategy in a laboratory setup, without conducting real cutting is proposed. Two mechatronic "Hardware in the Loop" simulators for chatter in turning and milling are presented, which simulate regenerative chatter experimentally without conducting real cutting tests. A simple cantilever beam, representing the MDOF dynamics of the machine tool structure constitutes the basic hardware part and the cutting process is simulated in real time on a DSP board. The values of the cutting parameters such as spindle speed and the axial width of cut can be changed on the DSP board and the closed loop interaction between the structure and the cutting process can be led to instability. The demonstrators are then used as test beds to investigate the efficiency of active damping, as a potential chatter stabilization strategy. Active damping is easy to implement, robust and does not require a very detailed model of the structure for proper functioning, provided a collocated sensor and actuator configuration is followed. The idea of active damping is currently being implemented in the industry in various metal cutting machines as part of the European Union funded SMARTOOL project (www.smartool.org), intended to propose smart chatter control technologies in machining operations.

The vibration damping property of plant fibres composites is of practical interest for commercial applications of biobased and eco-composites. Damping behaviour has been observed by experimentation and exploited in the marketing of sporting equipment but the origins of this behaviour have so far been only based on conjectures. In this thesis, the damping capacity of plant fibre composites was attributed to their chemical composition and the reversible interactions enabled by the breaking and reforming of hydrogen bonds under stress. The approach to explaining the mechanisms started with the characterisation of different plant fibre types to search for correlations between their physical and chemical structure. The investigation continued with quantifying the effect of hydrogen bonding compounds such as water, glycerol and polyglycerol on the damping coefficient of fibres and reinforced composites. The results of the polyol impregnation indicated that applying a pretreatment enhanced the vibration damping performance of flax reinforced composites, validating the hypothesis of the essential role played by hydrogen bonds in the fibres. The improvement in the damping coefficient of the composites was shown to be to the detriment of their stiffness. The compromised between the two properties was investigated in the final part of this thesis by using hybrid flax-carbon fibre reinforced composites.

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The piano first came into existence about 1709, but until the 1770's it was probably used most successfully as an accompanying instrument because of the small volume of tone it could produce. In its earlier stages the piano was not capable of producing even as big a tone as a large. sized harpsichord, During these seventy years piano builders experimented a great deal with the piano and its mechanisms, As with any instrument, some ideas were kept and improved, and others were tried and then discarded.

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Chan Kwong-wah. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 85-87). / Abstracts in English and Chinese. / LIST OF FIGURES --- p.vii / LIST OF TABLES --- p.xi / Chapter 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.1.1 --- Vibration Control --- p.1 / Chapter 1.1.2 --- Passive Damping and Particle Damping Technology --- p.2 / Chapter 1.2 --- Literature Review --- p.4 / Chapter 1.3 --- Research Objective --- p.7 / Chapter 1.4 --- Organization of the Thesis --- p.7 / Chapter 2 --- PARTICLE DAMPING CHARACTERISTICS AND FEASIBILITY --- p.9 / Chapter 2.1 --- Particle Damping Characteristics --- p.9 / Chapter 2.1.1 --- Energy Balance in SDOF System --- p.9 / Chapter 2.1.2 --- Energy Dissipation Mechanisms in Particle Damping --- p.10 / Chapter 2.2 --- Particle Damping Feasibility --- p.15 / Chapter 2.2.1 --- Cantilever Beam Experiment with Free Vibration --- p.15 / Chapter 2.2.2 --- Effectiveness of Particle Damping --- p.17 / Chapter 3 --- A STUDY ON PACKING RATIO AND GRANULE SIZE --- p.19 / Chapter 3.1 --- Experimental Setup --- p.19 / Chapter 3.2 --- Effect of Packing Ratio --- p.23 / Chapter 3.3 --- Effect of Granule Size --- p.24 / Chapter 3.4 --- Damping Ratio Estimation --- p.25 / Chapter 3.5 --- Trends of Damping Ratio against Packing Ratio --- p.28 / Chapter 3.6 --- Trends of Damping Ratio against Granule Size --- p.32 / Chapter 3.7 --- Conclusions --- p.35 / Chapter 4 --- APPLICATION OF PARTICLE DAMPING ON BOND ARM --- p.36 / Chapter 4.1 --- Identification of Structural Vibration --- p.37 / Chapter 4.2 --- Finite Element Modeling --- p.39 / Chapter 4.2.1 --- Model of Bond Arm --- p.39 / Chapter 4.2.2 --- Material Properties --- p.40 / Chapter 4.2.3 --- Modes of Frequencies --- p.40 / Chapter 4.2.4 --- Mode Shapes of Bond Arm --- p.41 / Chapter 4.3 --- Experimental Setup and Procedure --- p.41 / Chapter 4.4 --- Design of Particle Enclosure --- p.43 / Chapter 4.5 --- System Parametric Study --- p.44 / Chapter 4.5.1 --- Effect of Granule Sizes --- p.44 / Chapter 4.5.2 --- Effect of Packing Ratios --- p.47 / Chapter 4.5.3 --- Effect of Different Materials of Particle Enclosure --- p.50 / Chapter 4.5.4 --- Effect of Structural Form of Enclosure --- p.52 / Chapter 4.5.5 --- Effect of Number of Chambers Filled --- p.53 / Chapter 4.5.6 --- Effect of Different Locations of Particle Enclosure --- p.55 / Chapter 4.6 --- Conclusions --- p.56 / Chapter 5 --- TEST AND ANALYSIS OF BOND HEAD STAND WITH PARTICLE DAMPING --- p.57 / Chapter 5.1 --- Ways of Implementation --- p.58 / Chapter 5.1.1 --- Factor of Mode Shape --- p.59 / Chapter 5.1.2 --- Stress Concentration Analysis --- p.59 / Chapter 5.2 --- Experimental Setup --- p.60 / Chapter 5.3 --- Bond Head Stand with Small Force Excitation --- p.62 / Chapter 5.3.1 --- Measurement Data --- p.62 / Chapter 5.4 --- Bond Head Stand with Large Force Excitation --- p.70 / Chapter 5.5 --- Effect of Packing Ratio at Different Frequency Ranges --- p.71 / Chapter 5.6 --- Discussions --- p.80 / Chapter 6 --- CONCLUSION --- p.82 / Chapter 6.1 --- Summary --- p.82 / Chapter 6.2 --- Future Work --- p.84 / BIBLIOGRAPHY --- p.85 / APPENDIX

by Jia, Jiangying. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves ). / Abstracts in English and Chinese. / ABSTRACT --- p.i / 摘要 --- p.ii / ACKNOWLEDGEMENTS --- p.iii / TABLE OF CONTENTS --- p.iv / LIST OF FIGURES --- p.vii / LIST OF TABLES --- p.ix / Chapter CHAPTER ONE --- INTRODUCTION --- p.1 / Chapter 1.1 --- Background --- p.2 / Chapter 1.1.1 --- Vibration damping --- p.2 / Chapter 1.1.2 --- Carbon nanotubes --- p.4 / Chapter 1.1.3 --- Fabrication of carbon nanotube composites --- p.8 / Chapter 1.1.4 --- Literature review on carbon nanotube composites --- p.10 / Chapter 1.2 --- Research Objective --- p.13 / Chapter 1.3 --- Thesis Organization --- p.14 / Chapter CHAPTER TWO --- FABRICATION OF CNT AND CNT/EPOXY COMPOSITES --- p.15 / Chapter 2.1 --- Fabrication of CNT --- p.16 / Chapter 2.1.1 --- Fabrication requirements --- p.16 / Chapter 2.1.2 --- Substrate and catalyst preparation --- p.17 / Chapter 2.1.3 --- Aligned CNT film grown by PECVD method --- p.18 / Chapter 2.2 --- Fabrication of CNT/Epoxy Composite --- p.25 / Chapter 2.3 --- Measurement of CNT/Epoxy Composites --- p.31 / Chapter 2.4 --- Chapter Summary --- p.34 / Chapter CHAPTER THREE --- MODELLING OF THE CNT COMPOSITES --- p.35 / Chapter 3.1 --- Geometrical Configuration of Composites --- p.36 / Chapter 3.2 --- Critical Shear Stresses and “Stick-Slip´ح Behavior --- p.38 / Chapter 3.3 --- Nonlinear Viscoelastic Composite Model --- p.40 / Chapter 3.3.1 --- Maxwell model --- p.40 / Chapter 3.3.2 --- Three-parameter standard solid model --- p.45 / Chapter 3.4 --- Stress and Strain Evaluation --- p.50 / Chapter 3.5 --- Effective Moduli and Loss Factor of Composite --- p.56 / Chapter 3.6 --- Chapter Summary --- p.60 / Chapter CHAPTER FOUR --- PARAMETRIC STUDY OF THE CNT COMPOSITES --- p.61 / Chapter 4.1 --- Carbon Nanotube Dimensions --- p.62 / Chapter 4.2 --- Parametric Study --- p.65 / Chapter 4.3 --- Summary --- p.69 / Chapter CHAPTER FIVE --- CONCLUSIONS AND FUTURE WORK --- p.70 / Chapter 5.1 --- Conclusions --- p.70 / Chapter 5.2 --- Future Work --- p.72 / BIBLIOGRAPHY --- p.73 / APPENDIX --- p.78 / Chapter A. --- Epoxy Resin Datasheet --- p.78 / Chapter B. --- Matlab Program for Young´ةs Modulus Calculation --- p.80 / Chapter C. --- Matlab Program for Loss Factor Calculation --- p.82