published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

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M.Ing. (Mechanical Engineering) / This report describes an investigation into structural damping in simple steel structures. More specifictly, an attempt is made to obtain and compare the logarithmic decrement for different types of steel structures. The effect that welded and rivetted connections have on the logarithmic decrement is also examined. Four different types of steel are used, namely: mild steel and three types of chromium based steel. Vibration tests are performed on both cantiliver and simple bridge structures. An estimate of the inherent damping that is present in the vibrating structures are obtained from the approximate displacement-time response plots (as obtained from vibration tests). All the step input tests are modelled with a finite element. computer package to test the accuracy of the approximated response functions. Shaker tests are also performed on bridge structures. On the theoretical side the term damping is fully defined and discussed.

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

Two major areas were studied in this research to achieve more efficient and optimised method for the prediction of ship motion, and this research has two aims. The first aim was to improve an algorithm of the oscillatory problems for strip theory by means of reducing numerical integration using the desingularised method. A new way of distributing point sources was developed by the author in order to solve the boundary problem on the source distribution. Results showed that desingularsation can be utilised on rounded hull shapes. Although the desingularsation process reduces the computational time, the conventional method is more robust and stable due to the simple source panel distribution. The second aim was an investigation of viscous roll damping of ship motion with the influence of forward velocity, and several numerical simulations were developed in order to support wind-tunnel experimentation. The wind tunnel experimentation was conducted by using a 1.2 m NACA6521 modified cylindrical-bulb model to investigate the viscous effect on the rolling motion of the ship. Since viscous damping was very small under restrictions from the experimental condition, a normal method of collecting data of roll motion, in which a device is physically attached on the bulb model, was not suitable. As a solution, remote sensing was utilised to capture the motion picture by a digital video camera. A visual analysis was then conducted to obtain data of the roll motion of the bulb model inside the wind-tunnel test section. Two different numerical simulations were developed under the hypothesis that the forward velocity influences the boundary layer generation to cause viscous roll damping on the ship model hull. The first numerical simulation uses the energy method to produce damping coefficients, and the second numerical simulation requires solving the motion of equation numerically. It was discovered that the increase of forward velocity results in a linear increase of the viscous damping coefficient. The numerical simulation and experimental data agree closely. Therefore, the theory used to predict the viscous roll damping was shown to be reasonably accurate.

This thesis documents a PhD level research program, undertaken at the Industrial Institute Swinburne, Swinburne University of Technology between the years of 1997 and 2000. The research program investigated electromagnetic energy regenerative vibration damping; the process of recovering energy from damped, vibrating systems. More specifically, the main research objective was to determine the performance of regenerative damping for the application of vehicle suspension systems. This question emerged due to the need for continuous improvement of vehicle efficiency and the potential benefits possible from the development of regenerative vehicle suspension. It was noted, at the outset of this research, that previous authors had undertaken research on particular aspects of regenerative damping systems. However in this research, the objective was to undertake a broader investigation which would serve to provide a deeper understanding of the key factors. The evaluation of regenerative vibration damping performance was achieved by developing a structured research methodology that began with analysing the overall requirements of regenerative damping and, based on these requirements, investigated several important design aspects of the system. The specific design aspects included an investigation of electromagnetic machines for use as regenerative damping devices. This analysis concentrated on determining the most promising electromagnetic device construction based on its damping and regeneration properties. The investigation then proceeded to develop an 'impedance-matching' regenerative interface, in order to control the energy flows in the system. This form of device had not been previously developed for electromagnetic vibration damping, and provided a significant advantage in maximising energy regeneration while maintaining damping control. The results from this analysis, when combined with the issues of integrating such a system in vehicle suspension, were then used to estimate the overall performance of regenerative damping for vehicle suspension systems. The methodology and findings in this research program provided a number of contributing elements to the field, and provided an insight into the development of regenerative vehicle systems. The findings revealed that electromagnetic regenerative vibration damping may be feasible for applications such as electric vehicles in which energy efficiency is a primary concern, and may have other applications in similar vibrating systems.

Thesis (M.S.)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1982. / Includes bibliographical references (leaves 151-153).

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 344-354).