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Approved for public release, distribution is unlimited / Damping of welded structures is a subject of great interest and application for the navy as relates to ship shock survivability and acoustic transmission of ship noise. The purpose of this research is to study the effects of welding on damping. A generic model of a warship's hull structure was used to study damping effects. The model's natural frequencies and mode shapes were calculated using a finite element model prior to model testing. The frequency response and natural frequencies of the model were determined experimentally by exciting the model and measuring the response throughout the structure using Frequency Response Functions (FRF's). The results were compared with the finite element modeling. The damping ratio of the model in relation to position from excitation was calculated using the half-power point method and then a more detailed analysis of frequency dependent damping versus position was made using modal parameter extraction using the Complex Exponential Method. / Lieutenant, United States Navy

磁流變阻尼器可用於各種動態系統的半主動振動控制，非常有前景。在當前的磁流變阻尼器系統中，需要使用外加并分離的電源和動態傳感器。本論文提出并探索了自供能自傳感磁流變阻尼器。它將能源採集、動態傳感和磁流變阻尼三種技術集成到同一器件中，具有內置的發電機制，和速度/位移傳感能力。此多功能的集成可以對當前的磁流變阻尼器系統帶來眾多的益處，如更節能、更高的可靠性、尺寸及重量的減少、較低的成本、以及更少的維護需求。該研究成果可以促進各種動態系統，如懸架系統和義肢的發展。 / 在論文中，作者對自供能自傳感磁流變阻尼器的概念、原理、設計方法、設計難點及解決方案進行了探討，設計製作了兩件原型，並對原型進行了性能測試。作者提出并探索了幾種可與磁流變阻尼器集成的發電機制，和動態傳感的方法。對發電、動態傳感和阻尼力三種性能，進行了建模、理論分析、以及實驗驗證。作者提出并驗證了自供能自傳感磁流變阻尼器的數學模型，該模型考慮了單獨的功能以及多功能間的相互作用。本論文對自供能磁流變阻尼器系統進行了探討分析，包括能源產生與磁流變阻尼的相互作用、自供能判據、工作範圍和設計指引。還提出并探索了一個自供能控制器，以及一種複合的磁場隔離方法。 / Magnetorheological (MR) dampers are promising for semi-active vibration control of various dynamic systems. In the current MR damper system, separate power supply and dynamic sensor are required. This research is aimed to propose and investigate self-powered, self-sensing (SPSS) MR dampers, which integrate energy harvesting, sensing and MR damping technologies into one device. SPSS MR damper has self-contained power generation and velocity/displacement sensing capabilities. This multifunctional integration will bring great benefits such as energy saving, higher reliability, size and weight reduction, lower cost, and less maintenance for the use of MR damper systems. It will advance the technology of various dynamic systems such as suspensions and prostheses. / Concepts, principles, design methodology, key issues and solutions of SPSS MR dampers are studied. Two prototypes of the SPSS MR dampers are designed, fabricated, and tested. Several integrated power generation and sensing methods for MR dampers are proposed and investigated. Modeling, theoretical analyses, and experimental studies on power generation ability, sensing capability and damping force performances are conducted. Models of SPSS MR dampers considering individual functions and interactions are developed and validated experimentally. Systematic studies on the self-powered MR damper system are performed, including interaction between the power generation and MR damping, self-powered criterion, working range and design guidelines. Moreover, a self-powered controller and combined magnetic-field isolation method are proposed and investigated. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Chen, Chao. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 163-172). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / ABSTRACT --- p.i / 摘要 --- p.iii / TABLE OF CONTENTS --- p.vii / LIST OF FIGURES --- p.xi / LIST OF TABLES --- p.xvii / Chapter 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Background and Motivation --- p.2 / Chapter 1.1.1 --- MR fluids --- p.2 / Chapter 1.1.2 --- MR dampers --- p.3 / Chapter 1.1.3 --- Previous research on functional integration of MR dampers --- p.7 / Chapter 1.2 --- Research Objective --- p.10 / Chapter 1.3 --- Thesis Organization --- p.12 / Chapter 2 --- DESIGN OF SELF-POWERED, SELF-SENSING MR DAMPERS --- p.13 / Chapter 2.1 --- Concept and Key Issues of Multifunctional Integration --- p.14 / Chapter 2.2 --- Configurations of Different Methods of Multiple Functions --- p.17 / Chapter 2.3 --- Principles of SPSS MR Dampers --- p.18 / Chapter 2.3.1 --- Structure and operation principle of the first prototype --- p.18 / Chapter 2.3.2 --- Structure and operation principle of the second prototype --- p.21 / Chapter 2.3.3 --- Energy flow of SPSS MR damper --- p.25 / Chapter 2.4 --- Materials Used in Design --- p.27 / Chapter 2.5 --- Fabrication of Prototypes --- p.32 / Chapter 2.6 --- Experimental Setup --- p.35 / Chapter 2.7 --- Chapter Summary --- p.37 / Chapter 3 --- POWER GENERATION OF SELF-POWERED, SELF-SENSING MR DAMPERS --- p.39 / Chapter 3.1 --- Introduction to Electromagnetic Energy Harvesting --- p.40 / Chapter 3.2 --- Finite Element Method --- p.42 / Chapter 3.3 --- Slotted Power Generation Method --- p.44 / Chapter 3.3.1 --- Modeling and analysis of slotted power generation --- p.44 / Chapter 3.3.2 --- Experimental results of slotted power generation --- p.52 / Chapter 3.4 --- Slotless Power Generation Method --- p.56 / Chapter 3.4.1 --- Design considerations --- p.56 / Chapter 3.4.2 --- Modeling and analysis of slotless power generation --- p.57 / Chapter 3.4.3 --- Experimental results of slotless power generation --- p.62 / Chapter 3.5 --- Frequency Multiplication Effect of Generated Voltage --- p.65 / Chapter 3.6 --- Chapter Summary --- p.67 / Chapter 4 --- SENSING OF SELF-POWERED, SELF-SENSING MR DAMPERS --- p.69 / Chapter 4.1 --- Introduction to Self-sensing Ability --- p.70 / Chapter 4.1.1 --- Self-sensing for vibration control --- p.70 / Chapter 4.1.2 --- Self-sensing of SPSS MR damper --- p.71 / Chapter 4.2 --- Moving-spacer Velocity Sensing Method --- p.73 / Chapter 4.3 --- Velocity-extraction Method from Slotted Power Generator --- p.80 / Chapter 4.4 --- Velocity-extraction Method from Slotless Power Generator --- p.86 / Chapter 4.5 --- Chapter Summary --- p.90 / Chapter 5 --- DAMPING FORCE OF SELF-POWERED, SELF-SENSING MR DAMPERS --- p.93 / Chapter 5.1 --- Design of MR Damping Part --- p.94 / Chapter 5.2 --- Testing Results of MR Damping Force of the First Prototype --- p.97 / Chapter 5.3 --- Testing Results of Damping Force of the Improved Prototype --- p.101 / Chapter 5.4 --- Damping Force Modeling and Identification --- p.105 / Chapter 5.5 --- Chapter Summary --- p.110 / Chapter 6 --- INTERACTION ANALYSIS --- p.111 / Chapter 6.1 --- Modeling Summary and Magnetic Field Interactions of SPSS MRD --- p.112 / Chapter 6.1.1 --- Modeling summary of SPSS MR dampers --- p.112 / Chapter 6.1.2 --- Magnetic field interactions --- p.114 / Chapter 6.2 --- Analysis of a Versatile Self-powered MR Damper System --- p.122 / Chapter 6.3 --- Application to Vehicle Suspension Systems --- p.130 / Chapter 6.3.1 --- Modeling of suspension system --- p.131 / Chapter 6.3.2 --- Working range and vibration control efficiency under on-off controller --- p.133 / Chapter 6.4 --- Design Guidelines of Self-powered Working Range --- p.141 / Chapter 6.5 --- A Proposed Self-powered Controller --- p.146 / Chapter 6.6 --- Chapter Summary --- p.153 / Chapter 7 --- CONCLUSION AND FUTURE WORK --- p.155 / Chapter 7.1 --- Conclusion --- p.155 / Chapter 7.2 --- Future Work --- p.160 / Chapter 8 --- BIBLIOGRAPHY --- p.163 / Chapter 9 --- APPENDIX --- p.173 / Chapter A. --- MR Fluid Datasheet --- p.173 / Chapter B. --- Sectional Views of Prototypes --- p.175

Bibliography: leaves 94-97. Electronic publication; full text available in PDF format; abstract in HTML format. Electronic reproduction.[Australia] :Australian Digital Theses Program,2001.

Vibrating machinery must be isolated from a supporting structure if the vibration is likely to cause fatigue of components or annoyance to people due to direct vibration exposure or from the noise radiated by the vibrating structure. Active vibration isolation can be applied in these situations to extend the low frequency performance of passive vibration isolators. In this thesis, theoretical and experimental investigations are described for a vibrating rigid body that is passively and actively isolated from a beam and a cylinder, respectively. The focus of the work is to investigate the vibrational power transmitted by translational forces and rotational moments into the support structure. For the investigation of the simply supported beam, a classical mathematical model is examined and finite element modelling is used to predict the power transmission into the beam when active vibration control is used. The results show that power transmission by moments is significant and cannot be ignored when the vibrational power transmission into the support structure is actively controlled. To control the power transmission by translational forces and rotational moments, a novel six axis active vibration isolator and a novel six axis force transducer were constructed to be used in the experimental investigations. Using vibrational power transmission as a cost function to be minimized in active control experiments presents unique problems because negative values of translational power transmission are possible when power transmission from rotational moments is ignored or when phase errors occur in the transducer outputs. Active control attempts which converge the cost function to a negative value of power transmission along a particular axis can result in overall vibration levels in the structure which are greater than without active control. To prevent the increase in vibration levels, minimization of the squared value of power transmission is investigated as a potential cost function. A method is described to combine force and velocity signals into a signal which is proportional to the vibrational power transmission and is suitable for use with an existing filtered-x Least Mean Squares controller, so that the squared vibrational power transmission can be minimized. Experimental trials were performed to actively minimize the power transmission into a simply supported beam from a vibrating rigid body using a single axis and a six axis active vibration isolator. The purpose of the experimental work was to confirm the theoretical findings and to find a practical method to measure power transmitted by rotational moments. The vibrational power transmission from a vibrating rigid body that is passively and actively isolated from a cylinder was also investigated. The theoretical model of the cylinder was similar to the beam model, although the dynamics of the cylinder makes the solution more complicated. Two experimental trials were conducted to verify the theoretical model and involved the use of the single axis and the six axis active vibration isolators, respectively. / Thesis (Ph.D.)--School of Mechanical Engineering, 1999.

Thesis (M.S.)--Oregon State University, 1985. / Typescript (photocopy). Includes bibliographical references (leaves 81-82). Also available on the World Wide Web.

Analysis of the dynamic behavior on structures is one vital aspect of designing structures such as buildings and bridges. Determination of the correct damping factor is of critical importance as it is the governing factor of dynamic design. Damping on structures exhibits a very complex behavior. Different models are suggested in literature to explain damping behavior. The usefulness of a valid damping model depends on how easily it can be adopted to analyze the dynamic behavior. Ease of mathematically representing the model and ease of analyzing the dynamic behavior by using the mathematical representation are the two determining aspects of the utility of the selected model. This thesis presents a parametric representation of non-linear damping models of the form presented by [Jea86] and the mathematical techniques to use the parametrically represented damping model in dynamic behavior analysis. In the damping model used in this thesis, the damping factor is proportional to the amplitude of vibration of the structure. However, determination of the amplitude again depends on the damping of the structure for a given excitation. Also, the equations which explain the behavior of motion are differential equations in a matrix form that is generally linearly inseparable. This thesis addresses these challenges and presents a numerical method to solve the motion equations by using Runge-Kutta techniques. This enables one to use a given non-linear model of the form proposed by [Jea86] to analyze the actual response of the structure to a given excitation from wind, seismic or any other source. Several experiments were conducted for reinforced concrete and steel framed buildings to evaluate the proposed framework. The non-linear damping model proposed by [Sat03], which conforms to [Jea86] is used to demonstrate the use of the proposed techniques. Finally, a new damping model is proposed based on the actual behavior and the serviceability criteria, which better explains the damping behavior of structures.

Key point to development of environmentally friendly timber structures, appropriate to urban ways of living, is the development of high-rise timber buildings. Comfort properties are nowadays one of the main limitations to tall timber buildings, and an enhanced knowledge on damping phenomena is therefore required, as well as improved prediction models for damping. The aim of this work has consequently been to estimate various damping quantities in timber structures. In particular, models have been derived for predicting material damping in timber members, beams or panels, or in more complex timber structures, such as floors. Material damping is defined as damping due to intrinsic material properties, and used to be referred to as internal friction. In addition, structural damping, defined as damping due to connections and friction in-between members, has been estimated for timber floors. The thesis consists of six main parts. The first part is entitled “Contexts”, and is composed of four chapters. A general overview of the wood material and its structural use in buildings is presented in Chapter 1. Chapter 2 gives a thorough literature review on comfort properties of (timber) floors. Chapter 1 and Chapter 2 serve as justifications for the motivation of this work, expressed in Chapter 3, and the aim of the work, expressed in Chapter 4. The next part “Backgrounds” briefly describes the basic theories used along the thesis, for the analytical studies (Chapter 5), the experimental studies (Chapter 6), and the numerical studies (Chapter 7). The part “State of the art” is a general literature review on damping (Chapter 8). A particular accent is set on the derivation of various damping prediction models. The “Research” part summarizes the original research work. Chapter 9 briefly presents the background and main findings for each study, and Chapter 10 concludes and proposes suggestions for further research. The studies are detailed in four journal papers, which are integrally reported in the “Publications” part. Paper I focuses on the evaluation of material damping in timber beam specimens with dimensions typical of common timber floor structures. Using the impact test method, 11 solid wood beams and 11 glulam beams made out of Norway Spruce (Picea Abies) were subjected to flexural vibrations. The tests involved different spans and orientations. A total of 420 material damping evaluations were performed, and the results are presented as mean values for each configuration along with important statistical indicators to quantify their reliability. The consistency of the experimental method was validated with respect to repeatability and reproducibility. General trends found an increasing damping ratio for higher modes, shorter spans, and edgewise orientations. It is concluded from the results that material damping is governed by shear deformation, which can be expressed more conveniently with respect to the specific mode shape and its derivatives. Paper II deals with the prediction of material damping in Timoshenko beams. Complex elastic moduli and complex stiffness are defined to derive an analytical model that predicts the hysteretic system damping for the whole member. The prediction model comprises two parts, the first related to bending, and the second related to shear. Selected experimental damping evaluations from Paper I are used to validate the model and obtain fitted values of loss factors for two types of wood. The good agreement of the derived model with experimental data reveals an efficient approach in the prediction of material damping. In Paper III, a semi-analytical prediction model of material damping in timber panels is described. The approach is derived from the strain energy method and input is based on loss factors, which are intrinsic properties of the considered materials, together with material properties and mode shape integrals, whose calculation can easily be implemented in most finite element codes. Experimental damping evaluations of three types of timber panels are performed. These are particleboards, oriented strand board panels and structural laminated veneer panels. Fair goodness-of-fit between the experimental results and the prediction models reveals an efficient approach for the prediction of material damping in timber panels with any boundary conditions, knowing only the loss factors and the mode shapes. In Paper IV, dynamic properties of two timber floors are experimentally evaluated by impact method. Each floor uses one specified type of connectors, either screws or nails. A numerical model is developed using constrained degrees-of-freedom for the modeling of connectors. Numerical analyses have been performed, and show good agreement with experimental results. A procedure is written using the commercial finite element software Abaqus to predict material damping from a strain energy approach. Estimation of structural damping is performed as the difference between the experimentally evaluated total damping and the predicted material damping. The contribution from floor members to material damping is extensively investigated, and the needs for better prediction of damping are discussed. Specific details of some aspects of the work are included in the “Appendix” part.