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Effective-Property Characterization of Elastic Metamaterials for Advanced Wave Tailoring : 탄성 메타물질의 유효 특성 정의 및 이를 이용한 파동 테일러링

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dc.contributor.advisor김윤영-
dc.contributor.author이형진-
dc.date.accessioned2017-07-13T06:14:17Z-
dc.date.available2017-07-13T06:14:17Z-
dc.date.issued2014-02-
dc.identifier.other000000018172-
dc.identifier.urihttps://hdl.handle.net/10371/118377-
dc.description학위논문 (박사)-- 서울대학교 대학원 : 기계항공공학부, 2014. 2. 김윤영.-
dc.description.abstractThis work is mainly concerned with the development of a characterization methodology for determining the effective properties of anisotropic elastic metamaterials. Among the existing methods, the method using the scattering parameters of metamaterials has been known to be most efficient in electromagnetics owing to the robust performances. In the elastic regime, however, the conventional method using the scattering parameters cannot thoroughly characterize metamaterials due to the complex constitutive properties including the diagonal as well as the non-diagonal components in the stiffness tensor. Therefore, the method should be refined specifically for characterizing anisotropic elastic metamaterials.
In order to achieve the goal, the improved version of the characterization method using scattering parameters is developed in this work. The proposed method works in the two steps: one is to determine the effective constitutive properties involved in the scattering parameters for normal incidences and the other is to determine the rest of the properties involved in the scattering parameters for oblique incidences. While the conventional method just yields the diagonal stiffness components even working only for the metamaterials having the material principal axes coinciding with the coordinate axes, the proposed method is shown to work for various types of metamaterials yielding the whole effective properties.
By utilizing the developed characterization method, three types of novel elastic metamaterials are also proposed in this work and applied for the designs of elastic magnifying hyperlens, quasi-ideal mechanical bandpass filters, and wave mode converters, respectively. In order to design elastic magnifying hyperlens, metal-air-stratified metamaterials exhibiting an extremely anisotropy is used. Owing to the extreme property, the proposed hyperlens is shown to achieve high resolution images beyond the well-known diffraction limit, the fundamental limit for an imaging device. And, in order to design quasi-ideal mechanical bandpass filters, impedance-only-varying metamaterials are proposed and utilized for constructing effective impedance-varying phononic bandgap structures. The developed phononic bandgap structures are shown to exhibit quasi-ideal bandpass filter performances including a unity passband with the flat top, broad surrounding stopbands, and steep bandedges. Lastly, in order to design wave mode converters, the metamaterials exhibiting anomalous polarization characteristics are used. The developed mode converters are shown to robustly work for various environmental conditions while achieving the high conversion efficiencies.
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dc.description.tableofcontentsABSTRACT i
LIST OF TABLES ix
LIST OF FIGURES xi

CHAPTER 1. Introduction 1
1.1 Motivation 1
1.2 Research Objectives 4
1.3 Outline of Thesis 7

CHAPTER 2. Theoretical Background 11
2.1 Elastic Waves in Unbounded Anisotropic Solid Media 11
2.1.1 Stress-strain relations for anisotropic materials 12
2.1.2 The Christoffel equation 16
2.1.3 Slowness surfaces 18
2.2 Scattering Parameters of an Anisotropic Solid Material 21
2.2.1 Transfer matrix 21
2.2.2 Scattering parameters 26

CHAPTER 3. Proposition of S-Parameter Retrieval Method for Effective-Property Characterization of Anisotropic Elastic Metamaterials 31
3.1 Conventional S-Parameter Retrieval Method for Elastic Metamaterials 33
3.1.1 Retrieving methodology 33
3.1.2 Limitations 43
3.2 Proposed S-Parameter Retrieval Method for Anisotropic Elastic Metamaterials 46
3.2.1 Retrieving methodology 47
3.2.2 Effective properties for a normal incidence 49
3.2.3 Effective properties for an oblique incidence 54
3.2.4 Validation of retrieved effective properties 59
3.3 Issues in the S-Parameter Retrieval Method for Elastic Metamaterials 60
3.4 Summary 63

CHAPTER 4. Design of Elastic Magnifying Hyperlens for Sub-Wavelength Imaging by Using Extremely Anisotropic Metamaterials 83
4.1 Magnifying Hyperlens 83
4.2 Introduction of Metal-Air Multilayer Metamaterials for Extreme Anisotropy 84
4.2.1 Design and configuration 85
4.2.2 Effective-property characterization by the analytic homogenization method 86
4.2.3 Validation of the analytic homogenization method by the S-parameter retrieval method 91
4.3 Design of Elastic Magnifying Hyperlens 93
4.3.1 Validation of the performance by FEM simulations 94
4.3.2 Validation of the performance by experiments 96
4.3.3 Estimation of output/input power ratio 98
4.4 Summary 99

CHAPTER 5. Design of Quasi-Ideal Mechanical Bandpass Filters by Using Impedance-Only-Varying Elastic Metamaterials 113
5.1 Quasi-Ideal Bandpass Filters 113
5.2 Proposition of Impedance-Varying Phononic Bandgap Structures for Bandpass Filters 115
5.2.1 Theoretical analysis on the impedance variation 116
5.2.2 Theoretical analysis on the symmetrically impedance-varying phononic bandgap structures 123
5.3 Proposition of Impedance-Only-Varying Elastic Metamaterials 129
5.3.1 Configurations of the proposed metamaterials 129
5.3.2 Effective-property characterization by the S-parameter retrieval method 131
5.3.3 Realization of the impedance-varying HQWS structures 133
5.4 Design of Quasi-Ideal Bandpass Filters 135
5.4.1 Validation of the performance by FEM simulations 135
5.4.2 Tailoring of the bandpass-filter performance 139
5.5 Summary 140

CHAPTER 6. Design of Wave Mode Converters by Using Elastic Metamaterials Exhibiting Anomalous Polarizations 157
6.1 Wave Mode Converters 157
6.2 Proposition of Elastic Metamaterials Exhibiting Anomalous Polarizations 160
6.2.1 Configurations 160
6.2.2 Effective-property characterization by the S-parameter retrieval method 162
6.2.3 Anomalous wave propagation velocities 164
6.2.4 Anomalous polarization characteristics 167
6.3 Design of Wave Mode Converters 168
6.3.1 Methodology for wave mode converters 169
6.3.2 Validation of the performance by FEM simulations 172
6.3.3 Robust performance for various environmental conditions 176
6.4 Summary 179

CHAPTER 7. Conclusions 197

REFERENCES 201
APPENDIX 213
ABSTRACT (KOREAN) 215
ACKNOWLEDGEMENT 217
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dc.formatapplication/pdf-
dc.format.extent26829637 bytes-
dc.format.mediumapplication/pdf-
dc.language.isoen-
dc.publisher서울대학교 대학원-
dc.subjectAnisotropic elastic metamaterials-
dc.subjectS-parameter retrieval method-
dc.subjectElastic magnifying hyperlens-
dc.subjectMechanical bandpass filter-
dc.subjectWave mode converter-
dc.subject.ddc621-
dc.titleEffective-Property Characterization of Elastic Metamaterials for Advanced Wave Tailoring-
dc.title.alternative탄성 메타물질의 유효 특성 정의 및 이를 이용한 파동 테일러링-
dc.typeThesis-
dc.contributor.AlternativeAuthorLee, Hyung Jin-
dc.description.degreeDoctor-
dc.citation.pagesxvi, 217-
dc.contributor.affiliation공과대학 기계항공공학부-
dc.date.awarded2014-02-
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