Failure Behavior of the Piezoelectric Materials under Purely Electrical Loading

Failure Behavior of the Piezoelectric Materials under Purely Electrical Loading
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In this thesis, failure behavior of piezoelectric materials under purely electrical loading is investigated. Under purely electrical loading, piezoelectric material commonly shows two kinds of failure modes: fracture by crack growth and dielectric breakdown by formation of tubular channel or conducting path. Both unpoled and poled piezoelectric materials are considered in this study. The problems of the tubular channel growth in unpoled and poled PZT807 piezoelectric ceramics with cylindrical bar shape under electric fields, which have not been solved yet, are experimentally and numerically analyzed. Also, the interface failure problem of PZT C-201/C-3 piezoelectric bimaterial is experimentally and theoretically investigated. Finally, kinking of a conducting path between two dissimilar anisotropic dielectric materials, which can be considered as the unpoled piezoelectric materials, is analyzed using linear transformation method. The dielectric breakdown of an unpoled piezoelectric ceramic, PZT807, with a conductive channel, is investigated. Cylindrical bar specimens with a conductive channel are used for breakdown tests of the unpoled piezoelectric ceramic under purely electrical loads. Narrow tubular channels emanating from the head of the initial channel are observed in the specimens after breakdown occurs. The radius of the tubular channel that is created at the surface of the initial channel head is insensitive to various types of channel formation. The problem of a fine tubular channel that emanates from the initial channel head is numerically solved to evaluate the three-dimensional J integral, which is directly related to the energy that is available at breakdown, at the initiation of a new channel in the specimen. The critical J integral at the onset of breakdown is obtained. Tubular channel growth in a piezoelectric material with a conductive channel is investigated. Breakdown tests are performed on PZT807 samples with cylindrical bar shapes under purel
CHAPTER 1 INTRODUCTION 1 1.1 Motivation and Literature Survey . 1 1.2 Thesis Outline 3 CHAPTER 2 PIEZOELECTRIC CERAMICS. 5 2.1 Basic Features 5 2.2 Basic Equations 5 2.3 Constitutive Relations 6 2.4 Energy Considerations 7 2.5 Complex Variable Solution 8 CHAPTER 3 DIELECTRIC BREAKDOWN OF AN UNPOLED PIEZOELECTRIC MATERIAL WITH A CONDUCTIVE CHANNEL 13 3.1 Introduction 13 3.2 Experiment . 13 3.3 Numerical Analysis . 15 3.4 Numerical Results and Discussion 17 3.5 Summary 19 CHAPTER 4 TUBULAR CHANNEL GROWTH IN PIEZOELECTRIC CERAMICS UNDER ELECTRIC FIELDS . 20 4.1 Introduction 20 4.2 The Experiment 20 4.3 Numerical Analysis 22 4.4 Breakdown Resistance and Discussion 24 4.5 Summary 26 CHAPTER 5 ELECTRICAL FAILURE OF PIEZOELECTRIC CERAMICS WITH A CONDUCTIVE CRACK UNDER ELECTRIC FIELDS . 27 5.1 Introduction 27 5.2 Numerical Analysis 27 5.3 Numerical Results and Discussion . 30 5.4 Summary 31 CHAPTER 6 FAILURE BEHAVIOR OF A PIEZOELECTRIC BIMATERIAL WITH AN INTERFACIAL ELECTRODE 33 6.1 Introduction 33 6.2 Experimental Procedures 33 6.3 Experimental Results 34 6.4 Complex Variable Method . 34 6.5 Numerical Analysis 37 6.6 Summary 43 CHAPTER 7 Kinking of a Conducting Path in an Anisotropic Dielectric Bimaterial 44 7.1 Introduction 44 7.2 Formulation 44 7.3 Isotropic Dielectric Material 49 7.4 Statement of the Problem . 51 7.5 Numerical Verification 59 7.6 Summary 61 CHAPTER 8 CONCLUSIONS 63 REFERENCES 67 FIGURES 70 TABLES 104
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College of Engineering(공과대학) > Mechanical Engineering(기계공학) > Theses(기계공학 석박사 학위논문)
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