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This work was supported by the United States National Aeronautics and Space Administration, grant number: NNX10AJ14G; Technical monitor, Dr. Curtis E. Banks, NASA MSFC. I gratefully acknowledge the financial and technical support. I’m indebted to University of Alabama, Tuscaloosa for embracing me whole heartedly and giving me the kind of knowledge and exposure I had only dreamt of. I’m greatly thankful to my husband Madhav Rao, my best friend and soul mate. He has been my source of strength and has always led by example. If not for him, this graduate program would not have been possible. Finally I would like to thank my parents and in-laws for their unconditional support and encouragement. v
CONTENTS ABSTRACT …………………………………………...…….………………………………. ii LIST OF ABBREVIATIONS ………………………………………………………………. iii ACKNOWLEDGEMENTS ………………………………………………………………… iv LIST OF TABLES ………………………………………………………………………….. ix LIST OF FIGURES ………………………………………………………………………….. x CHAPTER 1. INTRODUCTION .............................................................................................. 1 CHAPTER 2. BACKGROUND ................................................................................................ 6 2.1 Introduction to Lamb waves ........................................................................................ 6 2.2 Lamb wave methods.................................................................................................... 7 2.3 Sensing methods .......................................................................................................... 8 2.4 Piezoelectric transducers and principle of operation................................................... 9 2.5 Actuation parameters................................................................................................. 10 2.6 Transverse crack ........................................................................................................ 12 2.7 Finite element analysis .............................................................................................. 12 2.8 Finite element analysis for optimization ................................................................... 13 CHAPTER 3. FABRICATION OF COMPOSITE PANEL .................................................... 15 CHAPTER 4. EXPERIMENTAL ANALYSIS ....................................................................... 18 vi
Page 1 and 2: EXPERIMENTAL ANALYSIS AND FEA MODEL
Page 3 and 4: ABSTRACT Reliable damage detection
Page 5: ACKNOWLEDGEMENTS I’m extremely gr
Page 9 and 10: 6.2.4 FFT analysis of a surface cra
Page 11 and 12: LIST OF FIGURES Figure 1.1. A picto
Page 13 and 14: Figure 5.16. Abaqus models showing
Page 15 and 16: Figure 7.3. A flow chart demonstrat
Page 17 and 18: To ensure performance and to improv
Page 19 and 20: extraction, damage sensitive featur
Page 21 and 22: 2.1 Introduction to Lamb waves CHAP
Page 23 and 24: an actuator located at one end of a
Page 25 and 26: material is such that electrical pu
Page 27 and 28: 2.6 Transverse crack In this thesis
Page 29 and 30: evolutionary algorithms [54] and st
Page 31 and 32: material setup was sealed in a vacu
Page 33 and 34: CHAPTER 4 EXPERIMENTAL ANALYSIS The
Page 35 and 36: This experimental system was found
Page 37 and 38: Figure 4.5. Experimental test resul
Page 39 and 40: width. The composite coupons were f
Page 41 and 42: Table 5.1. Material properties of I
Page 43 and 44: Table 5.3. Comparison of the exact
Page 45 and 46: Figure 5.5. FE model of a composite
Page 47 and 48: interlaminar stresses are dominant.
Page 49 and 50: Figure 5.9. Comparison of exact def
Page 51 and 52: Table 5.7. Material properties of t
Page 53 and 54: 5.4 PZT modeling The PZT actuator w
Page 55 and 56: a) b) Figure 5.16. Abaqus models sh
Page 57 and 58:
coupon with a surface crack. A pict
Page 59 and 60:
5.5.3 Embedded crack at various dep
Page 61 and 62:
5.08 mm 5.08 mm 5.08 mm Actuator en
Page 63 and 64:
CHAPTER 6 RESULTS AND DISCUSSION 6.
Page 65 and 66:
6.2 FFT analysis A fast Fourier tra
Page 67 and 68:
Figure 6.5. FFT spectrum based on A
Page 69 and 70:
a) b) Figure 6.8. An enlarged view
Page 71 and 72:
Figure 6.10. Complete FFT spectrum
Page 73 and 74:
enlarged view of the FFT spectrum a
Page 75 and 76:
Figure 6.15. A graphical representa
Page 77 and 78:
Start Abaqus .inp generation Abaqus
Page 79 and 80:
Damage classification was performed
Page 81 and 82:
and dynamic simulation benchmark te
Page 83 and 84:
REFERENCES [1] J. Teresko, "Boeing
Page 85 and 86:
aluminum plates," Ultrasonics, Ferr
Page 87 and 88:
[51] I. Bartoli, "Structural health
Page 89 and 90:
APPENDIX A: Conference contribution
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