Objectives BACKGROUND Lamb Wave Propagation In Plate With Different Depth Of Corrosion Defect.

TABLE OF CONTENTS CHAPTER CONTENT PAGES SUPERVISOR DECLARATION AUTHOR DECLARATION ii DEDICATION iii ACKNOWLEDGEMENT iv ABSTRACT v ABSTRAK vi TABLE OF CONTENT vii LIST OF TABLE ix LIST OF FIGURE x LIST OF SYMBOL xi CHAPTER I INTRODUCTION 1.0 Overview 1.1 Background 1.1.1 Technique to Generate the Lamb Wave Propagation Using Guided Wave 1.1.2 Lamb Wave Propagation 1.2 Advantages of Lamb Wave Propagation 1.3 Problem Statement

1.4 Objectives

1 1 2 3 4 5 5 CHAPTER II LITERATURE REVIEW 2.0 Overview of Literature Review 2.1 Dispersion Curve of Phase Velocity and Group Velocity 2.1.1 Dispersion Curve 2.1.2 Phase Velocity 2.1.3 Group Velocity 2.2 Symmetrical and Anti-symmetrical 2.3 Difference Between Guided Wave and Ultrasonic Testing

2.4 Material Properties of Plate and Wedge Material

2.4.1 General and Mechanical Properties of Aluminium plate

2.4.2 Wave properties of wedges

6 6 7 8 10 11 13 12 13 CHAPTER III METHODOLOGY 3.0 Overview of Methodology 3.1 Flowchart 3.2 Different Defects on the Wave Propagation 3.2.1 ABAQUS Simulation of Defect in Aluminium Plate 3.3 Excitation of Lamb Wave Propagation 3.3.1 Wave Excitation on Different Frequencies and Thickness 3.3.2 Wave Excitation on Different Geometry and Orientation 3.3.2.1 Oval Defect 3.3.2.2 Round Defect 3.3.3 Wave Propagation Behaviour and Modes Excitation 3.4 Excitation of Wave Based on Experimental Work 14 15 16 17 18 19 19 20 21 23 3.5 Specification of the Lamb Wave Tools and Apparatus 26 CHAPTER IV RESULTS 4.0 Overview 4.1 Wave Propagation Through A Defected Groove Structure For 1 m Aluminium Plate 4.1.1 Effect on Different Depth Thickness, h at Frequency of 100 kHz 4.1.2 Effect on Different Sinewave Frequency at Groove Depth of 4 mm 4.2 Wave Signal Through A Defected Groove Structure for Fabricated 1 m Aluminium Plate 4.2.1 Wave signal through different thickness of 100 kHz 4.2.2 Wave signal through different frequency at 4 mm depth thickness 4.3 Wave Propagation and Signal Through A Defect Structure for 5 m Aluminium Plate 4.3.1 Effect on Different Depth Thickness, h at Frequency of 100 kHz 4.3.2 Effect on Frequency on 4 mm Groove Defect Depth 4.3.3 Effect on Different Orientation at Frequency of 100 kHz and Defect Thickness of 4 mm 4.3.3.1 Oval Defect 4.3.3.2 Round Defect 29 30 38 44 44 47 50 50 58 64 64 70 CHAPTER V ANALYSIS AND DISCUSSIONS 5.0 Overview 5.1 Signal Behaviour on 1 m Aluminium Plate 5.1.1 Excitation of Different Defect Depth for U1 and U3 Components 5.1.2 Excitation of the Excitation on Different Frequency Signals For U1 and U3 Components 5.2 Wave Signal Behaviour Based on The Experimental Testing 5.2.1 Comparison of wave signals for experimental and simulation in the different thickness of 1 m groove defect 5.2.2 Comparison of wave signals for experimental and simulation in the different frequency of 1 m groove defect 5.3 Signal Behaviour On 5 m Aluminium Plate 5.3.1 Excitation on Different Defect Depth for U1 and U3 Components 5.3.2 Excitation of Different Frequency Signals for U1 and U3 Components 5.3.3 Excitation on Different Orientations in U1 and U3 Components a Oval defect b Round Defect 5.4 Relation Between A0-mode and S0-mode 76 77 77 80 82 82 86 89 89 92 95 95 98 100 CHAPTER VI CONCLUSION AND RECOMMENDATIONS 6.1 Conclusion 6.2 Recommendation 103 104 BIBLIOGRAPHY 105 APPENDIX 108 BLANK PAGE 111 LIST OF TABLES NO. TITLE PAGES 2.1 Material properties of Aluminium Plate 12 2.2 Wave velocity properties for wedge 13 3.1 The specification and function of the Apparatus setup for excitation of wave signals in 1m plate 26 5.1 peak-to-peak value for A0-mode and S0-mode at different depth thickness 101 LIST OF FIGURES NO. TITLE PAGES 1.1 Guided wave set up 3 2.1 Phase velocity and the frequency dispersion of the dispersion curve 8 2.2 Group velocity and the frequency dispersion of the dispersion curve 9 2.3 Anti-symmetrical mode 10 2.3 Symmetrical mode 10 3.1 Flow chart of the research activities 15 3.2 Illustration of groove defect on 1 m aluminium plate 16 3.3 Illustration of groove defect on 5 m aluminium plate 17 3.4 Cross section of groove depth of defect in 2-Dimension for 1 m and 5 m plate 17 3.5 Oval defect 10 mm x 200 mm in ABAQUS Simulation 19 3.6 Oval defect with different orientation 19 3.7 Round defect with four circle defects orientation 20 3.8 Round defect with multi flaw defects 20 3.9 Wave excitation behaviour when the signal is introduced 21 3.10 Force direction for S0-mode 22 3.11 Force direction for A0-mode 22 3.12 Fabricated of 40 mm groove defect with thickness of 2 mm, 3 mm and 4 mm of defect depth 23 3.13 Block diagram to develop the excitation of wave signal in 1 m aluminium plate experiment testing 24 3.14 Figure a and Figure b shows the apparatus setup for the transmitter and receiver wave from the pulser 25 3.15 The configuration for wave propagation excitation 26 4.1 Wave interaction behaviour when in contact with 2 mm defect 30 4.2 Figure a and Figure b shows the wave signal for amplitude against time in U1 and U3 components for 2 mm depth 31 4.3 Wave interaction behaviour when in contact with defect at 3 mm depth 32 4.4 Figure a and Figure b shows the wave signal for amplitude against time in U1 and U3 components for 3 mm depth 33 4.5 Wave interaction behaviour when in contact with defect for 4 mm depth 34 4.6 Figure a and Figure b shows the wave signal for amplitude against time in U1 and U3 components for 4 mm depth 35 4.7 Wave interaction behaviour when in contact with defect for 5 mm depth 36 4.8 Figure a and Figure b shows the wave signal for amplitude against time in U1 and U3 components for 5 mm depth 37 4.9 Wave interaction behaviour when in contact with defect at 80 kHz 39 4.10 Figure a and Figure b shows the wave signal for amplitude against time in U1 and U3 components at frequency of 80 kHz 39 4.11 Wave interaction behaviour when in contact with defect at 100 kHz 40 4.12 Figure a and Figure b shows the wave signal for amplitude against time in U1 and U3 components at frequency of 100 kHz 41 4.13 Wave interaction behaviour when in contact with defect at 120 KHz 42 4.14 Figure a and Figure b shows the wave signal for amplitude against time in U1 and U3 components at frequency of 120 kHz 43 4.15 Signal wave for experimental depth defect testing in 1 m aluminium plate for A0-mode 45 4.16 Signal wave for experimental depth defect testing in 1 m aluminium plate for S0-mode 46 4.17 Signal wave for experimental depth defect testing in 1 m aluminium plate for A0-mode 48 4.18 Signal wave for experimental depth defect testing in 1 m aluminium plate for S0-mode 49 4.19 Wave interaction behaviour for 2 mm thick groove defect 50 4.20 Figure a and b are the wave interaction behaviour for 3 mm thick groove defect 51 4.21 Wave interaction behaviour for 3 mm thick groove defect 52 4.22 Figure a and b are the wave interaction behaviour for 3 mm thick groove defect 53 4.23 Wave interaction behaviour for 4 mm thick groove defect 54 4.24 Figure a and b are the wave interaction behaviour for 4 mm thick groove defect 55 4.25 Wave interaction behaviour for 5 mm thick groove defect 56 4.26 Figure a and b are the wave interaction behaviour for 5 mm thick groove defect 57 4.27 Wave interaction behaviour for frequency of 80 kHz 58 4.28 Figure a and b are the wave interaction behaviour for frequency of 80 kHz. 59 4.29 Wave interaction behaviour for frequency of 100 KHz 60 4.30 Figure a and b are the wave interaction behaviour for frequency of 100 kHz. 61 4.31 Wave interaction behaviour for frequency of 120 KHz 62 4.32 Figure a and b are the wave interaction behaviour for frequency of 120 kHz. 63 4.34 Wave interaction behaviour for axial 180 deg oval defect 64 4.35 Figure a and b are the wave interaction behaviour for oval defect orientation. 65 4.36 Wave interaction behaviour for axial defect 90 deg 66 4.37 Figure a and b are the wave interaction behaviour for frequency of perpendicular defect 67 4.38 Wave interaction for oblique defect 45 deg 68 4.39 Figure a and b are the wave interaction behaviour for frequency of perpendicular defect 69 4.40 Wave interaction behaviour for 4 round defects 70 4.41 Figure a and b are the wave interaction behaviour for frequency of single round defects orientation 71 4.42 Wave interaction behaviour for 2 round defects 72 4.43 Figure a and b are the wave interaction behaviour for double defects orientation 73 4.44 Wave behaviour for 4 round defects orientation 74 4.45 Figure a and b are the wave interaction behaviour for 4 round defects orientation 75 5.1 Wave signals at U1 and U3 at different depth thickness in 1 m aluminium plate 79 5.2 Wave computational results at U1 for different thicknesses for 1 m aluminium plate 79 5.3 Wave computational results at U3 for different thicknesses for 1 m aluminium plate 80 5.4 Comparison of the wave signals with different frequencies in 1 m plate 81 5.5 Wave computational results at U1 for different frequency 82 5.6 Wave computational results at U3 for different frequency 82 5.7 Comparison of different depth thickness for experimental and simulation for A0-mode 84 5.8 Comparison of different depth thickness for experimental and simulation for S0-mode 85 5.9 Comparison of different frequencies for experimental and simulation for A0-mode 87 5.10 Comparison of different frequencies for experimental and simulation for S0-mode 88 5.11 Wave signals at U1 and U3 at different depth thickness in 5 m plate 90 5.12 Wave computational results at U1 for different thicknesses 91 5.13 Wave computational results at U3 for different thicknesses 91 5.14 Wave signals at U1 and U3 at different frequency 93 5.15 Wave computational results at U1 at different frequency 94 5.16 Wave computational results at U3 at different frequency 94 5.17 Wave signals at U1 and U3 at different oval orientation defect 95 5.18 Wave computational results at U1 at different oval orientation defect 96 5.19 Wave computational results at U3 at different oval orientation defect 97 5.20 Wave signals at U1 and U3 at different round orientation defect 98 5.21 Wave computational results at U3 at different round orientation defect 99 5.22 Wave computational results at U3 at different round orientation defect 99 5.23 Method to calculate peak-to-peak Vpp values for S0- mode and A0-mode for 2 mm depth thickness 100 5.24 The difference of amplitude between A0-mode and S0- mode in 5 m aluminium plate 101 5.25 The difference of amplitude between A0-mode and S0- mode in 5 m aluminium plate 102 LIST OF SYMBOL � � = group velocity of the incident longitudinal wave � � � ∅ = phase velocity of the incident longitudinal phase � = angle of the incident longitudinal wave � = Angular velocity, rads C = Wave speed of material, ms � = Wave number . CHAPTER I INTRODUCTION

1.0 OVERVIEW

This chapter will cover the overall introduction about the project background, problem statement of the project, objectives, and the scope of the project.

1.1 BACKGROUND

The theory of Lamb waves was originally been developed by Horace Lamb in 1916 to describe the characteristics of waves propagating in plates. According to Rose 2002, Lamb wave type propagation can travel not only in a thin plate but also in multi-layer plates, rods, tubes, pipe and others where the components of vector can be in parallel and perpendicular to the particle vibration in the vertical plane through the structure. The Lamb wave opposed to the horizontal shear wave where the particle motion is normal to the wave vector in a horizontal plane as the waves are propagates through the plate structure. The Lamb waves referred to plate waves where it had been introduce in guided wave propagation especially in the thin plate. The ability of the Lamb wave to travel in long distance to detect the defect within the plate Shelke 2011 currently had been experimented and analysed especially for non-destructive testing NDT. Therefore, when some high frequency wave is been shoot to the plate surface, the wave will be reflect back toward the transducer and the defect can be observe. The behaviour of the wave propagations is different due to the geometry and the thickness of the plate structure Salim et al. 2013. To study the wave propagation of the guided wave, the piezoelectric transducer, wedges and also thin plate are needed to excite the asymmetric and the symmetrical mode of the Lamb wave. Therefore, the reflected wave will be observed and the flaw pattern are been studied. 1.1.1 Lamb Wave Propagation Lamb waves can be generate in a plate with free boundaries with an infinite number of modes for both symmetric and anti-symmetric displacements within the layer. Lamb waves are similar to longitudinal waves, with compression and rarefaction, but they are bind by the sheet or plate surface causing a wave-guide effect. The partial wave technique where wave propagation in plates is considers as a combination of bulk waves that are reflecting between the boundaries of the plate. This method provides insight into the physical nature of the Lamb waves. Ghandhi 2010 1.1.2 Technique to Generate the Lamb Wave Propagation Using Guided Wave There are two common techniques to generate the guided waves such as using the angle beam transducer by pulsing a piezoelectric element on the wedge placed on a test plate which had produce a different variety of waves propagated in the structure. The piezoelectric will leads to the interference pattern of the wave vector. The second technique is by using the comb transducer where a number of elements are place on the structure with some spacing that pumps energy into the structure causing the guided wave to propagate in both directions along the structure. However, for this case, the technique used for the Lamb propagation is using the angle beam transducer where the piezoelectric element and wedge are need. Figure 1-1: Guided wave set up. Source: Salim 2013 The guided wave are consists of transducer, made by piezoelectric PZT, and also wedge so that the lamb wave can excite the symmetrical mode S0-mode and asymmetrical mode A0-mode in plate so that the wave propagation can be observed and analysed when propagates through the defects Salim 2013. The basic guided setup can be refers in Figure 1.1. The wave can travel in a long inspection distance where the frequencies for the S0-mode are between 80 kHz to 120 kHz using acrylic whereas; A0-mode is being excited using the aqualene wedge. When the Lamb wave propagate through the plate, the defect can be detect based on the dispersion curve based on the frequency used, therefore the behaviour of the defect can be measured and analysed Takahiro et al.2012. The Lamb waves often refer as the plate wave where the component of the extensional wave is perpendicular to the surface. The waves are generated when the longitudinal waves are intersects with a surface and it is very sensitive to a defects. Therefore, as the lamb wave can travel in a long distance, the defects can easily detected even the spaces are narrow and difficult to reach.

1.2 ADVANTAGES OF LAMB WAVE PROPAGATION