Ryerson University Digital Commons @ Ryerson Theses and dissertations 1-1-2010 Theoretical analysis of acoustic emission signal propagation in fluid-filled pipes M.N. Mahabubul Alam Chowdhury Ryerson University Follow this and additional works at:http://digitalcommons.ryerson.ca/dissertations Part of theElectrical and Computer Engineering Commons Recommended Citation Chowdhury, M.N. Mahabubul Alam, "Theoretical analysis of acoustic emission signal propagation in fluid-filled pipes" (2010).Theses and dissertations.Paper 846. This Thesis is brought to you for free and open access by Digital Commons @ Ryerson. It has been accepted for inclusion in Theses and dissertations by an authorized administrator of Digital Commons @ Ryerson. For more information, please [email protected]. THEORETICAL ANALYSIS OF ACOUSTIC EMISSION SIGNAL PROPAGATION IN FLUID-FILLED PIPES by M N Mahabubul Alam Chowdhury BSc in Electrical & Electronic Engg., Dhaka University of Engineering and Technology (DUET), Gazipur, Bangladesh, 1992 MSc in Electrical & Electronic Engg., Bangladesh University of Engineering and Technology (BUET), Dhaka, Bangladesh, 1997 A thesis presented to Ryerson University in partial fulfillment of the requirement for the degree of Master of Applied Science in Electrical and Computer Engineering. Toronto, Ontario, Canada, 2009 (cid:176)c N M Alam Chowdhury, 2009 Author’s Declaration I hereby declare that I am the sole author of this thesis. I authorize Ryerson University to lend this thesis to other institutions or individuals for the purpose of scholarly research. Signature I further authorize Ryerson University to reproduce this thesis by photocopying or by other means, in total or in part, at the request of other institutions or individuals for the purpose of scholarly research. Signature ii Theoretical Analysis of Acoustic Emission Signal Propagation in Fluid-filled Pipes, a thesis by M N Mahabubul Alam Chowdhury, presented to Electrical and Computer Engineering, Ryerson University, in partial fulfillment of the requirement for the degree of Master of Applied Science, 2009. Abstract The theoretical investigation of acoustical wave propagation in cylindrical layered media is the main interest of our research. The propagation of wire break or slip related acoustical signal in the buried water-filled Prestressed Concrete Cylinder Pipe (PCCP) is taken as a specific application. The PCCPs are widely used for potable- and waste-water distribution and transmission systems, which are generally located below the surface ground. Therefore, it is difficult to inspect or detect the damage caused by the wire-break or slip related events in the pipeline. In current practice, the acoustic emission (AE) monitoring system is used for random examination of prestressing wires by excavating or internal inspecting of the pipe walls, which is based on field data analysis. This gives only the localized knowledge of wire break or slip, which can be misleading, underestimated of the extent of corroded areas, deterioration or wire failure, due to the system resonance, acoustoelastic effect, loading effect, etc. There is no systematic theoretical analysis from the acoustic signal generation to propagation related to these effects, and hence, a common problem in AE technology is to extract the physical features of the ideal events, so as to detect the similar signals. The theoretical analysis is important to understand how the AE signal is generated by the leak, wire break or slip related events and how the path characteristics, excitation fre- quency, and modes of propagation physically affect the signal propagation. For this purpose, an acoustical model is developed from the Navier’s equation of motion. This can simulate vibrating AE signal propagation through the fluid-filled PCCP. The interaction of this prop- agation with the pipe structure is modeled by using Newton’s law of motion in equilibrium. The principle of virtual work is used to develop the fluid-structure interaction. iii In this work, the impact of the path on the spectral profiles of the vibrating AE signals in different locations throughout the pipes were investigated for low and high frequency excitation signals. At low frequency, there is only plane wave propagation, therefore the stoneley or tube mode analysis is used for this purpose. The tube wave effects on the acoustical wave propagation were observed from this analysis. At high frequencies, there also exist rayleigh or shear modes which exhibit oscillatory amplitudes in the fluid and a decaying amplitude in the pipe and the surrounding medium. The eigenfrequency and the modal analysis is used in this case. From the analyses, the phase velocity, group velocity, tube wave velocity, system resonance frequencies, cut-off frequencies were observed. The high frequency analysis has some special advantages over low frequency signal. This can provide an earlier indication of incipient faults, which is important to detect the AE event in early stage of pipe deterioration. Moreover, it was established that the frequency of propagating AE signal in the pressurizing fluid medium ranges up to 30kHz. Therefore, it is important to investigate the wave propagation of AE signal at these frequencies. This workexaminesthespectralcharacteristicsofAEsignalpropagationthroughthefluidcolumn inside the pipe within the range of sonic/ultrasonic frequency. The acoustic wave propagation in fluid-filled PCCP of various radius, stiffness and thick- ness of the pipe as well as different types of surrounding medium, is obtained by applying a numerical Finite Element Method (FEM). Finally, the results are compared with available analytical solutions. The proposed model is independent of sources, dimensions and medium characteristics. Therefore, it can be used for the analysis of acoustic wave propagation through any type of cylindrical shells immersed or surrounded by different types of medium. The current analysis, therefore, has fundamental importance in many applications. iv Acknowledgments Thecompletionofthisthesisinvolvescontributionsandassistancefrommanyindividuals. First of all, I would like to express my invaluable profound gratitude to my supervisors, Professor Dr. Lian Zhao from Dept of Electrical and Computer Engineering and Professor Dr. Zaiyi Liao from Dept of Architectural Science of Ryerson University, for their profes- sional directions, helpful comments, kind support and constant encouragement throughout the research period. I am greatly grateful to Professor Dr. Ramani Ramakrishnan of Architectural Science Department for his precious instruction. His dynamic thinks, broad and profound knowledge and patient instruction have given me a great help. ThisworkispartiallysupportedbytheOntarioCentresofExcellence(OCE)underGrant no. EE50196, National Sciences and Engineering Research Council (NSERC) of Canada un- der Grant no. DG 293237-04 and 313375-07, and Ryerson University research grant. I’m also grateful to these institutions for their financial support. The members of our lab supported me in my research work. I want to thank them for all their help, support, interest and valuable hints. Especially, I am obliged to Ran Wu, Thomas Behan for their assistance and valuable suggestions to complete my work. I am also grateful to Surinder Jassar, Meharoon Shaik, Lavanya Rajagopalan, Samuel Huang, and Ringo for their help during the preparation of my thesis and final presentation. I am very grateful for the love and support of my family and friends. Especially, I ap- preciate the patience of my son Sharear and my daughter Shareen during the time I was involved in carrying out this project. The morale support given by my wife Nazma is also greatly regarded. Above all, words cannot express my sincere thanks to the almighty God for showering countless blessings to me. v Contents 1 General Introduction 1 1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Review of Earlier Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.3 Non-destructive Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.4 Acoustic Emission Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.5 Acoustic Emission Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.6 Acoustic Emission Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.6.1 AE Signal Propagation . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.6.2 AE Signal Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.7 Motivation, Objectives and Scope of the Research . . . . . . . . . . . . . . . 13 1.8 Overview of the Proposed Work . . . . . . . . . . . . . . . . . . . . . . . . . 16 1.9 Organization of the Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2 Current Technology 19 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.2 Prestressed Pipe Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.2.1 Pipe Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.2.2 Pipe Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.2.3 Pipe Joint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 2.2.4 Corrosion in PCCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 2.2.5 Generation of AE Signal . . . . . . . . . . . . . . . . . . . . . . . . . 24 2.3 Acoustic Monitoring Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 2.4 Current Applied Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 2.4.1 Acoustic Emission Testing . . . . . . . . . . . . . . . . . . . . . . . . 27 2.4.2 Localization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 2.4.3 Testing Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 2.4.4 Typical AE Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.5 Applications of AET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 2.6 Advantages and Limitations of AET . . . . . . . . . . . . . . . . . . . . . . 31 2.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 vi 3 Mathematical Modeling 34 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 3.2 Model Formulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 3.3 Simple Physical Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 3.4 Homogeneous Acoustic Pressure Model . . . . . . . . . . . . . . . . . . . . . 38 3.5 Acoustic Source Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 3.5.1 Constant Volume Velocity Source . . . . . . . . . . . . . . . . . . . . 38 3.5.2 Constant Pressure Source . . . . . . . . . . . . . . . . . . . . . . . . 39 3.5.3 Source Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 3.5.4 Modeling the Source . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 3.6 Inhomogeneous Acoustic Pressure Model . . . . . . . . . . . . . . . . . . . . 40 3.7 Fluid vs Surrounding Medium Interaction . . . . . . . . . . . . . . . . . . . 41 3.7.1 Fluid-Structure Interaction . . . . . . . . . . . . . . . . . . . . . . . . 41 3.7.2 Structure-Fluid Interaction . . . . . . . . . . . . . . . . . . . . . . . . 43 3.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 4 Tube Wave Analysis 45 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 4.2 Significance of Tube Wave Analysis . . . . . . . . . . . . . . . . . . . . . . . 46 4.3 Tube Wave Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 4.4 Acoustical Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 4.5 Solution Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 4.5.1 Model Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 4.5.2 Boundary Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 4.5.3 Model Discretization . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 4.6 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 4.6.1 Effect of Pipe Elasticity . . . . . . . . . . . . . . . . . . . . . . . . . 51 4.6.2 Effect of Pipe Dimensions . . . . . . . . . . . . . . . . . . . . . . . . 53 4.6.3 Effect of Soil Medium . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 4.6.4 Effect of Guided Path . . . . . . . . . . . . . . . . . . . . . . . . . . 58 4.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 5 Eigenfrequency Analysis 59 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 5.2 Significance of Eigenfrequency Analysis . . . . . . . . . . . . . . . . . . . . . 60 5.3 Eigenfrequency and Modal Analysis . . . . . . . . . . . . . . . . . . . . . . . 61 5.3.1 Eigenfrequency Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 62 5.3.2 Modal Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 5.4 Boundary Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 5.4.1 Rigid Pipe with Infinite Stiffness . . . . . . . . . . . . . . . . . . . . 63 5.4.2 Elastic Pipe with Finite Stiffness . . . . . . . . . . . . . . . . . . . . 64 5.4.3 Radiation Boundary Conditions . . . . . . . . . . . . . . . . . . . . . 65 vii 5.5 Numerical Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 5.5.1 Finite Element Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 66 5.6 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 5.6.1 Rigid Pipe Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 5.6.2 Elastic Pipe with Finite Stiffness . . . . . . . . . . . . . . . . . . . . 70 5.6.3 Elastic Pipe with Outer Formation . . . . . . . . . . . . . . . . . . . 77 5.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 6 High Frequency Analysis 80 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 6.2 Significance of High Frequency Analysis . . . . . . . . . . . . . . . . . . . . . 80 6.3 Acoustical Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 6.4 AE Source Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 6.5 Numerical Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 6.5.1 Boundary Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 6.5.2 Discretization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 6.6 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 6.6.1 Fluid-filled Rigid Pipe . . . . . . . . . . . . . . . . . . . . . . . . . . 86 6.6.2 Fluid-filled Elastic Pipe . . . . . . . . . . . . . . . . . . . . . . . . . 96 6.6.3 Fluid-filled Elastic Pipe Surrounded by Soil . . . . . . . . . . . . . . 110 6.6.4 Fluid-filled Elastic Pipe Surrounded by Different Soil . . . . . . . . . 128 6.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 7 Conclusions and Recommendations 133 7.1 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 7.2 Future Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 A Principle of Virtual Work 139 B Stress, Strain and Displacements Relations 141 C List of Abbreviations 142 D List of Symbols 143 E List of Achievements 145 Bibliography 147 viii List of Tables 2.1 Typical core thickness of PCCP. . . . . . . . . . . . . . . . . . . . . . . . . . 22 4.1 Properties of the medium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 4.2 Properties of the soil sample. . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 5.1 Analytical and simulated results of cut-off frequency of the rigid pipe. . . . . 68 5.2 Analytical and simulated results of eigenfrequency of the rigid pipe. . . . . . 69 ix