In this study, the most part is acquainted with the effect of elbow pipe to the guided wave. Elbow pipes were most seen feature in work environment. It was difficult for inspection that the anti-symmetric of signal increased when it passed the elbow pipe by happening mode conversion. The study content includes the using modal solution of the finite element method to solve the dispersion curve of four different bend radius of elbow pipe, they were : 1.0 m, 0.6 m, 0.4 m and 0.2 m. Therefore, by using simulation of wave propagation and experiment to verify dispersion curve of bend pipe were accuracy. This study reveals that, the dispersion curve of elbow pipe is similar to that of straight pipe, and T(0,1) mode in the elbow pipe is most similar with it in straight pipe. Thus, the dispersion curve in elbow pipe and straight pipe were similar, but the effect of geometry of elbow pipe will make the symmetrical incident signal time delay and wave front will distortion, and then it will cause mode conversion. According to the experiment of this study, although the signal of feature behind the elbow pipe caused by mode conversion will make anti-symmetry of reflection signal increase, it still won¡¦t make shift between reflection signal location and real feature location. It is very difficult and complex for inspecting the particular geometry pipe. If we can use the modal analysis of finite element method to solve the dispersion curve of particular geometry pipe, the inspection can be improve.

This thesis studies Lamb waves for long-range pipeline inspection. The property of Lamb waves propagation and the sensitivity of defect detection will be evaluated in this thesis. There are two groups of waves propagation in plate, first group of waves are called symmetrical Lamb waves, and the second group are called anti-symmetrical Lamb waves. Furthermore, there are three different mode types exist in hollow cylinder, such as the longitudinal, torsional, and flexural modes. By solving the characteristic equation of the Lamb wave problem, the dispersion character of the Lamb waves can be found. The phase and group velocity for different Lamb modes obtained from the dispersion curve are also studied in this thesis. In the experimental setup, the longitudinal wave is incident at certain incident angles and velocities to generate Lamb waves propagated on the stainless steel plate and carbon steel hollow cylinder. When the longitudinal waves are in the constructive interference in the medium, only one Lamb wave will propagate. As a result, compare with the measured data and theoretical predictions of the group velocities, it is observed that angle beam longitudinal waves offer an accurate and workable method for Lamb waves generation. To evaluate the sensitivity and resolution of the Lamb waves testing, additional experiments for detecting defects are carried out in this thesis. It is found that a single and pure Lamb wave is very useful for detection defects. Moreover, selected the non-dispersive Lamb modes for detection can keep the propagating wave shape without changing; also, only minimum energy is decayed as wave propagated.

In this study, to discuss the effect of the boundary between pipeline and clamp support changed by different pressures to the propagation of guided wave in the pipeline is the main idea. In addition, the author simulates the wave propagation situation by using finite element method. In this work, T(0,1) torsional mode was used to discuss when adding different pressures to the clamp support, the change of its reflection coefficients in different frequencies by the axial symmetric property propagates in the cylinder pipe. In the simulation, we take the ¡§fictitious layer¡¨ was used to describe the situation between the clamp support and pipeline when adding different pressures. Moreover, the stiffness normal to the fictitious layer and the stiffness parallel to the fictitious layer were taken as material parameters to achieve the situation between clamp support and pipeline. According to experimental results, when the torque increases, the reflection coefficients will decrease with increasing frequency. The reflection coefficients are about 0.08 to 0.02. By the result of experiment and simulation, one can know that when adding torque on the clamp support increases, the reflection coefficient will decrease. In addition, the author also prove that if we change the stiffness parallel to the fictitious layer material factor, then the T(0,1) guided wave will be more sensitive by its action of particle motion.

Abstract This thesis studies the practical appraisal for pipeline inspection using the guided wave T(0,1) mode. The characteristic of reflected signals from the features of pipeline for various coated materials and fluid-filled pipes are also evaluated. The attenuation and the traveling distance of the guided wave are then calculated from the above-mentioned data for pipeline inspection in petro-chemical industries. In the experimental setup, the torsional mode is excited at one axial location using an array of transducers distributed around the circumference of the 6-inch test pipe. The reflected signals from various features, such as flanges, welds, supports, bends, defects and patches are analyzed at first at specific frequencies in the experiments. The effect of various coated material such as bitumen, PE and insulated material are also evaluated for the propagating torsional mode T(0,1) in the pipe. The results show that the attenuation of reflected signal is heavy for the bitumen-coated case because its viscosity is much higher than the other cases. Furthermore, the effect of pipe contents for defect detection using T(0,1) mode is investigated in this thesis. Various pipe contents, such as water, diesel oil, lubricant and fuel oil are deposit into the test pipe, respectively, to evaluate the influence to T(0,1). For the attenuation evaluation of reflected signal from flange in pipe, the reflected signal from an air-content pipe is measured for reference to compare with the measurements of other pipe contents in the experiments. The results show that the low viscosity liquid deposit in the pipe, such as water, diesel oil and lubricant, has no effect on the torsional mode; while the high viscous of the fuel oil deposit in the pipe attenuates the reflected signal heavily. It became evident that the torsional mode T(0,1) is most suitable for use in fluid-filled pipeline inspection.

Tremendous interest to the study of guided waves in pipe inspection in the oil, chemical, and power generating industries has peaked during the last decade. Since the advantages are inspecting long lengths of pipe quickly and without removing insulation. Recent researches in defects inspection are determined by reflection coefficients from the cracks. However, the purpose of this thesis is to excite at a single probe position and to receive the signals of guided waves with the form of loops. For the variations of wave profiles of guided wave, this thesis aimed at the largest energy distribution of wave profiles to proceed with the researches of mode conversion phenomena caused by defects. This thesis utilizes the partial loading source, and excites the non-axisymmetric and axisymmetric guided waves individually along the carbon steel pipes with circumferential defects and without defects to contrast and analyze. According to the change of wave profiles, we can find the variables that change wave profiles for different guided waves modes include propagating distance and frequency, and these cause that the circumferential energy distribution will change. For the non-axisymmetric guided waves in this thesis are non-dispersive, and its variations of phase velocity and group velocity are small, so the variations of wave profiles are also small. Moreover we study the mode conversion phenomena caused by defects from its position which the circumferential energy is largest. It also investigates new modes from mode conversion phenomena produced by defects more completely. Finally, we can predict the types and the number of new modes from mode conversion phenomena by phase velocity dispersion curve, and compare with the experiments well.

The detection of corrosion in pipes is of major importance to the oil and chemical industries. Current methods involving point-by-point inspection are available for the detection of general wall loss associated with corrosion, but unfortunately the current methods tend to be very slow, limited to single positions, thus make the inspection of the kilometers of pipeline typically found in industrial plants virtually impossible. Ultrasonic guided waves provide an attractive solution to this problem because they can be excited at one location on the pipe and will propagate many meters along the pipe, returning echoes indicating the presence of corrosion or other pipe features. Nevertheless such techniques still have many practical difficulties in application due to the complex characteristics of guided waves such as dispersion and mode conversion. This thesis studies guided waves influenced by the welded supports, a.k.a. pipe shoe. A research of the reflection of mode-converted guided waves from pipe shoes on pipes in the frequency range 18-32 kHz has been carried out. Measurements are made on a 6 inch bore diameter, 7.1mm wall thickness pipe. The axisymmetric symmetric T(0,1) mode is incident on the pipe shoes and the mode-converted guided waves are received in reflection. In parallel, a finite element model is used to simulate the experiments by using Ansys. Received signals are separated into single-mode with a mode extraction technique. This research reveals that when T(0,1) propagates through the pipe shoe, the energy of T(0,1) passes into the pipe shoe. The leakage phenomenon results in the complexity and misinterpretation of the echo.

Using ultrasonic guided waves improve a problem of time-consuming and laborious with conventional ultrasonic method involving point¡Vby-point inspection. In order to measure of hundreds meters of pipeline in oil and chemical industries, guided waves inspection technique is used and developed widely. For fast and long range inspection, a pulse-echo system is used to excite Lamb waves propagating along the pipe. The collection and analysis of the returning echoes indicate the present of corrosion. But if the pipe features, like bends or supports, are corrosive, the signal of corrosions is often covered with echoes of pipe features. Then it causes the inspection more difficult. In this study, the pipe feature which discussed is the welded support. The focus of the advanced analysis, Discrete Wavelet Transform, of the echoes reflected from the welded support on a 3 inch pipe by experimental and finite element method, so as to improve the ability of corrosion inspection on pipe features. To study the feasibility of the improvement in the effect of coherent noise for guided wave inspection by Wavelet analysis. Results show that original signals can not be differentiated by comparing with signals of normal support, general corrosive support, and support with notch. But after processing these three signals by Wavelet analysis, the situation of the 3 type supports from the signals can be differentiated. The simulated results of two different models and five exciting frequencies show the similar trend to the experimental results after Wavelet transform processing. It is success on separating the signals of normal support and corrosive support with Wavelet Analysis, and this method of this study is useful to improve the effect of coherency noise for guided wave inspection.

A rock bolt installed in field has only one short exposed end on the rock surface. This condition has posed challenges in field instrumentation and made it difficult to use the ultrasonic guided wave method for rock bolt monitoring. In rock bolt laboratory tests using ultrasonic guided waves, the input and receiving transducers are typically installed at the two exposed ends of a bolt. This is suitable to laboratory conditions but not practical in the field because one of the ends of a rock bolt is embedded in the rock mass. A method needs to be found to install the receiving transducer at a suitable location in the field for receiving valid wave data. In this thesis, a practical approach is proposed for conducting field tests with the installation of the receiving transducer on the grout surface near the exposed end of the bolt. The effects of the installation location of the receiving transducer are studied with numerical modeling. Experiments are conducted to verify the numerical modeling results. The results indicate that the data obtained from the receiving transducer installed on the grout surface at a proper location are representative and can be analyzed through the established correlations to determine the required parameters. Previous researches have mostly focused on the feasibility of the ultrasonic guided wave method for rock bolt tests and on the behavior of ultrasonic guided waves of fully grouted rock bolts in laboratory conditions. No further study has been performed to identify the grout defects in grouted rock bolts. Adequate understanding of the behaviour of ultrasonic guided waves in rock bolts with defects is therefore prerequisite for this method to be applied in practice. This thesis investigates the effects of some typical defects (e.g., an insufficient rebar length, a missing grout at the ground end, and a void in grout) in grouted rock bolts using the developed field measurement method and numerical modeling. The results are verified by laboratory tests using the equipment set-up established in this research. The results indicate that it is practically possible to identify those grout defects using ultrasonic guided waves.

This thesis investigates a novel optoelectronic platform based on the integration of superconductive structures, such as thin films and micro-constrictions, with optical waveguides for ultra-fast and ultra-sensitive devices with applications including high-speed optical communications, quantum optical information processing, and terahertz (THz) devices and systems. The kinetic-inductive photoresponse of superconducting thin films will be studied as the basic optoelectronic process underlying the operation of these novel devices. Analytical formulation for the non-bolometric response is presented, and experimental photodetection in YBCO meander-line structures will be demonstrated. A set of superconducting coplanar waveguides (CPW) are designed and characterized, which support the operation of the devices at microwave frequencies. Microwave-photonic devices comprising a microwave transmission line and a light-sensitive element, such as a meander-line structure, are designed and measured for implementation of optically tunable microwave components. In order to support low-loss and low-dispersion propagation of millimeter-wave and THz signals in ultra-fast and wideband kinetic-inductive devices, surface-wave transmission lines are proposed, incorporating long-wavelength Surface Plasmon Polariton (SPP) modes in planar metal-dielectric waveguides. The theory of superconducting optical waveguides, including analytical formulation and numerical methods, is developed in detail. The implementation of superconducting optical waveguides is discussed thoroughly, employing conventional dielectric-waveguide techniques as well as optical SPP modes. Superconductive traveling-wave photodetectors (STWPDs) are introduced as a viable means for ultra-fast and ultra-sensitive photodetection and photomixing. A modified transmission line formalism is developed to model STWPDs, where light is guided through an optical waveguide and photodetection is distributed along a transmission line. As an appendix, a systematic approach is developed for the analysis of carrier transport through superconducting heterostructures and micro-constrictions within the Bogoliubov-de Gennes (BdG) framework. The method is applied to study the role of Andreev reflection and Josephson-like phenomena in the current-voltage characteristics of inhomogeneous superconducting structures. I-V characteristics are experimentally demonstrated in YBCO micro-constrictions with potential applications in millimeter-wave and THz devices.

In this thesis, we proposed general forms of eigen-mode analysis for multilayer optical waveguides. This study discussed the periodic structure in transverse direction and used the slowly varying envelope approximation to approximate the wave function. Firstly, we presented a general method for analyzing the multilayer nonlinear optical waveguide structure by using modal theory. The nonlinear optical waveguide is a medium whose refractive index changes with the electric field intensity. The general method can also be degenerated into some other special cases for analyzing multilayer nonlinear optical waveguide. Secondly, a general method for analyzing the multilayer optical waveguides with photonic metamaterials characterized by simultaneously negative dielectric permittivity and magnetic permeability was studied. The research pointed out explicitly that the three-layer planar waveguide with photonic metamaterials could support forbidden regions. The complete set of modes of all possible solutions for the TE wave in photonic metamaterials optical waveguide was found. The transverse electric field distributions and dispersion relations in multilayer optical waveguides can be obtained by using these general forms. Finally, we used the general forms to design an all-optical mode converter which composed of a pair of multibranch optical waveguides. The analytical and numerical results show excellent agreement.