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Detection and criticality assessment of defects appearing in inaccessible locations in pipelines pose a great challenge for many industries. Inspection methods which allow for remote defect detection and accurate characterisation are needed. Guided wave testing (GWT) is capable of screening large lengths of pipes from a single device position, however it provides very limited individual feature characterisation. This paper adapts Plane Wave Imaging (PWI) to pipe GWT to improve defect characterization for inspection in nearby locations such as a few metres from the transducers. PWI performance is evaluated using finite element (FE) and experimental studies, and it is compared to other popular synthetic focusing imaging techniques. The study is concerned with part-circumferential part-depth planar cracks. It is shown that PWI achieves superior resolution compared to the common source method (CSM) and comparable resolution to the total focusing method (TFM). The techniques involving plane wave acquisition (PWI and CSM) are found to substantially outperform methods based on full matrix capture (FMC) in terms of signal-to-noise ratio (SNR). Therefore, it is concluded that PWI which achieves good resolution and high SNR is a more attractive choice for pipe GWT, compared to other considered techniques. Subsequently, a novel PWI transduction setup is proposed, and it is shown to suppresses the transmission of unwanted S 0 mode, which further improves SNR of PWI.

This paper is concerned with the design of magnetostrictive transducers for the excitation and detection of guided waves in metal pipes of small diameter (mm) and their application to the study of wave propagation in pipes filled with water or supercritical CO(2). Optimized system design is based on a simulation of the overall signal pathway which includes the electric circuit conditions at the transducers, mode excitability, and the wavenumber filtering effect of the spatial distribution of the exciting alternating magnetic field. A prototype system was built, and experimental observations on small diameter pipes indicated good agreement with expected results from simulations. The reassigned spectrogram has been used to compare expectation on the basis of guided wave dispersion curves for fluid-filled pipes with experimental data.

Planar coil electromagnetic acoustic transducers (EMATs) are investigated for the excitation and detection of Lamb waves in nonferromagnetic metallic wave-guides. Such EMATs are attractive for certain applications due to their omni-directional sensitivity to wave modes with predominantly in-plane surface displacement, such as the So Lamb wave mode. A model is developed that enables the modal content of the radiated Lamb wave field from a transmitting EMAT to be calculated, and the output voltage from a receiving EMAT to be predicted when a Lamb wave mode is incident on it. The predictions from this model are compared with experimental data obtained from 12 different EMATs tested on a 5-mm thick aluminum plate, and good agreement is obtained. The model then is used to analyze the different effects that contribute to the overall Lamb wave modal sensitivity of an EMAT. The relationship between coil geometry and wavelength is examined.

Numerous engineering components feature prismatic wedge-like structures that require nondestructive evaluation (NDE) in order to ensure functionality or safety. This article focuses on the inspection of the wedge-like seal fins of a jet engine drum, though the capabilities presented will be generic. It is proposed that antisymmetric flexural edge modes, feature-guided waves localized to the wedge tips, may be used for defect detection. Although analytical solutions exist that characterize the ultrasonic behavior of ideal wedges, in practice, real wedges will be irregular (containing, for example, truncated tips that are built onto an associated structure or have nonstraight edges), and therefore, generic methodologies are required to characterize wave behavior in nonideal wedges. This article uses a semianalytical finite-element (SAFE) methodology to characterize the guided waves in wedge-like features with irregular cross sections to assess their suitability for NDE inspection and compare them with edge modes in ideal wedges. The science and methodologies required in this article are necessary to select an appropriate operating frequency for the particular application at hand. In addition, this article addresses the practical challenge of excitation and detection of flexural edge modes by presenting a piezoelectric-based dry-coupled transducer system suitable for pulse-echo operation. This article, therefore, presents the scientific basis required for industrial exploitation, together with the practical tools that facilitate use. The study concludes with the experimental demonstration of the edge wave-based inspection of a seal fin, achieving a signal-to-noise ratio of 28 dB from a 0.75-mm radial tip defect. [ABSTRACT FROM AUTHOR]