Showing papers on "Guided wave testing published in 2018"

Method and repeater for broadband distribution

Abstract: Aspects of the subject disclosure may include, for example, a method that includes extracting first channel signals from first guided electromagnetic waves bound to an outer surface of a transmission medium of a guided wave communication system; amplifying the first channel signals to generate amplified first channel signals in accordance with a phase correction; selecting one or more of the amplified first channel signals to wirelessly transmit to at least one client device via an antenna; and guiding the amplified first channel signals to the transmission medium of the guided wave communication system to propagate as second guided electromagnetic waves, wherein the phase correction aligns a phase of the second guided electromagnetic waves to add in-phase with a residual portion of the first guided electromagnetic waves that continues propagation along the transmission medium

Launcher and coupling system to support desired guided wave mode

Abstract: Aspects of the subject disclosure may include, for example, a launcher that includes a hollow waveguide that guides a first electromagnetic wave conveying data from a transmitting device. A dielectric stub coupler receives the first electromagnetic wave from the hollow waveguide to form a second electromagnetic wave that propagates along a portion of the dielectric stub coupler adjacent to a transmission medium, wherein second electromagnetic wave propagates along the dielectric stub coupler via a first guided wave mode and a second guided wave mode, and wherein the portion has a length that supports a coupling of the second guided wave mode for propagation along an outer surface of the transmission medium.

Detection, Localisation and Assessment of Defects in Pipes Using Guided Wave Techniques: A Review.

Abstract: This paper aims to provide an overview of the experimental and simulation works focused on the detection, localisation and assessment of various defects in pipes by applying fast-screening guided ultrasonic wave techniques that have been used in the oil and gas industries over the past 20 years. Major emphasis is placed on limitations, capabilities, defect detection in coated buried pipes under pressure and corrosion monitoring using different commercial guided wave (GW) systems, approaches to simulation techniques such as the finite element method (FEM), wave mode selection, excitation and collection, GW attenuation, signal processing and different types of GW transducers. The effects of defect parameters on reflection coefficients are also discussed in terms of different simulation studies and experimental verifications.

The choice of ultrasonic inspection method for the detection of corrosion at inaccessible locations

Abstract: Inspection for corrosion and pitting defects in the petrochemical industry is vital and forms a significant fraction of the operating expenditure. Low frequency guided wave inspection is frequently employed as it gives large area coverage from a single transducer position. However, detection becomes problematic at inaccessible regions such as pipe supports or beyond T-joints since the low frequency guided waves produce a significant reflection from the feature itself, hence limiting the defect detectability of the method. This suggests testing at higher frequencies which helps to minimise the reflection from the feature and also improves the sensitivity to smaller defects. There are a number of guided wave and related techniques implemented for corrosion inspection including the S0 mode (at ∼ 1 MHz-mm), SH0 and SH1 modes (at ∼ 3 MHz-mm), CHIME, M-skip and Higher Order Mode Cluster (A1 mode at ∼ 18 MHz-mm). This paper presents a systematic analysis of the defect detection performance of each method with sharp and gradual defects, as well as their sensitivity to attenuative coatings, liquid loading, surface roughness and ability to test beyond features such as T-joints. It is shown by finite element analysis backed up by experiments that the A1 mode provides the best overall performance when dealing with surface features such as T-joints and coatings because of its low surface motion. Additionally a combination of two or more methods is suggested for corrosion inspection at inaccessible locations: The A1 mode in reflection for severe, sharp, pitting type defects; long range guided waves in reflection for large-area thinning and the SH1 mode in transmission for shallow, gradual defects.

Quantitative characterization of disbonds in multilayered bonded composites using laser ultrasonic guided waves

Abstract: A quantitative method for evaluating the sizes of defects has been proposed to be applied to laser ultrasonic guided waves testing multilayered bonded composites. The finite element model was built for studying on laser-generated ultrasonic waves in a bonded composite. A laser ultrasonic inspection system using lasers for generation and detection of ultrasonic waves was established to be utilized to conduct a series of experiments for verifying the simulation results. The lowest guided wave modes generated by a pulsed laser were used to characterize a bonded joint. The interaction of laser ultrasonic guided waves with disbonds was investigated to determine a reasonable source-receiver distance to reach a compromise between detection accuracy and efficiency. The −8 dB method has been proposed to measure the sizes of disbonds based on the scanning laser source technique, and the relative errors between the measurement sizes and the actual sizes are not more than 8%. The C-scan results based on laser ultrasonic guided waves jointed with the proposed quantitative method not only facilitate the visualization of disbonds, but also provide precise information on the bonded quality, which has great potential for on-line inspection of adhesively bonded composites.

Nonlinear features of guided wave scattering from rivet hole nucleated fatigue cracks considering the rough contact surface condition

Abstract: This article presents the investigation of nonlinear scattering features of guided waves from rivet hole nucleated fatigue cracks considering the rough contact surface condition. A small-size numerical model based on the local interaction simulation approach is developed, enabling the efficient analysis of the contact acoustic nonlinearity during the wave crack interactions. The study starts with an idealized breathing crack model possessing smooth, perfectly kissing contact surfaces. Then, the nature of rough crack surfaces is considered with randomly distributed initial openings and closures. Several distinctive aspects of the nonlinear scattering phenomenon are discussed: (1) the amplitude effect, which renders significantly different nonlinear response under various levels of excitation wave amplitudes; (2) the directivity and mode conversion features, which addresses the scattering direction dependence of the fundamental and superharmonic wave mode components; (3) the nonlinear resonance phenomenon, which maximizes the nonlinear response during the wave crack interactions at certain excitation frequency ranges. This study demonstrates that these nonlinear features are substantially influenced by the crack surface condition and differ much between an idealized breathing crack and a rough crack in most practical cases. Fatigue tests on a thin aluminum plate with a rivet hole is conducted to induce cracks in the specimen. An active sensor array surrounding the crack zone is implemented to generate and receive ultrasonic guided waves in various directions. Current work emphasizes on using a highly efficient numerical model to explain the nonlinear features of scattered waves from fatigue cracks considering the rough crack surface condition. These special features may provide insights and guidelines for nonlinear guided wave based nondestructive evaluation and structural health monitoring system design. The paper finishes with discussion, concluding remarks, and suggestions for future work.

Second order ultrasonic guided wave mutual interactions in plate: Arbitrary angles, internal resonance, and finite interaction region

Abstract: The sensitivity of ultrasonic wave interactions to material and geometric nonlinearities makes them very useful for nondestructive characterization. The ability of guided waves to interrogate inaccessible material domains, be emitted and received from a single surface, and penetrate long distances provides capabilities that bulk waves do not. Furthermore, mutual interactions between waves propagating in collinear or non-collinear directions provide excellent flexibility as to which types of waves are used, as well as their frequencies and interaction angles. While the interaction of bulk waves is well established, the mutual interaction of guided waves traveling in arbitrary directions in a plate is not and requires a general vector-based formulation. Herein, by vector-based calculations, the internal resonance criteria are formulated and evaluated for waves propagating in arbitrary directions in a plate. From the analysis, it is found that non-collinear guided wave interactions transfer power to secondary guided wave modes that is impossible for collinear interactions, which is completely analogous to bulk waves. For the case of tone burst-pulsed wave packets at nonzero interaction angles, the wave interaction zone has a finite size, and its size is dictated by many factors, including, for example, the group velocities of the waves, interaction angle, pulse duration, and dispersion. An analytical model is introduced for finite-sized interaction zones and used to demonstrate the effect of group velocity mismatch on the generation of secondary waves. In addition, finite element simulations are compared to the analytical model and provide additional insight into secondary wave generation and propagation.

Guided wave launcher with aperture control and methods for use therewith

Abstract: In accordance with one or more embodiments, a system includes an array of antennas. A plurality of transceivers is configured to generate first signals, in response to control signals. A controller is configured to generate the control signals to control, via the plurality of transceivers, an antenna aperture of the array of antennas. The array of antennas is configured to generate, in response to first signals, radiated waves according to the antenna aperture of the array of antennas, the radiated waves inducing a first guided electromagnetic wave that is guided by a surface of a transmission medium and propagates along the transmission medium without requiring an electrical return path.

Dynamic Time Warping Temperature Compensation for Guided Wave Structural Health Monitoring

Abstract: Guided wave structural health monitoring is widely researched for remotely inspecting large structural areas. To detect, locate, and characterize damage, guided wave methods often compare data to a baseline signal. Yet, environmental variations create large differences between the baseline and the collected measurements. These variations hide damage signatures and cause false detection. Temperature compensation algorithms, such as baseline signal stretch and the scale transform have been used to optimally realign data to a baseline. While these methods are effective in some conditions, their performance deteriorates in the presence of large temperature variations, long propagation distances, and high frequencies. In this paper, we use dynamic time warping to better align guided wave data and to overcome these errors. When compared with stretch-based methods, we show that the dynamic time warping is more robust to the above-mentioned errors and more accurately detects damage with weak ultrasonic signatures.

Local Interaction Simulation Approach for Efficient Modeling of Linear and Nonlinear Ultrasonic Guided Wave Active Sensing of Complex Structures

Abstract: This paper presents the local interaction simulation approach (LISA) for efficient modeling of linear and nonlinear ultrasonic guided wave active sensing of complex structures. Three major modeling challenges are considered: material anisotropy with damping effects, nonlinear interactions between guided waves and structural damage, as well as geometric complexity of waveguides. To demonstrate LISA’s prowess in addressing such challenges, carefully designed numerical case studies are presented. First, guided wave propagation and attenuation in carbon fiber composite panels are simulated. The numerical results are compared with experimental measurements obtained from scanning laser Doppler vibrometry (SLDV) to illustrate LISA’s capability in modeling damped wave propagation in anisotropic medium. Second, nonlinear interactions between guided waves and structural damage are modeled by integrating contact dynamics into the LISA formulations. Comparison with commercial finite element software reveals that LISA can accurately simulate nonlinear ultrasonics but with much higher efficiency. Finally, guided wave propagation in geometrically complex waveguides is studied. The numerical example of multimodal guided wave propagation in a rail track structure with a fatigue crack is presented, demonstrating LISA’s versatility to model complex waveguides and arbitrary damage profiles. This paper serves as a comprehensive, systematic showcase of LISA’s superb capability for efficient modeling of transient dynamic guided wave phenomena in structural health monitoring (SHM). [DOI: 10.1115/1.4037545]

Mode Selectivity of SH Guided Waves by Dual Excitation and Reception Applied to Mode Conversion Analysis

Abstract: Shear horizontally (SH) guided waves, generated by periodic permanent magnet arrays, have been used previously in nondestructive evaluation of metal plates and pipes. When an SH guided wave interacts with a defect or a change in sample thickness, the incident SH wave may undergo mode conversion. Analysis of mode conversion is complicated, due to the interference of several propagating modes in the received signal that can often temporally overlap. This paper proposes a mode selection technique to help understand the interaction of SH guided waves with changes in sample thickness. Using an understanding of the propagation characteristics of the guided waves, SH guided waves are sequentially generated and detected on both surfaces of the plate, capturing four distinct waveforms. By superposition of the detected signals, symmetric modes can be clearly separated from antisymmetric modes in the processed received signals. For this method to work well, the transducers used should have very similar responses and be precisely positioned on exactly opposite positions either side of the plate. Finite element simulations are also performed, mirroring the experimental measurements, and the results correlate well with the experimental observations made on an 8-mm-thick plate with a region of simulated wall thinning machined into the sample.

Structural health monitoring using torsional guided wave electromagnetic acoustic transducers

Abstract: Torsional guided wave inspection is widely used for pipeline inspection. Piezoelectric and magnetostrictive transducers are most commonly used to generate torsional guided waves. These types of tra...

Guided wave directional coupler and methods for use therewith

Abstract: In accordance with one or more embodiments, a directional coupler includes a first dielectric cable is configured to receive a first electromagnetic wave from the first port and to generate a second electromagnetic wave that propagates along a transmission medium in a first direction without requiring an electrical return path. A second dielectric cable is configured to couple a first portion of the second electromagnetic wave to a second port, wherein a second portion of the second electromagnetic wave continues to propagate in the first direction along the transmission medium. A third dielectric cable is configured to couple the second portion of the second electromagnetic wave to a third port and to isolate the third port from a third electromagnetic wave propagating along the transmission medium in a second direction that is opposite to the first direction.

Damage Imaging in Lamb Wave-Based Inspection of Adhesive Joints

Abstract: Adhesive bonding has become increasingly important in many industries. Non-destructive inspection of adhesive joints is essential for the condition assessment and maintenance of a structure containing such joints. The aim of this paper was the experimental investigation of the damage identification of a single lap adhesive joint of metal plate-like structures. Nine joints with different defects in the form of partial debonding were considered. The inspection was based on ultrasonic guided wave propagation. The Lamb waves were excited at one point of the analyzed specimen by means of a piezoelectric actuator, while the guided wave field was measured with the use of a laser vibrometer. For damage imaging, the recorded out-of-plane vibrations were processed by means of the weighted root mean square (WRMS). The influence of different WRMS parameters (i.e., the time window and weighting factor), as well as excitation frequencies, were analyzed using statistical analysis. The results showed that two-dimensional representations of WRMS values allowed for the identification of the presence of actual defects in the adhesive film and determined their geometry.

Ridge Resonance: A new Resonance Phenomenon for Silicon Photonics Harnessing Bound States in the Continuum

Abstract: We present a new resonant behavior based on bound states in the continuum in a guided wave silicon platform. The continuum has the form of a collimated beam of light which is confined vertically in a TE mode of a silicon slab. The bound state is a discrete TM mode of a ridge on the silicon slab. The coupling between the slab and ridge modes results in a single sharp resonance at the wavelength where they phase match. We experimentally demonstrate this phenomenon on a silicon photonic chip using foundry compatible parameters and interface it on-chip to standard single mode silicon nanowire waveguides. The fabricated chip exhibits a single sharp resonance near 1550 nm with a line width of a few nanometer, an extinction ratio of 25 dB and a thermal stability of 19.5 pm/C. We believe that this is the first demonstration of bound states in the continuum resonance realized using guided wave components.

Dispersion curves for Lamb wave propagation in prestressed plates using a semi-analytical finite element analysis

Abstract: Acoustoelastic techniques have been recently used to characterize the state of prestress in structures such as plates. The velocity of guided wave modes propagating through plates is sensitive to the magnitude and orientation of the initial state of stress. Dispersion curves for phase velocities of plate guided waves can be computed using the superposition of partial bulk waves (SPBW) method. Here, a semi-analytical finite element (SAFE) method is formulated for the acoustoelastic problem of guided waves in weakly nonlinear elastic plates. The SAFE formulation is shown to provide phase velocity dispersion curve results identical with those provided by the SPBW method for the problem of a plate under a uniaxial and uniform tensile stress. Analytical phase and group velocity dispersion curves are also obtained for a plate with an initial prestress gradient through its thickness using the SAFE method. The magnitude of the prestress gradient is shown to have a significant effect on phase and group velocities of the fundamental and first order Lamb modes, only in certain frequency-thickness regimes.

Observation of Guided Acoustic Waves in a Human Skull.

Abstract: Human skull poses a significant barrier for the propagation of ultrasound waves. Development of methods enabling more efficient ultrasound transmission into and from the brain is therefore critical for the advancement of ultrasound-mediated transcranial imaging or actuation techniques. We report on the first observation of guided acoustic waves in the near field of an ex vivo human skull specimen in the frequency range between 0.2 and 1.5MHz. In contrast to what was previously observed for guided wave propagation in thin rodent skulls, the guided wave observed in a higher-frequency regime corresponds to a quasi-Rayleigh wave, confined mostly to the cortical bone layer. The newly discovered near-field properties of the human skull are expected to facilitate the development of more efficient diagnostic and therapeutic techniques based on transcranial ultrasound.

Guided wave launcher with lens and methods for use therewith

Abstract: In accordance with one or more embodiments, a guided wave launcher includes an array of antennas that generates first near field signals. A dielectric lens is configured to guide the first near field signals to a surface of a transmission medium, the first near field signals inducing a first guided electromagnetic wave that is guided by the surface of the transmission medium and propagates along the transmission medium without requiring an electrical return path.

Calculation of Guided Wave Dispersion Characteristics Using a Three-Transducer Measurement System

Abstract: Guided ultrasonic waves are of significant interest in the health monitoring of thin structures, and dispersion curves are important tools in the deployment of any guided wave application. Most methods of determining dispersion curves require accurate knowledge of the material properties and thickness of the structure to be inspected, or extensive experimental tests. This paper presents an experimental technique that allows rapid generation of dispersion curves for guided wave applications when knowledge of the material properties and thickness of the structure to be inspected are unknown. The technique uses a single source and measurements at two points, making it experimentally simple. A formulation is presented that allows calculation of phase and group velocities if the wavepacket propagation time and relative phase shift can be measured. The methodology for determining the wavepacket propagation time and relative phase shift from the acquired signals is described. The technique is validated using synthesized signals, finite element model-generated signals and experimental signals from a 3 mm-thick aluminium plate. Accuracies to within 1% are achieved in the experimental measurements.

A variable-frequency structural health monitoring system based on omnidirectional shear horizontal wave piezoelectric transducers

Abstract: Structural health monitoring (SHM) is of great importance for engineering structures as it may detect the early degradation and thus avoid life and financial loss. Guided wave based inspection is very useful in SHM due to its capability for long distance and wide range monitoring. The fundamental shear horizontal (SH0) wave based method should be most promising since SH0 is the unique non-dispersive wave mode in plate-like structures. In this work, a sparse array SHM system based on omnidirectional SH wave piezoelectric transducers (OSH-PT) was proposed and the multi data fusion method was used for defect inspection in a 2 mm thick aluminum plate. Firstly, the performances of three types OSH-PTs was comprehensively compared and the thickness-poled d15 mode OSH-PT used in this work was demonstrated obviously superior to the other two. Then, the signal processing method and imaging algorithm for this SHM system was presented. Finally, experiments were carried out to examine the performance of the proposed SHM system in defect localization and imaging. Results indicated that this SHM system can locate a through hole as small as 0.12λ (4 mm) in diameter (where λ is the wavelength corresponding to the central operation frequency) under frequencies from 90 to 150 kHz. It can also locate multiple defects accurately based on the baseline subtraction method. Obviously, this SHM system can detect larger areas with sparse sensors because of the adopted single mode, non-dispersive and low frequency SH0 wave which can propagate long distance with small attenuation. Considering its good performances, simple data processing and sparse array, this SH0 wave-based SHM system is expected to greatly promote the applications of guided wave inspection.