Guided Wave Propagation Research Articles

A non-reference detection method of the external ultrasonic liquid level switch using the PZT

Oil tank level is an important control parameter in oil depot management. According to the principle that the liquid in the oil tank can absorb the guided wave propagation energy in the tank wall, this paper studied a non-reference detection method of external ultrasonic liquid level switch based on the signal energy change value between the current and the previously liquid level detection signal. The experimental results show that the ultrasonic guided wave with the center frequency of 30 kHz is sensitive and low misjudgment to liquid level detection. According to the experimental setup, the liquid level judgment threshold is set to 0.9890. The influence of the liquid on the guided wave propagation in the tank wall decreases with the frequency of the guided wave increase. Finally, the effectiveness of the proposed method is verified on a diesel oil tank. The research of this paper provides a method for the research of oil tank external liquid level switch technology, and provides an idea for the research of oil tank liquid level measurement based on ultrasonic guided wave.

A New Model of Ultrasonic Guided Wave Propagation in Blood Vessels and Its Propagation Characteristics

The identification of a blood vessel’s elastic properties by an ultrasonic guided wave mainly depends on the accurate propagation characteristics, which are obtained by solving the problem of elastic mechanics based on a thin-plate model. However, this method cannot accurately predict the characteristics for low frequencies. Since blood vessels are of a tubular structure, a hollow-cylinder model, constructed to model blood vessels, is proposed in this paper. Based on this model, the propagation characteristics and dispersion curves of the ultrasonic guided wave propagating along the axial direction are studied by expanding the state equation using Legendre polynomials. A detailed comparison between the results of the proposed model and the thin-layer-based model is presented. It is shown that the dispersion curves of the L (0,1) modes, calculated by the two different models, are a match for high frequencies but differ for low frequencies. The dispersion curve of the L (0,1) mode calculated by the proposed model is in good agreement with the results of the reported experiments. Then, the relationship between the propagation characteristics of ultrasonic guided waves and Young’s modulus is studied. It is discovered that the phase velocity and group velocity are significantly affected by Young’s modulus close to the cutoff frequency, which has important implications for the selection of the detection frequency to the characteristic parameter of vascular.

Stabilizing solitons of the cubic–quintic nonlinear Schrödinger equation by frequency-dependent linear gain-loss and delayed Raman response

We demonstrate transmission stabilization against radiation emission by frequency-dependent linear gain-loss and perturbation-induced frequency shifting for solitons of the cubic–quintic nonlinear Schrödinger (CQNLS) equation. We consider soliton propagation in a nonlinear optical waveguide with focusing cubic nonlinearity, defocusing quintic nonlinearity, and dissipative perturbations due to weak frequency-dependent linear gain-loss, cubic loss, and delayed Raman response. The frequency shifting is induced by delayed Raman response. Our perturbation analysis and numerical simulations with the perturbed CQNLS equation show that transmission stabilization with CQNLS solitons is indeed possible, and in this way provide the first demonstration of the stabilization method for solitons of a nonintegrable nonlinear wave model. Moreover, we find that transmission stabilization with energetic CQNLS solitons is realized with significantly smaller frequency shifts and pulse distortion compared with stabilization with energetic solitons of the cubic nonlinear Schrödinger equation. Therefore, our study also demonstrates that stabilization of energetic solitons by the method is significantly improved by the presence of defocusing quintic nonlinearity.

Ultrasonic guided waves through Coalesence of matrix cracks and delaminations in laminated composites

Composite fabric-matrix interface mismatch during manufacturing and applied loads cause matrix micro-cracks and their evolution toward interface delamination and stiffness reduction. Fatigue and impact loads can grow these matrix cracks further as early damage precursors, which are not easily detectable. We simulate ultrasonic guided wave propagation in laminated composite with matrix crack mixed delamination site to understand better detection possibilities for these damage precursors using the ultrasonic inspection method. Since extremely small wavelength ultrasonic waves attenuate rapidly in composites, whereas long wavelength guided waves may not produce high sensitivity to small-scale defects, therefore we attempt to analyze super-resolution quantitative scheme with suitable frequencies to correlate defect parameters. We employ a time-domain spectral finite element method for fast computation of high-frequency wavefield while accurately resolving the matrix crack-delamination geometric features. Its high-order field interpolation enables us to model the nearfield interactions of the waves with the transverse micro-cracks and further with an evolved macro-scale delamination. The computational scheme is aimed to scale to complex defect local field simulations and cover larger size composite structures. This is achieved due to a mathematically consistent diagonalized mass matrix property which makes the implicit time marching-based computation highly efficient for highly resolved and large-size finite element systems. The transient dynamic stress field around the cracks modulates the guided wave mode packets. We analyze the characteristics of the signal sensitivities due to the defect features, most notably, an interesting correlation between matrix crack density and frequency modulation or sub-band contribution. Wave interaction with the defect region creates weak but distinct reflection patterns while transmitting through the region. The study provides useful and new understanding towards defect size estimation and indicative measure of thickness wise layers of matrix cracks and its coalescence into delamination in terms of energy spectral density of the sub-bands.

A semi-analytical approach to anchorage system with defects considering radial leakage of guided wave

An equivalent model of a piecewise viscoelastic rod is proposed to investigate the propagation and attenuation characteristics of guided waves in an anchorage/pile foundation system. Based on the property that the leaking wave attenuates rapidly in a viscoelastic medium, the effective radius is introduced to characterize the influence area of the guided wave leaking from the rod to the surrounding rock/soil. The mixing rule of composite materials is used to obtain equivalent material parameters of the rod and the surrounding rock/soil. The semi-analytical solution for the dynamic response of each anchorage segment under arbitrary excitation is derived in the time domain by using Laplace transform and inversion. Then, a system of integral equations is derived from the continuity condition at the interface between segments and it is solved numerically. The comparison of the computational results in validation examples with the related experimental data and the analytical solutions available in references as well as the FEM demonstrates the applicability of the proposed one-dimensional simplified model and the semi-analytical approach. Moreover, the influences of excitation frequency, anchorage geometry, surrounding rock material, and bonding area on the characteristics of guided wave propagation are examined. In addition, the dispersion curves with different parameters and for multiple reflections are given. Finally, the anchorage length and position are identified by the time difference and wave velocity of the interface reflected wave.

Ultrasonic Nonlinearity Experiment due to Plastic Deformation of Aluminum Plate Due to Bending Damage.

The nonlinear ultrasonic evaluation technique is useful for assessing micro-defects and microstructure changes caused by fatigue or bending damage. In particular, the guided wave is advantageous for long-distance testing such as piping and plate. Despite these advantages, the study of nonlinear guided wave propagation has received relatively less attention compared to bulk wave techniques. Furthermore, there is a lack of research on the correlation between nonlinear parameters and material properties. In this study, the relationship between nonlinear parameters and plastic deformation resulting from bending damage was experimentally investigated using Lamb waves. The findings indicated an increase in the nonlinear parameter for the specimen, which was loaded within the elastic limit. Inversely, regions of maximum deflection in specimens with plastic deformation exhibited a decrease in the nonlinear parameter. This research is expected to be helpful for maintenance technology in the nuclear power plant and aerospace fields that require high reliability and accuracy.

Direct numerical simulation of acoustic wave propagation in ocean waveguides using a parallel finite volume solver

Numerical simulations based on the Finite Volume Method (FVM) solve the wave equation directly to provide highly accurate predictions of the sound field in ocean waveguides without model simplification and loss of generality. However, the huge computational complexity severely limits the application range of direct numerical solvers for underwater acoustic waves. In this paper, a highly scalable parallel algorithm for solving acoustic models using the cell-centred finite volume method was proposed, and a corresponding direct numerical solver was developed and validated. The paper has three main findings as follows. Firstly, the acoustic solver was implemented based on a generic framework for solving partial differential equations (PDEs), so that more complicated models such as fluid–sound coupling and sound–structure coupling could be easily extended. Secondly, the large spatial scales of underwater sound propagation can be efficiently calculated by parallel computing. Thirdly, our approach demonstrated high computational accuracy and the ability to support complex scenarios. We verify the accuracy and efficiency of the solver through experiments, and prove the solving ability of the solver in large-scale, complex structures and complex configurations.

Coupling Efficiency of a Spot Size Converter for Optical Fiber-Chip Connections

The light propagation in optical waveguide must be able to maintain low propagation loss, low coupling loss and scattering loss condition, especially in the junction. In this research, a spot size converter is proposed to preserve the lowest coupling loss. This optical converter is composed of a single mode optical fiber (SiO2) including inversed taper. The optical input signal from the optical fiber is launched into photonic integrated circuits and then coupled into the Si-Slab waveguide. Furthermore, linear form with the length dependence has been studied to obtain the optimal position of optical fiber and the chip and analyzed the coupling efficiency of it. The purpose of this research is to procure the optimal form of spot size converter. The simulation result shows the coupling loss of linear form is 0.62 dB and 0.24 dB on TE and TM mode condition respectively. Along with the increase in the taper length, the coupling loss obtained tends to decrease as well. So that, it can be assumed the design of a linear form with 100 μm taper length provides the highest coupling efficie ncy.

Arc Discharge System for Micromachining of Helical Fiber.

This article developed a micromachining system of arcing helical fiber with four electrodes to address the issues with conventional approaches to processing helical fibers, which have several uses. The technique may be utilized to create several types of helical fibers. First, the simulation demonstrates that the four-electrode arc's constant-temperature heating area is larger than the two-electrode arc's size. A large constant-temperature heating area is not only beneficial to the stress release of fiber, but also reduces the influence of fiber vibration and reduces the difficulty of device debugging. Then, a variety of helical fibers with various pitches were processed using the system presented in this research. By using a microscope, it can be observed that the cladding and core edges of the helical fiber are constantly smooth and the central core is tiny and off-axis, both of which are favorable for the propagation of optical waveguides. A low off-axis has been shown to minimize optical loss through modeling of energy coupling in spiral multi-core optical fibers. The transmission spectrum findings indicated that the device's insertion loss and transmission spectrum fluctuation were both minimal for four different types of multi-core spiral long-period fiber gratings with intermediate cores. These prove that the spiral fibers prepared by this system have excellent quality.

Ultrasonic guided waves as an indicator for the state-of-charge of Li-ion batteries

Conventional battery management systems rely on cell voltage, current, and temperature to predict the battery state-of-charge and state-of-health, but their accuracy is limited. To overcome this limitation, ultrasonic probing has been proposed as a novel battery monitoring technique. This paper introduces the use of ultrasonic chirp signals for the transfer of ultrasound-based battery monitoring techniques without requiring prior knowledge of the architecture of the cell. To validate this technique, small, lightweight piezoelectric disc transducers that can be easily installed on off-the-shelf battery pouch cells were utilized for large cells with a capacity of 12.5 Ah. Furthermore, the dominant frequency of the response signal to a Hanning-windowed tone burst signal was identified as a quantitative state-of-charge indicator. A predictive model was developed to compare the performance of this indicator with that of previous ultrasound-based state-of-charge prediction methods. The influence of the cell temperature and cycle age on ultrasonic guided wave propagation was also investigated and isolated for analysis.

Mode purification for multimode Lamb waves by shunted piezoelectric unimorph array

Guided wave-based nondestructive testing and structural health monitoring methods have been developed to exhibit attractive potentials and best prospects for rapid and sensitive detection of defects or damage in engineering structures. Different modes of guided waves can provide different sensitivities of damage detection. However, the multimode and mode conversion nature of guided waves poses significant challenges to mode purification of received signals. This study aims to design a metamaterial-based smart transducer for mode purification of Lamb waves in a plate, which can filter out an undesired mode of the Lamb wave to enhance sensing and actuating signals of a dominated mode. The smart transducer consists of a periodic array of shunted piezoelectric unimorphs with staggered polarization directions and is bonded on the surface of a host plate. Numerical and experimental results show that a local resonance bandgap for an anti-symmetric Lamb wave, rather than a symmetric Lamb wave, can be obtained and tuned through the shunting inductance circuit. Within such mode bandgap, the wave control for propagating a specific mode of the Lamb wave can be further realized, i.e., the mode of the Lamb wave is purified. The design presented herein offers enhanced capabilities in controlling guided wave propagation for engineering applications and nondestructive testing techniques.

Retraction

This article refers to:RETRACTED ARTICLE: Convergence study on ultrasonic guided wave propagation modes in an axisymmetric cylindrical waveguide

Numerical Simulations in Ultrasonic Guided Wave Analysis for the Design of SHM Systems—Benchmark Study Based on the Open Guided Waves Online Platform Dataset

Structural health monitoring (SHM) strategies based on ultrasonic guided waves are very promising regarding thin-walled lightweight structures. To study the performance of such systems, validated numerical analysis tools have to be used. For that procedure, a benchmark between two numerical methods will be presented. The first promising approach is the elastodynamic finite integration technique (EFIT). Miscellaneous research shows that its capability of capturing wave characteristics and interactions is advanced in various media and structures, including thin-walled composites. The second approach employs conventional shell-type finite elements following the Reissner–Mindlin theory for modelling layered composite structures. The advantage of using such finite element methods (FEM) is their high availability in general purpose simulation tools. As a reference model, the measurement data coming from the Open Guided Waves Project (OGW) was taken into account. The OGW dataset provides the experimental data of ultrasonic guided wave propagation in carbon fiber composite plates with an additional omega stringer. By using this contribution, this experiment was reproduced by simulation. The paper presents the results of a validation and motivates further research, such as in research related to the probability of detection analysis and numerical performance.

Dispersive Modal Characteristics of Guided Waves Propagating in Damaged Rails

The dispersive modal characteristics of propagating guided waves are useful for efficiently detecting defects in high-speed railway rails due to their advantages. This paper presents an effective method for directly analyzing the effect of defects in rails on the dispersive modal characteristics of propagating guided waves, which can be utilized for the defect detection in rails. By using the semianalytical finite element method and from the characteristic equations of the guided wave propagation in waveguides, a general perturbation method is developed to provide an exact relationship between the perturbations of structural stiffness caused by damage and the perturbations of dispersive modal characteristics of propagating guided waves. Thus, the phase velocity and group velocity for the damaged waveguide can be accurately predicted. From the obtained propagating guided wave modes, a mode selection index used for selecting effective guided waves for damage detection is introduced by evaluating the nodal displacements and energy concentrations on the rail surfaces. Finally, a numerical study for a high-speed rail is given to demonstrate the effectiveness of the proposed method for rail defect detection and propagating mode selection. The results of the numerical study show that the dispersive modal properties of propagating modes are affected by the location and size of defects in the rail, and the proposed method can give useful information for effective detection of defects in rails.

Well-posedness of wave scattering in perturbed elastic waveguides and plates: application to an inverse problem of shape defect detection

The aim of this work is to present theoretical tools to study wave propagation in elastic waveguides and perform multi-frequency scattering inversion to reconstruct small shape defects in elastic waveguides and plates. Given surface multi-frequency wavefield measurements, we use a Born approximation to reconstruct localized defect in the geometry of the plate. To justify this approximation, we introduce a rigorous framework to study the propagation of elastic wavefield generated by arbitrary sources. By studying the decreasing rate of the series of inhomogeneous Lamb mode, we prove the well-posedness of the PDE that model elastic wave propagation in two- and three-dimensional planar waveguides. We also characterize the critical frequencies for which the Lamb decomposition is not valid. By using these results, we generalize the shape reconstruction method already developed for acoustic waveguide to two-dimensional elastic waveguides and provide a stable reconstruction method based on a mode-by-mode spacial Fourier inversion given by the scattered field.

Semi-analytical hybrid approach for modelling smart structures and guided wave-based SHM systems for a laminate with multiple delaminations and surface-mounted inhomogeneities

An advanced semi-analytical hybrid approach for simulating the dynamic behaviour of guided waves-based SHM system is proposed here. The proposed numerical method simulates wave excitation, scattering and sensing in a multi-layered elastic waveguide with a system of internal delaminations and piezoelectric/elastic inhomogeneities mounted on the surface the waveguide. The frequency domain spectral element method is applied to describe wave motion in surface-mounted obstacles (piezoelectric transducers, stringers, joints etc.), while the advanced boundary integral equation method is employed to calculate piezo-induced or scattered wave-fields propagating in the multi-layered waveguide with multiple delaminations. The crack opening displacements at the delaminations are interpolated via weighted Chebyshev polynomials of the second kind taking into account square-root behaviour at the tips of delaminations. The collocation and Galerkin methods are applied to satisfy boundary conditions in the contact area between surface-mounted inhomogeneities and the multi-layered waveguide. The convergence, the accuracy and the computational costs of the hybrid method are analysed, and the comparison with the finite element method is provided. The presented novel hybrid method grants opportunity to analyse resonance frequencies of a laminate with multiple delaminations and surface mounted inhomogeneties, calculate energy flow transferred from an actuator into the waveguide and provide fast parametric analysis of guided wave propagation in the considered structures.

Guided wave propagation and skew effects in anisotropic carbon fiber reinforced laminates

Guided ultrasonic waves provide a promising structural health monitoring (SHM) solution for composite structures as they are able to propagate relatively long distances with low attenuation. However, the material anisotropy results in directionally dependent phase and group velocities, in addition to energy focusing, wave skewing, and beam spreading phenomena. These effects could lead to inaccurate damage localization if not accounted for. In this contribution, the guided wave propagation behavior (A0 mode) for a highly anisotropic, unidirectional carbon fiber reinforced polymer laminate is systematically investigated through both finite element analysis and non-contact laser measurements and compared to theoretical predictions. The directional dependency of phase and group velocity measured for a point and line source shows good agreement with theoretical predictions, once a correction for wave skew effects is applied. Wave skew angles were evaluated from the experimental and numerical wave propagation in multiple directions and matched theoretical predictions based on the phase slowness curve. Significant guided wave beam spreading from a line source was observed and quantified from both experiments and simulations and compared with theoretical predictions using the anisotropy factor. The impact of anisotropic guided wave propagation behavior on SHM is discussed.

On acoustic guided wave propagation in reinforced concretes and characterization of interface bonding damages

As a possible method for structural health monitoring, guided waves are excellent for hidden damage diagnosis due to their long propagation distance and high damage sensitivity. The multimodal and dispersion phenomena are the primary challenges in the use of guided wave technology for engineering applications. Currently, plate, thin-walled tube, and rod structures—where multimodality and dispersion are comparatively mild and simple to control—remain the major applications of guided wave technology. For more complicated civil engineering structures, severe multimodal and dispersion phenomena cause more difficult issues. The present work began with the study of round-faced reinforced concrete. The waveguide propagation characteristics are computationally analyzed with the assistance of theoretical calculation methods and sweeping frequency simulation experiments. These analytical tools are then creatively applied to threaded reinforced concrete, and the dispersion characteristics of this complex, axially periodically varying waveguide are successfully analyzed. The phenomenon of frequency band pass/stop is also discussed. In addition, this research provides ideas for nondestructive testing and inverse imaging in this field by means of deep learning of the interface debonding defect characteristics of reinforced concrete with the help of convolutional neural networks. This work can be applied not only to various complex reinforced concrete structures but can also be extended to waveguide propagation analysis and defect size data inversion in various complex periodic structures.

Numerical simulation of wave propagation in ice-covered ocean environments based on the equivalent-source method

Accurate modeling of sound propagation in ice-covered ocean environments can help with interpreting discrepancies between predictions and experimental observations in the changing Arctic Ocean; this is advantageous for environmental conservation, resource exploration, and naval applications. Building on the recent development of the equivalent-source (ES) method (ESM), herein, an ESM-based sub-ice model (ESM-SUBICE) is presented for wave propagation in an ice-covered ocean acoustic environment. The presented model solves exact governing equations for acoustic–elastic propagation in an ice-covered waveguide by expressing the wave solution in terms of a field superposition produced by several sets of ESs. Their unknown amplitudes are solved by strictly enforcing additional ice-layer boundary conditions. ESM-SUBICE achieves high efficiency using a water–seabed Green's function to automatically satisfy the boundary conditions at this interface. By further dividing the ocean environment into layers, ESM-SUBICE is extended for more general situations including stratified sound-speed structures and seabed range dependencies. ESM-SUBICE is benchmarked against a finite-element model, and it is found to produce high-quality solutions with high efficiency. Transmission-loss predictions for elastic, fluid, and free-surface ice representations in different ocean environments are compared to examine the effect of ice elasticity on propagation and scattering. The results suggest that the fluid representation is adequate for deep-water environments where the seabed is soft and the surface duct effect is insignificant; otherwise, for accurate predictions, the ice elasticity should be considered.

Transverse Electric Guided Wave Propagation in a Plane Waveguide with Kerr Nonlinearity and Perturbed Inhomogeneity in the Permittivity Function

The paper focuses on the problem of transverse electric wave propagation in a plane-shielded waveguide filled with a nonhomogeneous and nonlinear (Kerr) medium. The nonlinear part of the permittivity is characterized by the Kerr law in the focusing regime, while its linear part is a constant that is perturbed by a small continuous function. Such perturbation can be considered to be an attempt to take into account the inevitable presence of impurities in the medium, causing slight deviations in the dielectric permittivity. In the paper, the existence of solutions to the considered problem is proved, including solutions with and without linear counterparts. Some numerical results are presented as well.