Excitation of Guided Waves in Generally Anisotropic Layers Using Finite Sources

1994 ◽  
Vol 61 (2) ◽  
pp. 330-338 ◽  
Author(s):  
J. J. Ditri ◽  
J. L. Rose
Keyword(s):  
Phase Velocity ◽  
Nondestructive Evaluation ◽  
Guided Waves ◽  
Guided Wave ◽  
Wave Number ◽  
Excitation Spectra ◽  
Mode Expansion ◽  
Time Harmonic ◽  
Expansion Technique ◽  
Anisotropic Layers

The excitation of guided wave modes in generally anisotropic layers by finite sized strip sources placed on the surfaces of the layer is examined. The general problem of arbitrarily applied harmonic surface tractions is first solved using the normal mode expansion technique in conjunction with the complex reciprocity relation of elastodynamics. This general solution is then specialized to loading situations modelling those commonly used to excite guided waves in layers for use in nondestructive evaluation. The amplitudes of the generated modes are written as the product of an “excitation function” which depends only on the distribution of the applied tractions and an “excitability function” which depends only on the properties of the specific mode(s) being excited and which determines how receptive the modes are to the applied tractions. Expressions are obtained for the −9 dB wave number and phase velocity bandwidths (σβ and σν respectively) which determine the widths of the wavenumber or phase velocity excitation spectra at the −9 dB generation point. Finally, the problem of transient loading is addressed by superimposing time harmonic solutions via an integration over the dispersion curves of the layer.

scholarly journals Effects of Concrete on Propagation Characteristics of Guided Wave in Steel Bar Embedded in Concrete

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Zhupeng Zheng ◽  
Ying Lei
Keyword(s):  
Large Scale ◽  
Guided Waves ◽  
Density Ratio ◽  
Guided Wave ◽  
Wave Number ◽  
Propagation Characteristics ◽  
Civil Infrastructures ◽  
Steel Bar ◽  
Reinforced Concrete Member ◽  
Steel Bars

Techniques based on ultrasonic guided waves (UGWs) play important roles in the structural health monitoring (SHM) of large-scale civil infrastructures. In this paper, dispersion equations of longitudinal wave propagation in reinforced concrete member are investigated for the purpose of monitoring steels embedded in concrete. For a steel bar embedded in concrete, not the velocity but the attenuation dispersion curves will be affected by the concrete. The effects of steel-to-concrete shear modulus ratio, density ratio, and Poisson’s ratio on propagation characteristics of guided wave in steel bar embedded in concrete were studied by the analysis of the real and imaginary parts of the wave number. The attenuation characteristics of guided waves of steel bar in different conditions including different bar concrete constraint and different diameter of steel bar are also analyzed. Studies of the influence of concrete on propagation characteristics of guided wave in steel bars embedded in concrete will increase the accuracy in judging the structure integrity and promote the level of defect detection for the steel bars embedded in concrete.

scholarly journals Array-Based Guided Wave Source Location Using Dispersion Compensation

2021 ◽  
Vol 4 (4) ◽  
Author(s):  
Andrew Downs ◽  
Ronald Roberts ◽  
Jiming Song
Keyword(s):  
Experimental Data ◽  
Guided Waves ◽  
Dispersion Compensation ◽  
Back Propagation ◽  
Source Location ◽  
Guided Wave ◽  
Wave Number ◽  
Frequency Spectra ◽  
Wave Source ◽  
Bulk Waves

Abstract An important advantage of guided waves is their ability to propagate large distances and yield more information about flaws than bulk waves. Unfortunately, the multi-modal, dispersive nature of guided waves makes them difficult to use for locating flaws. In this work, we present a method and experimental data for removing the deleterious effects of multi-mode dispersion allowing for source localization at frequencies comparable to those of bulk waves. Time domain signals are obtained using a novel 64-element phased array and processed to extract wave number and frequency spectra. By an application of Auld’s electro-mechanical reciprocity relation, mode contributions are extracted approximately using a variational method. Once mode contributions have been obtained, the dispersion for each mode is removed via back-propagation techniques. Excepting the presence of a small artifact at high frequency-thicknesses, experimental data successfully demonstrate the robustness and viability of this approach to guided wave source location.

Dynamic Anti-Plane Behaviors on Two Dissimilar Piezoelectric Media with an Interfacial Non-Circular Cavity

2012 ◽  
Vol 525-526 ◽  
pp. 293-296
Author(s):  
Tian Shu Song ◽  
Dong Li ◽  
Ming Ju Zhang ◽  
Yue Fa Zhou
Keyword(s):  
Characteristic Parameter ◽  
Mapping Method ◽  
Wave Number ◽  
Circular Cavity ◽  
Piezoelectric Media ◽  
Conformal Mapping Method ◽  
Time Harmonic ◽  
Expansion Technique ◽  
Stress Concentration Factors ◽  
Piezoelectric Characteristic

Dynamic anti-plane behaviors are studied on two dissimilar piezoelectric media with an interfacial non-circular cavity subjected to time harmonic incident anti-plane shearing. Based on Greens function and conformal mapping method, the dynamic stress concentration factors at the edge of the non-circular cavity are obtained by applying the orthogonal function expansion technique. Numerical cases about two dissimilar piezoelectric media with an elliptic cavity are provided with different elliptic axial length ratio, different wave number and different piezoelectric characteristic parameter. The calculating results show that dynamic analyses are of importance at lower frequencies and larger piezoelectric characteristic parameters.

Crack detection in thick annular components using ultrasonic guided waves

2000 ◽  
Vol 214 (9) ◽  
pp. 1163-1171 ◽  
Author(s):  
J Qu ◽  
Y. H. Berthelot ◽  
L. J. Jacobs
Keyword(s):  
Crack Detection ◽  
Guided Waves ◽  
Numerical Solutions ◽  
Ultrasonic Inspection ◽  
Guided Wave ◽  
Ultrasonic Guided Waves ◽  
Time Harmonic ◽  
Solution Methods ◽  
Wave Technique ◽  
Steady State Time

This paper provides an overview of a study on circumferential guided waves in a thick annulus. Both steady state, time-harmonic waves and transient waves are considered. Several solution methods are reviewed and numerical solutions are presented for the propagation of ultrasonic circumferential waves in a thick, curved, two-dimensional annular waveguide. The modal content of the signal and the displacement profiles across the wall thickness are investigated. These studies provide valuable guidance in selecting optimal parameters for use in applications of the guided wave technique to the detection of cracks on the inner surface of annular components. Experimental results show that the technique can be used on parts with complex geometries (e. g. the pitch shaft of a helicopter) to detect cracks that would not be detectable by standard ultrasonic inspection.

scholarly journals Complex dispersion solutions for guided waves and properties of non-propagating waves in a piezoelectric spherical plate

2018 ◽  
Vol 10 (12) ◽  
pp. 168781401882069
Author(s):  
Xiaoming Zhang ◽  
Zhi Li ◽  
Jiangong Yu
Keyword(s):  
Guided Waves ◽  
Three Dimensional ◽  
Guided Wave ◽  
Wave Number ◽  
Polynomial Method ◽  
Propagating Waves ◽  
Complex Solutions ◽  
Spherical Plate ◽  
Complex Valued ◽  
Dispersion And Attenuation

The vibration modes of an elastic plate are usually divided into propagating and non-propagating (evanescent) kinds. Non-propagating wave modes are very important for guided wave inspection of defect size and shape. But it is difficult to obtain the complex solutions of the transcendental dispersion equation, corresponding to the non-propagating wave. In this article, we present an improved Legendre polynomial method to calculate the complex-valued dispersion and study properties of the non-propagating wave in a piezoelectric spherical plate. Comparisons with other related studies are conducted to validate the correctness of the presented method. The complete dispersion and attenuation curves are plotted in three-dimensional frequency-complex wave number space. The influences of material piezoelectricity and radius–thickness ratio on non-propagating waves in piezoelectric spherical plates are investigated. The amplitude distributions of the electric potential and displacement are also discussed in detail. All the results presented in this work can provide theoretical guidance for ultrasonic nondestructive evaluation and are promising to be applied to improve the resolution of piezoelectric transducers.

Stress Measurement in Seven-Wire Strands using Higher Order Guided Ultrasonic Wave Modes

2018 ◽  
Vol 2672 (41) ◽  
pp. 123-131
Author(s):  
Brennan Dubuc ◽  
Arvin Ebrahimkhanlou ◽  
Salvatore Salamone
Keyword(s):  
Phase Velocity ◽  
Measurement Accuracy ◽  
Guided Waves ◽  
Stress Measurement ◽  
Tensile Load ◽  
Stress Sensitivity ◽  
Higher Order ◽  
Guided Wave ◽  
Approximate Theory ◽  
Higher Order Modes

This paper investigates the use of higher order longitudinal guided modes for stress measurement within individual wires of a steel strand. The effect of stress on the phase velocity of higher order modes is studied using an approximate theory, which does not require the solution of dispersion curves. To validate the proposed approach, a prestressing bed was designed to apply a tensile load to a strand up to 25% ultimate tensile strength while recording guided wave signals. Guided waves were excited within individual wires of a strand, and the stress sensitivity of their phase velocity was used for stress measurement. Stress measurement was performed with higher order modes using the approximate theory with parameters for a steel of similar carbon content (Hecla 17), as well as with calibrated parameters. Using the Hecla 17 parameters, roughly 15% mismatch in stress was observed, whereas roughly 5% error was observed using calibrated parameters. Stress measurement was also performed using the fundamental mode, in order to compare the accuracy of higher order modes with the mode used previously in the literature. The greater stability of higher order modes across mode and frequency yielded significantly increased stress measurement accuracy, using both Hecla 17 and calibrated parameters.

Stress evaluation in seven-wire strands based on singular value feature of ultrasonic guided waves

2021 ◽  
pp. 147592172110053
Author(s):  
Qian Ji ◽  
Li Jian-Bin ◽  
Liu Fan-Rui ◽  
Zhou Jian-Ting ◽  
Wang Xu
Keyword(s):  
Dispersion Curve ◽  
Support Vector Regression ◽  
Stress Level ◽  
Guided Waves ◽  
Guided Wave ◽  
Singular Value ◽  
Support Vector ◽  
Support Vector Regression Model ◽  
Various Boundary Conditions ◽  
Wave Methods

The seven-wire strands are the crucial components of prestressed structures, though their performance inevitably degrades with the passage of time. The ultrasonic guided wave methods have been intensely studied, owing to its tremendous potential for full-scale applications, among the existing nondestructive testing methods, for evaluating the stress status of strands. We have employed the theoretical and finite element methods to solve the dispersion curve of single wire and steel strands under various boundary conditions. Thereafter, the singular value decomposition was adopted to work with the simulated and experimental signals for extracting a feature vector that carries valuable stress status information. The effectiveness of the vector was verified by analyzing the relationship between the vector and the stress level. The vector was also used as an input to establish a support vector regression model. The accuracy of the model has been discussed for different sample sizes. The results show that the fundamental mode dispersion curve offset on the high-frequency part and cut-off frequency increases as the boundary constraints enhance. Simulated and experimental results have demonstrated the effectiveness and potential of the proposed support vector regression method for evaluating the stress level in the strands. This method performs well even at low stress levels and the reliability can be enhanced by adding more samples.

Ultrasonic unilateral double-position excitation lamb wave defect detection and quantification method for ground electrode of transmission tower

2021 ◽  
pp. 1-15
Author(s):  
Kuan Ye ◽  
Kai Zhou ◽  
Ren Zhigang ◽  
Ruizhe Zhang ◽  
Chunsheng Li ◽  
...  
Keyword(s):  
Guided Waves ◽  
Power Transmission ◽  
Geometric Model ◽  
Guided Wave ◽  
Quantization Error ◽  
Dispersion Function ◽  
Stable Operation ◽  
Transmission Tower ◽  
Ultrasonic Guided Wave ◽  
Transmission Towers

The power transmission tower’s ground electrode defect will affect its normal current dispersion function and threaten the power system’s safe and stable operation and even personal safety. Aiming at the problem that the buried grounding grid is difficult to be detected, this paper proposes a method for identifying the ground electrode defects of transmission towers based on single-side multi-point excited ultrasonic guided waves. The geometric model, ultrasonic excitation model, and physical model are established, and the feasibility of ultrasonic guided wave detection is verified through the simulation and experiment. In actual inspection, it is equally important to determine the specific location of the defect. Therefore, a multi-point excitation method is proposed to determine the defect’s actual position by combining the ultrasonic guided wave signals at different excitation positions. Besides, the precise quantification of flat steel grounding electrode defects is achieved through the feature extraction-neural network method. Field test results show that, compared with the commercial double-sided excitation transducer, the single-sided excitation transducer proposed in this paper has a lower defect quantization error in defect quantification. The average quantization error is reduced by approximately 76%.

scholarly journals Longitudinal Guided Wave Inspection of Small-Diameter Elbowed Steel Tubes with a Novel Squirrel-Cage Magnetostrictive Sensor

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Yao Liu ◽  
Xiucheng Liu ◽  
Chehua Yang ◽  
Wenxin Guo ◽  
Bin Wu ◽  
...  
Keyword(s):  
Finite Element ◽  
Guided Waves ◽  
Mode Conversion ◽  
Small Diameter ◽  
Longitudinal Mode ◽  
Guided Wave ◽  
Wall Defect ◽  
Squirrel Cage ◽  
Simulation Results ◽  
Magnetostrictive Sensor

In the study, ultrasonic longitudinal mode guided waves were employed to detect defects in elbowed tubes (without welds) with a diameter of 10 mm. Finite element simulation results highlighted that the emitted L(0,1) mode guided waves experienced strong reflection and mode conversion at the elbow region to generate F(1,1) mode, followed by slow and weak F(2,1) mode. The guided wave reflected from the elbow with a through-wall defect was manifested as two overlapped wave packets, which were good indicators of a defective elbow. To conduct L(0,1) mode guided waves inspection on the small-diameter elbowed tubes, a novel tailored squirrel-cage magnetostrictive sensor was employed in the experiment. The new sensor employed the configuration of segmental iron-cobalt strips and small-size permanent magnet arrays. The entire sensor is composed of two identical C-shaped sensor elements and can be recycled and installed conveniently. Experimental results obtained from healthy and defective tubes were consistent with the conclusions obtained from finite element simulations. An artificial through-wall defect at the elbow and a notch defect at the straight part of the tube could be simultaneously detected by L(0,1) mode guided waves through comparing experimental signals with simulation results.

Guided Wave Focusing Mechanics in Pipe

2003 ◽  
Author(s):  
Takahiro Hayashi ◽  
Koichiro Kawashima ◽  
Zongqi Sun ◽  
Joseph L. Rose
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Guided Waves ◽  
Wave Structure ◽  
Guided Wave ◽  
Pipe Inspection ◽  
Specific Point ◽  
Wave Focusing ◽  
Beam Focusing ◽  
Subsequent Time

Guided waves can be used in pipe inspection over long distances. Presented in this paper is a beam focusing technique to improve the S/N ratio of the reflection from a tiny defect. Focusing is accomplished by using non-axisymmetric waveforms and subsequent time delayed superposition at a specific point in a pipe. A semi-analytical finite element method is used to present wave structure in the pipe. Focusing potential is also studied with various modes and frequencies.

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