Papers by Keyword: Guided Wave

Abstract: Matching layers of acoustic impedance are intensively studied in ultrasonic transducers for the efficiency of wave transmission. Large impedance mismatch between the active element of piezo and parent material in long range ultrasonic is also expected to have the similar affects on the ratio of the transmitted and reflected waves which can cause high reflection at the interface that result acoustic wave ringing and indicate low transmitted energy for inspection over large areas. This simulation study present analysis of Lamb wave propagation through a single matching layer from a piezoelectric transducers. It explains transmitted waves into aluminum plate using different materials of matching plates at thickness of quarter wavelength. Four matching plates with close to the computed value of acoustic impedance had been used in FEM simulations to study effect of the matching layers on the transmitted Lamb wave in aluminum plate. The results indicated slightly different phenomenon of multiple wave reflections from the transmitted S0 and A0 modes at boundary of the matching layer.

Abstract: Complicated Lamb wave propagation in structures can cause a misinterpretation in defect location and sizing during nondestructive inspections. A visualization of Lamb wave interactions with oval defects was carried out in our study to investigate the phenomenon of fundamental Lamb wave interaction around defect by using a reduced model of plate in ABAQUS. The visualized wave propagations with oval shape of through defects in plates demonstrated different patterns of wave interactions for the symmetric and anti-symmetric modes. The results also visualized the mode conversions around defects which converted from the incident waves. The visualized changes on the wave structures due to wave interaction with defects is important to increase our understanding on the guided wave propagation and reduce misinterpretation in nondestructive inspection when using the wave modes during inspection on large structures.

Abstract: Ultrasonic guided wave quantitative detection technology has not been widely studied; this limits the application and development of guided waves testing technology greatly. For the quantitative detection study of notches in pipes, the theoretical model of guided waves interacted with notches has been built. Through the model, the relation formula between reflection coefficient and defects axial length and depth has been derived. The relation curves have been plotted based on the relation formula. And then, experiment method was used to verify the curves, the two methods can agree with each other. At last, the size of the defect was evaluated through the theoretical relation curves, the evaluation agrees with the practical size relatively. The research results provide necessary guide in theory to the defects quantification of guided wave detection.

Abstract: Among many structural health monitoring (SHM) methods, guided wave (GW) based method has been found as an effective and efficient way to detect incipient damages. In comparison with other widely used SHM methods, it can propagate in a relatively long range and be sensitive to small damages. Proper use of this technique requires good knowledge of the effects of damage on the wave characteristics. This needs accurate and computationally efficient modeling of guide wave propagation in structures. A number of different numerical computational techniques have been developed for the analysis of wave propagation in a structure. Among them, Spectral Element Method (SEM) has been proposed as an efficient simulation technique. This paper will focus on the application of GW method and SEM in structural health monitoring. The GW experiments on several typical structures will be introduced first. Then, the modeling techniques by using SEM are discussed.

Abstract: This paper introduced a nondestructive testing (NDT) method of using guided wave to detect debonding in composite bonding structure, which is based on the model of guided wave energy leakage, and the simulation analysis shown that the diameter of debonding could be quantified by E-x curve. The experiments were carried out on a composite bonding structure, and the results provide that the model established is correct, and that the method of quantifying debonding by E-x curve is effective.

Abstract: It is of great significance to monitor and quantify the defects in the thin segmental spherical shell components. In the paper the guided wave’s inspiring method has been obtained from the wave-mode conversion based on the theory of the guided wave propagating in the thin spherical shell. Using the wavelet to process the testing signal, and the ellipse localization imaging algorithm, the defect’s localization and orientation can be detected accurately. Experimental results show the defect’s direction and location can be detected effectively and clearly.

Abstract: Dispersion curves present fundamental information on guided waves such as wavelength and dispersivity as well as phase and group velocities at a certain frequency, which is essential for the application of guide wave technology. A numerical method based on modal analysis using ANSYS software was presented to calculate the dispersion curves of guided waves in rod. The mode shapes of different modes of guided waves were obtained and discriminated, and the dispersion curves of rod were extracted. The numerical result and the analytical ones matched very well, which verified the effectiveness of this method. This numerical method can be applied to arbitrary waveguide which can be considered as a periodic structure with constant cross-section.

Abstract: The chirp signal can bring some useful information for structural non-destructive evaluation (NDE) applications due to its broad frequency components with different sensitivity to defects that exist in test pieces. This paper introduces a defect imaging method based on the chirp signal. When a chirp signal is used as excitation in the guided wave detection system, tone burst results can be gotten from the response easily. Numerical simulation results show that this method simplifies the procedure to find the best exciting frequency and guided wave mode for the hole defect detection, and yields more accurate defect imaging results with arc imaging algorithm.

Abstract: This paper focuses on the multiple crack detection of steel pipelines using PZT-based guided waves. Numerical simulations of cracked pipes based on ultrasonic guided-waves are conducted by using the ANSYS finite element software. Based on the analysis of the reflected signal, the arrival time of the crack reflection waves are determined and the crack positions are accurately evaluated by the calculation of the travel time and group velocity of the PZT-based guided waves. The crack parameters are numerically altered to determine how the parameters impact the sensitive degree of the pipe crack damage. To validate the efficiency of the numerical simulation, an experiment of the multiple crack detection for the same parameter pipe with the numerical model is performed in the laboratory, and the results match well with the numerical simulation.

Abstract: The guided-wave technology is very efficient in inspecting a large portion of pipe. In order to study the propagation property of guided wave in pipe and the interaction between guided waves and defects, pipe model was established using 3D solid finite element in the software ANSYS. Tangential displacements were prescribed on the nodes in the pipe end and the propagating of T(0,1) mode guided wave in pipes was simulated. The detecting signals for the pipe model with different defects were extracted, which matched very well with experimental result.