Ultrasonic guided waves in elliptical annular cylinders
23 Sep 2015-Journal of the Acoustical Society of America (Acoustical Society of America)-Vol. 138, Iss: 3
TL;DR: The studies reveal that even a small degree of ovalness can affect mode shapes and velocities in thin pipes, and this may be important for practical inspection applications.
Abstract: This paper studies the influence of cross-section ovalness or ellipticity on lower order axisymmetric guided wave modes in thin pipes. The second longitudinal mode L(0,2) and the fundamental torsional mode T(0,1) are studied, as these are of interest to current pipe inspection. The semi-analytical finite element (FE) method is mainly used, with three-dimensional FE simulations for visualization and cross-validation of results. The studies reveal that even a small degree of ovalness can affect mode shapes and velocities. The effect is more pronounced on the L(0,2) mode than on T(0,1) and this may be important for practical inspection applications.
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TL;DR: In this article, the feasibility of using ultrasonic feature guided waves (FGW) for rapid screening of typical 90° bends made of quasi-isotropic composite laminates is explored.
59 citations
Cites background from "Ultrasonic guided waves in elliptic..."
...In recent years, one particular branch of guided waves confined to local structural variation - feature guided waves (FGW) have received much attention and been discussed in the literature extensively [5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]....
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TL;DR: In this paper, a feature guided wave (FGW) was used for rapid screening of the bond line between a stiffener and a carbon fiber reinforced polymer (CFRP) composite panel.
Abstract: Adhesive bonding is widely used in aerospace composite structures. A continuous well-cured bond can offer good joint strength and improved fatigue and impact resistance, and is therefore crucial to the performance of the entire structure. This paper explores the feasibility of using feature guided waves (FGW) for rapid screening of the bond line between a stiffener and a carbon fiber reinforced polymer (CFRP) composite panel. Such FGWs are capable of focusing the wave energy along the stiffener and the bond layer, with limited radiation to the adjacent plate. The Semi-Analytical Finite Element (SAFE) approach is employed to understand the modal properties of FGWs that exist in the structure, and criteria are suggested to choose proper mode-frequency combination that is sensitive to adhesive defects. A shear horizontal type FGW mode is identified to be well suited, as it is easy to excite, and propagates with little dispersion and relatively low attenuation, while it retains sufficient energy around the bond layer. Both 3D Finite Element (FE) simulations and experiments are performed to study the interaction of the selected FGW mode with defects in the adhesive bond, and the results show excellent agreement. The reflection behavior and the wave-defect resonance phenomenon are investigated, which demonstrate the capability of the FGW for the bond line inspection.
50 citations
TL;DR: In this article, a numerical tool is developed for the modal study of immersed waveguides with arbitrary cross sections, by coupling the Semi-Analytical Finite Element (SAFE) method with Perfectly Matched Layer (PML).
34 citations
TL;DR: Semi-Analytical Finite Element simulations revealing the capability of energy confinement carried by two types of guided modes in 90° carbon fiber/epoxy (CF/EP) bends and the feasibility of using such confined guided waves for rapid inspection of bent composite plate structures is discussed.
29 citations
Cites background from "Ultrasonic guided waves in elliptic..."
...As noted above, this is related to FGW phenomena discussed in the literature [27,36,28,29,31]....
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TL;DR: In this article, a fiber Bragg grating based technique was proposed to detect anomalies or defects in plate structures with transverse bends, both in the case of defect-free and transverse defects.
Abstract: Harnessing of ultrasonic guided waves confined in local features such as bends and welds, known as feature-guided waves, has emerged as a promising technique for non-destructive testing and structural health monitoring of industrial and aerospace structures. This article introduces a fiber Bragg grating based technique which uses feature-guided waves to detect anomalies or defects in plate structures with transverse bends. We are able to obtain good consistency between simulation and experimental results, both in the case of defect-free bent plates and those with transverse defects. Such results establish fiber Bragg gratings as a viable alternative to conventional techniques for structural health monitoring of bent plates.
20 citations
Cites background from "Ultrasonic guided waves in elliptic..."
...Recently, the above challenge has been addressed using ultrasonic guided waves confined to locally extended features such as welds, bends, thinning or thickening regions (Fan and Lowe, 2009, 2012; Pattanayak et al., 2015; Rajagopal and Pattanayak, 2015; Ramdhas et al., 2013)....
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References
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TL;DR: In this paper, a two-dimensional semi-analytical finite element (SAFE) method is applied to provide a modal study of the elastic waves that are guided by the welded joint in a plate.
Abstract: The inspection of large areas of complex structures is a growing interest for industry. An experimental observation on a large welded plate found that the weld can concentrate and guide the energy of a guided wave travelling along the direction of the weld. This is attractive for non-destructive evaluation (NDE) since it offers the potential to quickly inspect for defects such as cracking or corrosion along long lengths of welds. In this paper, a two-dimensional semi-analytical finite-element (SAFE) method is applied to provide a modal study of the elastic waves that are guided by the welded joint in a plate. This brings understanding to the compression wave that was previously observed in the experiment. However, during the study, a shear weld-guided mode, which is non-leaky and almost non-dispersive, has also been discovered. Its characteristics are particularly attractive for NDE, so this is a significant new finding. The properties for both the compression and the shear mode are discussed and compared, and the physical reason for the energy trapping phenomena is then explained. Experiments have been undertaken to validate the existence of the shear weld-guided mode and the accuracy of the FE model, showing very good results.
75 citations
TL;DR: This paper focuses on the faster bend-guided mode that is similar to the S0 (fundamental symmetric) Lamb mode in flat plates that is shown to be more strongly generated in smaller angle bends.
35 citations
TL;DR: In this paper, the authors developed an asymptotic procedure that encapsulated the essential physics within a single ordinary differential equation for the problem of trapped modes within elastic waveguides.
32 citations
TL;DR: The influence of bends constituting annular polygonal structures on ultrasonic guided waves propagating along their axis is investigated and a slower bend-guided mode that is similar to the A0 (fundamental anti-symmetric) Lamb mode in flat plates is identified.
Abstract: The influence of bends constituting annular polygonal structures on ultrasonic guided waves propagating along their axis is investigated. Considering a single bend as a bent plate connects this problem to the better-understood physics of guided waves in straight plates. Using a three-dimensional finite element simulation validated with experiments, bends in plates are shown to act as features that can concentrate and guide ultrasonic energy along their length. Two interesting feature-guided modes are identified when the bent plate is subjected to “in-plane” or axial excitation applied uniformly along a through-thickness line bisecting the bent edge. Of these, the faster traveling mode has properties similar to, but travels at group velocities lower than, the S0 (fundamental symmetric) Lamb mode in flat plates. This paper however focuses on the slower bend-guided mode that is similar to the A0 (fundamental anti-symmetric) Lamb mode in flat plates. This mode is shown to be more strongly generated in smaller...
27 citations
TL;DR: In this article, a model of trapped modes in 3D elastic plates is considered, where the trapped modes propagate unattenuated along the weld and exponentially decay with distance transverse to it.
Abstract: Trapped modes in 3D elastic plates are considered as a model of waves that are guided along, and localized to the vicinity of, welds. These waves propagate unattenuated along the weld and exponentially decay with distance transverse to it. In the direction of propagation (y), there is no change in geometry and we assume that waves have the form exp(iβy). An asymptotic long-wave theory provides numerical values of the trapped mode frequencies and gives conditions at which trapping can occur; these depend on the components of the wave number in different directions and variations of the plate thickness. The results of this long-wave theory are compared with a numerical solution of the full governing equations.
18 citations