Low frequency axisymmetric longitudinal guided waves in eccentric annular cylinders.
19 Jun 2015-Journal of the Acoustical Society of America (Acoustical Society of America)-Vol. 137, Iss: 6, pp 3253-3262
TL;DR: The studies show that even a small eccentricity in the pipe can cause a loss in the L(0,2) mode axisymmetry, leading to its confinement in the thinned side of the pipe cross-section and also a reduction in mode velocities.
Abstract: This paper studies the effect of axially uniform eccentricity on the modal structures and velocities of the lower order axisymmetric guided wave mode L(0,2) in circular tubes or pipes. The semi-analytical finite element method is mainly used, supported by fully three-dimensional finite element models and validated using experiments. The studies show that even a small eccentricity in the pipe can cause a loss in the L(0,2) mode axisymmetry, leading to its confinement in the thinned side of the pipe cross-section and also a reduction in mode velocities. The physics of this phenomenon is related to the feature-guiding and mode confinement effects noted in recent years in the literature, particularly studies on waveguides with local cross-section variations and curvature.
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TL;DR: Semi-Analytical Finite Element (SAFE) method simulations reveal the existence of a new family of Shear Horizontal (SHB) type of FGW mode in 90° bends in plate structures, demonstrating the SH-like nature of a bend-confined mode identified in studies of power flow across the bend.
26 citations
TL;DR: In this article, the interaction of the SHB wave with transverse and longitudinal defects in the bend region is studied using 3D finite element simulations validated by experiments, and the results show that SHB mode yields improved through-thickness defect resolution capabilities as compared to regular plate guided SH waves in view of mode confinement and higher frequencies used.
Abstract: The authors have recently reported on the attractive properties of shear-horizontal type feature guided (SHB) waves for the inspection of 90° plate bends. Further to this, here the interaction of the SHB mode with transverse and longitudinal defects in the bend region is studied using 3D finite element simulations validated by experiments. Trends are discussed in light of the underlying wave mechanics principles. The results show that the SHB mode yields improved through-thickness defect resolution capabilities as compared to regular plate guided SH waves in view of mode confinement and higher frequencies used.
26 citations
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 "Low frequency axisymmetric longitud..."
...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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TL;DR: Fiber Bragg gratings are shown to be effective in detecting changes to L(0,2) modal characteristics, providing a novel route to health monitoring of pipe assets.
14 citations
TL;DR: Semi-analytical finite element simulations are used to demonstrate the existence of a longitudinal guided ultrasonic mode confined or trapped in the Noodle regions, and reveal that this mode has attractive properties for rapid screening of Noodle joints, including strong energy concentration, low dispersion, and attenuation.
Abstract: This paper studies the feasibility of using ultrasonic guided waves for fast inspection of conformal deltoid radius filler or “Noodle” regions of joints in stringer composite structures. Semi-analytical finite element simulations, supported by experiments and three-dimensional finite element models, are used to demonstrate the existence of a longitudinal guided ultrasonic mode confined or trapped in the Noodle regions. Studies reveal that this mode has attractive properties for rapid screening of Noodle joints, including strong energy concentration, low dispersion, and attenuation. Discussing the physics of mode confinement in light of material differences and geometry, the phenomenon is shown to be related to feature-guiding effects noted in literature recently.
13 citations
References
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TL;DR: In this paper, the propagation of free harmonic waves along a hollow circular cylinder of infinite extent is discussed within the framework of the linear theory of elasticity, and a characteristic equation appropriate to the circular hollow cylinder is obtained by use of the Helmholtz potentials for arbitrary values of the physical parameters involved.
Abstract: The propagation of free harmonic waves along a hollow circular cylinder of infinite extent is discussed within the framework of the linear theory of elasticity. A characteristic equation appropriate to the circular hollow cylinder is obtained by use of the Helmholtz potentials for arbitrary values of the physical parameters involved. Axially symmetric waves, the limiting modes of infinite wavelength, and a special family of equivoluminal modes are derived and discussed as degenerate cases of the general equations.
702 citations
TL;DR: In this article, the authors provide a vision of ultrasonic guided wave inspection potential as we move forward into the new millennium and provide a brief description of the sensor and software technology that will make ultrasonic guidance wave inspection commonplace in the next century.
Abstract: Ultrasonic guided wave inspection is expanding rapidly to many different areas of manufacturing and in-service inspection. The purpose of this paper is to provide a vision of ultrasonic guided wave inspection potential aswe move forward into the new millennium. An increased understanding of the basic physics and wave mechanics associated with guided wave inspection has led to an increase in practical nondestructive evaluation and inspection problems. Some fundamental concepts and a number of different applications that are currently being considered will be presented in the paper along with a brief description of the sensor and software technology that will make ultrasonic guided wave inspection commonplace in the next century.
623 citations
TL;DR: In this paper, the authors present a review of the studies of the propagation of the waves and their sensitivity to defects which have been conducted in order to provide a sound scientific basis for the method.
581 citations
TL;DR: In this article, the authors used a commercial finite element (FE) code to study the propagation characteristics of ultrasonic waves in annular structures and demonstrated the potential of the FE method for problems when an analytical solution is not possible because of complicated component geometry.
Abstract: This paper reports on the application of guided waves techniques to nondestructively determine the structural integrity of engineering components. Specifically, this research uses a commercial finite element (FE) code to study the propagation characteristics of ultrasonic waves in annular structures. In order to demonstrate the accuracy of the proposed FE technique, the propagation of guided waves in a flat plate is examined first. Next, the propagation of guided waves in thick ring structures is investigated. Finally, these FE results are compared to analytical and experimental results. The results of this study clearly illustrate the effectiveness of using the FE method to model guided wave propagation problems and demonstrate the potential of the FE method for problems when an analytical solution is not possible because of “complicated” component geometry.
553 citations
TL;DR: In this article, the reflection of the L(0, 2), axially symmetric guidea elastic wave from notches in pipes is examined, using laboratory experiments and finite element simulation.
Abstract: The reflection of the L(0, 2), axially symmetric guidea elastic wave from notches in pipes is examined, using laboratory experiments and finite element simulation The result show that the reflection coefficient of this mode is very close to a linear function of the circumferential extent of the notch, and is a stronger function of the through thickne depth of the notch. The motivation for the work was the development of a technique for inspecting chemical plant pipework, but the study addresses the nature of the reflection function and has general applicability.
292 citations