Scattering of the fundamental shear horizontal mode in a plate when incident at a through crack aligned in the propagation direction of the mode

Ratassepp, Madis; Lowe, M. J. S.; Cawley, P.; Klauson, Aleksander

doi:10.1121/1.2987426

Cited by 54 publications

(37 citation statements)

References 22 publications

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“…Such complex wave scattering requires a combination of advanced non-contact visualization techniques to characterize scattered wave fields from defects such as experimental models and computational simulations. Some excellent visuals of scattering of compression and shear wave modes from axially and normally aligned cracks, finite slits and notches are provided in Staszewski et al (2007) and Ratassepp et al (2008). In these cases, the experimental models are significantly large such that mode interference is minimized by the separation achieved with the different speeds at which modes travel through the structure.…”

Section: Plate Wave Solutionsmentioning

confidence: 98%

Guided wave mode selection for health monitoring of sub-surface hidden defects on fuel weep holes

Doherty

Chiu

2013

The Journal of the Acoustical Society of America

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The in situ health monitoring of defects on the blind side of open holes using ultrasonic plate waves is a challenging problem. Scattering phenomena in this hard-to-inspect region can be used indicate the presence of the defect. This is especially advantageous if these phenomena give rise to the scattering of a wave mode that is unique to the interaction between the incident wave mode and defect. When the defect in question is located within an inaccessible structure, an understanding of how the incident ultrasonic elastic wave field can be scattered from this hidden defect propagates to the accessible surface is important. This paper presents a series of computational investigations to highlight the essential physics that explains the scattering phenomena by a defect located on the blind side of an open hole. The work presented is relevant to the monitoring of defects located in hard-to-inspect regions of future unitized metallic and composite structures. The outcomes advance the knowledge base of inspection of hard-to-access regions with actuators and sensors placed in easily accessible locations.

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Section: Plate Wave Solutionsmentioning

confidence: 98%

Guided wave mode selection for health monitoring of sub-surface hidden defects on fuel weep holes

Doherty

Chiu

2013

The Journal of the Acoustical Society of America

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“…The concept was demonstrated by monitoring the metal loss due to general corrosion and sand erosion in aircraft structures. Cawley [11][12] studied the characteristics of pulse-echo reflection of the SH0 wave from part-thickness elliptical defects in plates via finite element analysis and experimental measurements. It was shown that the reflection ratio spectrum of the SH0 mode from an elliptical defect exhibited a periodic pattern due to interference between reflections from the two edges of the defect.…”

Section: Introductionmentioning

confidence: 99%

Experiments on non-destructive testing of grounding grids using SH0 guided wave

Jiao¹,

Xi²,

He³

et al. 2012

insight

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Grounding grids are widely used in substations to maintain the safe operation of operators and power apparatus. In this paper, an electromagnetic ultrasonic technique is proposed to diagnose the degradation of grounding grids. Firstly, the propagation of guided waves in an infinite plate is studied. It is shown that the lower shear horizontal wave (SH0) has several unique features that are attractive for long-range non-destructive testing (NDT). Secondly, the propagation of guided waves in a rectangular section bar is investigated experimentally. It is found that the SH0 wave excited by an electromagnetic acoustic transducer (EMAT), compared to a Lamb wave excited by a piezoelectric transducer, has a more powerful transmission capability in a rectangular section bar. Thirdly, SH0 wave experiments are conducted on plates with different widths; it is found that the variation in width has little influence on the propagation of the SH0 wave when the width of the plates is greater than the width of the EMAT transducers. Fourthly, experiments are conducted on a rectangular section bar in the laboratory to investigate the sensitivity of the SH0 wave to defects and the surrounding environment. It is found that SH0 wave testing offers an effective way to evaluate the health condition of a rectangular section bar. Finally, the proposed technique is applied to the NDT of a grounding grid in the field.

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“…the fundamental symmetric wave (S0) and shear horizontal wave (SH0). Previous studies [12,13] have considered SH0 Lamb wave propagation due to its non-dispersive properties, however, experimentally exciting only the SH0 wave is difficult compared to exciting S0. In this study, only S0 Lamb wave excitation will be considered.…”

Section: Computational Set-up and Proceduresmentioning

confidence: 99%

“…The scattered wave fields when an incident elastic wave impinges on a crack have been investigated for bulk waves [9][10][11], and more recently, for Lamb waves [12,13]. It is known that an infinitesimal crack is equivalent to a point source consisting of body-force doublets with different forcing combinations that correspond to different crack opening modes [14].…”

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confidence: 99%

Scattering of the Fundamental Symmetrical Lamb Wave Mode by a Small Edge Crack in an Isotropic Plate

Vien¹,

Nadarajah²,

Chiu³

et al. 2015

JMEA

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Lamb waves have a relatively slow geometrical decay of amplitude with propagation distance, which makes them well suited for wide-area inspection and SHM (structural health monitoring). This paper presents an extensive computational study of the interaction of the fundamental symmetrical Lamb wave mode (S0) with a through-thickness edge crack in an isotropic plate. The incident wave is generated by a point source that is symmetrical with respect to the plate's midplane, and whose time dependence is a 10-cycle Hanned windowed toneburst of centre frequency below the cut-off for the first order shear-horizontal mode (SH1), so that the only propagating modes are S0 and SH0. Results are presented showing the angular dependence of the S0 and SH0 scattered fields for various angles of incidence. The dependence of scattering amplitude on crack size is also studied, with a view to facilitating the inverse problem of determining crack size from measurements of the scattered field. It is shown that the scattered field due to a small crack can be considered to be equivalent to a point source consisting of a combination of force doublets that depend on the angle of incidence. The implications of these results for SHM are briefly discussed.

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Scattering of the fundamental shear horizontal mode in a plate when incident at a through crack aligned in the propagation direction of the mode

Cited by 54 publications

References 22 publications

Guided wave mode selection for health monitoring of sub-surface hidden defects on fuel weep holes

Guided wave mode selection for health monitoring of sub-surface hidden defects on fuel weep holes

Experiments on non-destructive testing of grounding grids using SH0 guided wave

Scattering of the Fundamental Symmetrical Lamb Wave Mode by a Small Edge Crack in an Isotropic Plate

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