Guided wave scattering by geometrical change or damage: Application to characterization of fatigue crack and machined notch

This paper aims at providing a framework for assessing the detection and localization performance of guided wave-based structural health monitoring (SHM) imaging systems. The assessment exploits a damage identification metric (DIM) providing a diagnostic of the structure from an image of the scatterers generated by the system, allowing detection, localization, and size estimation of the damage. Statistical probability of detection (POD) and probability of localization (POL) curves are produced based on values of the DIM for several damage sizes and positions. Instead of relying on arduous measurements on a significant number of structures instrumented in the same way, a model-based approach is considered in this paper for estimating POD and POL curves numerically. This approach is first illustrated on a simplistic model, which allows characterizing the robustness of the SHM system for various levels of noise in test signals. An experimental test case using a more realistic case with an artificial damage is then considered for validating the approach. A good agreement between experimental and numerical values of the DIM and derived POD and POL curves is observed.

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“…A more complex representation of the damage would implement the directivity pattern of the damage. 51–53…”

Section: Gw-based Shm System Assessmentmentioning

confidence: 99%

“…The damage is assumed to be equivalent to an omnidirectional point-like reflector which amplitude is assumed to grow as the size of the damage increases. A more complex representation of the damage would implementing the directivity pattern of the damage [51,52,53].…”

Section: Introduction To the Model-based Assessmentmentioning

confidence: 99%

A model-based approach for statistical assessment of detection and localization performance of guided wave–based imaging techniques

Moriot

Quaegebeur

Duff

et al. 2017

Structural Health Monitoring

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“…We produce additional statistically significant values outside the true area of the damage due to acoustic shadowing and diffraction. [51][52][53] These effects could potentially be reduced or removed by using multiple receivers to gain multiple perspectives on the damage or by improving the damage model. Prior work has shown the ability to improve localization performance by incorporating diffusion 54 and scattering 55 properties in matched field processing and similar localization methods.…”

Section: Localizationmentioning

confidence: 99%

Statistical partial wavefield imaging using Lamb wave signals

Harley

Chia

2017

Structural Health Monitoring

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This article presents a baseline-free, model-driven, statistical damage detection and imaging framework for guided waves measured from partial (i.e. non-dense) wavefield scans. Wavefield analysis is an effective non-contact technique for nondestructive evaluation. Yet, there are several limitations to practically implement wavefield methods. These limitations include slow data acquisition and a lack of statistical reliability. Our approach addresses both of these challenges. We use sparse wavenumber analysis, sparse wavenumber synthesis, and data-fitting optimization to accurately model damagefree wavefield data. We then combine this model with matched field processing to image damage from a small number of partial wavefield measurements. We further derive a hypothesis test based on extreme value theory to statistically detect damage. We test our framework with Lamb wave measurements from a steel plate. With 70 experimental wavefield measurements, we achieve an empirical probability of damage detection of more than 98%, an empirical probability of false alarm of less than 0.17%, and an accurate image of the damage.

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“…15 The scattering patterns of the A 0 mode at defects at a circular hole were investigated experimentally, evaluating the far field measured on radial lines using the Hankel transform. 17 Significant differences in the scattering patterns between a machined notch and fatigue crack emanating from the hole were found, depending on the ratio of the wavelength to defect length and direction. A similar methodology was also employed to compare the A 0 mode scattering patterns at impact damage and artificial delaminations in composite plates, 18 and for the detection and monitoring of short fatigue cracks emanating from holes using higher order guided wave modes.…”

Section: Introductionmentioning

confidence: 96%

“…Far-field scattering patterns for a long, through thickness notch emanating from a hole of varying diameter were validated experimentally for a range of excitation frequencies [15]. The scattering patterns of the A0 mode at defects at a circular hole were investigated experimentally, evaluating the far field measured on radial lines using the Hankel transform [17]. Significant differences in the scattering patterns between a machined notch and fatigue crack emanating from the hole were found, depending on the ratio of the wavelength to defect length and direction.…”

Section: Introductionmentioning

confidence: 99%

Guided wave sensitivity prediction for part and through-thickness crack-like defects

Fromme

2019

Structural Health Monitoring

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Guided waves allow for the efficient structural health monitoring of large structures using phased or distributed arrays of sensors. The sensitivity for specific defects can be improved by accounting for the angular scattering pattern. The scattering of the fundamental anti-symmetric guided wave mode (A0 Lamb mode) at through-thickness and part-through crack-like defects was studied experimentally and from three-dimensional finite element simulations. Experimentally, the scattered field around manufactured notches of different depths and lengths in an aluminium plate was measured using a laser interferometer. The scattered field was extracted by taking the complex difference in the frequency domain between baseline measurement and measurements around the defect. Good agreement was found between measurements and three-dimensional finite element simulations, and the amplitude and directionality pattern of the scattered field can be predicted accurately. The angular directionality pattern of the scattered field depending on the direction of the incident wave relative to the crack-like defect orientation, depth and length relative to the wavelength was investigated. For short and part-thickness defects, the main scattering effect is a reduction of the (forward) wave propagating past the defect with very limited backscattered amplitude. Significant energy scattered back towards the incident wave direction was only found for perpendicular incidence on long and deep defects. Even for large defects, almost no energy is scattered in certain directions from the defect, possibly complicating defect detection. Based on the predicted amplitude and angular dependency of the scattered guided waves, the sensitivity for defect detection using localized and distributed structural health monitoring sensor array systems can be quantified.

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Guided wave scattering by geometrical change or damage: Application to characterization of fatigue crack and machined notch

Cited by 16 publications

References 31 publications

A model-based approach for statistical assessment of detection and localization performance of guided wave–based imaging techniques

A model-based approach for statistical assessment of detection and localization performance of guided wave–based imaging techniques

Statistical partial wavefield imaging using Lamb wave signals

Guided wave sensitivity prediction for part and through-thickness crack-like defects

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