Lamb wave (A0 mode) scattering directionality at defects

Fromme, Paul

doi:10.1063/1.4974570

Cited by 5 publications

(12 citation statements)

References 19 publications

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“…The velocity of the out-of-plane displacement was measured using a laser interferometer every 5 degrees on a circle around the notch with a radius of 30 mm. The full time traces of the measured signals were bandpass filtered (75 kHz -125 kHz) and averaged (20 averages) in a digital oscilloscope before being transferred to the measurement PC [29,8]. Similar to the FE simulations, an initial measurement was done for each excitation transducer before the milling of the notch to capture the incident wave field, and then for each notch depth.…”

Section: Methodsmentioning

confidence: 99%

“…The scattered wave field around 20 and 6 mm long notches was measured on a large, 5-mm-thick aluminium plate (size: 1.5 m × 1 m). 27,29 The 20-mm-long notch (width: 1 mm) was milled in four steps to give a varying depth of 1.25 mm (1/4 thickness), 2.5 mm (1/2 thickness), 3.75 mm (3/4 thickness) and through thickness. The notch had straight edges but rounded corners due to the milling tool (diameter of 1 mm) and a flat bottom for the part-through depths.…”

Section: Methodsmentioning

confidence: 99%

“…For both incident wave directions, almost no energy is scattered along the defect orientation (90° or 270°). Previously, the scattering patterns had also been compared to FE simulations for a crack (zero width) [29], where in general similar angular scattering patterns, but, depending on the geometry, some differences of the amplitudes were observed.…”

Section: Comparison Of Experimental and Simulation Scattering Patternsmentioning

confidence: 99%

“…The influence of the defect length relative to the wavelength ( = 19 mm) was investigated for through-thickness and ½ thickness defects oriented perpendicular (0°) and at an angle (45°) to the direction of the incident wave [29]. Figures 9 and 10 show respectively the angular scattering patterns and maximum scattered amplitude for through thickness (Fig.…”

Section: Defect Lengthmentioning

confidence: 99%

“…This contribution investigates the angular dependency and directionality pattern of the A0 Lamb wave mode scattered at a crack-like defect (notch) in a plate, depending on the angle of the incident wave relative to the defect orientation and on the notch length relative to the wavelength. It is partially based on previous conference proceedings papers [8,[27][28][29], where the employed methodology and preliminary results were presented. The scattered wave fields predicted from Finite Element (FE) simulations and measured experimentally were compared and show good agreement for part-through and through thickness notches of different lengths.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Comparison Of Experimental and Simulation Scattering Patternsmentioning

confidence: 99%

Section: Defect Lengthmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Fromme

2019

Structural Health Monitoring

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A Lamb wave-based crack evaluation method in plate-like structures using specular reflections and tip diffractions

Zhang¹,

Liang²,

Lin³

et al. 2020

Smart Mater. Struct.

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The comprehensive assessment of crack angle, length and profile could provide an important reference for the non-destructive evaluation of plate-like structures. In this paper, we aim at fully exploiting information carried by reflections, so that details of the crack could be displayed as much as possible. Firstly, the Lamb wave reflections from a crack are classified into specular waves and tip diffractions. Under the linear assumption of crack profile, the specular waves could be regarded as being transmitted from the mirror point of the actuator with respect to the crack line, thus the corresponding reflection points can be located with geometric methods. On the other hand, diffractions are used to visualize crack tips where a fusion strategy is adopted to get the localization image. Both reflection points and tips are not only interpolated to show the crack position and profile, but also linearly fitted to display the crack trend for the estimation of its length and angle. Numerical investigations and experiments are carried out on different cracks, and related parameters are also discussed. Results show that the proposed method could make an accurate crack evaluation and reconstruct a detailed crack shape.

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Imaging slit in metal plate using aerial ultrasound source scanning and nonlinear harmonic method

Osumi

Yamada

Ito

2020

Acoust. Sci. & Tech.

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We previously proposed a stable high-speed visualization measurement method that combines nonlinear harmonics with aerial ultrasonic wave source scanning. In this paper, a more efficient method is proposed to visualize a slit flaw in a metal plate. The results show that visualization of the propagation of ultrasonic waves was possible by wave source scanning. Harmonic propagation was also visible. The slit in the metal plate was visualized with the same accuracy as that of the previous laser probe scanning method.

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Lamb wave (A0 mode) scattering directionality at defects

Cited by 5 publications

References 19 publications

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

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

A Lamb wave-based crack evaluation method in plate-like structures using specular reflections and tip diffractions

Imaging slit in metal plate using aerial ultrasound source scanning and nonlinear harmonic method

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