<i>Ultrasonic Waves in Solid Media</i>

Rose, Joseph L.

doi:10.1121/1.428552

Cited by 1,123 publications

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“…The group velocity for the symmetric and anti-symmetric modes has been calculated by the standard approach of solving numerically the Rayleigh-Lamb equation [11] for isotropic sheets. The group velocity plots for the modes for the 1 mm and 3 mm thick sheets with the corresponding FFTs of figure 7 directly below them are shown in figure 8.…”

Section: Experimental Results On Defect Free Aluminium Sheetsmentioning

confidence: 99%

“…From figure 2, one can see that that the S 0 mode should be generated more efficiently by the laser source at the frequency thickness product of 0.5 MHz-mm when compared to 2.21 MHz-mm, where there is almost zero in-plane displacement at the surface. These have been calculated using the standard technique of firstly solving the relevant Rayleigh-Lamb equations to find the phase velocity of a particular mode at a particular frequency thickness product, and then taking this result to calculate the displacement through the thickness of the plate [11]. Figure 2 Relative displacement of the in-plane and out of plane components in a 1 mm thick aluminium sheet for the S 0 mode Lamb wave at frequency-thickness products of 0.5 MHz-mm (left) and 2.21 MHz-mm (right).…”

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confidence: 99%

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Detection of cracks in metal sheets using pulsed laser generated ultrasound and EMAT detection

et al. 2011

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A pulsed Nd:YAG laser with an approximately Gaussian beam shape is directed onto the surface of an aluminium sheet at an energy density below which damage by laser ablation occurs, generating Lamb waves in the sheet. The laser beam is raster scanned across the surface of the sample. The Lamb waves travel radially outwards from the generation point and are detected some distance away by an electromagnetic acoustic transducer with sensitivity to in-plane displacements of the sheet. A number of static EMATs are located around the edges of the sheet, some distance from the generation point.The presence of a crack-like defect on the sheet can be detected by either a sudden change in the ultrasonic waveform or by an enhancement in the frequency content of the waveform when the laser beam illuminates directly onto the crack.

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Section: Experimental Results On Defect Free Aluminium Sheetsmentioning

confidence: 99%

mentioning

confidence: 99%

Detection of cracks in metal sheets using pulsed laser generated ultrasound and EMAT detection

et al. 2011

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“…Inspection of oil and gas pipelines, power plants, railways and aircraft are applications where ultrasound has become a standard tool. A more comprehensive review of the existing methods can be found in the book by Rose [11].…”

Section: Background and Motivationmentioning

confidence: 99%

“…Hence, each reflection of either the shear or the compressional wave creates both a shear and a compressional wave, known as mode conversion. The dispersion relation for the Lamb waves can be found in several textbooks, see for instance Rose [11], and can be expressed as…”

Section: G Waag: Air-coupled Ultrasound For Plate Thickness Measuremmentioning

confidence: 99%

Air-coupled ultrasonic through-transmission thickness measurements of steel plates

Waag

Hoff

Norli³

2015

Ultrasonics

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“…When using Lamb waves, mode conversion can occur between all of the wave modes that are supported at the frequency-thickness of inspection, with more modes available at higher frequency-thicknesses [22,25] . Following interaction, these waves propagate away from the defect with velocities determined by the mode (shown in figure 2), and enhancement is only observed close to the defect when these reflected and mode converted waves arrive within the same time window as the incident mode [22] .…”

Section: Near-field Enhancementsmentioning

confidence: 99%

Characterisation of hidden defects using the near-field ultrasonic enhancement of Lamb waves

Clough

Edwards

2015

Ultrasonics

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Defects that propagate from the inside of a structure can be difficult to detect by traditional non-destructive inspection methods. A non-contact inspection method is presented here that uses the near-field interactions of ultrasonic Lamb waves to detect defects propagating into a 1.5 mm thick aluminium sheet from the opposite side to that which is inspected. Near-field interactions of the S0 Lamb waves with the defects are shown to give rise to a characteristic increase in the wave magnitude, which is used to position and characterise these hidden defects. It is shown that such defects are difficult to detect from a study of their influence on ultrasonic transmission alone. Single defects of different depths, and systems of multiple defects with varying separations and relative depths, are successfully detected in both experimental trials and FEM simulations. Reliable single defect detection is achieved for defects with a minimum depth of 30% of the plate thickness, and resolution of multiple defects is achieved for defect separations of 5 mm.

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Ultrasonic Waves in Solid Media

Cited by 1,123 publications

References 0 publications

Detection of cracks in metal sheets using pulsed laser generated ultrasound and EMAT detection

Detection of cracks in metal sheets using pulsed laser generated ultrasound and EMAT detection

Air-coupled ultrasonic through-transmission thickness measurements of steel plates

Characterisation of hidden defects using the near-field ultrasonic enhancement of Lamb waves

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