NDE/NDT Demonstration- Guided Wave Testing 2018-05-17T14:14:04+00:00

NDE/NDT Demonstration – Guided Wave

Guided Wave Testing for Crack Detection

Vantage Research Platform For Materials Science and NDE/NDT

Lamb waves in plate A form simple, clear progression envelops.
(on left, without defect)
Lamb waves in plate B form complex progression envelops.
(on right, with defect)

Guided waves are a mode of ultrasound propagation that is confined in long structures with distinct boundaries. Lamb waves are the guided waves propagating in plates.

In the schematic, a tilted longitudinal wave is guided into an aluminum plate using a wedge. Part of the incident wave is refracted into shear waves due to mode conversions. The shear and longitudinal waves propagate further in the plate and are reflected and refracted at boundaries. At some distance away, superpositions of the waves that have same phases and velocities form static wave progression envelopes, which are usually referred to as Lamb waves.

Due to boundary effects, Lamb wave propagation is more complex than bulk waves. Single mode excitation of Lamb waves may be achieved by tuning frequency and incident angle (phase velocity). In this example, the transmit frequency was 2.1 MHz and the incident angle was 45 degrees.

A single lamb wave mode A2 was excited in plate A
(on left, without defect).

In addtion to mode A2, two other lamb waves modes (S1and S2) are observed in plate B due to the defect.

Lamb wave dispersion curves are useful for defect detection in plate structures.

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