A Non-Contact Technique for Damage Monitoring in Submerged Plates Using Guided Waves

Abstract

This paper discusses a non-contact and in situ damage-monitoring methodology in submerged plates using ultrasonic guided waves. Specific Lamb wave modes sensitive to near-surface and sub-surface damages have been identified. These modes are further utilized for non-contact scanning of the plates to identify the presence, as well as extent, of damage. Effective combination of specific Lamb wave modes leads to comprehensive inspection of the submerged plate structures. The developed methodology is successfully applied for monitoring notches and corrosion in plate. The data generated from scanning the plates have been pictorially represented in the form of defect maps.

Ultrasonic guided waves for monitoring corrosion in submerged plates

“…The comparison of actual corrosion with notches on the plate using this mode indicates a close match (Figure b). In notched specimens, with increase in the depth of the notch, drop in signal was observed up to 37.5% depth of the notch using the surface sensitive mode.…”

“…The signals received in the standard immersion transducers were used for the detection of notches and circular holes. Recently, the present authors have demonstrated the efficacy of different Lamb wave modes in monitoring notches of different depths in immersed plates .…”

“…Selection of these frequencies is based on the principle of lower material attenuation, scattering and mode conversions at lower frequencies. The authors demonstrated the efficacy of using specific guided wave modes of S 0 at 0.5 MHz and S 1 at 1 MHz for detecting notches in submerged plates . It is established that each Lamb wave mode interacts uniquely with the notch defects.…”

“…The behaviour of the mode can be compared in cases of deep notches and pitting corrosion. The transmission of waves through notches in the plate and that in actual corrosion had a close match (Figure b).…”

Outlier Analysis and Artificial Neural Network for the Noncontact Nondestructive Evaluation of Immersed Plates

“…Sharma and Pathania [11,12] investigated the propagation of thermoelastic waves in a plate bordered with inviscid liquids. Sharma and Mukherjee [13,14] presented a static noncontact system based on two immersion transducers to generate and detect leaky waves in an immersed plate. Finally, Lee et al…”